Mm In Carapace Width Research Articles

Tiwaripotamon keeae sp. nov. (Crustacea: Decapoda: Potamidae), a new miniature species of freshwater crab from the China-Vietnam border in Napo, Guangxi

A new miniature species of freshwater crab from the genus Tiwaripotamon Bott, 1970 (Potamidae), is described from a montane karst area in southern Napo, at the China-Vietnam border. It is the twelfth known species of the genus, and is also the smallest known, with the largest adult specimen observed barely exceeding 20 mm in carapace width. Apart from the small size, features of the eyes, carapace and ambulatory legs further set Tiwaripotamon keeae sp. nov. apart from its congeners. Pairwise genetic distances of the mitochondrial cytochrome oxidase subunit I (COI) gene also support it as a distinct species.

Some data on status of the herd of horsehair crab (<i>Erimacrus isenbeckii</i>) in the northwestern Tatar Strait

The data of trap surveys and observations aboard fishing vessels conducted in the northwestern Tatar Strait (northward from Cape Zolotoy) in 2009–2022 are analyzed. Horsehair crabs dwell along the entire continental coast from Cape Zolotoy in the south to Cape Nakatov in the north, but commercial aggregations with the density on average 232 ind./km2 are concentrated in the southern part of this area (south of 49о N). Seasonal bathymetric migrations of the crab include the fall moving of commercial males from the depths of 10–40 m to the depths of 40–60 m for wintering and their return to shallows in spring. Two dense wintering aggregations are formed usually between Cape Peschany – Cape Mapatsa and southward from 48о00′ N, whereas sparse summer aggregations are widely distributed along the coast. Regardless the season, the aggregations density decreases from south to north. The males are generally larger in the southern aggregations than in the northern ones (on average, 100.3 and 89.8 mm of carapace width, respectively), the difference is statistically significant (p < 0.0001). The stock of horsehair crab in the northwestern Tatar Strait has increased in the last 20 years from136 tons in 2003 to 1580 tons in 2022. Over the past 10 years, the optimal allowable catch in the Primorye subzone north of Cape Zolotoy was utilized less than 50 %. There is no specialized fishery of horsehair crab; the species is caught mainly as bycatch for other shelf crab species. High current level of the stock gives a good background for commercial removal of at least 158 t of horsehair crab without damage to the local population of this species.

Occurrence, infestation rate, and spatiotemporal distribution of the African pea crab (Afropinnotheres monodi) inhabiting Mediterranean mussels (Mytilus galloprovincialis) from southern Portugal

AbstractThe present study aimed to analyze the occurrence and prevalence, infestation rate and intensity, host–guest colonization pattern, morphometric relationships, and spatiotemporal distribution of the African pea crab (Afropinnotheres monodi) inhabiting the shell of Mediterranean mussels (Mytilus galloprovincialis) from the Algarve coast and Ria Formosa lagoon (southern Portugal). Sampling campaigns were performed with a trimestral periodicity in 2018–2019 and comprised 13 collecting sites distributed in the Ria Formosa, along the Algarve coast, and in an offshore mussel farm. Altogether, 10,109 individuals of M. galloprovincialis in a broad range of sizes (9.0–91.2 mm in shell length) were sampled, among which 571 host mussels (14.6–73.6 mm in shell length) contained a total of 598 individuals of A. monodi, corresponding to an infestation rate of 5.6% (prevalence rate of 5.9% due to multiple occurrences). The sample of pea crabs also covered an extensive range of sizes (1.7–14.5 mm in carapace width) and included eight juveniles, 163 males, and 427 females (82 hard females and 345 soft females, of which 128 were non‐ovigerous and 217 ovigerous). Overall, hard (13.9%) and soft (58.5%) females prevailed over males (27.6%), corresponding to female‐biased sex ratio of 1 male:2.6 females. In terms of infestation intensity, 95.4% of host mussels contained a single pea crab, with multiple infestations (two or three crabs inside a single mussel) being more frequent in the lagoon than along the coast. Morphometric relationships between host shell length and pea crab carapace width were highly correlated (r values ranged .218–.631), although there were no significant differences between sexes or female demographic categories and maturity stages. Overall, the present study provided further insights into the colonization of M. galloprovincialis by A. monodi.

Burrow utilization by the Japanese mitten crab <i>Eriocheir japonica</i> in the clay sediment of a freshwater river of Kyushu, Japan

This is the first record of the burrows of the Japanese mitten crab Eriocheir japonica. Morphologies of the burrows found in the clay sediment used by this crab were recorded by excavating them in a small freshwater river in Japan. Only E. japonica was found inside 2 of the 10 burrows examined (15 crabs and one crab, respectively), and the other 8 were empty. Crabs of various sizes (6.1–47.0 mm in carapace width) were collected from inside the occupied burrows. Burrow morphology ranged from single tunnels to complex burrows with multiple openings and tunnels. Openings (2–10 cm in diameter) were mostly located underwater. The single tunnels were 14–65 cm long. Considering the different digging habits of other burrowing animals found in this area, it can be concluded that E. japonica constructed these burrows. Burrows resembled those of the Chinese mitten crab E. sinensis, but were different in their location (freshwater vs. tidal), sediment type (clay vs. sand and silt), opening placement (mainly underwater vs. intertidal) and occupation rate (low vs. high). The low occupation rate suggests that E. japonica do not always rest in their burrows and rather prefer to hide beneath the riverbed’s large rocks. These results reflect the adaptation of E. japonica to the unstable environment of Japanese rivers.

Seasonal variation in population structure and sexual maturity of Sylviocarcinus pictus (Decapoda: Trichodactylidae) in a Neotropical intermittent river

Sylviocarcinus pictus is a South American freshwater crab recently recorded for the first time in the Caatinga biome. Our objective was to characterize the population and reproductive biology of S. pictus from the semi-arid northeastern region of Brazil and verify the influence of seasonal environmental changes in this population. The crabs were collected from a stretch of Guaribas River, PI, Brazil, every month between October 2013 and September 2014. The crabs were identified, sexed and the carapace width (CW) was measured. Physiological sexual maturity was determined based on the gonadal development stage. A total of 178 crabs were obtained (111 males and 67 females), with a sex ratio biased towards males 1.66:1. The number of crabs collected was higher in the months of drought. Males and females reach physiological sexual maturity with 36.80 and 34.20 mm of CW, respectively. The occurrence of individuals with developed or developing gonads throughout the study indicates that these crabs reproduce continuously during the year, although recruitment was higher in February and May. Our results indicate that this population uses a reproductive strategy to optimize its reproductive fitness in an intermittent environment.

Reproductive Biology of Land Crabs (Gecarcoidea lalandii) in Ly Son Island, Quang Ngai Province – Vietnam

The reproductive biology of the land crab Gecarcoidea lalandii was documented for the Ly Son Island, Quang Ngai Province, Vietnam. Approximately 30 crabs, collected every month in the 12-month period from August 2019 to July 2020, were analyzed gonadal development stages, sex ratio, spawning season, fecundity and size at first sexual maturity. Results showed that number of male and female crab in nature was not significantly different. Gonadal of the crab passed through five stages of maturation. The crab spawns continuously during the spawning season. In nature, the crab can mature whole year-round with a higher proportion from January to August and the peak maturation from June to July. The spawning season is of this species is only on the raining period from June to July. Length at first sexual maturity of the crab was 53.91 mm of carapace width for female and 50.39 mm male crab. The absolute fecundity varied in 473,000-820,000 eggs ind-1 and highly related to body weight. The current findings provide the scientific foundation for fishery resource management and artificial breeding of the land crab in Ly Son.

Behavior response of blue swimming crab (Portunus pelagicus) to the different entrance gates of collapsible pot

The behavior of blue swimming crab (BSC) (Portunus pelagicus) to the collapsible pot is observed to redesign the entrance of the pot with high effectiveness. The purpose of this study is to analyze the behavior response of BSC to the entrance gate of the collapsible pot by laboratory experiments. The behavior response of the BSC (100-150 mm of carapace width (CW), n= 15) to the two angles of the entrance gate, that were 200 as control and 400 as a modification of the collapsible pot. The movement and speed of the crab to the entrance gate were observed by using CCTV Camera. The results showed that the percentage of crabs failed to find the entrance was higher than crab that be successful to enter the pot. The crab that failed to find the entrance was 43% for control and 52% for modification pot, while the crab that be successful to enter was 24% for control pot and 19% for modification pot. There were five movement patterns of crab to the pot i.e. straight to entrance, side to entrance, side to side, entrance to side, and straight to side. The average speed of entrance crab was 127.89 ± 46.48 for control, and 88.45 ± 5.74 for modification pot. Keywords: behavior, response, blue swimming crab, collapsible pot, Portunus pelagicus

SIZE AT SEXUAL MATURITY OF NIPA-OBLIGATE CRAB Labuanium politum (CRUSTACEA: SESARMIDAE); HARVESTING PLAN PRECEDING COMMERCIALISATION

Labuanium politum (De Man, 1887) is in demand for consumption in certain parts of Sarawak, Malaysia. It is still in the initial stage of commercialisation as one of the local food sources and for subsistence income. In the interim, questions have been raised on how to reconcile the needs between resource utilisation and conservation. Herein, this study aimed to estimate the size at sexual maturity of L. politum and suggesting possible sustainable harvesting guideline to conserve the natural stocks. A total of 288 individuals comprised 149 males and 139 females, of which 12 were berried, that were examined for the stages of gonad. Size at sexual maturity, SM50 is at 14 mm of carapace width for males and 19 mm for females. The size at sexual maturity estimations fitted with the morphological observations of gonad stage in the current study. Highest frequency of individuals with fully developed gonad were observed in July and August and this suggests the harvesting seasons should be ideal in the preceding months to allow higher success rate in mating. The present study aimed to develop strategies that will ensure a sustainable harvest for this species in Sarawak, Malaysia.

Reproductive biology of the orange mud crab Scylla olivacea (Herbst, 1796) from the Pichavaram mangroves of south-east India

The present study was conducted to assess the size distribution, sex ratio, size at first sexual maturity, fecundity and spawning season of the commercially important orange mud crab Scylla olivacea (Herbst, 1796) in Pichavaram mangroves in south-east India. This study is the first contribution to the knowledge of reproductive biology of S. olivacea from the Indian coast. Size distribution analysis in the fishery revealed the irrational exploitation of undersized S. olivacea. The estimated sex ratio deviated from equality, being 1:0.87, revealing a male domination. Size at first sexual maturity was determined to be 87 mm in carapace width (CW) in females. Fecundity ranged from 1.16 to 3.53 million in females of 76 to 135 mm CW. Breeding takes place year-round with a peak in pre-monsoon, indicating that it is a prolific breeder. Results revealed that immature individuals of S. olivacea contributed significantly to the catches and thus an effective management of the resource by framing minimum legal size is crucial so that the females are allowed to spawn at least once prior to capture.

Population dynamics and development of the rhizocephalan Sacculina carcini, parasitic on the shore crab Carcinus maenas.

The ecologically important shore crab Carcinus maenas is commonly infected in its native range by the rhizocephalan Sacculina carcini. However, several aspects of this host-parasite interaction are poorly understood. Here, we analyse data from approximately 60000 Danish crabs to unravel factors governing infection patterns in time and space, and according to host sex and size. Female crabs were more frequently infected (12.6%) than males (7.9%). Sites with high salinity supported the highest infection prevalence. Infection prevalence peaked in summer (10 to 15%) and winter (20 to 35%) due in part to emergence of virginal externae in summer (main outbreak) and autumn (minor outbreak) preceded by peaks in crabs with lost externa (scars). Younger externae and scars dominated among males, whereas adult externae were most frequent among females. Infection prevalence increased with size in females but decreased in males, and modified (feminized) males showed lower scar frequency than unmodified ones. Modified males occurred frequently among the smaller size classes, whereas unmodified males dominated the larger size classes. Externa size was positively related to host size in both genders (same linear relationship). Molecular analyses suggested that hosts below 16 mm in carapace width do not become infected. Dissections of infected hosts revealed marked reduction of ovaries, whereas testes were unaffected by sacculinization. Our study demonstrates great spatio-temporal variation in infection prevalence mainly related to the parasite's life history. S. carcini appears capable of infecting all host sizes except the smallest. Owing to incomplete feminization of males, infections are rapidly lost from the larger and highly profitable male hosts.

POPULATION BIOLOGY OF Panopeus lacustris DESBONNE 1867 ( BRACHYURA: PANOPEIDAE ) IN PIAUÍ COASTAL, BRAZIL

Os espécimes de Panopeus lacustris foram identificados, separados quanto ao sexo e mensurados para obtenção das seguintes dimensões: largura da carapaça, comprimento da carapaça, altura do corpo, comprimento do maior quelípodo, largura do maior quelípodo, altura do maior quelípodo, largura do abdômen, e comprimento do gonopódio. O tamanho médio da largura de carapaça e o peso médio diferiram estatisticamente entre os sexos. Os machos foram mais frequentes na classe 22,41 |-- 25,75, e as fêmeas na classe 19,06 |-- 22,41. Os dados biométricos foram submetidos a uma regressão, utilizando-se uma função do tipo potência (y=axb). A LC com a qual ocorre a maturação sexual morfológica é de 12,32 mm em machos e de 12,00 mm em fêmeas. Constatou-se que 50% dos machos apresentam-se maduros fisiologicamente com 11,35 mm de LC e as fêmeas com 10,61 mm. A razão sexual para o total de caranguejos examinados foi 1:1,15 (machos:fêmeas). Os dados coletados sugerem que o período reprodutivo dessa espécie é contínuo. Os resultados encontrados no presente estudo são comuns para populações de Brachyura, e indicam que a população de P. lacustris se encontra estável no ambiente.

Successful Identification and Discrimination of Hatchery-Reared Blue Crabs (Callinectes sapidus) Released into the Chesapeake Bay Using a Genetic Tag

ABSTRACT Before animals reared in captivity can be used as a model for study or as a supplement for wild populations, it is important to demonstrate that they can integrate with high success and without adversely affecting the natural population. For the blue crab Callinectes sapidus (Rathbun, 1896), coded wire tags have been used to positively discriminate hatchery-raised individuals from wild. This technique can be prohibitively expensive, however, due to high start-up costs and manpower needs during implantation, and mortality as a result of the tagging process is also a consideration. To reduce costs and increase the number of possible individuals monitored per unit effort, the suitability of the mitochondrial gene nad2 as a genetic tag to identify hatchery-produced crabs was tested. Batches of juvenile crabs approximately 20 mm in carapace width were implanted with wire tags and released into a variety of locations in the upper Chesapeake Bay. Juveniles were later recaptured from release sites and sc...

Growth and Longevity of the Red Rock CrabCancer productus(Randall, 1840)

ABSTRACT Although the native red rock crab Cancer productus is an important component of Pacific northwest nearshore communities and recreational crab fisheries, little is known about its life history. Growth in crustaceans is incremental and age classes overlap, making these investigations difficult. An array of techniques was used to estimate growth and longevity of C. productus in a marine preserve at the University of Washington Friday Harbor Laboratories. These included size-frequency distribution analysis of young crabs in their nursery habitat, growth inside cages, and mark-recapture studies. The growth rate in C. productus varies greatly, with adult males exhibiting greater molt increments and molt frequencies than females. For crabs less than 80 mm in carapace width, males and females grow at the same rate: attaining 30–65 mm carapace width at age 1, and 60–95 mm at age 2. Maximum carapace widths of males and females were 171 and 150 mm, respectively, and maximum longevity is estimated to be at l...

Population Biology of Uca maracoani in a Tropical Mangrove

The aim of the present study was to characterize the population dynamics of the fiddler crab Uca maracoani in a mangrove area of the Formoso River, state of Pernambuco, northeast of Brazil. Samplings were performed monthly (April 2009 to March 2010) by one collector during 30 min at the low tide. A total of 1198 individuals (753 males and 445 females) were sampled, and all of them had measured the carapace width (CW), the major cheliped propodus length of males (CPL) and the abdomen width of females (AW). Sex and the ovigerous condition were recorded. Mean size of males (CW) (22.9 ± 6.61 mm) was significantly greater than that of females (20.2 ± 5.2 mm). Morphological sexual maturity estimated for males and females was 15.8 and 13.8 mm of CW, respectively. In the size-frequency distribution of both sexes, the population showed two cohorts, consisting of a juvenile group and an adult group. Sex ratio was diverted in favor of males (1.6:1.0), and males were more frequent in larger size classes. The reproductive period was based on the low rate of ovigerous females found throughout the year, occurring from June to August 2009. The recruitment was continuous throughout the year, but more intense during spring. Results of the present study are the first recorded from the state of Pernambuco and not only enabled a better comprehension of the population biology of U. maracoani along its latitudinal distribution, but also allowed to observe the population stability in the Formoso River mangrove.

Hábitat y historia de vida de Pachychelles laevidactylus (Crustacea, Anomura, Porcellanidae) en el intermareal rocoso de Mar del Plata, Argentina

RESUMEN Se analizó la estructura del hábitat, el crecimiento relativo, la heteroquelia, la estructura poblacional, la madurez morfométrica y la fecundidad de Pachycheles laevidactylus Ortmann, 1892, durante Abril, Mayo y Junio del 2005, en sustratos naturales de Mar del Plata, Argentina (38°02'S, 57°31'W). La cobertura algal, la exposición al oleaje y el tiempo de inmersión varió de manera significativa entre estratos y entre meses. La morfometría de las quelas no manifestó diferencias entre sexos. Las hembras mostraron el abdomen más grande que los machos. Si bien existió la heteroquelia, no se detectó lateralidad. Las tallas (ancho de caparazón) estuvieron comprendidas entre 0.67 mm a 9.3 mm para los machos, y entre 1.07 mm a 10.65 mm, para las hembras. La densidad de organismos varió entre meses y entre los estratos. La estructura poblacional, para el periodo de estudio, se explicó en función de la estructura del hábitat. La madurez morfométrica de las hembras fue registrada a los 4.38 mm de ancho de caparazón. El número de huevos se correlacionó positivamente con la talla de las hembras ovígeras con un mínimo de 2 huevos y un máximo de 160, pero esa relación dependió del avance en el desarrollo de los embriones.

Amphipods as potential prey of the Asian shore crab Hemigrapsus sanguineus: Laboratory and field experiments

The invasive crab Hemigrapsus sanguineus has a generalist diet, consuming primarily macroalgae and sessile and sedentary invertebrate prey. To assess the dietary importance of motile prey, predation by H. sanguineus on the amphipod Hyale plumulosa was examined in laboratory and field experiments. Male and female crabs 7–27mm in carapace width were offered H. plumulosa in laboratory microcosms with and without sediment (sand and rocks) present. Despite sex differences in claw morphology, male and female H. sanguineus consumed similar numbers of amphipods. Large crabs of both sexes consumed fewer H. plumulosa than small crabs, and consumption was lower when sediment was present. Crab abundance was then manipulated in the field in randomized complete block experiments in the lower rocky intertidal zone. In three 14-day experiments, H. sanguineus had no negative effect on amphipod abundance. In fact, excluding crabs from cages led to lower amphipod densities. The results of the 2-species predator–prey laboratory experiments did not transfer to the natural environment, suggesting that complex interactions exist between H. sanguineus and motile amphipod prey in rocky intertidal areas.

Abundance of non-native crabs in intertidal habitats of New England with natural and artificial structure.

Marine habitats containing complex physical structure (e.g., crevices) can provide shelter from predation for benthic invertebrates. To examine effects of natural and artificial structure on the abundance of intertidal juvenile crabs, 2 experiments were conducted in Kingston Bay, Massachusetts, USA, from July to September, 2012. In the first experiment, structure was manipulated in a two-factor design that was placed in the high intertidal for 3 one-week periods to test for both substrate type (sand vs. rock) and the presence or absence of artificial structure (mesh grow-out bags used in aquaculture, ∼0.5 m2 with 62 mm2 mesh openings). The Asian shore crab, Hemigrapsus sanguineus, and small individuals of the green crab, Carcinus maenas, were observed only in the treatments of rocks and mesh bag plus rocks. Most green crabs were small (<6 mm in carapace width) whereas H. sanguineus occurred in a wide range of sizes. In the second experiment, 3 levels of oyster-shell treatments were established using grow-out bags placed on a muddy sand substrate in the low intertidal zone: mesh grow-out bags without shells, grow-out bags with oyster shells, and grow-out bags containing live oysters. Replicate bags were deployed weekly for 7 weeks in a randomized complete block design. All crabs collected in the bags were juvenile C. maenas (1–15 mm carapace width), and numbers of crabs differed 6-fold among treatments, with most crabs present in bags with live oysters (29.5 ± 10.6 m−2 [mean ± S.D.]) and fewest in bags without shells (4.9 ± 3.7 m−2). Both C. maenas and H. sanguineus occurred in habitats with natural structure (cobble rocks). The attraction of juvenile C. maenas to artificial structure consisting of plastic mesh bags containing both oyster shells and living oysters could potentially impact oyster aquaculture operations.

Top-down vs. bottom-up drivers of recruitment in a key marine invertebrate: investigating early life stages of snow crab

AbstractMany snow crab fisheries have fluctuated widely over time in a quasi-cyclic way due to highly variable recruitment. The causes of this variability are still debated. Bottom-up processes related to climate variability may strongly affect growth and survival during early life, whereas top-down predator effects may be a major source of juvenile mortality. Moreover, intrinsic density-dependent processes, which have received much less attention, are hypothetically responsible for the cycles in recruitment. This study explored how climate, larval production, intercohort cannibalism and groundfish predation may have affected recruitment of early juvenile snow crab in the northwest Gulf of St Lawrence (eastern Canada) over a period of 23 years. Abundance of early juvenile snow crabs (2.5–22.9 mm in carapace width), representing the first 3 years of benthic life, came from an annual trawl survey and was used to determine cohort strength. Analyses revealed a cyclic pattern in abundance of 0+ crabs that may arise from cohort resonant effects. This pattern consisted of three recruitment pulses but was reduced to two pulses by age 2+, while the interannual variability of cohort strength was dampened. This reconfiguration of the earliest recruitment pattern was dictated primarily by bottom water temperature and cannibalism, which progressively overruled the pre-settlement factors of larval production and surface water temperature that best explained abundance of 0+ crabs. The results strongly suggest that bottom-up and density-dependent processes prevail over top-down control in setting the long-term trends and higher-frequency oscillations of snow crab early recruitment patterns.

Studies on the Prevalence of Sacculina Spp. Infestation in Portunus Sanguinolentus (Herbst, 1783) from Parangipettai Coastal Waters, Southeast Coast of India

The presence of the external sacs on parasitic barnacles is the most unusual characteristic found in these genera. This barnacle belongs to genus rhizocephala that parasitizes crabs. Parasitization by sacculinids induces severe modifications in morphology, behavior and reproduction of their host (Brachyuran crabs: Portunus sanquinolentus). The present field study was carried out two landing center from Annankoil and Mudasalodai during January 2011– December 2011. It was found that total catch of infected crab was 12.4% from Annankoil and Mudasalodai landing center. The frequently infected male and female crab ratio was 66.3% and 33.7%. External parasites were found on crabs ranging from 56 mm to 88 mm in carapace width.

Gonadal development in the freshwater crab Sylviocarcinus pictus (H. Milne Edwards, 1853) (Brachyura: Trichodactylidae) from the Guamá river, state of Pará, Brazil

The development stages of male and female gonads in the freshwater crab Sylviocarcinus pictus (H. Milne Eduards, 1853) were described through macroscopic and microscopic (histology) examinations. The histological description was based on 40 specimens (20 each sex). Four gonadal development stages were found for females: immature, ripening, mature and spawned. The following female cells were found: ovogonia, oocytes in initial vitellogenesis, oocytes in advanced vitellogenesis, follicular cells and post-ovulatory follicles. Three development stages were found for males: immature, maturing and mature, with the indication of: spermatogonia, spermatocytes, spermatids, spermatozoids and spermatophores. These data suggest the pattern described in the literature. Size at sexual maturity was 32.3 mm of carapace width for males and 31.5 mm for females. The gonadal stages observed macroscopically by volume and color were validated through histological analysis and proved to be useful method for the rapid identification of sexual maturity in the species. The present study offers previously unpublished data on the reproductive biology of Sylviocarcinus pictus.