Reproductive season-based plasticity in the size and strength of female crayfish (Faxonius obscurus) claws.

Animal weapons are morphological traits that improve the fighting ability of the wielder and are associated with competition. These traits are typically sexually dimorphic, with males possessing weaponry and females lacking weaponry. However, in some cases, like in many crustaceans, both males and females wield enlarged claws, which may function as weapons. Further, animal weapons may vary in their size, shape, and performance, with theory predicting that selection pressure for weaponry should be the highest when the importance of fights is the greatest, such as during a reproductive season. However, the degree and direction of selection may vary based on sex and season, with females potentially benefiting from wielding larger weapons during nonreproductive seasons. Crayfishes offer an ideal system to investigate how weapon phenotypes change across reproductive seasons since both males and females undergo a form alteration associated with reproduction. Thus, we investigated whether female Allegheny crayfish, Faxonius obscurus, claws change in size, shape, or pinching strength based on whether a female is in a reproductive or nonreproductive form. We found that female F. obscurus claws are larger and stronger during the reproductive season. These findings align with previous research on males of the same species. We discuss how predictions about the relationship between seasonality and weapon investment may differ based on sex.

Description of a new species of crayfish in the genus Faxonius (Decapoda: Cambaridae) from the Lower Ohio River Drainage, with evidence of glacial influence on the distribution of some crayfish species throughout the Ohio River basin.

Variation in morphology of Faxonius jeffersoni has been documented since the 1960s. However, a taxonomic review of the species had not been conducted. In order to clarify if F. jeffersoni exhibited a variety of character traits, or was comprised of multiple taxa, genetic and morphological analyses were conducted. As a result, we revealed that F. jeffersoni sensu lato was comprised of two non-sister taxa. A new species of crayfish, Faxonius elix n. sp., is described herein. Further analysis shows evidence of glacial influence on the distribution of crayfish species of the genus Faxonius throughout Kentucky, Illinois, and Indiana along the glacial maximum.

Redescription of Euastacus clydensis Riek, 1969 (Crustacea: Parastacidae), a valid species of spiny crayfish from southern New South Wales, Australia.

The Giant Sydney Crayfish (Euastacus spinifer (Heller, 1865)) was thought to have a wide range in New South Wales, Australia, spanning some 600 km north-south. A recent extensive molecular phylogenetic and population genomic analysis of E. spinifer across its geographical range revealed strong population structure corresponding to several major geographically correlated clades, the southernmost clade being the most genetically divergent and clearly a separate species. This southern clade corresponds to the junior synonym E. clydensis Riek, 1969 and is sister to the clade comprising the remaining populations of E. spinifer and Euastacus vesper. We formally remove E. clydensis from the synonymy of E. spinifer, increasing the recognised number of species of Euastacus to 54. Euastacus clydensis is redescribed based on type and other material, and is distinguished from E. spinifer by differences in abdominal spination and the form of the antennal scaphocerite. Euastacus clydensis has a restricted southern New South Wales range in the Shoalhaven and Jervis Bay-Clyde River catchments, from Moss Vale south to the vicinity of Clyde Mountain; much of the known range of E. clydensis was burnt in the 2019-2020 eastern Australian megafires.

Cambarus ectopistes sp. nov., a new stream-dwelling crayfish (Decapoda: Cambaridae) from the French Broad, Pigeon, and Nolichucky River watersheds in the Appalachian Mountain region of North Carolina and Tennessee, USA.

The Cataloochee Crayfish, Cambarus ectopistes sp. nov., is a large, stream-dwelling crayfish that occupies a narrow noncontiguous distribution within the Appalachian Mountain region running through the Upper Tennessee River basin, in the French Broad, Pigeon, and Nolichucky watersheds along the Tennessee and North Carolina border. It is split from the southernmost extent of the C. robustus species complex, and is morphologically and genetically most similar to a second undescribed member of the group endemic to the upper Nolichucky River watershed in North Carolina. Cambarus ectopistes sp. nov. can be distinguished from other members of the C. robustus complex and co-distributed congeners by a combination of characters, including body size, coloration, and morphology of the chela and rostrum. The new species is typically found in channel and edge habitats of moderate to large perennial streams with large cobbles and boulders.

Genetic diversity, phylogenetic position and morphometric analysis of Astacus colchicus (Decapoda, Astacidae): a new insight into Eastern European crayfish fauna.

The phylogeny of European crayfish fauna, especially with respect to Eastern European species, is still far from being completely resolved. To fill this gap, we analyzed most of the European crayfish species focusing on the phylogenetic position of the endemic crayfish Astacus colchicus, inhabiting Georgia. Three mitochondrial and one nuclear marker were used to study evolutionary relationships among European crayfish species, resulting in the unique phylogenetic position of A. colchicus indicating independent species status to A. astacus. Phylogenetic analyses revealed a deep molecular divergence of A. colchicus in comparison to A. astacus (6.5-10.9% in mtDNA and 1.1% in nDNA) as well as to Pontastacus leptodactylus and P. pachypus (5.5-10.0% in mtDNA and 1.4-2.4% in nDNA). Absent ventral process on second male pleopod and abdominal somites II and III with pleura rounded lacking prominent spines clearly indicate taxonomic assignment to the genus Astacus; however, the species is distributed almost in the middle of Ponto-Caspian area typical by occurrence of the genus Pontastacus. Several morphological indices linked to head length, carapace, and total body length and width were found to demonstrate apparent differences between A. colchicus and A. astacus. Although this study provides a novel insight into European crayfish phylogeography, we also point out the gaps in comprehensive study of the P. leptodactylus species complex, which could reveal details about the potential species status of particular species and subspecies within this genus.

Comparative morphology of crayfish mandibles, with insight into their evolution.

Mandibles of representatives of the Holarctic crayfish families Astacidae, Cambaridae, and Cambaroididae were examined using SEM, and the results were analyzed in a phylogenetic framework. The intraspecific variability of the incisor process was found to be higher than its interspecific variability, mainly due to extensive abrasion of its ridge during intermolt periods. The plesiomorphic state of the crayfish mandibles highlights the dentate-crenate type of the incisor process and the extensive ribbed molar field with a multicuspidate caudal part, typical of the two parastacid crayfish examined for comparison. For Holarctic crayfish, the initial evolutionary type of the incisor is also the dentate-crenate one, but the molar field has a bowl-shaped caudal part and reduced cephalic part, both of which have been shown, for example, for Cambaroides. Similar mandibles are also widely present in American cambarids, which further evolved a blade-like incisor process (some Faxonius spp.) or a tricuspidate or double-bladed caudal molar field (some Procambarus spp.). The molar field in Astacidae crayfish is subdivided and rugose. The results of the present study indicate that little phylogenetic information is conveyed by the mandible shape at the species or genus level. Evolutionary changes are indicated mainly on the level of the main crayfish families. RESEARCH HIGHLIGHTS: Mandible shape can be an additional characteristic to distinguish crayfish families and selected genera. Obvious differences exist in the molar process rather than in the incisor ridge.

Size, shape, and sex-dependent variation in force production by crayfish chelae.

The ability to generate large closing forces is important for many animals. Several studies have demonstrated that bite or pinching force capacity is usually related to the linear dimensions of the closing apparatus. However, relatively few studies have applied geometric morphometrics to examine the effects of size-independent shape on force production, particularly in studies of crustacean pinching force. In this study, we utilized traditional and geometric morphometric techniques to compare the pinching force of Procambarus clarkii crayfish to their chela morphology. We found that males possessed larger chelae and pinched harder than females, but that their chela shape and size were weak predictors of strength. Female pinching force was significantly affected by both chela size and shape, with shape variation along the short axis of the claw contributing most to pinching force. We discuss our results in the context of reliable signaling of strength by males and females, and the different selective forces acting on chela shape in the two sexes.

Recent Incidence of Paragonimus westermani Metacercariae in Freshwater Crayfish, Cambaroides similis, from Two Enzootic Sites in Jeollanam-do, Korea.

An epidemiological study was performed to know the recent infection status of Paragonimus westermani metacercariae (PwMc) in freshwater crayfish, Cambaroides similis, from 2 streams in Jeollanam-do, Republic of Korea. Crayfish were collected from creeks in Bogil-do (Island), Wando-gun, and in a creek near Daeheung Temple in Haenam-gun. The infection rate of crayfish with PwMc in Bogil-do was 89.8%, and the metacercarial burden was 37 PwMc per the infected crayfish. Crayfish in a creek near Daeheung Temple were larger and twice heavier than those in Bogil-do. Of them, 96.5% were infected with PwMc. An average of 140 metacercariae was found in the infected crayfish, almost quadruple to those of Bogil-do. There was a strong correlation between the number of PwMc and body weight of the crayfish. These results suggest that P. westermani metacercariae are still prevalent in crayfish of the 2 regions in Jeollanam-do, Korea.

MARS: A protein family involved in the formation of vertical skeletal elements.

Vertical organizations of skeletal elements are found in various vertebrate teeth and invertebrate exoskeletons. The molecular mechanism behind the development of such structural organizations is poorly known, although it is generally held that organic matrix proteins play an essential role. While most crustacean cuticular organizations exhibit horizontal chitinous layering, a typical vertical organization is found towards the surface of the teeth in the mandibles of the crayfish Cherax quadricarinatus. Candidate genes encoding for mandible-forming structural proteins were mined in C. quadricarinatus molt-related transcriptomic libraries by using a binary patterning approach. A new protein family, termed the Mandible Alanine Rich Structural (MARS) protein family, with a modular sequence design predicted to form fibers, was found. Investigations of spatial and temporal expression of the different MARS genes suggested specific expression in the mandibular teeth-forming epithelium, particularly during the formation of the chitinous vertical organization. MARS loss-of-function RNAi experiments resulted in the collapse of the organization of the chitin fibers oriented vertically to the surface of the crayfish mandibular incisor tooth. A general search of transcriptomic libraries suggested conservation of MARS proteins across a wide array of crustaceans. Our results provide a first look into the molecular mechanism used to build the complex crustacean mandible and into the specialized vertical structural solution that has evolved in skeletal elements.

The chronic effects of terbuthylazine-2-hydroxy on early life stages of marbled crayfish (Procambarus fallax f. virginalis).

This study assessed the chronic effects of terbuthylazine-2-hydroxy (T2H), one of the main terbuthylazine degradation products, on early life stages of marbled crayfish (Procambarus fallax f. virginalis) by means of mortality, growth rate, early ontogeny, oxidative stress, antioxidant defence and histopathology. The crayfish were exposed to four concentrations of the tested substance as follows: 0.75µg/l (environmental concentration), 75, 375 and 750µg/l for 62days. Concentrations over 75µg/l caused lower weight compared to the control group. T2H at 750µg/l caused delay in ontogenetic development. Levels of thiobarbituric acid reactive substances and total superoxide dismutase activity were significantly (p<0.01) lower in groups exposed to 375 and 750µg/l T2H. Crayfish in these treatments also showed alteration of tubular system including disintegration of tubular epithelium with complete loss of structure in some places of hepatopancreas and wall thinning up to disintegration of branchial filaments with focal infiltrations of hemocytes. In conclusion, chronic terbuthylazine-2-hydroxy exposure in concentrations up 75µg/l (100 times higher than environmental concentration) affected growth, ontogenetic development, antioxidant system, caused oxidative stress and pathological changes in hepatopancreas of early life stages of marbled crayfish.

The sublethal effects of (2,4-Dichlorophenoxy) acetic acid (2,4-D) on narrow-clawed crayfish (Astacus leptodactylus Eschscholtz, 1823).

2,4-D is a widely used phenoxy herbicide, potentially toxic to humans and biota. The objective of the present study was to reveal short term sublethal effects of 2,4-D on narrow-clawed freshwater crayfish (Astacus leptodactylus Eschscholtz, 1823), based on histology, total haemocyte counts, selected haemolymph parameters, and oxidative stress parameters. In the laboratory conditions crayfish specimens were exposed to 9 mg L-1 of 2,4-D for one week. Experiments were conducted under semi-static conditions in 20 L-capacity aquaria where 10 freshwater crayfish were stocked per aquarium. Exposure (experimental) and control groups were used and the experiments were repeated two times. No mortality and behavioural changes were recorded during the experiments. Total haemocyte counts decreased significantly, while haemolymph glucose levels increased (P<0.05), when compared to the control group. Haemolymph levels of calcium, chloride, sodium, potassium, magnesium, total protein, and lactate did not change. Exposure resulted with increased levels of malondialdehyde (MDA) only in hepatopancreas. However, results of gill FOX assay showed a significant decrease in oxidative stress parameters (P<0.05). MDA levels of gill and abdominal muscle tissues and FOX levels of hepatopancreas and abdominal muscle tissues did not change when compared to the control group. Significant histopathological alterations were observed both in hepatopancreas (multifocal deformations in tubule lumen) and gill tissue (melanisation of gill lamella). Exposure of crayfish even to a sublethal concentration of 2,4-D alters histopathology and lipid peroxidation due to stress. Biomarkers studied here seem to be useful for the assessment of adverse/toxic effects of pesticides on non-target, indicator aquatic organisms.

A new species of crayfish in the genus Orconectes (Decapoda: Cambaridae) from the Tennessee River Drainage with comments on and key to members of the O. juvenilis Species Complex.

The crayfish subgenus Procericambarus (genus Orconectes) found in the Eastern Highlands of the United States represents a rich assemblage of stream-dwelling macroinvertebrates. While the taxonomic status and distribution of its members were clarified in a previous study, newly diagnosed characters and newly collected specimens warranted a revision to previous hypotheses of Procericambarus membership in the southeastern United States. Using morphological characters, we describe herein a new species of crayfish occurring in the Tennessee River drainage of northern Alabama and southwestern Tennessee. We also provide a revised key for the identification of members of O. juvenilis Species Complex.

Cambarus (Depressicambarus) clairitae, a new species of crayfish (Decapoda: Cambaridae) from Alabama with a review of the halli Group in the subgenus Depressicambarus.

Cambarus (Depressicambarus) clairitae, new species, is an epigean crayfish from two drainages of the Locust Fork system in Blount and Jefferson counties, Alabama. It belongs to the halli Group in the subgenus Depressicambarus. The new species is morphologically most similar to Cambarus (Depressicambarus) englishi. They differ in a several morphological characters. Cambarus englishi has a more strongly recurved central projection, a wider areola, and a more distinct and set off rostral acumen than the new species. It also has light gray to white antennae while the antennae of the new species are brown. In addition to the description of the new species, the halli Group in Alabama is discussed.

Cloning and Expression of Ecdysone Receptor and Retinoid X Receptor from Procambarus clarkii: Induction by Eyestalk Ablation.

Ecdysone receptor and retinoid X receptor are key regulators in molting. Here, full length ecdysone receptor (PcEcR) and retinoid X receptor (PcRXR) cDNAs from Procambarus clarkii were cloned. Full length cDNA of PcEcR has 2500 bp, encoding 576 amino acid proteins, and full length cDNA of PcRXR has 2593 bp, in which a 15 bp and a 204 bp insert/deletion splice variant regions in DNA binding domain and hinge domain were identified. The two splice variant regions in PcRXR result four isoforms: PcRXR1-4, encoding 525, 520, 457 and 452 amino acids respectively. PcEcR was highly expressed in the hepatopancreas and eyestalk and PcRXR was highly expressed in the eyestalk among eight examined tissues. Both PcEcR and PcRXR had induced expression after eyestalk ablation (ESA) in the three examined tissues. In muscle, PcEcR and PcRXR were upregulated after ESA, PcEcR reached the highest level on day 3 after ESA and increased 33.5-fold relative to day 0, and PcRXR reached highest the level on day 1 after ESA and increased 2.7-fold relative to day 0. In the hepatopancreas, PcEcR and PcRXR dEcReased continuously after ESA, and the expression levels of PcEcR and PcRXR were only 0.7% and 1.7% on day 7 after ESA relative to day 0, respectively. In the ovaries, PcEcR was upregulated after ESA, reached the highest level on day 3 after ESA, increased 3.0-fold relative to day 0, and the expression level of PcRXR changed insignificantly after ESA (p > 0.05). The different responses of PcEcR and PcRXR after ESA indicates that different tissues play different roles (and coordinates their functions) in molting.

Two new species of South American freshwater crayfish genus Parastacus Huxley, 1879 (Crustacea: Decapoda: Parastacidae).

Two new species of Parastacus Huxley, 1879 are described from material collected in the state of Rio Grande do Sul, southern Brazil: Parastacus fluviatilis sp. nov. from highland streams and Parastacus caeruleodactylus sp. nov. from wetlands. Parastacus fluviatilis sp. nov. is distinguished mainly by large chelipeds with dense setae cover on the cutting edge of fingers, telson subtriangular with two lateral blunt spines and strongly concave ventral surface of lateral process of thoracic sternites 6 and 7. Parastacus caeruleodactylus sp. nov. is distinguished mainly by blue cheliped fingers and a large gap between them, reduced abdomen, dorsal and ventral margins of dactylus, propodus and carpus of second pair of pereiopods with tufts of long setae and mid-dorsal carina of exopod of uropods unarmed. According to IUCN Red List criteria both species are considered endangered. Habitat characterization and a method for defining the shape of second abdominal pleura are also provided.

Cambarus (Jugicambarus) adustus, a new species of crayfish from northeastern Kentucky delimited from the Cambarus (J.) aff. dubius species complex.

A new species of burrowing crayfish, Cambarus (Jugicambarus) adustus, is described from Lewis County in northeastern Kentucky, USA. The new species is most similar morphologically to C. dubius. Cambarus adustus coloration differs from C. dubius by lacking red, orange and blue hues, and instead is brown over the entire body surface. Morphological differences between C. dubius and C. adustus exist in the form I male gonopod, with C. adustus possessing a caudal knob, while C. dubius does not. In addition, the lateral carapace of C. adustus is distinctly tuberculate, whereas in C. dubius the carapace lacks extensive tuberculation. Cambarus (J.) adustus appears to have an extremely small geographic range (~19.5 km2), and as such we suggest its consideration for both state and federal levels of protection.

High-resolution structural and elemental analyses of calcium storage structures synthesized by the noble crayfish Astacus astacus.

During premolt, crayfish develop deposits of calcium ions, called gastroliths, in their stomach wall. The stored calcium is used for the calcification of parts of the skeleton regularly renewed for allowing growth. Structural and molecular analyses of gastroliths have been primarily performed on three crayfish species, Orconectes virilis, Procambarus clarkii, and more recently, Cherax quadricarinatus. We have performed high-resolution analyses of gastroliths from the native noble crayfish, Astacus astacus, focusing on the microstructure, the mineralogical and elemental composition and distribution in a comparative perspective. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) observations showed a classical layered microstructure composed of 200-nm diameter granules aligned along fibers. These granules are themselves composed of agglomerated nanogranules of 50nm-mean diameters. Denser regions of bigger fused granules are also present. Micro-Raman spectroscopy show that if A. astacus gastroliths, similarly to the other analyzed gastroliths, are mainly composed of amorphous calcium carbonate (ACC), they are also rich in amorphous calcium phosphate (ACP). The presence of a carotenoid pigment is also observed in A. astacus gastrolith contrary to C. quadricarinatus. Energy-dispersive X-ray spectroscopy (EDX) analyses demonstrate the presence of minor elements such as Mg, Sr, Si and P. The distribution of this last element is particularly heterogeneous. X-ray absorption near edge structure spectroscopy (XANES) reveals an alternation of layers more or less rich in phosphorus evidenced in the mineral phase as well as in the organic matrix in different molecular forms. Putative functions of the different P-comprising molecules are discussed.

A New Crayfish of the Genus Cambarus (Decapoda: Cambaridae) From the Flint River Drainage in Northern Alabama and South Central Tennessee, U.S.A.

Examination of specimens of the crayfish species Cambarus (Hiaticambarus) longirostris and two recently described crayfish revealed the existence of an undescribed species from the Flint River watershed in northern Alabama and southern Tennessee. Cambarus (Hiaticambarus) lentiginosus differs from C. longirostris, C. (Hiaticambarus) andersoni, and C. (Hiaticambarus) diupalma in aspects of carapace and chela morphology and pigmentation pattern. Cambarus (H.) lentiginosus possesses a median carina on the dorsal surface of the acumen of the rostrum, a distinctly enlarged tubercle near the base of the opposable surface of the dactyl, and a speckled pigmentation pattern over a light base color; these characters are lacking in other known Hiaticambarus species. The known range of the species is restricted to the Flint River watershed. Cambarus (H.) lentiginosus is considered Endangered using American Fisheries Society conservation categorization.

A new burrowing crayfish of the genus Fallicambarus Hobbs, 1969 (Decapoda: Cambaridae) from the Red River Drainage of the southcentral United States.

A new primary burrowing crayfish, Fallicambarus schusteri, is described from the Red River drainage of extreme southeastern Oklahoma and southwestern Arkansas and is placed in the subgenus Fallicambarus. The species occurs in roadside ditches that seasonally flood and have silt and silt-loam dominated soils. Falllicambarus schusteri differs from all other members of the genus Fallicambarus in possessing a thin gradually tapering central projection and a wide triangular cephalic process on the first pleopod of form I males, a sufflamen on the cheliped, and an antennal scale that is widest at its midpoint.

Effects of Different Social and Environmental Conditions on Established Dominance Relationships in Crayfish.

Like most social animals, crayfish readily form dominance relationships and linear social hierarchies when competing for limited resources. Competition often entails dyadic aggressive interactions, from which one animal emerges as the dominant and one as the subordinate. Once dominance relationships are formed, they typically remain stable for extended periods of time; thus, access to future resources is divided unequally among conspecifics. We previously showed that firmly established dominance relationships in juvenile crayfish can be disrupted by briefly adding a larger conspecific to the original pair. This finding suggested that the stability of social relationships in crayfish was highly context-dependent and more transient than previously assumed. We now report results that further identify the mechanisms underlying the destabilization of crayfish dominance relationships. We found that rank orders remained stable when conspecifics of smaller or equal size were added to the original pair, suggesting that both dominant and subordinate must be defeated by a larger crayfish in order to destabilize dominance relationships. We also found that dominance relationships remained stable when both members of the original pair were defeated by larger conspecifics in the absence of their original opponent. This showed that dominance relationships are not destabilized unless both animals experience defeat together. Lastly, we found that dominance relationships of pairs were successfully disrupted by larger intruders, although with reduced magnitude, after all chemical cues associated with earlier agonistic experiences were eliminated. These findings provide important new insights into the contextual features that regulate the stability of social dominance relationships in crayfish and probably in other species as well.