Abstract Current conservation legislation and protection is species driven within the State of Tennessee. Without rigorous systematic assessment, a species’ conservation status may be inaccurate if unable to account for confounding undescribed species. This results in mismanagement and the inability for conservation intervention to occur, limiting possible benefits for species of greatest conservation need. We used an integrative approach to investigate and address the morphological disparity within Cambarus pristinus Hobbs, 1965, the pristine crayfish, using morphological, molecular, and geologic information. Our results validate the recognition of two species within the C. pristinus species complex. We resolve this taxonomic issue by delimiting and describing Cambarus acicularis n. sp., the Tablelands crayfish. Cambarus acicularis n. sp. differs from all other members of the genus by the following combination of characters: gonopod of form I males with central projection directed caudally at an angle < 90° to the main axis of shaft, cephalic margin of the central projection extended distally forming an elongated, needle-like process, and a prominent, lobe-like caudal process (caudal knob) present at the lateral base of the central projection. It is further differentiated from C. pristinus by having longer fingers on the chela, longer rostrum and acumen, narrower antennal scale, and a slenderer merus. Conservation status recommendations are made herein and include observations that are important to understand the growing conservation threats on the Cumberland Plateau. The species has a limited distribution and warrants conservation attention. We also demonstrate the importance and advocacy of publicly available datasets for underfunded taxa groups like crayfishes.
Abstract Deep-sea amphipods frequently cling to elevated biogenic structures such as cnidarians and poriferans to provide elevation advantages and refuge. Clinging behaviour is rarely documented in amphipods from hadal depths (>6,000 m), likely reflecting sampling bias associated with the predominant use of baited traps which preferentially target taxa from scavenging guilds. We report the first documented observation of clinging behaviour by a hadal scavenging amphipod species from the family Stegocephalidae Dana, 1852. The specimens represent an undescribed species belonging to the genus Parandaniexis Schellenberg, 1929 and is here referred to as Parandaniexis sp. JAVA. This species was observed during baited lander deployments and a submersible dive at depths of 7,168–7,192 m in the Java Trench (East Indian Ocean). Parandaniexis sp. JAVA was observed in high numbers (>100 individuals) with many competing successfully for bait with the characteristic hadal lysianassid scavengers Bathycallisoma schellenbergi (Birstein & Vinogradov, 1958) and species of Eurythenes S.I. Smith in Scudder, 1882. Individuals of Parandaniexis sp. JAVA repeatedly adopted elevated, stationary positions on biotic and abiotic structures rather than partaking in the feeding aggregation. This prolonged station-holding behaviour distinguished Parandaniexis sp. JAVA from the sympatric hadal scavengers also observed throughout the deployments.
Abstract Pseudohelice subquadrata (Dana, 1851) is an endangered and marine-protected varunid crab that inhabits the upper intertidal zone of Jeju Island, South Korea. We provide the first detailed description of its embryonic development by inducing spawning through controlling water temperature and photoperiod during approximately two years of laboratory rearing. Ovigerous females were maintained at 25°C and up to 10 eggs were collected daily from a single ovigerous female to document morphological development and changes in egg diameter. Embryonic development required 16–19 days, during which mean egg diameter increased from 262 ± 6 μm at the beginning of development to 354 ± 8 μm immediately before hatching. Development was divided into ten stages: precleavage, cleavage, blastula, intermediate multicell gastrula, gastrula, nauplius, eye-formation, thoracico-pleonal, heartbeat, and prehatch. Egg color gradually changed from orange to dark brown or black as eye pigmentation and chromatophores developed. Heart activity was first observed 3–5 days before hatching, with rates ranging 60–130 beats per minute. Hatching occurred predominantly during the dark phase under a 15 h light:9 h dark photoperiod, and the number of hatched larvae per female ranged 6,500–27,000 across spawning events. These findings provide fundamental information on the embryogenesis of P. subquadrata and a comparative reference for embryonic development in varunid crabs. They also provide baseline data for broodstock management, ex situ propagation, and future conservation programs for this endangered species.
Abstract A new genus, Clavatovillus n. gen., is established for Anamathia beauchampi Alcock & Anderson, 1894, a poorly known epialtid crab originally described from western Bay of Bengal. Examination of fresh specimens shows that the species differs from Crocydocinus Lee, Richer de Forges & Ng, 2019 s. str., where it was placed provisionally, as well as allied genera, in that the epi- and mesobranchial regions of the carapace are distinctly inflated medially, compressing the urogastric region, the outer margin of basal antennal article is strongly convex, the merus of the third maxilliped is not auriculiform, the male pleon is proportionately narrower, the male sternite 8 is clearly visible when the pleon is closed, the margins of the ambulatory merus, carpus, and propodus are smooth, rounded, without crista, and densely lined with distinct clavate setae. The rediscovery of this rare deep-sea taxon after more than a century highlights the underestimated diversity and taxonomic complexity of majoid crabs in the Indian Ocean.
Abstract The American lobster, Homarus americanus H. Milne Edwards, 1837, is a well-studied species, particularly because of the high economic importance of its fishery in the United States and Canada. The first year of a lobster’s life, which spans both pelagic and benthic phases, is critical to understanding fishery health and has become a major focus of laboratory and field studies. Despite increasing research efforts, the field lacks standardized methodologies for evaluating early life history (ELH). There is a need for a compilation of information on best practices across common methods in ELH American lobster research to inform future work. We provide a comprehensive overview of the American lobster’s ELH, guidance on field study designs, including long-term monitoring surveys and laboratory techniques, and recommendations for biological endpoints. The information presented is intended to equip researchers at all career stages with the tools needed to design and conduct successful work on the complex early life history phases of the American lobster. Our goal is to increase and facilitate comparable results among studies in support of sustainable fisheries for American lobster and other crustaceans with similar life histories.
Abstract Azerbaijan hosts a historically contentious crayfish fauna shaped by the complex biogeography of the Ponto-Caspian region and a legacy of Soviet-era taxonomy. Crayfish species richness in the region has varied from one to six species, largely due to unresolved synonymies of Pontastacus Bott, 1950, the mixing of freshwater and Caspian brackish-water taxa, and persistent misinterpretations of early literature. The review provides the first comprehensive, country-level synthesis of the crayfish species of Azerbaijan evaluated within a modern systematic and biogeographic framework. By reassessing historical records, taxonomic revisions, and regional distribution data, we clarify the composition and status of crayfish taxa attributed to the fauna. The available evidence demonstrates that only two species, Pontastacus leptodactylus (Eschscholtz, 1823) and the endemic P. pylzowi (Skorikov, 1907), are reliably established in freshwater environments. Pontastacus eichwaldi (Bott, 1950) is known in the Lankaran sector of the Caspian basin but remains unverified, while the Caspian brackish-water P. pachypus (Rathke, 1837) and P. kessleri (Schimkewitsch, 1886) cannot be considered freshwater components of the fauna. The frequently cited Astacus astacus Kessler, 1876 is shown to represent a taxonomic artifact rather than a valid element. Documented population declines in the two confirmed freshwater species underscore the need for renewed field surveys, molecular barcoding to resolve species boundaries, and targeted conservation measures.
Abstract A new fossil pinnotheroid crab, Pinnotheres prochowniki n. sp., from the upper Miocene (Tortonian) Little Cove Point Member of the St. Marys Formation of Maryland, USA, and St. Marys or Eastover Formation of Virginia, USA, is described based on sixteen specimens, marking the first occurrence of a pinnotheroid from the Chesapeake Group. These pinnotheroids exhibit remarkable preservation, many specimens of which are fully articulated, and at least one specimen retains preserved pleopods and gills. These crabs also appear to exhibit preferential association with the surf clam Mactrodesma subponderosa Ward, 1992, with all but two being found within their shells and none being found in association with any other potential host species. The exceptional preservation of these pea crabs can be attributed in part to this symbiotic relationship, as the host clam served to protect the crabs from being destroyed by taphonomic processes.
Abstract In the midwater, earth’s largest habitat by volume, the evolution of animal bodies is shaped by unique selective pressures associated with navigating through and feeding in a dimly-lit habitat with few places to hide. Holopelagic hyperiid amphipods (suborder Hyperiidea H. Milne Edwards, 1830), which are often found associated with gelatinous zooplankton, possess a strikingly varied array of appendage morphologies, much greater than do their benthic relatives, yet the functions of most of these structures remain unknown. We attempt to systematically categorize and describe variation in appendage morphology across hyperiids and other midwater amphipod groups, including Lysianassoidea Dana, 1849; Aristioidea Lowry & Stoddart, 1997; Stegocephalidae Dana, 1852; Pardaliscidae Boeck, 1871, and others. We hypothesize functions for specific appendage types and features, with the paired goals of 1) connecting in situ and laboratory observations of swimming, predation, and host association behavior to morphology, and 2) inferring the ecology and behavior of new and poorly known species based on pereopod morphology. Increasing our understanding of the function of these structures will help us to address broader questions about the evolution and diversification of amphipod morphology as it relates to locomotion and trophic interactions, and how animals more broadly have adapted to moving and feeding in midwater habitats.
A combination of traditional and new kinds of characters is used to delineate three cold-water cyclopoid copepod species, Cyclops gracilipes Sars, 1903, C. floessneri nom. nov., and C. abyssorum Sars, 1863, which are distributed in southern Siberia, Mongolia, and Europe, respectively. The species name Cyclops glacialis Fl & ouml;ssner, 2001, a junior primary homonym of Cyclops glacialis Brady, 1910, is replaced herein by a new name, Cyclops floessneri nom. nov. Morphological analysis revealed one trait in males, the number of aesthetascs on the first antennulary segment, that could be used alone for species discrimination. A few morphological characters differing in frequency of variable states suggest that C. gracilipes and C. floessneri nom. nov. are more closely related to one another than either is to C. abyssorum, which is consistent with the single-base-pair difference in the 18S ribosomal RNA barcode between C. abyssorum and the other two Cyclops species in contrast to no difference between C. gracilipes and C. floessneri nom. nov. The timing of DNA excision occurs at the 4th cleavage division in C. gracilipes and the fifth in C. abyssorum (undetermined in C. floessneri nom. nov.). The amounts of excised DNA are large, vary interspecifically, similar to 24-48 pg DNA of germline DNA content, and account for more than half of the germline-limited DNA in each species. Nonetheless, the reduced somatic genome sizes of these three species remain large (similar to 6-11 pg) compared to the somatic genomes of warm-water cyclopoids. Chromatin diminution may possess several adaptive roles likely to be co-opted exaptations. In closely related taxa that undergo chromatin diminution and in which differences in morphology or DNA barcodes are minor or absent, chromatin diminution may provide a clear marker of speciation events.
Geographic origin authentication is increasingly important for maintaining transparency, product value, and sustainability in fisheries and aquaculture supply chains. Rapid and non-destructive screening tools nevertheless remain limited for high-value crab species. We used principal component analysis (PCA) to evaluate whether image-based geometric morphometrics could discriminate the geographic origin of the horsehair crab Erimacrus isenbeckii (Brandt, 1848). Landmark coordinates were extracted from dorsal and ventral photographs of individuals collected from three major Japanese production regions (Oshamanbe, Kamaishi, and Noto), and analyses were conducted separately by sex and body region. PCA revealed substantial overlap among regions in dorsal carapace morphology for both males and females, indicating limited geographic resolution. Male ventral abdominal morphology also showed weak differentiation. By contrast, female ventral landmarks produced clear separation among regions, suggesting that reproductive morphology captures biologically meaningful geographic variation. These results demonstrate that image-based morphometrics provides a rapid, non-destructive approach for preliminary origin screening. Although morphometric signals may be influenced by physiological factors such as molt stage and body condition, integration with automated imaging and complementary molecular methods could enhance their robustness. Our proposed workflow highlights the potential of image-derived morphometrics as a practical tool for seafood traceability and quality-control systems in fisheries and aquaculture processing pipelines.
Colombia's freshwater ecosystems are recognized as global biodiversity hotspots; however, the spatial distribution of its decapod fauna remains poorly synthesized. We provide the most comprehensive assessment to date of Colombia's freshwater shrimps and crabs, spanning 38 subregions across all six major natural regions. By synthesizing a 173-year longitudinal dataset (1853-2026) comprising 157 species and 17,731 specimens from 21 international museums and research institutions, our analysis reveals significant regional heterogeneity in biodiversity and establishes a high-resolution baseline for species distribution. We delineate clear patterns of species occurrence and characterize regional endemism. To ensure robust comparisons across areas with varying sampling intensities and environmental characteristics, we employed the Shannon and Simpson indices alongside a geometric index, effectively integrating species richness with distribution data. These findings establish a foundational framework for future biogeographic research and inform targeted conservation strategies for Colombian freshwater decapods.
Brachyuran crabs of the genus Mithraculus White, 1847 are primary consumers that represent important reservoirs of biomass and energy in the Caribbean Sea ecosystem. We provide a study of the occurrence and size distribution M. sculptus (Lamarck 1818) and M. corype (Herbst, 1801), found in coastal lagoons of the southern Mexican Caribbean. A total of 329 individuals were found in the sampled area, with higher abundance during the rainy season. The Mahahual sampling site showed the highest abundance, coinciding with a seabed covered by coral rubble and sand with seagrass. The lagoons of the southern Mexican Caribbean supported the presence of M. corype and M. sculptus, likely driven by coral degradation and the ecological succession of reef substrate towards seagrass, algae, and coral-rubble bottoms. These results highlight the importance of Mithraculus species as indicators of increasing abundance of primary producers such as algae and seagrass. This pattern may be linked to the loss of coral in the Mexican Caribbean, which has facilitated the establishment of these primary producers and the subsequent restructuring of trophic chains.
Investigated are the microbial communities of the stomach, gut, and faeces of pre-adult and adult Pontastacus leptodactylus (Eschscholtz, 1823) naturally infected with the oomycete Aphanomyces astaci, the causative agent of crayfish plague. Using shotgun metagenomics, we characterised bacterial, archaeal, fungal, viral, and eukaryotic assemblages across samples and developmental stages of the crayfish to explore microbiome structure and potential microbial interactions. Bacterial communities were dominated by Proteobacteria, although their abundance decreased in adult gut and stomach samples, accompanied by increases in Firmicutes, Mycoplasmatota (Tenericutes), and viral taxa. Fungal communities exhibited tissue-specific patterns, with Glomeromycetes and Umbelopsidomycetes prevalent in the gut, Saccharomycetes in faeces, and Ustilaginomycetes and Malasseziomycetes enriched in adult stomachs. Despite this variation, gut and stomach samples suggested the presence of a stable core microbiome. Viral communities were dominated by Caudovirales (phages), particularly in the adult stomach, indicating potential roles in shaping microbial composition. Faecal samples showed higher diversity and evenness compared to gut and stomach samples, highlighting their role as microbial reservoirs. Overall, microbiota composition appeared to be more strongly influenced by tissue type than by developmental stage.
Stream-bank erosion threatens freshwater ecosystems globally, yet traditional stabilization methods using cement, synthetic polymers, and riprap cause significant environmental damage through habitat degradation and greenhouse gas emissions. Biopolymers offer a sustainable alternative, but their ecotoxicological effects on aquatic organisms remain unknown. We evaluated the acute toxicity of exopolysaccharides (EPS) produced by Rhizobium tropici ATCC (R) 49672 on Procambarus clarkii, a burrowing crayfish that directly interacts with stream bank soils. A 96-hour static renewal test following ASTM guidelines exposed 69 crayfish individuals to EPS concentrations ranging from 0% to 33.33% (0-3333 ppm). Dose-response relationships were analyzed using logistic regression, with model validation performed through probit regression and nonparametric interpolation. The estimated LC50 was 8.78% (878 ppm; 95% CI: 780-975 ppm), classifying EPS as "practically nontoxic" according to EPA toxicity categories. Clear concentration-dependent mortality was observed, with no mortality at <= 5% (500 ppm) and 100% mortality at >= 25% (2,500 ppm). Correlation analyses confirmed that specimen weight did not influence toxicity response (P = 0.513), validating the use of mixed-size populations. The substantial safety margin between typical field application concentrations (< 1%, < 100 ppm) and the LC50 value suggests minimal risk to P. clarkii and potentially similar tolerant Procambarus species at environmentally relevant exposures. These findings nevertheless cannot be extrapolated to the broader aquatic community without additional testing of more sensitive taxa, including fishes, aquatic insects, mollusks, amphibians, and flow-adapted crayfish species. This preliminary assessment provides foundational ecotoxicological data supporting the potential integration of microbially-produced biopolymers into sustainable watershed management strategies, while highlighting the need for comprehensive multispecies toxicity testing before widespread implementation.
This study, the first extensive study on a species from the Mexican Atlantic slope, is part of a national project focused on the systematics of the amphidromous species of Macrobrachium Spence Bate, 1868, which occur in coastal drainage basins of Mexico. Five amphidromous species of Macrobrachium have been found to occur in this region: M. acanthurus (Wiegmann, 1836), M. carcinus (Linnaeus, 1758), M. heterochirus (Wiegmann, 1836), M. hobbsi Nates & Villalobos in Villalobos Hiriart & Nates Rodr & iacute;guez, 1990, and M. olfersii (Wiegmann, 1836). We studied specimens of the putative M. acanthurus (type locality: coast of Brazil) from basins of the states of Tamaulipas, San Luis Potos & iacute;, Veracruz, Tabasco, Chiapas, and Campeche. Comparison of their COI haplotypes with M. acanthurus sequences from Costa Rica, Panama, and Brazil deposited in the GenBank revealed high genetic distance (9.3 to 10.4%) between them. Maximum likelihood and Bayesian inference analyses performed by using concatenated 16S-COI sequences to investigate the evolutionary relationship of our haplotypes and other Macrobrachium species in the GenBank showed the Mexican haplotypes in a separate clade from its closest entity the M. acanthurus clade from regions south of Mexico. The wide COI genetic distance and the phylogenetic inference of the 16S-COI haplotypes show that our specimens correspond to M. mexicanum (De Saussure, 1857), a cryptic species previously considered a junior synonym of M. acanthurus. We studied photographs of four syntypes of M. mexicanum and conclude that their morphological characteristics fit well with our studied individuals.
An isolated population of the gill louse Salmincola californiensis (Dana, 1852) infecting native Rio Grande cutthroat trout, Oncorhynchus virginalis virginalis (Girard, 1856), in Whale Creek, Colorado, USA, was recently identified as a putative cryptic species based on its phylogenetic position relative to other populations, comprising a distinct clade that is reciprocally monophyletic to a second clade that included all other S. californiensis individuals examined. We assessed morphological features coupled with DNA barcode sequences to test this hypothesis. Our results reveal only slight morphological and genetic differences between the Whale Creek population and other populations of S. californiensis distributed across the range of the species. In particular, S. californiensis from Whale Creek has slightly fewer mandibular teeth (five) than other North American populations (usually six) and exhibits similar to 4.5% genetic distance from other haplotypes of the species. All other morphological characters were indicative of S. californiensis, and the genetic distance is less than the similar to 10-19% distances observed between other Salmincola species. These morphological and genetic differences do not justify recognition of the Whale Creek population as a new species, merely as an isolated population that appears to be in the process of diverging.
Bathynomus doederleini Ortmann, 1894, a deep-sea isopod, is a benthic scavenger in the northwestern Pacific. Little is known about its habitat and intraspecific variation in body size in relation to depth. We examined habitat depth, body-size distribution, and range limits of B. doederleini along the western coast of Kyushu, Japan using baited traps deployed at of 151-821 m deep. A total of 1,152 individuals were collected, with the highest catch per unit effort (CPUE) between 400 and 500 m. CPUE declined sharply below 700 m, likely due to thermal constraints and interspecific competition. Body size varied significantly with depth. Minimum body size increased with depth, whereas maximum body size remained constant. Smaller individuals were more abundant in shallower, warmer waters, suggesting ontogenetic habitat segregation, possibly driven by metabolic and competitive factors. No brooding individuals were captured, supporting previous findings that reproductive females tend to be underrepresented in baited traps. Results show that B. doederleini exhibits depth-related niche partitioning. Our study area likely represents the northernmost distribution limit of the species in the East China Sea. The study highlights the importance of trap type and environmental gradients in understanding the ecology of deep-sea species.
Invasive marine species pose significant threats to marine ecosystems, with reproduction often facilitating their establishment and spread. The European green shore crab, Carcinus maenas (Linnaeus, 1758), is a global marine invader, but its reproduction has rarely been studied in the Southern Hemisphere. We assessed ovarian development, size at sexual maturity, fecundity, and reproductive period of invasive female C. maenas in Gulf St Vincent, South Australia. We compared these reproductive traits with published data of C. maenas from native and invasive populations worldwide. Female crabs were collected monthly from March to November 2018, and their ovaries staged macroscopically and histologically to determine sexual maturity and reproductive period. Fecundity was measured in gravid crabs collected from 2018 and earlier surveys. Population structure analyses indicated a male-biased sex ratio and size-dependent patterns of ovarian development. Female C. maenas reached morphometric maturity at 30.2 mm carapace width (CW) and gonadal maturity at 29.8 mm CW, consistent with estimates from other regions. Mean fecundity (210,847 eggs per clutch, range 29,048-526,521) was higher than previously reported for the species. The reproductive period spanned eight months (April to November), coinciding with water temperatures below 20 degrees C. Our findings characterise the reproductive biology of C. maenas in its invasive range in southern Australia, contributing to our understanding of the mechanisms driving global establishment and spread of the species.
The landscape of fear model predicts prey behavior based on the presence and movement of predators. Yet, other environmental cues, such as safety, may also play a role in prey behavior. To test whether safety cues and fear cues influence prey behavior, we observed the sheltering choices and duration of the crayfish Faxonius rusticus (Girard, 1852) when directly exposed to a predator (largemouth bass, Micropterus nigricans Cuvier, 1828). Since bass are gape-limited predators, we varied the gape ratio between the size of the crayfish and size of the bass to alter threat level. We also provided shelters with a different number of openings as crayfish prefer shelters with less access points. As gape ratio between the crayfish and the M. nigricans increased, the amount of time that the crayfish spent in shelter also increased. There was nevertheless no significant difference in which particular shelter was used. Crayfish preferred shelters with lower numbers of openings when a predator was present compared to when a predator was absent. Our research suggests that there is an influence on behavior from both fear and safety cues, and to obtain a more accurate prediction of predator avoidance behavior both fear and safety cues must be included.
Most farmed shrimp worldwide are Indo-Pacific warm-water species and cannot be efficiently or economically cultivated in high-latitude regions due to falling water temperatures during autumn and winter. Consequently, indoor aquaculture systems are essential for maintaining production efficiency and ensuring biosecurity in these areas. We examined inorganic nitrogen dynamics of the water, feed utilisation, growth performance, and proximate composition of the Pacific white shrimp, Litopenaeus vannamei (Boone, 1931), and biofloc in a 42-day indoor culture treatment using biofloc technology (BFT) and a recirculating aquaculture system (RAS). Three sets of four treatments were evaluated under limited water-exchange conditions: BFT1 (C:N = 6; carbon supplementation only), BFT2 (C:N = 9; feed supplementation only), BFT3 (C:N = 15; feed plus carbon supplementation), and RAS (feed supplementation in a clean-water recirculating system). No significant variations were seen in the physicochemical parameters of water, as well as in suspended solids, volatile suspended solids, and total suspended solids (P > 0.05), although total ammonia nitrogen, NO2-, NO3-, and total inorganic nitrogen exhibited substantial change across the treatments (P < 0.05). The BFT2 and BFT3 treatments exhibited the best growth and the lowest feed conversion ratio (FCR), succeeded by the RAS system. The protein and lipid content of shrimp and biofloc exhibited significant differences among the treatments (P < 0.05); however, moisture and ash content did not show significant differences (P > 0.05). In the BFT systems, biofloc developed under a lower C:N ratio (BFT2, C:N = 9), dominated by microalgae and specific bacterial communities, supported better shrimp growth than biofloc formed under higher C:N conditions. This strategy may also reduce production costs by minimising carbon-source inputs and lowering oxygen demand. The findings demonstrate that well-managed BFT systems can achieve performance equal to or better than RAS while potentially reducing feed costs and improving nutrient recycling.
