22 June 2018

Vogt, 2018

Vogt G. 2018. Glair glands and spawning in unmated crayfish: a comparison between gonochoristic slough crayfish and parthenogenetic marbled crayfish. Invertebrate Zoology 15(2): 215–220. https://doi.org/10.15298/invertzool.15.2.02, http://kmkjournals.com/journals/Inv_Zool/IZ_Index_Volumes/IZ_15/IZ_15_2_215_220_Vogt


In the period before spawning, freshwater crayfish females develop glair glands on the underside of the pleon. These glands produce the mucus for a gelatinous tentlike structure in which the eggs are fertilized and attached to the pleopods. Long-term observation of females of the sexually reproducing slough crayfish, Procambarus fallax, kept in captivity revealed that the glair glands developed in late winter and late summer of each year independently of the presence of males. In mated females, they secreted their contents shortly before spawning. In contrast, unmated females of slough crayfish did
neither empty their glair glands nor spawn. Their glands persisted for an unusually long period of time and disappeared only during the next moult. Apparently, slough crayfish females use information on sperm availability to either spawn or save the resources. Females of marbled crayfish, Procambarus virginalis, a parthenogenetic all-female descendant of slough crayfish, developed glair glands in approximately the same periods of the year but generally spawned despite of the lack of males. These findings suggest that in marbled crayfish glair secretion and spawning is decoupled from mating. Therefore, the species pair P. fallax and P. virginalis seems to be particularly suitable to investigate the regulation of spawning in freshwater crayfish.

Keywords: freshwater crayfish • glair gland • spawning • mating • Procambarus fallaxProcambarus virginalis

Zoo babies

Marbled crayfish are featured in this year’s Cincinnati Zoo’s Zoo Babies display! The Zoo’s website shows they are part of the display, but no more. I do complement their photographer for the particularly cute crayfish pic (above) on their site.

I reached out to the Zoo, and heard back from Mandy Pritchard, who is the “World of the Insect Team Leader” at the zoo. (Now there’s a great job title.) She was kind enough to send me a couple of pictures of the display:

There’s a very nice shirt available. Unfortunately, it’s doesn’t seem to be available in adult sizes.

Based on the description in the display, I think these are the sexual slough crayfish and not Marmorkrebs. But it’s fun to see crayfish on display nevertheless!

External links

Zoo Babies
The "Amazing" Marbled Crayfish - Youth Garments

19 June 2018

Herrmann and colleagues, 2018

Herrmann A, Schnabler A, Martens A. 2018. Phenology of overland dispersal in the invasive crayfish Faxonius immunis (Hagen) at the Upper Rhine River area. Knowledge and Management of Aquatic Ecosystems 419: 30. https://doi.org/10.1051/kmae/2018018


The non-indigenous crayfish Faxonius immunis (Hagen) is the dominant crayfish species at the Upper Rhine River system since his detection in 1993. As an invasive alien species, it is one of the biggest threats to aquatic biodiversity in the area. By dispersing over land, the species has a high potential to colonize small ponds created for threatened amphibians and dragonflies. Shortly after invasion, the fast growing population of F. immunis is changing the habitat drastically. In June 2016, our team started a local information campaign including citizen science project where the local people south of Karlsruhe, Baden-Wuerttemberg, Germany, could contact us when they spot a crayfish migrating over land to assess the activity of overland dispersal on a regional scale. Until January 2018, we got a total of 98 responses. Thirty-nine include suitable information including 33 records of overland dispersal of F. immunis. The species was recorded on land throughout the year, except February and July. Additionally, single observations of overland dispersal of other invasive crayfish species, naming Procambarus clarkii (Girard), Pacifastacus leniusculus (Dana), Procambarus virginalis (Lyko) and Faxonius limosus (Rafinesque), were recorded.

Keywords: amphibian conservation • citizen science • management • biological invasions • non-indigenous species

08 June 2018

If this is 2018, this must be Estonia

Estonia has now become the...

Wait a second, I’ve lost count.

  1. Germany.
  2. Italy.
  3. Netherlands.
  4. Hungary.
  5. Croatia.
  6. Slovakia.
  7. Romania.
  8. Sweden.
  9. Ukraine.
  10. Czech Republic.
  11. ...
Eleventh European country where Marmorkrebs have been found in outdoors. This is according to a press release from the Estonian Research Council. The crayfish were collected last year, not recognized as Marmorkrebs until the end of the year, and a repeat visit at the end of May confirmed a population was there.

I have updated the map of Marmorkrebs introductions accordingly.

External links

The marbled crayfish have established themselves in Narva power plant

30 May 2018

Scholz and colleagues, 2018

Scholz S, Richter S, Wirkner CS. 2018. Constant morphological patterns in the hemolymph vascular system of crayfish (Crustacea, Decapoda). Arthropod Structure & Development 47(3): 248-267. https://doi.org/10.1016/j.asd.2017.12.005


We present a study of the hemolymph vascular system of the marbled crayfish, Procambarus fallax f. virginalis, the only crayfish species known to be parthenogenetic. To identify potential evolutionary patterns, we compared data from a total of 48 specimens of P. fallax with 22 specimens of Orconectes limosus. Visualizations (2D and 3D) were carried out using a combination of classical and modern morphological techniques. Our data were compared to the existing literature. Like all Decapoda, both P. fallax and O. limosus have a hemolymph vascular system, consisting of a globular heart with seven off-branching arteries. We were able to visualize in detail the heart of crayfish for the first time, i.e., the heart muscle itself, with its loose bundles of myofibrils, as well as the valves and flaps of ostia and arteries. Furthermore, the branching patterns of the seven artery systems were analyzed. Anatomical structures identified to be consistent in all specimen of both species were combined, and a proposed schematic anatomy established of the hemolymph vascular system of crayfish.

Keywords: artery • circulatory system • evolutionary morphology • heart

Nentwig and colleagues, 2018

Nentwig W, Bacher S, Kumschick S, Pyšek P, Vilà M. 2018. More than “100 worst” alien species in Europe. Biological Invasions 20(6): 1611–1621. https://doi.org/10.1007/s10530-017-1651-6


“One hundred worst” lists of alien species of the greatest concern proved useful for raising awareness of the risks and impacts of biological invasions amongst the general public, politicians and stakeholders. All lists so far have been based on expert opinion and primarily aimed at representativeness of the taxonomic and habitat diversity rather than at quantifying the harm the alien species cause. We used the generic impact scoring system (GISS) to rank 486 alien species established in Europe from a wide range of taxonomic groups to identify those with the highest environmental and socioeconomic impact. GISS assigns 12 categories of impact, each quantified on a scale from 0 (no impact detectable) to 5 (the highest impact possible). We ranked species by their total sum of scores and by the number of the highest impact scores. We also compared the listing based on GISS with other expert-based lists of the “worst” invaders. We propose a list of 149 alien species, comprising 54 plants, 49 invertebrates, 40 vertebrates and 6 fungi. Among the highest ranking species are one bird (Branta canadensis), four mammals (Rattus norvegicus, Ondatra zibethicus, Cervus nippon, Muntiacus reevesi), one crayfish (Procambarus clarkii), one mite (Varroa destructor), and four plants (Acacia dealbata, Lantana camara, Pueraria lobata, Eichhornia crassipes). In contrast to other existing expert-based “worst” lists, the GISS-based list given here highlights some alien species with high impacts that are not represented on any other list. The GISS provides an objective and transparent method to aid prioritization of alien species for management according to their impacts, applicable across taxa and habitats. Our ranking can also be used for justifying inclusion on lists such as the alien species of Union concern of the European Commission, and to fulfil Aichi target 9.

Keywords: Aichi target 9 • environmental impacts • generic impact scoring system (GISS) • prioritization of alien species • risk assessment • socio-economic impacts

23 May 2018

Rymut, 2018

Rymut, JA. 2018.Determining the effects of nitric oxide on Procambarus fallax forma virginalis. Poster given at the International Crustacean Congress IX, Washington DC, USA, 22-25 May 2018. http://www.birenheide.com/ICC2018/program/singlesession.php3?sessid=P, poster P.33.


Ethanol (EtOH) effects inducible nitric oxide synthase (iNOS) activity by inhibiting the production of iNOS in cells. Acute doses increase the production of nitric oxide (NO) and endothelial NOS (eNOS). At higher dosages, ethanol impairs endothelial functions. NO has been found to suppress the feeding response in pond snails, Lymnaea stagnalis, induce synaptic depression in crayfish, and inhibit the swimming rhythm of Xeonpus laevis tadpoles. This in vivo study will be performed in order to determine if synaptic depression is caused by free radical NO and determine if overall movements are decreased in Procambarus forma fallax virginalis (P.f.f virginalis) in the presence of NO. It was hypothesized that there will be a depression in synaptic activity and less movement in crayfish exposed to free radical NO. A probe will be inserted near the cerebral ganglion to assess depression in synaptic inputs. Movement will be tested by placing crayfish into a partitioned tank and counting each movement across a partition as one movement. Movement will be tested on both an individual and group level to determine if group activity will be a variable factor. NO will be introduced through the usage of ethanol, an L-arginine supplement, and chlorhexidine​ in an approximate range of five to ten​ parts per million (​5 ​mg/L​ and 10 mg/L​).

Keywords: None provided.

Update, 30 May 2018: At the author’s request, here is the updated abstract from the poster as it was presented at the meeting (above).

Ethanol (Et-OH) effects inducible nitric oxide synthase (iNOS) activity by inhibiting the production of iNOS in cells. Acute doses increase the production of nitric oxide (NO) and endothelial NOS (eNOS). At higher dosages, ethanol impairs endothelial functions. NO has been found to suppress the feeding response in pond snails, Lymnaea stagnalis, induce synaptic depression in crayfish, and inhibit the swimming rhythm of Xenopus laevis tadpoles (Aonuma, et al. 2000). This in vivo study has been performed in order to determine if synaptic depression is caused by NO, and if overall movements are decreased in Procambarus forma fallax virginalis (P.f.f virginalis) and Procambarus blandingii, in the presence of NO. Movement was assessed in a labeled gridded tanks of water, denatured ethanol (3 ppm), L-arginine (Reagent grade, 1ppb) and chlorhexidine (99.95%, 1ppb). There was an evident trend over a time interval of 6 minutes ≤ t ≤ 8 minutes, where the control, ethanol and chlorhexidine all had a stark drop off in activity, whilst L-arginine had a stark increase. It is hypothesized that this could be due to a metabolic pathway of L-arginine is converted through nitric oxide synthase (NOS) to L-citrulline (Racke, et al. 2010); whereas ethanol has proven to inhibit iNOS, and due to the cytostatic characteristics of chlorhexidine, it can be assumed that the correlation of chlorhexidine to ethanol lies in this pathway as well. Synaptic depression is shown where L-arginine is present, over a time interval of 0 ms ≤ t ≤ 10ms (Aonuma et al. 2010); as found in the study, there is a correlation between L-arginine and chlorhexidine pre-wash, and it is hypothesized that this is from the terminal guanylyl group.