26 November 2019

DeLeon and colleagues 2019

DeLeon H III, Garcia J Jr., Silva DC, Quintanilla O, Faulkes Z, Thomas JM III. 2019. Culturing embryonic cells from the parthenogenetic clonal marble crayfish (Marmorkrebs) Procambarus virginalis Lyko, 2017 (Decapoda: Astacidea: Cambaridae). Journal of Crustacean Biology 39(6): 758–763. https://doi.org/10.1093/jcbiol/ruz063.

Abstract

The parthenogenetic marbled crayfish, or Marmorkrebs (Procambarus virginalis Lyko 2017), is an emerging model organism. We describe a method to isolate cells from early-stage embryos and culture them in vitro. The identity of the cells was confirmed by sequencing the cytochrome c oxidase subunit I (COI) gene. This technique can be applied for use in the manipulation of embryonic parthenogenetic crayfish cells.

Keywords: cell culture • embryos • invasive species • model organisms • ontogeny • techniques

21 November 2019

Travel awards for International Association of Astacology 2020

Applications are now open for five Student Travel Awards (US$500) for the 23rd Biennial Symposium of the International Association of Astacology, in Hluboká nad Vltavou, Czech Republic, from 29 June 2010 to 3 July 2020.

The deadline for Student Travel Award applications is 10 February 2020. Award notifications will be no later than 15 March 2020. Questions can be emailed to Jim Furse, chair of the Student Travel Awards committee: j.furse@griffith.edu.au.

Applicants must be society members by the application deadline and be presenting at the symposium. Student memberships are free for the first year. (Processing membership applications may take a few days, however.) Information on membership is available here or by emailing Jim Stoeckel at jimstoeckel@auburn.edu.

External links

International Association for Astacology
2020 IAA conference website

07 November 2019

Linzmaier, 2019

Linzmaier SM. 2019. Ecology and evolution in novel communities: The marbled crayfish and its interaction partners. Doctoral thesis, Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin. http://dx.doi.org/10.17169/refubium-25647

Abstract

Ecosystems worldwide are undergoing drastic changes caused by the intentional and unintentional transfer of species between them. This anthropogenic process has accelerated within the last centuries, creating novel ecosystems which harbor species assemblages devoid of a shared evolutionary history. When novel organisms interact with their new environment and the members of the invaded community, they often exhibit different or even new traits compared to established species. These interactions can thus be difficult to predict, and they can have far-reaching consequences on biotic and abiotic components of the ecosystem. Especially differences in trophic interactions and behaviors can cause the most severe repercussions of species invasions. Therefore, a deeper understanding of the mechanisms underlying the invasion process informs general ideas of community assembly and can help predict potential invasions and the risks associated with it. To gain an understanding of the interactions within novel communities, this dissertation combines empirical and theoretical approaches from the fields of community, invasion and behavioral ecology. The first chapter of the thesis presents a framework for risk assessments of novel organisms based on trophic interactions. A fundamental ecological principle, the functional response (i.e. the per-capita consumption rate as a function of resource density) is used to identify and quantify trophic traits of novel organisms linked to invasion success. The new approach presented in this chapter prioritizes and selects subsets of trophic links within the system in question and demonstrates the application of functional responses while including multiple potential interaction partners in the invaded system. The invasion of marbled crayfish Procambarus virginalis into Germany and a resident non-native congener (spiny-cheek crayfish Faxonius limosus) are used to illustrate the framework. However, the framework is applicable to a variety of novel organisms and invasion scenarios. The second chapter implements the framework from Chapter 1 by executing the aforementioned example within a laboratory study and the parameterization of a mechanistic functional response model. Predator-prey interactions between the crayfish species and individuals feeding on a key aquatic primary consumer (Dreissena spp.) are examined in great detail to mechanistically explain trophic-trait differences. Data from video-recordings of foraging and feeding events are used to model and predict functional responses from independently derived predation parameters. In addition, modeled and empirically observed functional responses are linked to individual behavioral traits. Furthermore, this chapter demonstrates and discusses the explanatory power of the predation parameters on functional responses. The third chapter assesses and compares behavioral traits that are important for the invasion success of crayfish species. Individual traits related to interspecific interactions – such as agonistic behavior between two crayfish and the response to predators, but also activity, which is related to foraging – are tested therein. In addition, correlations between behaviors, or so-called behavioral syndromes, are evaluated. This chapter also compares behavioral differences between naïve aquarium and naturalized individuals of marbled crayfish, and discusses the overall importance of the observed behavioral traits for novel communities. In the fourth and final chapter, the prey-choice of marbled crayfish compared to that of established spiny cheek crayfish from field sites were investigated in the laboratory and contrasted with diet data from invaded lakes. Also, the trophic position and trophic niche size are determined to assess the ecological function of each species. To understand what resources the species use and which prey items or resources are mostly impacted, preferences and consumption rates were measured in predator-free environments and computed from stable isotopes of lake ecosystems. This part of the dissertation delivers insights into the in situ impacts of marbled crayfish in invaded food webs by highlighting particularly important interactions in an ecosystem context. My thesis provides a novel interaction framework applicable for risk assessments of novel organisms (Chapter 1). It advances fundamental principles of ecology and invasion biology by providing a detailed, mechanistic examination and modeling of predator-prey interactions (Chapter 2), including the behavioral aspects (Chapter 3) and the food web effects (Chapter 4) of the novel, invasive marbled crayfish and a functionally similar comparator species, the spiny-cheek crayfish.

Keywords: ecological novelty • functional responses • freshwater crayfish • behavioral syndromes • biological invasions • over-invasions • trophic niche • predator–prey interactions

Sciency thinking on Marmorkrebs

The Sciency Thoughts blog by Joe Bauwens has a nice summary of a paper on Marmorkrebs in Madagascar from earlier this year. Go check it out!

External links

Assessing the impact of the introduced and highly invasive Marbled Crayfish on freshwater ecosystems in Madagascar.

15 September 2019

Mauvisseau and colleagues, 2019

Mauvisseau Q, Tönges S, Andriantsoa R, Lyko F, Sweet M. 2019. Early detection of an emerging invasive species: eDNA monitoring of a parthenogenetic crayfish in freshwater systems. Management of Biological Invasions 10(3): 449–460. https://doi.org/10.3391/mbi.2019.10.3.04

Abstract

Procambarus virginalis, also known as the Marmorkrebs is a highly invasive crayfish species characterized by parthenogenetic reproduction. As conservation management plans rely on the accuracy of the presence and distribution information of invasive species, a reliable method is needed for detecting such species in aquatic systems. We developed and validated a qPCR-based assay for monitoring P. virginalis at low abundance, by detecting their eDNA traces left in freshwater systems. We were able to implement this new assay in-situ at two separate lakes in Germany, where the crayfish were known to be present. Furthermore, we did not detect the pathogenic fungus Aphanomyces astaci in the locations where the Marmorkrebs were detected. We conclude that the use of eDNA is therefore a reliable tool for the early detection of this “perfect invader”.

Keywords: eDNA detection • lakes • Marmorkrebs • crayfish plague • qPCR

09 September 2019

Forum Flusskrebse theme issue

Forum Flusskrebse is a German-language society for the study of crayfish. They have a regular periodical (Google Translate calls it a “newspaper”). Issue #30 has three articles on Marmorkrebs.

• Genetically equal and yet different: advantages and benefits of marble crayfish for research
Genetisch gleich und doch verschieden: Vorteile und Nutzen des Marmorkrebses für die Forschung


• The zoo trade as an entry path for invasive species: what we can learn from marble crayfish
Der Zoohandel als Einschleppungspfad für invasive Arten: Was wir vom Marmorkrebs lernen können

• Environment-induced plasticity of a parthenogenetic crayfish: Population ecology of the marble crayfish Procambarus virginalis in southwestern Germany
Umweltinduzierte Plastizität eines parthenogenetischen Flusskrebses: Populationsökologie des Marmorkrebses Procambarus virginalis in Südwestdeutschland

The English translations are courtesy of Google Translate and may not be entirely accurate, but I hope they give a passable idea of what the work is about.

This periodical is available in the society’s shop for 10€.

Hat tip to Günter Vogt.

External links

Forum flusskrebse 

28 August 2019

Ercoli and colleagues, 2019

Ercoli F, Kaldre K, Paaver T, Gross R. 2019 First record of an established marbled crayfish Procambarus virginalis (Lyko, 2017) population in Estonia. BioInvasions Records 8(3): 675-683. https://doi.org/10.3391/bir.2019.8.3.25

Abstract

Invasive marbled crayfish Procambarus virginalis (Lyko, 2017) is spreading alarmingly fast across European countries and beyond. Early maturation, parthenogenetic reproduction mode and high growth rate contribute to a high potential invasiveness. Marbled crayfish can pose severe effects on native communities impacting the native crayfish populations being carrier of the crayfish plague disease caused by Aphanomyces astaci. Here we report the first record of marbled crayfish in Estonia. In total, 104 individuals were found in the artificially warm outflow channel of the cooling system of Balti Power Plant, entering to the water reservoir of the River Narva. Molecular analyses confirmed the morphological identification of captured specimens as a marbled crayfish. Four out of six marbled crayfish individuals exhibited the presence of crayfish plague agent, though at very low level. This suggests that marbled crayfish can potentially be a new vector of crayfish plague in Estonian freshwater ecosystems containing native noble crayfish Astacus astacus populations. Monitoring and eradication actions are urgently needed not only in the outflow channel where the species was found but in the whole water reservoir and River Narva itself.

Keywords: invasive crayfish • NICS • crayfish plague • reservoir • artificial refuge trap • mitochondrial DNA


20 August 2019

Haubrock and colleagues, 2019

Haubrock PJ, Kubec J, Veselý L, Buřič M, Tricarico E, Kouba A. 2019. Water temperature as a hindrance, but not limiting factor for the survival of warm water invasive crayfish introduced in cold periods. Journal of Great Lakes Research 45(4): 788-794. https://doi.org/10.1016/j.jglr.2019.05.006

Abstract

The success of non-native species establishment depends on various abiotic and biotic factors that determine the outcome of an introduction event. Limiting temperature ranges have been studied for various non-native species; however, such previous assessments of species-specific temperature thresholds may be inadequate. Because several non-native crayfish species prefer warmer water temperatures, introductions were generally assumed to occur during preferable, warmer periods. However, despite the generality, traditionally considered ‘warm-water’ species are gradually appearing in new habitats, which were previously considered too cold for successful establishment. Newly discovered overwintering abilities of these species are likely related to the winter stratification in lentic ecosystems, which maintain tolerable conditions. To understand better the survivability of two such non-native species, red swamp crayfish Procambarus clarkii and marbled crayfish Procambarus virginalis individuals were abruptly subjected to a thermic shock which lowered the water temperature from 20°C (room temperature) to 6°C, 4°C and 2°C, thus mimicking the release by pet owners during various phases of winter. The survival rate and foraging activity were monitored for up to 98 days. Procambarus clarkii showed a considerable higher survival rate at low temperatures (4°C, 2°C) compared to that of P. virginalis with neither sex nor size differences evident. Our findings reveal the ability of warm water invaders to withstand a shock during introduction at low temperature periods without acclimation. Considering these newly discovered shifts in physiological limitations, particularly for the red swamp crayfish, this may indicate a higher threat for areas with colder conditions.

Keywords: mortality • pet trade • biological invasion • thermocline

Guo and colleagues, 2019

Guo W, Kubec J, Veselý L, Hossain MS, Buřič M, McClain R, Kouba A. 2019. High air humidity is sufficient for successful egg incubation and early post-embryonic development in the marbled crayfish (Procambarus virginalis). Freshwater Biology 64(9): 1603-1612. https://doi.org/10.1111/fwb.13357

Abstract

  1. Severe weather events, such as long‐term droughts, are challenging for many freshwater species. To survive drought, freshwater crayfish tend to inhabit shelters or burrows where they can remain in contact with water or high humidity environments. However, it is not known whether embryogenesis or post‐embryonic development can occur without free standing water.
  2. To address this question, three experiments were conducted using artificial burrows with high air humidity and using marbled crayfish (Procambarus virginalis Lyko, 2017) as a model species. Marbled crayfish are capable of parthenogenetic reproduction, burrow extensively and are able to travel long distances over land. In the first experiment, ovigerous females were transferred to simulated burrows without free water, but with high air humidity. A control group of females were kept in burrows with free water. Successful hatching was achieved in both groups.
  3. In the second experiment, ovigerous females were transferred to simulated burrows with no free water but high air humidity and post‐embryonic development were observed. Following successful hatching, offspring moulted to the second developmental stage (stage 2 juveniles). Stage 2 juveniles remained viable without free water for 20 days, but further development was not observed. However, when some of these stage 2 juveniles were placed back into fully aquatic conditions (experiment 3), they moulted to stage 3 within 4 to 8 days.
  4. These results demonstrated the ability of marbled crayfish to undergo terminal phases of embryogenesis, including hatching, as well as early post‐embryonic development under high air humidity conditions only. Post‐embryonic development was suspended in the absence of free water, and successfully resumed when re‐immersed.
  5. This similar ability to tolerate drought‐like conditions during post‐embryonic development may also occur in other crayfish species, especially primary burrowers. This unprecedented life history trait may be crucial for inhabiting ecosystems with rapidly changing water regimes. In drying climates, it may confer advantages on some crayfish species (including some invasive species) over others.

Keywords: burrow • drought • hyporheic dweller • macroinvertebrate • ontogeny

19 August 2019

Écrevisse marbrées en France

Marmorkrebs have been found in the wild in France. As of now, all I know is this tweet from Marc Collas:

The marbled crayfish (Procambarus virginalis) has just been discovered in France on the basin of the river Moselle. This is the first observation of this species in France #crayfish #ecrevisse #marmorkrebs #biodiversite


It is perhaps not surprising that Moselle River is the first location where Marmorkrebs have been found in France. The river borders Germany, which has been ground zero for Marmorkrebs introductions. It is a tributary for the Rhine River. It’s possible that the crayfish were introduced in Germany and spread into France.


More information as I learn it. The map of Marmorkrebs introductions has been updated accordingly.

External links

Marc Collas on Twitter
River Moselle

25 July 2019

Hossain and colleagues, 2019c

Hossain MS, Kouba A Buřič M. 2019. Morphometry, size at maturity, and fecundity of marbled crayfish (Procambarus virginalis). Zoologischer Anzeiger 281: 68-75. https://doi.org/10.1016/j.jcz.2019.06.005

Abstract

Morphometric ratios, relationships and condition factors provide information regarding growth patterns, population dynamics and well-being of individuals in particular environments. Ecology of any species is then better understandable through life history traits and reproductive potential. The present study is aimed at exploring the morphometric and reproductive patterns of the parthenogenetic marbled crayfish, Procambarus virginalis. Marbled crayfish exhibited positive allometric growth and statistically significant common length-weight relationships. Abdomen width, claw length, width, and height increase significantly faster than the chosen most robust body size parameter, postorbital carapace length (POCL). Conversely, total length, carapace length, carapace width, and abdomen length grow proportionally slower than POCL. The condition factor was higher than the threshold value of ∼1 indicating the well-being of the crayfish used. Marbled crayfish, at their first reproduction, were recorded as long as 42.8 ± 10.8 (31.5–73.5) mm total length with a mean fecundity of 89.72 ± 56.9 (22–349) eggs. The relative fecundity (per 1 mm of POCL) of females reproducing for the first time was significantly lower compared to those reproducing repeatedly. Fecundity and relative fecundity exhibited a significant linear relationship with the carapace length and weight of mothers. As a tool for total fecundity estimation, the number of eggs on the third pair of pleopods was counted and plotted against size of mothers, and total fecundity. The number of eggs attached to the third pair of pleopods very closely correlates with the carapace length, weight and total fecundity. Based on our results, it can be concluded that abdomen width and claw growth is allometric compared to POCL which confirms the importance of these body parts. Fecundity parameters were confirmed to have a tight relationship to marbled crayfish size. Clutch size estimation can be used in future research based on the close correlation of egg counts on third pleopods and total fecundity.

Keywords: growth • reproduction • Procambarus virginalis • morphometry • fecundity

08 July 2019

Weiperth and colleagues, 2019

Weiperth A, Gál B, Kuøíková P, Langrová I, Kouba A, Patoka J. 2019. Risk assessment of pet-traded decapod crustaceans in Hungary with evidence of Cherax quadricarinatus (von Martens, 1868) in the wild. North–Western Journal of Zoology 15(1): 42-47. http://biozoojournals.ro/nwjz/content/v15n1/nwjz_e171303_Weiperth.pdf

Abstract

The pet trade is one of the most important sources of introduction of freshwater non-native decapod crustaceans. Precise and timely identification of potentially hazardous species is necessary for the effective prevention of new introductions. Here, we present a list of species of ornamental freshwater decapod crustaceans pet-traded in Hungary and their risk assessment, including the probability of establishment based on climate matching. The list contains 13 shrimps, eight crayfish, two crabs, and one hermit crab. Three crayfish, Cherax destructor, Procambarus clarkii, P. virginalis, and one crab, Eriocheir sinensis, were classified in the high-risk category. During field sampling, we found three individuals of C. quadricarinatus that were probably released or escaped from aquaria. These are the first records of this species in the wild of Carpathian Basin. We strongly recommend further educating hobbyists about the risks related to the escapes and releases of high-risk taxa, as well as monitoring of the region for their occurrence.

Keywords: Carpathian Basin • crayfish • crab • hermit crab • invasiveness • ornamental animal • redclaw • shrimp

Vogt and colleagues, 2019

Vogt G, Dorn NJ, Pfeiffer M, Lukhaup C, Williams BW, Schulz R, Schrimpf A. 2019. The dimension of biological change caused by autotriploidy: A meta-analysis with triploid crayfish Procambarus virginalis and its diploid parent Procambarus fallax. Zoologischer Anzeiger 281: 53-67. https://doi.org/https://doi.org/10.1016/j.jcz.2019.06.006

Abstract

The biological changes caused by autotriploidy are poorly studied in animals. To investigate this issue in depth, we compared genetics, morphology, life history, ecology and behaviour of the triploid marbled crayfish and its diploid parent, slough crayfish Procambarus fallax. We performed a meta-analysis of our data and literature data. Our COI based molecular tree, consisting of 27 species of Cambaridae, confirmed the close taxonomic relationship between marbled crayfish and P. fallax. Comparison of both crayfish revealed similarities in mitochondrial gene sequences, morphological characters, colouration, body proportions and behaviours. Considerable differences were recorded with respect to chromosome number in somatic cells, haploid genome size, DNA methylation level, body size, fecundity, longevity, population size structure, invasiveness, and the range of inhabited biomes. These differences have dimensions that are otherwise only observed between species supporting earlier proposed raising of marbled crayfish from P. fallax forma virginalis to a new species named Procambarus virginalis. Particularly noteworthy is the enhancement of the fitness traits that probably resulted from evolutionary changes in gene expression. These alterations and the transition from sexual reproduction to parthenogenesis are likely responsible for the increased invasiveness of marbled crayfish in tropical to cold-temperate biomes.

Keywords: autopolyploidy • marbled crayfish • genetics • morphology • life history • ecology

24 June 2019

Announcement: 23rd International Association of Astacology symposium


The 23rd International Association of Astacology symposium will be hosted the University of South Bohemia in the Czech Republic from June 29 to July 3, 2020.

The symposium will be held in Hotel Štekl, near the beautiful Hluboká nad Vltavou Château (pictured).

Planned topics including species diversity and distribution, conservation, physiology, genetics, ecology, ethology, diseases, fishery and aquaculture.

In addition to the scientific program, events will include trips to the experimental facilities of the University of South Bohemia, natural crayfish locality in the Šumava National Park, the Hluboká nad Vltavou Château, beer tasting with the Budweiser Budvar Brewery, the Český Krumlov UNESCO Heritage castle, and wooden rafting.

Abstract submission runs from 1 December 2019 to 15 April 2020.

Early registration deadline: 31 March 2020
Regular registration: 30 April 2020Late registration: 31 May 2020

External links

23rd Symposium of the International Association of Astacology

17 June 2019

Hossain and colleagues, 2019b

Hossain MS, Kubec J, Grabicová K, Grabic R, Randák T, Guo W, Kouba A, Buřič M. 2019. Environmentally relevant concentrations of methamphetamine and sertraline modify the behavior and life history traits of an aquatic invertebrate. Aquatic Toxicology 213: 105222. https://doi.org/https://doi.org/10.1016/j.aquatox.2019.105222

Abstract

Pharmaceutically active compounds are major contaminants of aquatic environments that show direct and indirect effects on aquatic organisms even at low concentrations. The aim of this study was to assess the effects of the illicit drug methamphetamine and the antidepressant sertraline on clonal marbled crayfish Procambarus virginalis. Crayfish exposed to the environmentally relevant concentrations of methamphetamine of ∼1 μg L−1 did not exhibit significant differences from unexposed controls in distance moved, velocity, and activity level with or without available shelter. Sertraline-exposed (∼1 μg L−1) crayfish were significantly more active, regardless of available shelter, and moved greater distances when shelter was available, compared to control crayfish. Crayfish exposed to methamphetamine and sertraline spent significantly more time outside the shelters compared to controls. Sertraline-exposed crayfish spawned more frequently and showed higher mortality than controls. The results suggest that the low environmental concentrations of the tested compounds could alter the behavior and life history traits of crayfish, resulting in higher reproductive effort and mortality.

Keywords: aquatic pollutants • behavior • crayfish • life history traits • pharmaceuticals • Procambarus virginalis

07 June 2019

Updates from Denmark

It’s rare for crayfish news to get a follow-up, but the first record of Marmorkrebs in Denmark has attracted more attention by doing what Marmorkrebs do: reproducing.

Danish Marmorkrebs in berry

With the help of a Google Translate and guesswork (“crayfish” seems to translate into a lot of weird English words), I think the article says (in part):

It was bad news for the Danish nature when a marbled crayfish was found in Karup Å near Skive in February. It was the first time that the marbled crayfish was found in Denmark.

In other countries, the crayfish has done a lot of damage to nature, as it can fertilize itself and eat almost everything on its way. So since then, it has been kept in captivity at Aqua Aquarium in Silkeborg. Now it has succeeded in cloning itself and thus getting six kids.

If it first gets hold of the watercourses in Denmark, it is completely hopeless to stop it again, says Morten Vissing, is a zoologist at Aqua Aquarium and Animal Park.

“You have seen many strange things, but this is one of the things that hit everything. After all, it is not an animal that exists naturally. You have taken some animals from nature, and you have bred in colors and sizes. Then one has reached a species where today only females exist, and they are then able to clone themselves. It’s incredibly mysterious,” says Morten Vissing.

The marbled crayfish is the only species of crab known to reproduce asexually.

Vissing seems to imply that Marmorkrebs were bred deliberately, which is probably not the case. And either Vissing or the newspaper should read about spinycheek crayfish, which can reproduce asexually.


Related posts

Nothing like a Dane: the European invasion continues

External links

Den uønskede marmorkrebs har klonet sig selv (The unwanted marbled crayfish has cloned itself)

Celebrate diversity: Another member of Club Asexual

Asian water dragon (Physignathus cocincinus)

The list of parthenogenetic species slowly inches up. This time, it’s the Asian water dragon (Physignathus cocincinus) that continues increasing the list.

According to an interview on NPR, this discovery was made almost by happenstance. The policy of the zoo where the animals was kept was to toss unfertilized eggs. But someone thought, “Let’s try incubating them. It doesn’t take any time.”

Thus are discoveries made. Most eggs went bad, but the Asian water dragon’s... did not.

This makes me wonder just how many more species are capable of both sexual and asexual reproduction, and if there is a way to systematically test for this instead of just hoping for lucky accidents. 

References

KL Miller, Castañeda Rico S, Muletz-Wolz CR, Campana MG, McInerney N, Augustine L, Frere C, Peters AM, Fleischer RC. 2019. Parthenogenesis in a captive Asian water dragon (Physignathus cocincinus) identified with novel microsatellites. PLOS ONE 14(6): e0217489. http://doi.org/10.1371/journal.pone.0217489

External links

05 June 2019

Lipták and colleagues, 2019

Lipták B, Veselý L, Ercoli F, Bláha M, Buric M, Ruokonen TJ, Kouba A. Trophic role of marbled crayfish in a lentic freshwater ecosystem. Aquatic Invasions 14(2): 299-309. https://doi.org/10.3391/ai.2019.14.2.09

Abstract

Species’ introductions may cause severe adverse effects on freshwater ecosystems and their biota. The marbled crayfish, Procambarus virginalis Lyko, 2017, is an invasive parthenogenetically reproducing crayfish with rapid reproduction, maturation and tolerance to a wide range of environmental conditions, which was introduced to many sites across Europe during the last decade. Due to its recent speciation and limited number of field studies, the knowledge of trophic interactions of the marbled crayfish in freshwater food webs is scarce. An invaded area located in Central Europe was studied to identify the marbled crayfish food web interactions using analysis of carbon 13C and nitrogen 15N isotopes. This study brings the first insight into the trophic ecology of marbled crayfish in lentic freshwater ecosystems. Algae and detritus were identified as the most important food sources for the marbled crayfish, while zoobenthos and macrophytes were less important. Moreover, the marbled crayfish was found to be an important food source for top fish predators, but marginal for omnivorous fish. Being able to utilize energy from the bottom of the trophic food web, the marbled crayfish may have important roles in the ecosystem, transferring energy to higher trophic levels. It processes allochthonous and autochthonous matter in the ecosystem, thus being a competitor to other organisms with similar food preferences and impacting zoobenthos, algae and macrophytes through predation or direct consumption. To sum up, the marbled crayfish has a strong ability to utilize food sources from different trophic levels, and, thanks to its life history, can be a highly adaptable invader.

Keywords: biological invasion • Central Europe • parthenogenetic species •
Procambarus virginalis • stable isotope

27 May 2019

Concealed crayfish and The Hidden Half

Marmorkrebs rarely make appearances in pop culture. Based on this summary from the Financial Times, I want to read this.

Michael Blastland’s recent book, The Hidden Half, argues that much of the variation we see in the world around us is essentially mysterious. Mr Blastland’s opening example is the marmorkrebs, a kind of crayfish that reproduces parthenogenetically — that is, marmorkrebs lay eggs without mating and those eggs develop into clones of their mothers.

Place two clones into two identical fish tanks and feed them identical food. These genetically identical creatures raised in apparently identical environments produce genetically identical offspring who nevertheless vary dramatically in their size, form, lifespan, fecundity, and behaviour. Sometimes things turn out very differently for no reason that we can discern. We might as well call that reason “luck” as anything else.

There’s a preview on Good Reads of the first chapter, which includes most of the stuff on Marmorkrebs. I’d like to point out that this is similar in some ways to an older post here on the blog about similarity and variation.


Related posts

How Marmorkrebs can make the world a better place

External links

The Hidden Half (publisher’s site)

Neil Woodford shows it can be hard to tell luck from judgment

25 May 2019

Gatzmann, 2019

Gatzmann F. 2019. DNA methylation in the marbled crayfish Procambarus virginalis. Doctoral dissertation, The Faculty of Bio Sciences, Heidelburg University. https://doi.org/10.11588/heidok.00026426

Abstract

The all-female marbled crayfish Procambarus virginalis is a freshwater crayfish which is the only known obligatory parthenogen among the decapod crustaceans. Marbled crayfish are recent descendants of the sexually reproducing slough crayfish Procambarus fallax and have most likely emerged through a recent evolutionary macromutation event in P. fallax. Marbled crayfish reproduce by apomictic parthenogenesis, where oocytes do not undergo meiosis and all offspring are genetically identical clones of the mother. Nevertheless, marbled crayfish show a high degree of phenotypic variation and are a highly invasive species, where (through parthenogenesis) a single animal can establish a whole population. Moreover, they have been distributed via the pet trade and anthropogenic releases, and have formed stable populations in a variety of ecological habitats. Earlier this year, our group performed whole-genome sequencing for 11 marbled crayfish animals from different populations and countries, and found only four non-synonymous single nucleotide variances in coding regions. Since the marbled crayfish’s remarkable adaptability is not due to genetic variability, it is crucial to investigate epigenetic programming in this organism. I present here a comprehensive analysis of DNA methylation in marbled crayfish. Whole-genome bisulfite sequencing data was used to directly compare methylation patterns from multiple replicates in different tissues and from different marbled crayfish and Procambarus fallax animals. These methylation maps were integrated with RNA-seq and ATAC-seq data to comprehensively analyse the interplay between DNA methylation, chromatin accessibility, and gene expression. I found 18% of CpGs in marbled crayfish to be methylated. Repeats showed overall low methylation levels, with the exception of a single class of DNA transposons, which was ubiquitously methylated. DNA methylation was mainly targeted to the coding regions of housekeeping genes in marbled crayfish. In contrast to paradigmatic mammalian methylomes, I only observed very moderate methylation differences between tissues for both gene bodies and promoters. I did, however, identify a set of approximately 700 genes that showed a high variance in their methylation across tissues and animals. Gene body methylation was significantly inversely correlated with gene expression variability. Interestingly, the marbled crayfish shows overall lower methylation levels and higher gene expression variability than its parent species P. fallax. Since plasticity in gene expression can be a beneficial trait for adapting to new environments, this trait might contribute to the marbled crayfish’s adaptive and invasive success. The integrative analysis of DNA methylation, chromatin accessibility, and gene expression revealed that genes with highly methylated gene bodies were located in regions of poorly accessible chromatin and showed stable expression patterns. In contrast, lowly methylated genes were found in more accessible chromatin when stably expressed, and in more condensed chromatin when variably expressed. In this context, gene body methylation might function to stabilise gene expression in regions of limited chromatin accessibility. These findings broaden our knowledge of evolutionary conservation of DNA methylation patterns in invertebrates and provide novel insights on the interplay between gene body methylation, chromatin accessibility, and gene expression.

Note: Access restricted until 17 January 2020.

21 May 2019

“Step away from the aquarium...”

On this blog, I am frequently reporting new reports of Marmorkrebs as invaders, so it’s nice when Marmorkrebs are not bad news.

A news article in Ireland reports that a pet owner voluntary gave up Marmorkrebs kept in tanks to parks officials. In looking at the pet crayfish trade, one of my biggest concerns is the level of enforcement. It’s important for people not only to know that laws about the pet trade exist, but that they are people who genuinely do enforce those laws.

Unfortunately, this good piece of news is outweighed by two pieces of bad news. First is another outbreak of crayfish plague in Ireland.

The second is that there is a non-native crayfish population of Australian yabbies (Cherax destructor) in Ireland, the first time any non-native crayfish has gotten a toehold in the island. In a previous paper, I didn’t find anyone selling C. destructor as pets (Faulkes 2017). Several unidentified species sold as pets were described as “blue,” which fits C. destructor well. So it’s possible they were someone’s pets.

References

Faulkes Z. 2017. Slipping past the barricades: the illegal trade of pet crayfish in Ireland. Biology and Environment: Proceedings of the Royal Irish Academy 117(1): 15-23. https://doi.org/10.3318/BIOE.2017.02

External links

Warning issued over 'severe and increasing' threat to native crayfish species
Invasive species and diseases threat to native crayfish

17 May 2019

First Marmorkrebs on Twitter!

Set the wayback machine to a decade ago. Ten years ago, Marmorkrebs debuted on Twitter. The First to Tweet account says:

The first to tweet ‘Marmorkrebs’ was @DoctorZen in 2009!

It is a bit of a cheat, though, since the tweet was about this blog more than Marmorkrebs.

Enjoying that Marmorkrebs.blogspot.com was a finalist for Open Laboratory 2008.

16 May 2019

Marmorkrebs in the Middle East


I heard from astacologist Chris Lukhaup today that marbled crayfish are now in the rivers and ponds on Israel. Yes, plural.

This represents another signifcant expansion of Marmorkrebs across the globe, as it is the first report in western Asia. 

I don’t have more details at this time as to location and such, but am sure it will be forthcoming. I have updated the map of Marmorkrebs introductions with a generic pin for all of Israel at this time.

Thanks to Chris for giving me permission to share this.

23 April 2019

Veerappan 2019

Veerappan V. 2019. The effects of peptide neuromodulators on temperature responses in the crustacean nervous system. University of Illinois University Research Symposium: 351. https://ir.library.illinoisstate.edu/rsp_urs/351

Abstract

Temperature perturbations affect neuronal activities by altering the intrinsic ionic conductances that underlie the electrical properties of neurons. High temperatures can lead to an excessive increase in conductance and a shunt of neuronal responses, which decreases cell excitability and eventually causes a loss of neuronal activity. Surprisingly, though, many neuronal circuits continue to function in spite of these challenges, suggesting that they possess compensatory mechanisms to overcome the detrimental effects of temperature. In the crustacean stomatogastric ganglion even small temperature increases lead to loss of neuronal activity. Previous studies have shown that the presence of a neuropeptide released from modulatory projection neurons rescues the neuronal activity by counterbalancing the excessive conductance increase caused by high temperatures. However, it is not clear whether this rescue mechanism is common to many neurons or an idiosyncrasy of the stomatogastric system. We address this question using primary cell cultures derived from neural tissue of the marbled crayfish, Procambarus virginalis. Cell cultures allow us to characterize the responses of crustacean neurons from many different origins independent from circuit influences, and to test their responses to temperature challenges. Because neuropeptides are ubiquitously present in the nervous system and marbled crayfish survive large temperature fluctuations with seemingly few effects on behavioral effects, we hypothesize that most, if not all crustacean neurons have the ability to overcome temperature perturbations and that peptide modulators enable them to do so. To test our hypothesis we are challenging cultured neurons with temperature changes and analyze (1) the collective neuronal responses by measuring field potentials and (2) individual and collective neuronal responses using calcium imaging. Neurons will be raised under constant temperature conditions for a prolonged time period to exclude homeostatic adaptations of their temperature responses. To analyze how far cultured neurons withstand temperature fluctuations, we will compare their activities before and during a transient increase in temperature. We will determine the role of peptide modulators in temperature compensation by subjecting neurons to different modulators and observing changes in their temperature responses. We predict that, like neurons in the stomatogastric ganglion, cultured neurons can withstand fluctuations in temperature better in presence of neuromodulators. This would indicate the essential role played by the peptide neuromodulators in restoring neuronal activity when faced with changes in temperature.

Keywords: None provided.

27 March 2019

Lidova and colleagues, 2019

Lidova J, Buric M, Kouba A, Velisek J. 2019. Acute toxicity of two pyrethroid insecticides for five non-indigenous crayfish species in Europe. Veterinarni Medicina 64(03): 125–133. https://doi.org/10.17221/136/2018-VETMED

Abstract

Pyrethroid insecticides are highly toxic to many aquatic organisms. The aim of this study was to evaluate the toxicity of the commercial products Cyperkill 25 EC (active compound 250 g/l cypermethrin) and Decis Mega (active compound 50 g/l deltamethrin) for European non-indigenous marbled crayfish Procambarus virginalis, red swamp crayfish Procambarus clarkii, signal crayfish Pacifastacus leniusculus, spiny-cheek crayfish Orconectes limosus and yabby Cherax destructor. These data will provide a baseline for potential programmes to eradicate alien crayfish from Europe (EU Regulation No. 1143/2014; Commission Implementing Regulation No. 2016/1141) and are also relevant globally. The 96hLC50 values of Cyperkill 25 EC were 0.09, 0.17, 0.18, 0.19 and 0.30 µg/l for spiny-cheek crayfish, red swamp crayfish, marbled crayfish, signal crayfish and yabby, respectively. In the same order, the 96hLC50 values of Decis Mega were 0.76, 0.16, 0.21, 0.03 and 0.27 µg/l. The toxicity of the insecticides was similar and species-specific, possibly reflecting the size difference of the tested animals. This study shows that cypermethrin and deltamethrin are highly toxic to the tested crayfish species at low concentrations. This high sensitivity, along with the low accumulation in the food chain and short-term persistence in the aquatic environment, suggests that they are suitable biocides for eradicating crayfish in the wild. Stagnant, closed water bodies with newly emerging invaders are ideal sites for possible application, although local conditions must be considered.

Keywords: biological invasion • insecticide • cypermethrin • deltamethrin • eradication • invasive species

20 March 2019

Takahashi and colleagues, 2019

Takahashi K, Yamaguchi E, Fujiyama N, Nagayama T. 2019. The effects of quality of shelters and prior residence on marmorkrebs (marbled crayfish). Journal of Experimental Biology 222(6):. https://doi.org/10.1242/jeb.197301

Abstract

Many animals fight over a limited valuable resource. In marmorkrebs (marbled crayfish), large animals usually defeated small opponents but they were frequently beaten by small opponents who were shelter owners. A prior residence effect of marbled crayfish was analyzed quantitatively. More than 2 hr of residency in a shelter was sufficient for small owners to defeat large intruders. Small animals that stayed in a shelter for 24 hr still tended to win following removal of the shelter 10 min before pairing with large intruders, but 2 hr residents were occasionally beaten by large intruders without the support of shelters during pairings. The prior residence effect thus developed depending on the time of residency. To clarify whether the strength of the prior residence effect was affected by the quality of a shelter, large and small owners with different combinations of two high and low quality of shelters were paired. When both large and small owners possessed a high quality shelter, the frequency of agonistic bouts was reduced. Even if agonistic bouts occurred, the win frequency of small owners was almost equal to that of large owners. Thus, the residence effect on small owners was sufficiently strong to overcome the physical disadvantage of small animals to large opponents. By contrast, small owners of low quality shelters were frequently beaten by large owners with the shelters of same or better quality. We conclude that the outcomes of fighting over the resource shelter are highly dependent on both the perception of shelter quality and body size differences.

Keywords: agonistic encounter • owner: intruder • perception • winner effect • residence effect

18 March 2019

International Crayfish Conference 2019

The International Conference on Crayfish will be in Europe this year, organized by Blue Centre Gotland, Swedish University of Agricultural Sciences. and University of Eastern Finland. This conference is open to both researchers and crayfish farmers.

For more information, contact Gunilla Rosenqvist (gunilla.rosenqvist@geo.uu.se) or Lennart Edsman (Lennart.edsman@slu.se).

External links

Internationell kräftkonferens 27 - 30 augusti 2019

07 March 2019

Bradshaw, 2019

Bradshaw L. 2019. The genetic authentication of Malagasy crayfish samples. South Carolina Junior Academy of Science. 270. https://scholarexchange.furman.edu/scjas/2019/all/270

Abstract

The marbled crayfish (Procambarus virginalis) is a relatively new species that emerged by macromutation nearly 30 years ago from Procambrus fallax. Despite its short existence, it has already become an invasive species because of its ability to reproduce clonally and its environmental adaptability. The marbled crayfishes’ high adaptability allows it to thrive in diverse conditions throughout the globe. It is very important to correctly identify marbled crayfish because, to do epigenetic research with them, we need to know the epigenetic profile. This experiment analyzed two Malagasy crayfish samples to test if they were Procambarus virginalis. This work was necessary because it is the only way to distinguish between different crayfish species besides morphology which is subjective. DNA was isolated from the abdominal tissue of 2 unknown crayfish samples, analyzed by PCR, and compared to known DNA reference sequences. The results for crayfish #1 were inconclusive because the insert was not incorporated by the plasmid, but it was confirmed that crayfish #2 was Procambarus virginalis. Future work on the marbled crayfish will be to help establish a methylome sequence. This methylome sequence will show average methylations to the DNA, helping further understand the epigenetics of clonal tumor evolution.

Keywords: None provided.

Banned in Japan?


The Japanese newpaper The Mainichi is reporting that Marmorkrebs could soon be added to Japan’s list of “Invasive Alien Species.”

The article notes that there have been a couple of isolated cases of Marmorkrebs found in the wild in Japan (as noted on the map of introductions). The article provides the first confirmation I know of – unsurprising though it is – that Marmorkrebs are readily available in the pet trade there.

Looking at the Ministry’s page on invasive species, crayfish are already regulated to some degree. The PDF of regulated species say all crayfish (“Any species of the families Astacidae, Cambaridae, and Parastacidae”) are “Required to have a Certificate Attached during their importation in order to verify their types.” But this does nothing once a species is in the national pet trade and being distributed within Japanese borders.

Marmorkrebs would join all the species of Astacus and Cherax, the signal crayfish (Pacifastacus leniusculus), and the rusty crayfish (Faxonius rusticus, still listed as Orconectes in the Japanese documents) as an invasive.

External links

Environment ministry plans to add marbled crayfish to list of invasive species

05 March 2019

Stara and colleagues, 2019

Stara A, Kubec J, Zuskova E, Buric M, Faggio C, Kouba A, Velisek J. 2019. Effects of S-metolachlor and its degradation product metolachlor OA on marbled crayfish (Procambarus virginalis). Chemosphere 224: 616-625. https://doi.org/10.1016/j.chemosphere.2019.02.187

Abstract

Increasing production of energy crops in Europe, mainly maize and rapeseed, has altered patterns of pesticide use in recent decades. The long-term effects of S-metolachlor (S-M) and of its metabolite metolachlor OA (M-OA) at the environmentally relevant concentration of 4.2 μg  L−1 and at 42 μg  L−1 (ten-fold concentration) on marbled crayfish (Procambarus virginalis) were evaluated in a 28-day exposure and after a subsequent 28-day recovery period. Indicators assessed were behaviour; biochemical haemolymph profile; oxidative and antioxidant parameters of gill, hepatopancreas, and muscle; and histology of hepatopancreas and gill. Results showed biochemical haemolymph profile (lactate, alanine aminotransferase, aspartate aminotransferase, inorganic phosphate), lipid peroxidation in hepatopancreas, and antioxidant parameters (catalase, reduced glutathione, glutathione S-transferase) of hepatopancreas and gill of crayfish exposed to S-M and M-OA to significantly differ from controls (P < 0.01). Antioxidant biomarker levels remained different from controls after a 28-day recovery period. Differences in behaviour including speed of movement and velocity, and histopathological damage to gill and hepatopancreas were associated with S-M and M-OA exposure and persisted after 28 days in S-M- and M-OA-free water. Results suggest harmful effects of low concentrations of S-M and its metabolite M-OA on non-target organisms and provide information for assessing their effects at environmentally relevant concentrations.

Keywords: herbicide • metabolite • crustacean • biomarkers • histology • recovery

19 February 2019

Velisek and colleagues, 2019

Velisek J, Stara A, Zuskova E, Kubec J, Buric M, Kouba A. 2019. Effects of s-metolachlor on early life stages of marbled crayfish. Pesticide Biochemistry and Physiology 153: 87-94. https://doi.org/10.1016/j.pestbp.2018.11.007

Abstract

The effects of s-metolachlor chronic exposure at concentrations of 1.1 μg/L (maximal real environmental concentration in the Czech Republic), 11 μg/L (environmental relevant concentration) and 110 μg/L on early life stages of marbled crayfish (Procambarus virginalis) was evaluated under laboratory conditions. All s-metolachlor exposures resulted in higher mortality, delay ontogenetic development with accompanied slower growth and excited behaviour (increase of total distance moved and walking speed). Significantly lower superoxide dismutase, catalase, glutathione S-transferase activity and reduced glutathione level was observed at two higher tested concentrations (11 and 110 μg/L) of s-metolachlor compared with the control. S-metolachlor in concentrations 110 μg/L showed alteration of the tubular system of hepatopancreas including focal disintegration of tubular epithelium and notable reduction in epithelial cells number, especially B-cells. In conclusion, potential risk associated with using of s-metolachlor in agriculture, due to effects on non-target aquatic organisms as documented on early life stages of marbled crayfish in this study, should be taken into account.

Keywords: herbicide • Procambarus virginalis • ontogenetic development • behaviour • antioxidant enzymes • toxicity test

Hossain and colleagues, 2019

Hossain MS, Kubec J, Kouba A, Kozák P, Buřič M. 2019. Still waters run deep: marbled crayfish dominates over red swamp crayfish in agonistic interactions. Aquatic Ecology 53(1): 97-107. https://doi.org/10.1007/s10452-019-09675-7

Abstract

Intra- and interspecific interactions contribute to the successful establishment and consequent spreading of species in the environment, which became particularly apparent in the context of ongoing biological invasions. The parthenogenetic marbled crayfish, Procambarus virginalis, Lyko 2017 is recently recognized as an emerging invader due to its high adaptability, fast growth, early maturation, and high fecundity. The present study explored the interaction patterns of size-matched (including 15 body parts morphometry evaluation) pairs of marbled crayfish and red swamp crayfish Procambarus clarkii, a well-known highly aggressive and widely distributed invader of freshwater ecosystems. Despite this, marbled crayfish won significantly more fights and establish dominancy in more cases in both premature and mature experimental trials. Premature red swamp crayfish pairs were more active in contact and fight initiation than mature. In mature, the dominance over female red swamp crayfish was 100%, in males it reached 60%. Premature marbled crayfish dominated in more than 75% pairs. Agonistic behaviour and intensity of fights significantly dropped after establishment of dominance in particular (size and sex) pairs. Therefore, we confirmed that sex and age (size) have effects on agonistic behaviour in crayfish as well as the dominance of marbled crayfish within similarly sized specimens. Despite described behavioural patterns, we can expect that the situation in the potential sympatric occurrence of both species will not be as clear as found in experimental conditions due to greater maximal size of red swamp crayfish.

Keywords: competition • dominance • interaction • Procambarus virginalisProcambarus clarkii

16 February 2019

Nothing like a Dane: the European invasion continues

Another European country has become home to Marmorkrebs. The Copenhagen Post Online is reporting a single Marmorkrebs was found on the main body of Denmark, Jutland, near the town of Skive.


It’s been a few months since I updated the map of Marmorkrebs introductions, so I supposed this was due. It feels like Marmorkrebs in every European nation is as inevitable as no deal Brexit at this point. Maybe Lichtenstein can hold out.

External links

Self-fertilising invasive crayfish discovered in Denmark

09 February 2019

Andriantsoa and colleagues, 2019

Andriantsoa R, Töngesm S, Panteleit J, Theissinger K, Carneiro VC, Rasamy J, Lyko F. 2019. Ecological plasticity and commercial impact of invasive marbled crayfish populations in Madagascar. BMC Ecology 19: 8. https://doi.org/10.1186/s12898-019-0224-1

Abstract

Background

The marbled crayfish (Procambarus virginalis) is a monoclonal, parthenogenetically reproducing freshwater crayfish species that has formed multiple stable populations worldwide. Madagascar hosts a particularly large and rapidly expanding colony of marbled crayfish in a unique environment characterized by a very high degree of ecological diversity.

Results

Here we provide a detailed characterization of five marbled crayfish populations in Madagascar and their habitats. Our data show that the animals can tolerate a wide range of ecological parameters, consistent with their invasive potential. While we detected marbled crayfish in sympatry with endemic crayfish species, we found no evidence for the transmission of the crayfish plague pathogen, a potentially devastating oomycete. Furthermore, our results also suggest that marbled crayfish are active predators of the freshwater snails that function as intermediate hosts for human schistosomiasis. Finally, we document fishing, farming and market sales of marbled crayfish in Madagascar.

Conclusions

Our results provide a paradigm for the complex network of factors that promotes the invasive spread of marbled crayfish. The commercial value of the animals is likely to result in further anthropogenic distribution.

Keywords: marbled crayfish • Madagascar • ecology • habitat diversity • crayfish plague • farming

02 February 2019

Kubec and colleagues, 2019

Kubec J, Hossain MS, Grabicová K, Randák T, Kouba A, Grabic R, Roje S, Buřič M. 2019. Oxazepam alters the behavior of crayfish at diluted concentrations, venlafaxine does not. Water 11: 196. https://doi.org/10.3390/w11020196

Abstract

Pharmaceutically active compounds are only partially removed from wastewaters and hence may be major contaminants of freshwaters. Direct and indirect effects on aquatic organisms are reported at dilute concentrations. This study was focused on the possible effects of environmentally relevant concentrations (~1 µg L−1) of two psychoactive compounds on the behavior of freshwater crayfish. Experimental animals exposed to venlafaxine did not show any behavioral alteration. Crayfish exposed to the benzodiazepine oxazepam exhibited a significant alteration in the distance moved and activity, and the effects were different when individuals were ready for reproduction. Results suggested that even the low concentration of selected psychoactive pharmaceuticals could alter the behavioral patterns of crayfish, as reported for other pharmaceuticals. These results provide new information about the possible adverse effects of pharmaceuticals at dilute concentrations. From previous knowledge and our results, it is obvious that different compounds have different effects and the effects are even specific for different taxa. Detailed studies are therefore needed to assess the possible ecological consequences of particular substances, as well as for their mixtures.

Keywords: environmental pollution • pharmaceuticals • freshwaters • crayfish

14 January 2019

Shinji and colleagues, 2019

Shinji J, Gotoh H, Miyanishi H, Lavine MD, Lavine LC. 2019. The activin signaling transcription factor Smox is an essential regulator of appendage size during regeneration after autotomy in the crayfish. Evolution & Development 21(1): 44-55. https://doi.org/10.1111/ede.12277

Abstract

Members of the phylum Arthropoda, comprising over 80% of total animal species, have evolved regenerative abilities, but little is known about the molecular mechanisms mediating this process. Transforming growth factor β (TGF‐β) signaling mediates a diverse set of essential processes in animals and is a good candidate pathway for regulation of regeneration in arthropods. In this study we investigated the role of activin signaling, a TGF‐β superfamily pathway, in limb regeneration in the crayfish. We identified and cloned a downstream transcription factor in the activin pathway, Smox, and characterized its function with regard to other elements of the activin signaling pathway. Gene knockdown of Smox by RNAi induced regeneration of complete but smaller pereopods after autotomy. This indicates that activin signaling via Smox functions in regulation of pereopod growth and size. The expression levels of both Smox and the activin receptor babo were closely correlated with molting. The expression level of Smox increased when babo was knocked down by RNAi, indicating that Smox and babo transcription are linked. Our study suggests that the Babo‐Smox system in activin signaling is conserved in decapods, and supports an evolutionary conservation of this aspect of molecular signaling during regeneration between protostomes and deuterostomes.

Keywords: None provided.