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Freshwater crayfish are amongst the largest macroinvertebrates and play a keystone role in the ecosystems they occupy. Understanding the global distribution of these animals is often hindered due to a paucity of distributional data. Additionally, non-native crayfish introductions are becoming more frequent, which can cause severe environmental and economic impacts. Management decisions related to crayfish and their habitats require accurate, up-to-date distribution data and mapping tools. Such data are currently patchily distributed with limited accessibility and are rarely up-to-date. To address these challenges, we developed a versatile e-portal to host distributional data of freshwater crayfish and their pathogens (using Aphanomyces astaci, the causative agent of the crayfish plague, as the most prominent example). Populated with expert data and operating in near real-time, World of Crayfish™ is a living, publicly available database providing worldwide distributional data sourced by experts in the field. The database offers open access to the data through specialized standard geospatial services (Web Map Service, Web Feature Service) enabling users to view, embed, and download customizable outputs for various applications. The platform is designed to support technical enhancements in the future, with the potential to eventually incorporate various additional features. This tool serves as a step forward towards a modern era of conservation planning and management of freshwater biodiversity. [ABSTRACT FROM AUTHOR]

Freshwater crayfish are amongst the largest macroinvertebrates and play a keystone role in the ecosystems they occupy. Understanding the global distribution of these animals is often hindered due to a paucity of distributional data. Additionally, non-native crayfish introductions are becoming more frequent, which can cause severe environmental and economic impacts. Management decisions related to crayfish and their habitats require accurate, up-to-date distribution data and mapping tools. Such data are currently patchily distributed with limited accessibility and are rarely up-to-date. To address these challenges, we developed a versatile e-portal to host distributional data of freshwater crayfish and their pathogens (using Aphanomyces astaci, the causative agent of the crayfish plague, as the most prominent example). Populated with expert data and operating in near real-time, World of Crayfish™ is a living, publicly available database providing worldwide distributional data sourced by experts in the field. The database offers open access to the data through specialized standard geospatial services (Web Map Service, Web Feature Service) enabling users to view, embed, and download customizable outputs for various applications. The platform is designed to support technical enhancements in the future, with the potential to eventually incorporate various additional features. This tool serves as a step forward towards a modern era of conservation planning and management of freshwater biodiversity.

• Native crayfish predominantly inhabit partially to highly fragmented freshwaters. • Native crayfish populations face moderate to high levels of threat. • Large uninvaded river sections can potentially be occupied by signal crayfish. Indigenous crayfish species (ICS) have suffered a significant decline in recent decades due to various threats including anthropogenic habitat degradation with resulting fragmentation, and the introduction of non-indigenous crayfish species (NICS). However, only a few studies have assessed and quantified these threats on a broad landscape scale. We aim to highlight the impact of these interacting pressures within the Sava and Drava basins in Slovenia, Croatia, and Hungary. Our aims were to (1) asses the fragmentation caused by artificial and natural barriers; (2) calculate a threat index using fragmentation, spatial distances to established NICS populations, urban settlements and roads; (3) conduct current habitat suitability modeling (HSM) using various biotic and abiotic environmental parameters. The target species in this area are the ICS Astacus astacus , Austropotamobius torrentium and Pontastacus leptodactylus as well as the invasive NICS Pacifastacus leniusculus and Faxonius limosus. Our analyses revealed that the Croatian and Hungarian segments of the Drava and Sava basins exhibit relatively low fragmentation levels, whereas the Slovenian basins are highly fragmented mainly due to a dense hydropower network. All ICS populations within each sub-basin in the study area are moderately to highly threatened according to our threat index calculation. The HSM showed, that only 14.1% and 11.6% of freshwater habitats are suitable for A. torrentium and A. astacus , respectively. In contrast, NICS could occupy substantial portions (up to 22%) of the total riverscape. The results affirmed the highly alarming situation, as native crayfish were once widely distributed across less unfragmented freshwaters of the Danube basin. Our analyses and findings will be helpful to enhance the existing frameworks for safeguarding the remaining ICS populations, predicting the possible spread of NICS, and help to improve sustainable management practices for freshwater ecosystems. [ABSTRACT FROM AUTHOR]

We outline a framework for evaluating scientific evidence of sentience, focusing on pain experience. It includes eight neural and cognitive-behavioural criteria, with confidence levels for each criterion reflecting the reliability and quality of the evidence. We outline the rationale for each criterion and apply our framework to a controversial sentience candidate: decapod crustaceans. We have either high or very high confidence that true crabs (infraorder Brachyura) satisfy five criteria, amounting to strong evidence of sentience. Moreover, we have high confidence that both anomuran crabs (infraorder Anomura) and astacid lobsters/crayfish (infraorder Astacidea) meet three criteria--substantial evidence of sentience. The case is, as yet, weaker for other infraorders, such as penaeid shrimps, highlighting important research gaps. Having demonstrated our framework's application to decapod crustaceans, we hope that future research will apply it to other taxa. [ABSTRACT FROM AUTHOR]

Although a large number of rivers stretches in Southeast Europe (SEE) have a pristine status compared to the rest of Europe, these ecosystems and their freshwater biodiversity are perceptibly threatened. Since crayfish species are known to cover a wide spectrum of ecological functions they are considered as keystone species and ecosystem engineers. Therefore, their decline may substantially impair local biodiversity and ecosystem services. In this manuscript we present a brief overview of the status of the native freshwater crayfish and their habitats in SEE. Different forms of physical habitat degradation as well as invasive alien crayfish species and their pathogens (e.g., Aphanomyces astaci) are simultaneously threatening endangered populations all over SEE. Even though all native crayfish species are listed in the IUCN Red List, so far none of the 33 LIFE rehabilitation projects performed in SEE, has crayfish as target species in their agenda. Furthermore, SEE countries rarely designated Natura 2000 sites for native crayfish. We propose future studies to assess the distribution and functional role of crayfish species in SEE, as well as to develop habitat suitability models for these species during future conservation projects. [ABSTRACT FROM AUTHOR]

Branchiobdella bulgariensis sp. n. is described from the River Topolnitza near the village of Dushantzi, Bulgaria. The main morphological character distinguishing the new species from Branchiobdella parasita (Braun, 1805) is the form of the spermatheca with spermathecal ampulla consisting of almost spherical proximal part and a narrower cylindrical or bulb-like distal part. In contrast, B. parasita is characterised by oval spermatheca. Another feature distinguishing these two species from one another is the form of peristomium: in B. bulgariensis, the dorsal lip of peristomium has four lobes while, in B. parasita, the peristomium is "simple, thin-skinned" (Braun, 1805) and "bears eight micro-tentacles" (Henle, 1835). The only known host of B. bulgariensis sp. n. is Austropotamobius torrentium. The new species has been found so far at several sites in Bulgaria and unknown locality in Slovakia. An unusual character for the order Branchiobdellida is described, i.e. ontogenetic development of jaws of B. bulgariensis resulting in a different shape of these structures in specimens of different age. [ABSTRACT FROM AUTHOR]

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At the territory of Bosnia and Herzegovina Austropotamobius pallipes (Lereboullet, 1858) is present mainly in the Neretva basin, partly in the Una and Tsetina river basins (Trožić-Borovac et al., 2012). This species was registered at elevations from 180 to 1024 m a. s. l., but most habitats are located at elevations from 300 to 600 m a. s. l. Based on indirect data, one can state that more than 2/3 of the crayfish population in the Neretva basin is concentrated in the Neretvica basin. Our studies showed that the crayfish are very irregularly distributed in the Neretvica basin. The crayfish are almost absent at well-flushed habitats without CPOM (deposits of coarse particulate organic matter, e. g., fallen leaves), as well as at habitats with monotonous boulders or gravel-sand bottom. The study of the size structure of the crayfish population showed the presence of juvenile crayfish with a size of less than 5 cm in the Neretvica River course. The most balanced structure of the crayfish population represented by juvenile as well as adult species is observed in Gorovnik. [ABSTRACT FROM AUTHOR]

Copyright of Natura Croatica is the property of Natura Croatica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Knowledge & Management of Aquatic Ecosystems is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Henri de Saussure described 44 species of decapod; these are listed, the location of the type specimens is given where known and the current nomenclatural combination is given. Type specimens of 34 of the species have been identified in the collections of the Museum d'histoire naturelle de Geneve, and label data and the condition of the specimens are reported for each of these. [ABSTRACT FROM AUTHOR]

Copyright of Knowledge & Management of Aquatic Ecosystems is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The taxonomic classification of European crayfish is neither fully examined nor generally accepted as a unifying scheme. At present, one of the most obvious differences exists between astacologists from Western and Eastern Europe. In the present paper, an analysis of the information published on the systematics of European crayfish over the last decades was conducted against the background of own observations on features with importance for the systematics of narrow-clawed crayfish (Astacus (Pontastacus) leptodactylus) from Poland. The objective of this analysis was to standardize the nomenclature of European crayfish at the level of genera. The presented proposal for a taxonomy recognizes three genera within the family Astacidae in Europe: Austropotamobius, Astacus, and Pontastacus. The main (morphological, zoogeographical and ecological) criteria for considering the genus Pontastacus a separate genus are of a discriminatory strength similar to the widely accepted criteria for the separation of the genus Austropotamobius. Further studies on the taxonomy and ecology of crayfish from eastern Europe using modern techniques such as molecular genetics are strongly recommended.

Austropotamobius torrentium (SCHRANK, 1803) is the smallest of the European native crayfish species and has probably never been of economic interest. It is confined to headwaters and adapted to cold water with high flow through and rocky environments. These properties make the stone crayfish a useful species for population genetics and phylogeographic studies. Representatives were collected from 18 localities throughout southern Germany and analysed with two mitochondrial genetic markers. Initial results revealed that German populations of A. torrentium from the Danube and Rhine tributaries share identical haplotypes in 528 basepairs of 16S rRNA and 658 basepairs of the COI gene. Rare haplotypes of the COI genes were occasionally encountered and apparently restricted to southwestern Bavaria. Only three variable sites were found over a length of 658 basepairs in 45 German, Swiss and Austrian stone crayfish resulting in five different haplotypes, with the prevalence of one most common haplotype. Here we show that in German populations rare haplotypes are not randomly distributed, but found in higher frequencies in the Bavarian Alps of the Allgäu and in adjacent Tyrol. On the other hand, stone crayfish population from the Bavarian Forest and the Rhine tributaries appear genetically impoverished, so far only showing the most common haplotype. Consequently, there are significant differences between the Allgäu populations and the rest of the German populations in haplotype frequencies, resulting in a relatively high FST value. This finding is of importance for future conservation efforts of stone crayfish populations in Germany and Austria.

In Bavarian freshwater systems, the stone crayfish Austropotamobius torrentium is still present in many headwaters of Danubian tributaries. Since the 1960s an alien species, the signal crayfish Pacifastacus leniusculus, was introduced several times independently in Germany. Compared to the previously introduced Orconectes limosus, this species also invaded higher reaches of freshwater streams, thereby becoming a direct competitor of A. torrentium. In addition, it carried the crayfish plague, Aphanomyces astaci, which is lethal to European species. So far, there are only few documented populations of Pacifastacus leniusculus from upper streams in Bavaria and to our knowledge no reports of coexistence with the stone crayfish, which may be outcompeted by this much larger species due to direct interactions or reproductive superiority. In this study, we document the distribution of the stone crayfish in Bavaria and give evidence for a contact zone of Austropotamobius torrentium and apparently uninfected Pacifastacus leniusculus in the western Bavarian Forest, with a limited range of overlap and a slow upward displacement of the native species in the time frame of three years. Comparative studies of reproductive biology in the field and in the laboratory showed higher fecundity, faster juvenile growth and earlier hatching of the introduced species. These new aspects of the biology of the two involved species suggest an ecological superiority of P. leniusculus and may explain the long-term displacement of the native species, even in the absence of the crayfish plague Aphanomyces astaci.

The stone crayfish Austropotamobius torrentium (Schrank, 1803) is widely distributed in Southeastern and Central Europe. However, this information has not been verified until recently because of: • ignorance about biogeographic notion and hydrography and • ignorance of data in the literature. Overcoming these problems during the last decade, the distribution pattern of the stone crayfish has now become apparent in Europe. It is known from Luxembourg and Germany to the west, from Turkey to the east, from Germany and the Czech Republic to the north and from Greece to the south. It is absent in the northeastern part of the Pannonian basin as well as in Poland and Ukraine. Its presence in Luxembourg and the Czech Republic may be related not to natural distribution but to introduction by humans through history. The discovery of the stone crayfish in Italy and Turkey as well as its re-discovery in France during the 1990s proves the biogeographic conception that this animal belongs to the Danubian fauna. It probably originates from the southwestern part of the Pannonian basin.

L’habitat préférentiel des écrevisses à pattes blanches Austropotamobius pallipes (Lereboullet, 1858) a été analysé dans trois cours d’eau de Corrèze, grâce à la combinaison de trois méthodes de capture (pêche au filet de type Surber, pêche électrique et pêche à la main de nuit). Parmi ces méthodes, la plus efficace pour la capture des juvéniles s’est avérée être le filet de type Surber, qui a permis la capture de 536 individus. Suite à cette étude, il apparaît que les écrevisses adultes recherchent de préférence les berges constituées de racines ou avec des cavités, les blocs, les galets, la végétation aquatique et les souches pour s’abriter durant le jour, tandis qu’elles fréquentent préférentiellement les graviers, les galets et les blocs pendant leurs déplacements nocturnes. Les juvéniles s’abritent de préférence dans les galets, les blocs, les végétaux aquatiques et les berges composées d’amas de radicelles. Dans certains cas, la réduction, voire la disparition d’un habitat particulièrement favorable aux juvéniles peut être compensée par une colonisation plus importante d’autres habitats habituellement délaissés.

Les populations d'Austropotamobius pallipes ont été analysées sur deux sites d'un ruisseau forestier de Normandie, au cours de six années pour le site aval et de cinq années pour le site amont. Au début de chaque automne des échantillons ont été prélevés à l'aide de filets à mailles fines (3 mm), après avoir délogés les animaux en remuant le substrat. Comme cette technique est peu sélective les juvéniles de l'année sont capturés. Un codage différentiel par coupure des différentes parties de la queue a permis de suivre l'évolution des cohortes. Des résultats acquis, il est possible de définir des classes d'âge et de calculer les tailles moyennes des individus de chaque classe pour suivre l'évolution de la croissance. L'augmentation de la taille est régulière et suit un modèle linéaire avec le temps. La croissance est faible (10,6 à 18,8 mm par an), les individus au-delà de 90 mm sont très rares. La durée de vie est de 5 à 6 ans en aval, 4 à 5 ans en amont, la reproduction débutant la 3ème année. La période de croissance est réduite aux mois d'été, elle est maximum la 2ème et 3ème années. La croissance en 2ème et 3ème années est inversement proportionnelle à celle acquise l'année précédente. La croissance est plus forte en amont du ruisseau qu'en aval, avec une séparation plus nette des cohortes, mais il existe un étalement plus grand de celles-ci en relation avec une température plus élevée. La variabilité interannuelle de l'étalement des cohortes est plus faible en amont pour un taux de croissance plus variable. La variabilité des tailles augmente avec l'âge ; elle se stabilise ensuite, alors que le taux de croissance se réduit. Au cours de l'étude la taille a tendance à augmenter et les différences intercohortes à se réduire, en relation avec des hivers plus doux. Le sex-ratio est équilibré ; la croissance des mâles est plus élevée que celle des femelles en aval, alors qu'en amont la croissance des deux sexes est comparable. Cette étude montre que dans un même ruisseau, des stations peu éloignées peuvent avoir des populations qui présentent des évolutions différentes, malgré un environnement a priori stabilisé par le couvert forestier. Austropotamobius pallipes paraît être très sensible aux variations thermiques et, par conséquent, l'étude à long terme de sa croissance pourrait être un bon indicateur des changements climatiques.

Crayfish are charismatic creatures of high interest to humans, among others playing key roles in freshwater ecosystems. Considering the significance of indigenous crayfish species (ICS) as well as the risks posed by non-indigenous crayfish species (NICS) that may dissemite a crayfish plague pathogen Aphanomyces astaci, astacological research has advanced particularly in Europe. In this context, crayfish distribution patterns are of fundamental importance. Focused on all crayfish established in the Greek wild, we provide an updated distribution and maps, combining extensive review of existing literature as well as newly emerging sources, largely represented by increasingly important citizen-science data. Obtained results demonstrate that ICS, mainly the Astacus astacus and Austropotamobius torrentium, remain relatively well settled in the country. The last ICS, Astacus leptodactylus, was translocated in few places outside its native range, leading to the formation of new flourishing populations and at least in one case it sustains commercial exploitation. Concerning NICS, a single population of Pacifastacus leniusculus is also established in the artificial lake Agra (Region of Central Macedonia) and keeps spreading. Unfortunately, there are only few methods under a very narrow range of conditions making successful eradication of unwanted NICS populations feasible. This option is even more difficult as this population is commercially exploited and traded. Since further potentially problematic NICS are also pet-traded in the country, educating public and communicating highlighted issues are the most effective ways limiting their releases and consecutive establishment in the wild.

Seasonality in the immune defence of invertebrates can coincide with environmental variation but whether it is endogenously regulated, via biological clocks, or affected by previous immune challenges remains unclear. Using the native noble crayfish (Astacus astacus) held under constant laboratory conditions for a year, we explored (1) potential endogenous seasonal variation in immune defence, i.e. the encapsulation response, (2) the potential positive effect of repeated challenges with a standardized immune insult in subsequent seasons, i.e. long-lasting immune priming, and (3) whether long-lasting immune priming is dependent on endogenous seasonality. Independent measurements of the encapsulation response in different seasons revealed significant variation and a decrease in autumn. This result indicates previously undetected endogenous seasonal variation in invertebrate immunity. The weaker immune defence observed in autumn, i.e. the reproductive season of crayfish, might be caused by a circannual clock. When corrected for endogenous seasonality, we found no evidence for long-lasting immune priming. [ABSTRACT FROM AUTHOR]

Austropotamobius pallipes is a vulnerable crayfish, and therefore it is necessary to analyse reproduction in the extant populations. Details of the female annual reproductive cycle in a Mediterranean population are provided for two consecutive years. Maternal-size-related variables and date of collection have been considered in relation to the number of ovarian and pleopodal eggs. Reproductive data from 2587 females collected by hand and traps are reported. In total, 204 (14.69%) and 231 (15.93%) individuals in 2003 and 2004, respectively, were ovigerous. Demonstrable differences exist between ovarian and pleopodal egg counts. In particular, ovarian egg counts were considerably higher than expected pleopodal egg numbers. Mating begins in November and is followed by egg laying in early December-January. Berried females occur until May-June, when hatching occurs. The numbers of both ovarian and pleopodal eggs are correlated with the size of females, although fecundity slightly decreases in larger females. The histology of the reproductive organs of both sexes is also analysed. [ABSTRACT FROM AUTHOR]

This study observed agonistic interactions and contests between size-matched form I vs. form I, form II vs. form II, and form I vs. form II males to establish baseline dominance orders and behavioral dynamics for Procambarus suttkusi (Choctawhatchee Crayfish). Three types of initiation behaviors, or attacks, were observed during each interaction: ambivalent contact, claw raise, and lunge. Feeding competition studies were also performed to assess the relationship between the winners of the agonistic interactions and feeding contests. Only form I vs. form I contests showed a decline in the number of interactions observed over time, but the duration of each individual agonistic interaction declined for all three types of behaviors during the thirty-minute recording period. Winners and losers did not preferentially use the same initiation behaviors as used in other studies. Previous studies also documented form I dominating form II males, but form I males did not dominate form II males in the present study. Winners of the agonistic contests won significantly more feeding contests. The results of the current study suggested that behavioral dynamics and form dominance may be species specific and that careful consideration of size differences are necessary in order to examine form dominance. [ABSTRACT FROM AUTHOR]

Orconectes williamsi (Williams' Crayfish) is a rare stream-dwelling crayfish that is endemic to the upper White River basin of Arkansas and Missouri. It was described in the 1960s from a type locality in Madison County, AR, and the three localities named in the description comprise the published range of the species in Arkansas. In contrast, 27 locations have been reported in Missouri. This study surveyed a semi-random selection of stream sites in the Arkansas portion of this range in order to characterize the crayfish communities and evaluate the status of O. williamsi in Arkansas. A total of 2372 crayfishes were collected at 68 sites, including 197 Williams' Crayfish from 23 sites. Orconectes meeki meeki (Meek's Crayfish) was the crayfish species most commonly associated with O. williamsi, occurring sympatrically at 87% of sites occupied by O. williamsi. Orconectes williamsi was found in small streams, with coarse substrates and no aquatic vegetation. Orconectes williamsi showed a strong preference for riffle habitats. Due to its limited range and habitat requirements, O. williamsi is moderately imperiled in Arkansas and should be considered rare and vulnerable range-wide. [ABSTRACT FROM AUTHOR]

Introductions of nonnative crayfish species have resulted in the global decline of native crayfish populations, including those in North America. Historically, the North American range of Orconectes limosus (Spinycheek Crayfish) extended from Maine, southward into northern Virginia, including West Virginia's eastern panhandle. A 1988-1989 survey of the eastern panhandle of West Virginia resulted in the capture of only 14 O. limosus, but an abundance of the nonnative Orconectes virilis (Virile Crayfish). These data along with additional unpublished accounts of declines of O. limosus populations prompted our survey of eastern West Virginia. In 2005 and 2006, crayfishes were collected from streams within the West Virginia range of the O. limosus, including historic capture locations. Our collection of 600 individuals comprised crayfishes from 3 species: O. virilis, Orconectes obscurus (Allegheny Crayfish), and Cambarus bartonii bartonii (Common Crayfish). The nonnative O. virilis was present at 26 of the 30 sites, whereas O. limosus was absent from all collections. Our results may indicate extirpation of some or all populations of O. limosus in eastern West Virginia, but absence data may also reflect a low detection probability of individuals from small populations. Competition between the nonnative O. virilis and O. limosus have been reported elsewhere, and likely explains the extirpation of populations of O. limosus in West Virginia. [ABSTRACT FROM AUTHOR]

The present study was carried out to evaluate the effects of selectivity of fyke-nets of different mesh size on Astacus leptodactylus (Eschscholtz, 1823), in lake Eğirdir in Turkey. Crayfish were sampled monthly using fyke-nets of 26 mm (control), 34 mm (traditional), and 42 mm (increased) mesh size from July to December 2007. Differences in the mean size, weight, and number of crayfish caught with each mesh size were determined. The average length and weight were found to increase proportionally to mesh size. The highest mean weight (g) (± SD) (41.07 ± 4.61) was achieved at 42 mm mesh size compared with mean weights of 32.76 ± 4.53 and 29.29 ± 4.37 at sizes of 34 and 26 mm, respectively. The same trend was observed in mean TL of crayfish caught at 42, 34, and 26 mm size, but no significant difference was detected in mean length and weight for male and female crayfish. The weight of crayfish caught in 42 mm mesh was 8.3% higher than that in 34 mm mesh size. The lowest number of crayfish was caught with the 42 mm mesh size, while the highest number was captured with 34 mm mesh. This study shows that increasing mesh size has a positive effect on selectivity, because the mean total length L50 in the catch approximates the minimum landing size for this species in Turkey. L50 values (total length) for female, male, and combined sexes were 9.93 ± 0.41 cm, 9.73 ± 0.34, and 9.93 ± 0.34 cm for 42 mm, and 6.54 ± 0.60 cm, 7.28 ± 0.30, and 7.09 ± 0.3 cm for 34 mm, respectively. It was presumed that 34 mm mesh size, which is commercially used, has poor selectivity. On the other hand, 34 mm mesh size caused a loss in marketable crayfish among the three tested mesh sizes. The 42 mm mesh size provided the most appropriate selection of the crayfish, compared with sizes of crayfish at 34, and 26 mm mesh, respectively. Meanwhile, as mesh size increases, the female escape ratio becomes higher than the male escape ratio. Thus, increase in mesh size of nets will have a positive impact not only on preserving a sustainable stock, but also sparing labour and time to be spent on fishing operations. [ABSTRACT FROM AUTHOR]

Theoretical models of animal assessment and decision strategies have assumed animals possess accurate information about themselves. The imperfect nature of self-assessment could cause animals to make inaccurate decisions during agonistic encounters. By manipulating sensory information used in self-assessment in crayfish, Orconectes rusticus, it may be possible to alter either decision-making paradigms or outcomes associated with agonistic encounters. We examined the role of self-assessment in the agonistic behaviour of crayfish by using differing shelter sizes to alter self-assessment of size. Similar-sized crayfish were kept in tanks with small, medium, and large shelters (relative to body size) and subsequently were fought against size-matched, naive opponents in novel chambers to remove resource value as a variable. Crayfish in small shelter treatments initiated and won more fights than crayfish in other shelters. Crayfish in the small shelter treatment had shorter durations of fight when compared to crayfish with the medium and large shelters. These results are consistent with the concept that crayfish placed in smaller shelters may be self-assessing their physical size and, thus, their fighting ability, higher than crayfish in larger shelters. Based on these results, current theoretical models need to include the role of inaccurate self-assessments in agonistic decision making paradigms. [ABSTRACT FROM AUTHOR]

The presence of two male morphs in crayfishes of the family Cambaridae is well established, but the selective value of this trait is unknown. Measurements of growth following molts to Form I and Form II were used to examine the hypothesis that alternating between the two molts may serve as an adaptation allowing animals to efficiently increase overall body size. The results revealed that the change in carapace length was significantly greater in animals molting to Form II, whereas changes in chela length and width were significantly greater in animals molting to Form I. These differences allow animals to maximally increase body length when molting to Form II and maximally increase chela size when molting to Form I. [ABSTRACT FROM AUTHOR]

In the mouthparts of the crayfish, we find the flagellar exopods of the symmetrical 1st, 2nd, and 3rd maxillipeds, which do not participate in food processing but occasionally generate water currents by their repetitive beating. Earlier, we have observed and filmed the flagellar movements in freely behaving Procambarus cubensis reared in the laboratory, and suggested that these movements were an overt expression of the excited state of the crayfish. Recently, we used a high-speed scan camera (100-240 fps) to observe and document the flagellar movements in the tethered crayfish. Beating of all six flagella occurs with the same frequency (8.3-8.4 Hz). There is, however, an obvious phase shift between various ipsilateral and bilaterally symmetrical flagella. All right and left flagella can beat simultaneously, or only one side can be active. Each flagellum can stop for a short time, which, however, has no influence on the beating of the other flagella. Flagellar movements seen in slowly displayed video-movies are complex and variable in their trajectories, and each flagellum is moving in its own manner. It is suggested that each flagellum has its own central pattern generator, and that activation of all ipsilateral flagella concurrently is established by common higher commands. [ABSTRACT FROM AUTHOR]

The differentiation of the female reproductive system from a macroscopic and microscopic point of view was studied in Cherax quadricarinatus. For this characterization, 184 females were dissected and processed for the histological analysis. From the differentiation of the ovary up to its maturity, three ovarian morphotypes could be distinguished macroscopically: parallel strands without any contact between them, an H-shaped ovary, and a Y-shaped ovary. These morphotypes were compared within the Astacida. Four ovarian developmental stages were recognized based on ovary color, and the histological structure and relative proportion of cellular types. The post-spawning ovary was also characterized. The components of the female reproductive system sheath were described and its modifications in the ovary and oviducts were determined and compared. Theoretical aspects of the study of sexual differentiation in C. quadricarinatus were discussed within a phylogenetic framework. [ABSTRACT FROM AUTHOR]

Asymmetry in traits of sexual relevance may impair copulation behaviour and sexual performance of males, ultimately resulting in a fitness cost. Freshwater crayfish males use chelae, a sexually selected trait, to secure and position the female prior to and during mating. Thus, a relatively large chelae asymmetry, resulting from accidental loss and regeneration of one cheliped after autotomy, could have great consequences for male sexual behaviour. We studied copulatory behaviour and sperm expenditure of males paired to a mated female in Austropotamobius italicus, a freshwater crayfish species where both male and female mate multiply and where last-mating males are able to actively remove previously deposited sperm. We aimed at assessing whether male sperm removal and expenditure varied according to sperm allocated by first-mating males, and according to copulation behaviour and phenotypic traits (carapace length, chelae length and relative chelae asymmetry) of second-mating males. Second-mating males did not adjust their ejaculate size in relation to first-mating male ejaculate, nor to the first-mating male’s sperm removed. Moreover, the amount of sperm removed by second-mating males increased with increasing first-mating males ejaculate size, and first-mating male sperm remaining after removal did not correlate with the original first-mating male ejaculate size. Interestingly, the amount of sperm removed by second-mating males decreased with increasing relative chelae asymmetry, while increasing with male body size. However, second-mating (but not first-mating) asymmetric-clawed males produced larger ejaculates than symmetric-clawed ones. Importantly, the proportion of second-mating male sperm remaining after the two matings did not vary with relative chelae asymmetry nor with body size of second-mating males. Thus, small, asymmetric-clawed crayfish males appear to adopt sperm allocation tactics that allow them to fully compensate for their inferior sperm removal ability. [ABSTRACT FROM AUTHOR]