Crab Potamon Research Articles

Crabs as snake predators? An observation from southern Italy leading to a comprehensive review

The recent elevation of the Western Grass Snake, Natrix helvetica, from subspecies status prompted an assessment of its natural history and ecological traits compared to closely related species. We report an unusual predation attempt by the freshwater crab Potamon fluviatile on N. helvetica sicula from Sicily, indicating an ecological interaction previously overlooked in this species. The observation suggests that this crab may utilise snakes’ muscle tissue as an additional nutrient source. This predator-prey interaction, although probably rare, adds to the understanding of the dynamics between crabs and snakes, shedding light on their interaction in freshwater habitats. To provide context for our observation and highlight its rarity, we searched through scientific literature and online sources to generate a comprehensive review of the phenomenon that examines the predatory behaviour of crabs on snakes.

Lethal grip for an endangered endemic frog: The freshwater crab Potamon karpathos (Decapoda, Potamidae) preys on Karpathos water frog Pelophylax cerigensis (Anura, Ranidae)

Invertebrate predation on amphibians is widespread, although unreported in Europe. Here, we present documented predation of the Karpathos water frog (Pelophylax cerigensis) by the crab Potamon karpathos. Pelophylax cerigensis is an endangered, endemic species exclusively found on the Rhodes and Karpathos Islands in the South Aegean Sea, Greece. The Karpathos population is at risk due to limited suitable habitats and a scarcity of freshwater bodies on the island. From April to October, when there is no rain on the island, frogs and crabs cohabitate, sharing the same shallow ditches. Incidents of frog predation by crabs are common, indicated by numerous individuals with amputated limbs and scars, representing an additional threat to the endangered frog. Further research on the interactions between the two species is urgently required, as it has direct conservation implications.

Uncovering glacial footprints and identifying phylogeographic units in the freshwater crab Potamon elbursi Pretzmann, 1962 (Decapoda: Potamidae) based on mitochondrial data

The current patterns of biodiversity have significantly been affected by glacial-interglacial cycles during the Pleistocene period. True freshwater crabs are considered as poor dispersers and terrestrial barriers restrict gene flow between their local populations. Recent studies, however, suggest that certain environmental conditions, such as periods of heavy rainfall and humidity, can facilitate their between-drainage dispersal and will result in the evolution of homogenous genetic patterns among different drainage systems. Here we tested this hypothesis by comparing populations of the endemic freshwater crab Potamon elbursi Pretzmann, 1962 distributed in two drainage systems, the Caspian Sea and Namak Lake, in northern Iran. Our results based on the genetic analysis of 70 new and 61 previously published sequences of the mitochondrial cytochrome oxidase subunit I gene revealed a substantial haplotype diversity in some populations and high levels of local population structuring in others. Initially, we found mixed evidence of genetic differentiation and connectivity among drainages and populations. Genetic differentiation between the two drainages only became apparent after the Sepirdood population (which belongs to the Caspian Sea drainage) was excluded. Subsequently, the two drainages showed significant genetic distinctions, with a limited gene flow between them. Our demographic analyses supported recent population bottlenecks, followed by a rapid demographic and/or spatial expansion dating back to the Pleistocene climatic fluctuations. Species distribution modelling suggests that precipitation during warm weather conditions profoundly affects the distribution of P. elbursi. This study indicates that freshwater crabs can override short land barriers under favorable weather conditions and will have conservation implications in the face of contemporary climatic fluctuations.

Phylogeography of the freshwater crab Potamon persicum (Decapoda: Potamidae): an ancestral ring species?

The Zagros Mountains, characterized by complex topography and three large drainage systems, harbor the endemic freshwater crab Potamon persicum in Iran. Our study delves into the evolutionary history of P. persicum, utilizing two mitochondrial and one nuclear marker. We collected 214 specimens from 24 localities, identifying 21 haplotypes grouped into two major evolutionary lineages. Substantial differentiation exists between drainage systems and lineages. Historical demographic analysis revealed a significant decrease in population size during the late Holocene, accompanied by a recent population bottleneck. Species distribution modeling has revealed eastward shifts in suitable habitats between the last glacial maximum and the present day. Following the last glacial maximum, habitat fragmentation occurred, resulting in the establishment of small populations. These smaller populations are more vulnerable to climatic and geological events, thereby limiting gene flow and accelerating genetic differentiation within species. Historical biogeographic analysis traced the origin of P. persicum to the western Zagros Mountains, with major genetic divergence occurring during the Pleistocene. Our genetic analyses suggest that P. persicum may have shown a genetic pattern similar to a classical ring species before the Pleistocene. The Namak Lake sub-basin could have served as a contact zone where populations did not interbreed but were connected through gene flow in a geographic ring. Currently, genetic separation is evident between basins, indicating that P. persicum in the Zagros Mountains is not a contemporary ring species. Also, our biogeographical analysis estimated that range evolution may have been driven initially by dispersal, and only during the late Pleistocene by vicariance.

Predation of a grass snake Natrix natrix by a Peloponnesian freshwater crab Potamon pelops

Predation of a grass snake Natrix natrix by a Peloponnesian freshwater crab Potamon pelops

Breeding cycle and seasonal biochemical changes in the gonads of the North African freshwater crab Potamon algeriense (Bott, 1967) (Brachyura: Potamidae)

Breeding cycle and seasonal biochemical changes in the gonads of the North African freshwater crab Potamon algeriense (Bott, 1967) (Brachyura: Potamidae)

Diet composition of the North African freshwater crab, Potamon algeriense (Bott, 1967) in Oued Zegzel (Northeast of Morocco)

ABSTRACT This is the first study of the diet composition of the North African freshwater crab Potamon algeriense by examining stomach contents. Crabs were collected during 1 year, October 2018 to September 2019, from Oued Zegzel, a mountain stream in the Northeast of Morocco. From a total of 72 crabs captured, only 35 males and 30 females had stomach contents that could be analyzed. Diet composition analysis was carried out using the frequency of occurrence and the percentage point methods. Stomach content analysis showed that P. algeriense was found to be an opportunistic omnivore capable of ingesting both vegetal and animal materials, with a predominance of vegetal tissues. High values of the feeding index were observed from summer to late autumn; however, lower values were recorded during the wet season.

Diversity and Distribution of the Inland Water Decapods of Sicily (Crustacea, Malacostraca)

The current knowledge of Sicilian inland water decapod malacostracans is scarce and an updated synopsis on species distribution is lacking. Therefore, we reviewed the checklist and recent distribution of Sicilian inland water decapods based on published and unpublished records and novel observations with the aim of providing an exhaustive repository, also to be used as a sound baseline for future surveys. Overall, five native decapod species occur in the study area, i.e., the atyid shrimp Atyaephyra desmarestii, the palaemonid shrimps Palaemon adspersus, P. antennarius, and P. elegans, and the freshwater crab Potamon fluviatile, and their current local distributions are described. In addition, three alien species were recorded: the common yabby Cherax destructor and the red swamp crayfish Procambarus clarkii, strictly linked to inland waters, and the Atlantic blue crab Callinectes sapidus, a mainly marine species that can also colonise the lower stretches of rivers and coastal brackish waters. The collected data suggest the existence of a partial segregation of native versus non-native species, with the latter currently confined to coastal water bodies and the lower stretches of rivers. Moreover, the exclusively freshwater caridean A. desmarestii and P. antennarius show a parapatric distribution in the study area, which may suggest the existence of mutual exclusion phenomena. The results obtained raise some concerns about the effects of alien species on the native biota, and dedicated monitoring and management strategies should be implemented in order to better understand and mitigate their impact.

The Mitochondrial Genome of the Freshwater Crab Potamon fluviatile, the First Sequenced Representative of the Subfamily Potaminae and Its Phylogenetic Position within Potamidae

This paper reports the mitogenome of Potamon fluviatile collected from the Maltese islands, representing the first such study on species from the subfamily Potaminae. The mitogenome was analysed through next-generation sequencing and annotated. The genome was found to contain 37 genes that include 13 protein coding genes, 22 tRNA genes, two rRNA genes and a non-coding region. The gene order was compared to that of other Potamidae species, while protein coding and rRNA genes were used to evaluate the phylogenetic position of Potamon with other species of freshwater crabs. This study contributes to the genetic resources available for the genus Potamon.

Reproductive behaviour of the North African freshwater crab Potamon algeriense (Bott, 1967) (Brachyura: Potamidae)

ABSTRACT Laboratory and field observations of courtship, copulation, spawning, incubation, and maternal care were made on the endemic North African freshwater crab Potamon algeriense. Mating occurred throughout the year but no discernible courtship behaviour was recorded. However, a forced copulation strategy is practiced by the larger males. The occurrence of ovigerous females extended from June to September with a peak in July (38%). Spawning behaviour took place out of the water and the incubation period lasted 45 ± 2 days. Ovigerous females returned to the stream a few hours before hatching of the eggs. The occurrence of brooding females (females carrying juvenile crabs) extended from July to October, with the highest number in August (36%). Posthatching maternal care was recorded, which lasted between 7 to 10 days before juveniles left their mother’s abdominal cavity for an independent life.

Effects of Physicochemical Variables of Superficial Waters on the Abundance of the North African Freshwater Crab Potamon algeriense (Bott, 1967).

The large number of pollutants discharged into the aquatic environment may influence the physicochemical and biological qualities of the aquatic ecosystem. This study discloses the global quality of the surface waters and the effect of physicochemical variables on the abundance of the African freshwater crab Potamon algeriense inhabiting Zegzel watercourse, a mountain stream in the northeast of Morocco. Physicochemical variables including streamflow, water temperature, pH, dissolved oxygen, suspended matter, chloride, calcium, magnesium, ammonia, nitrite, nitrate, orthophosphate, and organic matter were evaluated monthly for one year (October 2017-September 2018). The evaluation of the physicochemical quality showed that the waters of all the stations studied are between the excellent and good quality classes concerning all the physicochemical variables and highlights also two variations with a tendency towards degradation, one spatial from upstream to downstream and the other seasonal from the wet to the dry period. The abundance of crabs was recorded to exhibit a positive correlation with dissolved oxygen, calcium (N = 44) (p < 0.01), and magnesium. However, a negative correlation has been noticed for streamflow (N = 1) (p < 0.01), water temperature, pH, suspended matter, chloride, ammonia, nitrite, nitrate, orthophosphate, and organic matter. The results obtained reveal that besides the biotic variables, the distribution of P. algeriense also depends on these specific environmental variables.

Links between introduced fish and zooplanktonic and zoobenthic food sources in the food webs of two reservoirs of a semi-arid zone in Algeria

Few studies have focused on the trophic functioning of the reservoirs in Algeria. The study of the gut contents of fish species, as well as the analysis of the stable isotopes of 13C and 15N in the environment, were carried out on samples collected during spring 2010 in two reservoirs: Ghrib and Harreza of the upper Cheliff plain (Algeria) within a semi-arid climate zone. In each of the reservoirs, 13C and 15N were measured in sediments, particulate organic matter (POM), macrophytes, zooplankton, zoobenthos and fish. The isotopic analysis shows that the carbon values that supply both reservoirs, Ghrib and Harreza, were −31.16 ± 0.05 < 13C < −18.01 ± 0.21‰ and −30.82 ± 0.07 < 13C < −17.24 ± 3.50‰, respectively. The carnivorous fish Sander lucioperca, and Abramis brama, an omnivorous fish, were allocated to the top of the food web in Ghrib and Harreza reservoirs, respectively. In the latter, a reservoir with low hydrodynamism and depth, the food web is simpler with a single fish species, which benefits from both benthic and pelagic sources. In Ghrib, a deeper dam with stronger hydrodynamics, only the riverine crab Potamon algeriense exploits the benthic sources, whereas fish mainly feed on zooplankton.

Habitat separation of the crab potamon potamios and the crayfish pontastacus leptodactylus in Lake eğirdir, Turkey

Freshwater decapods rarely co-occur. The crab Potamon potamios and the narrow-clawed crayfish Pontastacus leptodactylus complex usually do not share the same pond even if they live in sympatry. An exception, however, is Lake Eğirdir (Turkey), where both species are present. The aim of our study was to analyze the distribution patterns of the two species in this large lake in more detail, to better understand their ecological roles and possible interaction patterns. Our study indicated a strong segregation between the species, with crabs almost exclusively inhabiting the lake’s shore area. Although the crab populations seem to have diminished recently (the reason is still unclear), they still defend this region against crayfish. More than half of the crayfish specimens and more than one quarter of the crabs had at least one melanized spot, which could be a symptom of the crayfish plague (Aphanomyces astaci). Measures are needed to guarantee the survival of indigenous crabs, which are impacted by several threats.

A freshwater crab Potamon (Brachyura: Potamidae) from the middle Miocene Lake Bugojno (Gračanica, Bosnia and Herzegovina), with notes on potamid taphonomy

The middle Miocene site of Gracanica in Bosnia and Herzegovina, where limnic sediments of the former Lake Bugojno are exposed, yielded remains of a crab. The single specimen represents a freshwater brachyuran classified in the open nomenclature as Potamon sp. With an age of ~ 15 Ma, the Gracanica specimen is the oldest Potamon occurrence from southern Europe. An articulated female individual with preserved pereiopods suggests autochthonous or parautochthonous nature of the specimen. Presence of cuticular disks in the studied specimen confirms that these structures, previously identified in decayed crab specimens in actualistic taphonomic experiments, can be preserved in the fossil record. If found isolated, the disks may confirm the presence of decapods in studied assemblages and can be considered an additional tool for identification of otherwise rare freshwater crab fossils.

Multiple Pleistocene refugia and repeated phylogeographic breaks in the southern Caspian Sea region: Insights from the freshwater crab Potamon ibericum

AbstractAimPhylogeographic studies on a number of Western Palaearctic taxa imply that the southern Caspian Sea region served as a refugium during the Last Glacial Maximum (LGM). Nevertheless, the LGM biogeography of the terrestrial and freshwater organisms in this region is poorly understood. By studying phylogeography of a species of freshwater crab, we unravel the location of probable local refugia and colonization patterns across this topographically complex landscape.LocationSouthern Caspian Sea region.TaxonThe freshwater crab Potamon ibericum.MethodsWe inferred the demographic history of Potamon ibericum using 163 mtDNA Cox1 sequences from 16 localities. For a subset of specimens, we amplified mtDNA 16S and four nuclear markers (28S, Histone3, Enolase, NaK) to confirm the phylogeographic structure. We tested Pleistocene expansion–contraction dynamics, using species distribution modelling (SDM) and assessed morphological variability by geometric–morphometric methods.ResultsMitochondrial markers revealed the existence of three parapatrically distributed lineages in the western, central and eastern parts of the region. The more conserved nuclear markers did not reflect this. The SDM revealed the fundamental niche expansion of P. ibericum along the southern Caspian Sea during the LGM, agreeing with results from the Cox1 data of demographic expansions. Despite strong morphological resemblance, geometric–morphometrics elucidated clinal carapace shape variation.Main ConclusionsConsidering the Caspian Sea level fluctuations during the late Pleistocene, we hypothesize a scenario of demographic contraction during interglacial/warmer conditions, due to the Caspian Sea transgression and latitudinal range shift within the narrow distribution of the species between the southern Caspian Sea and northern slopes of the Alborz Mountains. During the glacial periods, the sea regressed and moist and warm conditions, characterizing glacial refugia, became prevalent in the region and caused isolated populations to expand. Our study confirms the deep transverse phylogeographic break, previously identified for Darevskia lizards in the region, and adds support to the presence of several LGM refugia in the southern Caspian Sea region.

Morphometric characterization of the freshwater crab Potamon elbursi Pretzmann, 1962 in the Caspian Sea and Namak Lake hydrographic systems

The freshwater crab Potamon elbursi Pretzmann, 1962 is widely distributed in northwestern Iran, occurring in two separate hydrographic systems, one draining into the Caspian Sea and a second into Namak Lake. A total of 192 specimens from the two drainage systems were analyzed: 122 specimens from the Caspian drainage and 70 specimens from the Namak Lake drainage. Fourteen measurements of body dimensions were taken for traditional morphometric analyses, and eight landmarks and two semi-landmarks from the carapace were used for geometric-morphometric analyses. Morphometric analyses were performed with the aid of SPSS ver. 22 and geometric analyses using PAST ver. 2.14 and MorphoJ ver. 1.06d software. Adults and juveniles were separated using the K-means method, and puberty-size calculations revealed females reach morphometric puberty at smaller sizes than males. Sexual size dimorphism (SSD) and allometric growth findings revealed that males have longer carapaces, higher body height, and larger chelae, probably due to optimizing mating with females, whereas females have broader pleonal somites and a wider posterior carapace, likely because of more energy investment in egg care and reproduction. Although separate comparison of sexes between the two drainages showed no significant differences between females (in traditional morphometry), population comparisons (excluding pleonal characters) provide evidence for a significant distinction with partial overlapping. Poor dispersal ability and philopatric behaviour, as often known to occur in freshwater crabs, is probably responsible for such intraspecific differentiation in P. elbursi.

Life history traits and patterns of sexual dimorphism in the freshwater crab Potamon ibericum (Bieberstein, 1809) (Decapoda: Brachyura: Potamidae) from the western Alborz Mountains, Iran

The assessment of life history traits can help to better understand the population dynamics of the respective species. We present some life history traits of the freshwater crab Potamon ibericum (Bieberstein, 1809) from the western Alborz Mountains, Iran. Carapace size at the onset of morphometric maturity was estimated using the breakpoint of the relative growth of the chela and abdomen in males and females, respectively, by implementing piecewise linear regressions. In order to quantify variations in the estimated breakpoint, a bootstrap resampling method was applied. Allometric trajectories of chelar dimensions were also applied to juveniles and adults. Sexual size dimorphism was evaluated using the dimensions of the carapace and chelae, and patterns of the carapace shape dimorphism were investigated by implementing geometric morphometric analysis. The results showed that females reach morphometric maturity at smaller sizes than males, which could be of advantage in the fluctuating environment of their freshwater habitat in order to mate as soon as possible and increase fecundity. Positive allometric trends in the length of the major chela was observed in adults of both sexes, and the possible adaptive forces on the evolution of this pattern are discussed. Results of sexual dimorphism analyses confirmed male-biased sexual size dimorphism and functional adaptation of carapace shape in both sexes.

The late Pleistocene origin of the Italian and Maltese populations of Potamon fluviatile (Malacostraca: Decapoda): insights from an expanded sampling of molecular data

Evidence available for most inland water and terrestrial organisms highlights the significant role played by southern Italy, Sicily and the Maltese islands as refuges during Pleistocene climatic fluctuations. However, to date, the hypothesis that these areas may have acted as Pleistocene refugia for the freshwater crab Potamon fluviatile has not been explicitly tested, and a recent origin of local P. fluviatile populations was proposed on the basis of a small set of analysed molecular data. We have thus expanded the currently available data set on the population genetic structure of P. fluviatile through dedicated samplings in Sicily (Italy, 18 specimens), the Maltese Islands (Malta, 15 specimens) and the island of Corfu (Greece, seven specimens), with the explicit aim of testing the role of southern Italy, Sicily and the Maltese archipelago as refugia where early Pleistocene or pre-Quaternary populations of the freshwater crab could have persisted to date. Based on the analysis of both novel and published cytochrome c oxidase subunit I (COI) sequence data, we gathered evidence supporting a recent origin of the southern Italian, Sicilian and Maltese populations of Potamon fluviatile from the Balkans, thus rejecting the hypothesised Pleistocene persistence in the area of pre-existing local populations of the same species.

Acclimatization and Feeding of Zoea Larvae of Mud Crab Potamon Ebonyicum (Crustacea: Decapoda: Potamidae) in South-East Nigeria

Acclimatization and Feeding of Zoea Larvae of Mud Crab Potamon Ebonyicum (Crustacea: Decapoda: Potamidae) in South-East Nigeria

Food Habits of the American BullfrogLithobates catesbeianusin the City of Kyoto, Central Japan

Abstract: By forced vomiting of stomach contents, we examined the diet of Lithobates catesbeianus inhabiting the city region of Kyoto, central Japan. Among various animal taxa consumed, crustaceans, including Asellota and Oniscoidea in juveniles and introduced American crayfish Procambarus clarkii and native crab Potamon dehaani in adults, occupied the largest proportion in number. In volume, the crayfish and crab also comprised the larger part, and the rest was composed mainly of beetles, bugs, and centipedes. Food habits of L. catesbeianus from Kyoto are characterized by the following points: (1) the frog tends to take a smaller number of larger prey as its body size increases; (2) aquatic prey animals, especially crustaceans, seem to be more important than terrestrial ones; (3) feeding intensity seems to be constant throughout the active seasons, including the breeding season; and (4) vertebrates comprise only very small proportion of the diet, despite their apparent availability, strongly contrasting ...