Mangrove Crab Research Articles

The Effect of Different Moon Phases to the Dynamics of Total Cholesterol and Glycogen Content of Mangrove Crab (Scylla Olivacea) Cultured with Silvofishery System

The Effect of Different Moon Phases to the Dynamics of Total Cholesterol and Glycogen Content of Mangrove Crab (Scylla Olivacea) Cultured with Silvofishery System

Fine-scale conditions across mangrove microhabitats and larval ontogeny contributes to the thermal physiology of early stage brachyurans (Crustacea: Decapoda).

Most marine ectotherms require the successful completion of a biphasic larval stage to recruit into adult populations. Recruitment of larvae into benthic habitats largely depends on biological interactions and favourable environmental conditions such as the inescapable diurnal thermal and tidal exposures. Hence, assessing how different taxa metabolically respond to variations in temperature is imperative to understand the community and ecosystem dynamics at both local and global scales. The present study aimed to investigate the effects of acute temperature variation on the physiology of stage-specific brachyuran larvae collected from different microhabitats at two mangrove forests in South Africa. Results indicate that the conditions within microhabitats, which larvae experience, likely influence their physiology, based on respirometry, to short-term acute temperature exposures. Furthermore, the larval thermal optimum shifted ontogenetically to become increasingly eurythermic as individuals developed from stage I zoea through to megalopa. Mangrove crab larvae in their early stages are hence increasingly vulnerable to acute temperature exposures, which could be particularly harmful to the persistence of populations if thermally stressful events increase in magnitude and frequency.

Leaf-litter consumption slows crab growth but transforms mangrove food chains

Leaf litter consumption has implications for growth and nutrient balances of mangrove crabs and mangrove trophic pathways. This study (1) addressed the impact of leaf litter quality and quantity on crab life history and growth, and (2) proposed keystone roles of crabs in mangrove material fluxes. Estimates of crab standing stocks, growth, and carbon and nitrogen mass balances were obtained for a field population of Parasesarma messa, a primary consumer of leaf litter in Queensland mangroves. P. messa exhibited slow growth and individuals took >>4 yr to reach maximum size. Females appeared to breed once per year with high reproductive effort relative to other crabs. An apparent trade-off between growth and reproduction in the dry-wet transition season was caused by a shortage of available leaf litter. A nitrogen mass balance indicated that the population ingested twice the amount of nitrogen that could be supplied by leaf litter. Assuming mortality was mainly due to predation, the estimated loss to predators (28 kg ha-1 yr-1) supported a hypothesis that crab consumption by fish short-circuits mangrove food chains. Faecal production by crabs (0.48 Mg C ha-1 yr-1 and 0.03 Mg N ha-1 yr-1) represents a substantial contribution to deposit-feeding food chains. P. messa is a keystone species whose impact on ecosystem processes is large relative to its abundance and biomass.

Development Strategy of Mangrove Crabs (<i>Scylla</i> sp.) Cultivation in Gorontalo Province

Mangrove crabs (Scylla sp.) are important economic fishery commodities that will be developed in Gorontalo Province. Mangrove crabs have large and prospective market opportunities in the domestic and foreign market. The mangrove crabs demand in this country is very high. Market demand for mangrove crabs has not been able to be fulfilled, because of the limited catch and the production of aquaculture which is still very minimal. The problem is how the development of mangrove crab cultivation will be applied in Gorontalo Province. The purpose of this research was to study and determine the development strategy of mangrove crab cultivation in Gorontalo Province in accordance with the potential and carrying capacity of the environment. The researched method was survey method with observational data collection and random sampling techniques. Data analysis was performed descriptively and SWOT analysis. Based on the SWOT analysis the strength (S) most influential on the development of mangrove crab culture in Gorontalo Province is government support and profitable business prospects (0.66), while the biggest weakness is the limited capital (0.54) and the low quality of human cultivation resources (0,48), and the biggest opportunity (O) is economic value (Very popular, because it is delicious and contains high nutritional value) (0.8), and threat (T) environmental degradation (0.8). Based on the quadrant of the analysis is in quadrant 1 (Growth Oriented Strategy). Keywords: Development, Strategy, Scylla spp, Cultivation, Gorontalo Province

Pembuatan pakan alami untuk pengembangan kepiting cangkang lunak di Desa Pulau Cawan Kecamatan Mandah kabupaten Indragiri Hilir

Mud crabs are mangrove crabs that are cultivated and harvested when molting so that their shells become soft and easy to consume. The purpose of this activity is to increase people's income in Desa Pulau Cawan, Kecamatan Mandah, Kabupaten Indragiri Hilir, through soft shell crab cultivation by introducing environmentally friendly cultivation techniques, but it can produce added value in terms of improving the family's economy through soft-shell crab cultivation, one of which is training in making natural feed. This is based on information from farmers who have never received training on feed manufacturing. Through the foster village program, knowledge and technology are given about techniques for making natural feed from lime water and spinach extract as a substitute for vitamalt which is quite expensive. The methods used in the Community activities of the foster Village are lectures, discussions and direct practice with POKDAKAN, starting with the preparation of spinach extract, trash fish, lime water, mixing and drying. The results of the evaluation of the counseling participants showed that 24 participants had never known about making natural feed from lime water and spinach extract as soka crab feed. After participating in this training activity there was an increase of 86.96% in knowledge about how to make natural feed. The partner's assessment of the implementation of this activity is 52.17% strongly agree that this natural feed can be made independently; 52.17% strongly agree that giving lime water and spinach extract to the artificial feed mixture of trash fish has an effect on the acceleration of the molting process in crabs and does not affect the survival of crabs; 60.87% strongly agreed that it could be an alternative livelihood; strongly agree that the molting process in soft-shell crab cultivation is the same as when the crabs are given a vitamolt, which is 20 days.

Spatio-temporal variability of Brachyura larval assemblages in mangroves of the Gulf of Guayaquil’s inner estuary

Mangroves are the dominant coastal vegetation in tropical estuaries and host a large diversity of brachyuran crabs. Crab larvae have adapted to dynamic hydrological conditions in estuaries using several physiological and behavioral strategies. Changes in crab larval assemblages can be monitored in time in order to detect ecological changes occurring within estuaries. For this study, we sampled quarterly crab larval assemblages in two sub-estuaries (Salado and Churute) of the Gulf of Guayaquil (GG) during 2016–2017. The largest community dissimilarities occurred between sub-estuaries, with Salado having higher morphological diversity and larval densities than Churute. Temporal patterns were only evident within each sub-estuary, and in relation to total and individual morpho-species density values. Ocypodidae larvae were dominant across samples; with zoea I of the red mangrove crab (Ucides occidentalis) showing maximal density values during spring tides. Hydrological parameters (i.e., turbidity, conductivity, salinity and temperature) contributed to only 19% of the variability in biota, demonstrating that crab larvae are physiologically adapted to a wide range of water conditions. This study established an ecological baseline for future studies using crab larval assemblages in the assessment of ecological changes occurring in mangrove tidal creeks of the GG. However, longer time-series monitoring data and description of new species and stages of crab larvae are necessary to better assess potential future changes.

Economic Valuation of Mangrove Forest in Tanakeke Island, Takalar District, South Sulawesi Province

Mangrove forests on Tanakeke Island provide many benefits, both direct and indirect benefits. All the benefits received/enjoyed by the community so far have never been calculated/valued in money so sometimes the community does not realize how much value is actually given by this mangrove forest and how much it contributes to their income. Resource economic valuation is a method used to estimate the monetary value of goods and services provided by mangrove forest resources. The purpose of this study was to determine the total economic value of the benefits of mangrove forests on Tanakeke Island. The total economic value of the benefits of mangrove forests is derived from the value of direct benefits (tree, firewood, charcoal, seaweed stake, fish and mangrove crabs), indirect benefits (anchoring abrasion and intrusion), optional benefits, existence benefits and inheritance benefits. Based on the results of calculations, the total economic value of mangrove forests on Tanakeke Island is Rp73,563,108,250.00/year or Rp127,492,388.00/ha/year. Direct benefits provide the greatest value of Rp44,173,560,000.00/year (60.05%), then indirect benefits of Rp14,257,696,532.00/year (19.38%), the benefit of being Rp10,597,566,668.00/year (14.41%), the inheritance benefit of Rp4,417,356,000/year (6.00%) and optional benefits of Rp116,929,050/year (0.16%).

Biochemical composition and caloric values of different body segments of the female mangrove crab (Scylla olivacea)

Biochemical composition and caloric values of different body segments of the female mangrove crab (Scylla olivacea)

Checklist of brachyuran mangrove crabs of Kerala, India

Checklist of Brachyuran mangrove crabs from Kerala, west coast of India has been listed in this paper with re-validation of nomenclature since many of the crab species has been re-named so far and no report has been made from Kerala mangroves. A total of 18 truly mangrove crabs were identified from different mangroves associated with estuaries along western coastline of Kerala state. Among which 4 crab genera were re-named and re-validated and all species were photo-documented during the present study. The paper enlists the taxonomic account of the true mangrove crabs known so far from Kerala mangrove ecosystems

Habitat, Sexual and Allometric Influences on Morphological Traits of Intertidal Crabs

Intertidal crabs display distinct morphological traits that allow differential interactions with biotic and abiotic features of the intertidal landscape, but are also influenced by allometry and sexual selection. This study aimed to explore the influence of sexual, allometric and habitat factors on morphological variation in the intertidal mangrove crab assemblage. A standardized photographic protocol was developed using readily available, low-cost technology to capture the morphology of carapaces and claws as sets of Cartesian landmarks. Digitization errors were 1 to 2 orders of magnitude smaller than the variation among individuals. In Tubuca seismella and Tubuca signata (superfamily Ocypodoidea), species that have traditionally been studied for sexual dimorphism, standardized major claw sizes were 2.8 and 3.7, respectively, times larger for males than females. Sexual dimorphism in claw size was also observed for Metopograpsus frontalis and Parasesarma longicristatum (superfamily Grapsoidea), with the largest claw in males being 15% and 33%, respectively, larger than in females. In contrast to size, claw shape did not relate to sex, except for T. seismella. Carapace shape, although variable among individuals and displaying asymmetry, was unrelated to sex. Claw and carapace shapes displayed high correlations, with values around 0.78. Carapace shapes grouped into taxonomic families and linked to habitat preferences, while claw shapes varied along a taxonomic gradient. These results complement studies on crab morphology that focus on specific factors or species, and stress the importance of multiple, interacting factors including sexual, allometric and habitat influences as drivers of morphological trait variability.

Gonadal Development of Tree-Climbing Mangrove Crab Episesarma mederi (H. Milne Edwards, 1853) from Capiz, Philippines

Gonadal Development of Tree-Climbing Mangrove Crab Episesarma mederi (H. Milne Edwards, 1853) from Capiz, Philippines

Microplastic Ingestion by Periwinkle Snail Littoraria scabra and Mangrove Crab Metopograpsus quadridentata in Pramuka Island, Jakarta Bay, Indonesia

Microplastic has been known to contaminate our marine environment. This research aim was to determine the abundance of microplastic in mangrove periwinkle snail Littoraria scabra and mangrove crab Metopograpsus quadridentata in Pramuka Island, Jakarta Bay, Indonesia. Pramuka Island was chosen as the research site because this island is densely populated and received waste from Jakarta Bay. Samples of mangrove snails were taken by purposive random sampling method of 10 individuals with shell lengths ranging from 1.5 to 2.7 cm, and 9 individuals crab with circa 6 cm carapace wide were collected. Analysis of microplastic abundance was done by isolating microplastic in each sample. Isolation in the sample was done by dissolving tissue of animals in a 65% nitric acid (HNO3 ) solution for 24 h and sodium chloride (NaCl) was added to increase density of solution. Sample was observed under microscope. The results obtained 3 types of microplastic found in the body of snail (fiber, film, and fragment) and 4 types in crab (fiber, film, fragment, and granula). Fiber has the highest percentage in snail (66.89%) and crab (68.72%). The average of microplastic abundance were 86.88 particles/individual in snail and 327.56 particles/individual in crab, respectively. This result indicated that the coastal area of Pramuka Island has been polluted by the microplastics. There was positive correlation between microplastic abundance and the body weight of snail (r=0.9778), and body weight of crab (r=0.9193).

Natural Recovery of the Crab Ucides cordatus (Ocypodidae) in Replanted Mangroves on the Brazilian Amazon Coast

The recovery of degraded mangroves may favor the reestablishment of the diversity and abundance of benthic organisms, including those of commercial importance. Here, we assessed (i) the degree of population recovery of the exploited mangrove crab Ucides cordatus in nine areas of replanted mangroves, and (ii) the influence of dominant mangrove species on density and population parameters of this species. Our results indicate that the U. cordatus population has been reestablished successfully in all replanted areas. A total of 1620 inhabited burrows (1.8 ± 0.5 burrows m−2) were counted, and 423 crabs were captured (57.7% males and 42.3% females). Almost a third (33.2%) of the male crabs was of legally harvestable size (6.4 ± 0.3 cm carapace width), while the others (66.8%; 5.0 ± 0.8 cm) can be considered for future fishery. The densities of burrows were higher in areas dominated by R. mangle and L. racemosa. Both males and females were larger in areas dominated by L. racemosa, while they were heavier at the sites dominated by R. mangle and L. racemosa. The return of the local crab population exhibiting density and structure similar to those found in preserved habitats highlights the success of the rehabilitation of impacted mangroves.

Osmotic and ionic regulation, and modulation by protein kinases, FXYD2 peptide and ATP of gill (Na+, K+)-ATPase activity, in the swamp ghost crab Ucides cordatus (Brachyura, Ocypodidae).

We analyzed the modulation by exogenous FXYD2 peptide and by endogenous protein kinases A and C, and Ca2+-calmodulin-dependent kinase, of gill (Na+, K+)-ATPase activity in the semi-terrestrial mangrove crab Ucides cordatus after 10-days acclimation to different salinities. Osmotic and ionic regulatory ability and gill (Na+, K+)-ATPase activity also were evaluated. (Na+, K+)-ATPase activity is stimulated by exogenous pig kidney FXYD2 peptide, while phosphorylation by endogenous protein kinases A and C and Ca2+/calmodulin-dependent kinase inhibits activity. Stimulation by FXYD2 and inhibition by protein kinase C and Ca2+/calmodulin-dependent kinase are salinity-dependent. This is the first demonstration of inhibitory phosphorylation of a crustacean (Na+, K+)-ATPase by Ca2+/calmodulin-dependent kinase. At low salinities, the (Na+, K+)-ATPase exhibited a single, low affinity ATP-binding site that showed Michaelis-Menten behavior. Above 18‰S, a second, cooperative, high affinity ATP-binding site appeared, corresponding to 10-20% of total (Na+, K+)-ATPase activity. Hemolymph osmolality was strongly hyper-/hypo-regulated in crabs acclimated at 2 to 35‰S. Cl- was well hyper-/hypo-regulated although Na+ much less so, becoming isonatremic at elevated salinity. (Na+, K+)-ATPase activity was greatest in isosmotic crabs (26‰S), decreasing notably at 35‰S and also diminishing progressively from 18to 2‰S. Hyper-osmoregulation in U. cordatus showed little dependence on gill (Na+, K+)-ATPase activity, suggesting a role for other ion transporters. These findings reveal that the salinity acclimation response in U. cordatus consists of a suite of enzymatic and osmoregulatory adjustments that maintain its osmotic homeostasis in a challenging, mangrove forest environment.

Intestinal Tract Microbe Communities Associated with Horseshoe Crabs from Beibu Gulf, China.

Until now, there has been little research on the intestinal microbial community of horseshoe crabs. To fill this gap, we investigated the microbiome composition of the Chinese horseshoe crab, Tachypleus tridentatus, and the mangrove horseshoe crab, Carcinoscorpius rotundicauda. We sequenced the 16S rRNA gene of intestinal bacterial species and compared the microbial community structure and diversity. Next, we show that the total effective bacterial sequence was 36,865 reads, and the average annotated operational taxonomic unit (OTU) number was 240. Through hierarchical clustering analysis and principal coordinate analysis samples from two horseshoe crab species, we found that the intestinal flora of the same horseshoe crab species was relatively concentrated, while the microbiome of a different horseshoe crab species were significantly separated. Cluster analysis showed that two samples, one from Chinese horseshoe crabs and one from mangrove horseshoe crabs, had similar microbial community structure, while other samples were relatively discrete. The gut microbiota of the mangrove horseshoe crab were dominated by the phyla Tenericutes (42.71%), Firmicutes (24.27%), and Proteobacteria (20.39%), while the top three phyla in the Chinese horseshoe crab intestinal tract were Tenericutes (57.19%), Proteobacteria (22.14%), and Bacteroidetes (7.38%). To intuitively understand the similarity and overlap of the OTU composition of each group, we performed Venn diagram analysis. The two species shared 284 OTUs, accounting for 81.8% of the total. This indicates that although there is high similarity between mangrove and Chinese horseshoe crab in gastrointestinal microbial community structure, there are also some differences, which deserve further discussion.

Comparison of morphometric identification of species in juvenile mangrove crabs (Genus Scylla) by automated and local approaches

Morphological species identification in juvenile Scylla is now possible using image analysis of frontal lobe spines. The differences found are subtle and require automation using a mobile application. Considering the bulk of crablets to be sorted for trading, distinct features that can help stakeholders distinguish the species of juveniles at a glance is still needed. In this study, morphometric analysis of dorsal carapace features was performed to identify more obvious features for species identification. Principal component analysis of ten morphometric characters from 1186 juveniles revealed only two clusters with Scylla olivacea creating a separate group from S. tranquebarica and S. serrata. The most distinguishable ratio for S. olivacea, determined through discriminant analysis and ANOVA, was the ratio of the frontal median spine height to the frontal width at 0.035 (p = 0.002). There is an emerging market for S. olivacea in the soft-shell crab industry. Selection of this smaller but useful species can aid fishers in setting appropriate prices for traded crablets and minimize predation to the larger S. tranquebarica and S. serrata. Testing if the ratio can be detectable by visual approximation is ongoing as well as alternative features based on local practices.

Structural characteristics of crab burrows in Hong Kong mangrove forests and their role in ecosystem engineering

Crab burrowing activity impacts several important biogeochemical processes within mangrove forests. Burrow morphology has been shown to be variable between brachyuran families, hence the community structure and composition of burrowing crabs may have the potential to impact ecosystems differently. By increasing belowground surface area, volume and bacterial microhabitats, large and complex burrows may differ from smaller and simpler burrows in their impact to nutrient and organic matter distribution. The central aim of this work was to provide a detailed quantification of the scale to which different mangrove crab families impact Hong Kong mangrove ecosystem through their burrowing activities. To achieve this goal, we recorded burrow densities and described specie-specific burrow morphology, through casts and 3D scans, of eight crab species belonging to four families, across three mangrove forests. Where present, the large and complex burrows of Parasesarma bidens (Sesarmidae) increased the total below ground air-sediment surface area per m2 by ~190% and accounted for ~1.9% of excavated volume per m3 of mangrove sediment. On average, the burrows of Metaplax spp. (Varunidae) increased the surface area by ~55%, while the ocypodid and dotillid species accounted for a 10–25% increase across sites. Due to its densities and the complexity of its burrows, P. bidens showed to exert a wide impact on Hong Kong mangrove ecosystems unrivalled by other species. By incorporating species-specific burrow characteristics and actual burrow densities, we were able to accurately estimate the differential bioengineering role of the dominant mangrove crab species. Due to the functional role of crab bioengineering, our estimates are critical to assess Hong Kong mangrove ecosystem functioning and health.

The analysis of economic feasibility from Bubu Dasar fishing gear (Bottom fish pots) in Tepian Muara Sembakung, Nunukan (Indonesia)

The society of Tepian Muara Sembakung village, Nunukan Regency (Indonesia) render Sembakung waters as a potential resource that can be used as one of their income. The fisherman used Bubu Dasar fishing gear (Bottom fish pots). This research aims to analyze the economic feasibility business model of Bubu Dasar fishing gear (Bottom fish pots) in Tepian Muara Sembakung, Nunukan Regency, Indonesia. The sampling was conducted for 3 months, from November 2019 to January 2020. The research used a quantitative descriptive method with a case study approach. The Data was collected using survey with interview, observation based on catches from bottom fish pots as many as 14 times, and laboratory-scale method by doing identification of main catch, such as giant prawns (Macrobrachium rosenbergii) and by-catch composition like mangrove crab (Scylla serrata); catfish (Pangasius hypophthalmus); crossbreed fish (Plotosus canius); cand hopstick fish (Toxotes jaculatrix). The results obtained an average daily income of fishermen was IDR 379,286 with an average gross income in each month was IDR. 3,792,857 with total expenses in the form of maintenance costs, depreciation costs and operational costs of IDR. 444,868, so the average profit of fishermen in each month was IDR. 3,347,990. The business analysis can be seen from the average ROI index value as 33.4; the average BEP index value was 12.4 and the average benefit cost ratio (B/C ratio) index was 8.5, so the results of the three indices explain that the bottom fish pots business analysis results are profitable and worthy of profit catching giant prawns (M.rosenbergii) using bottom fish pots in Tepian village, Sembakung subdistrict, Nunukan district.

Burrowing crabs in arid mangrove forests on the southwestern Arabian Gulf: Ecological and biogeographical considerations

Many species of mangrove crabs are essential in the formation of mangrove ecosystems, and the bioturbation resulting from the excavation of their underground chambers is directly correlated with substrate oxygenation and carbon and nitrogen cycling within the ecosystem. This study examines the ecological and biogeographical characteristics of bioengineering crab assemblages that inhabit the environmentally challenging arid mangroves in the southwestern Persian-Arabian Gulf. Results demonstrated that a hyper-arid environment could directly impact crab diversity, reducing it to only one species per niche or coastal zone. A biogeographic comparison revealed an exclusive divergence of species composition in each Gulf region. Variations in seasonal temperatures were found to have a direct influence on the abundance of species and how the zonation is driven by sediment composition and trophic relations. Two crabs – Nasima dotilliformis in the salt march (supratidal zone) and Macrophthalmus (Mareotis) depressus in the intertidal – were considered to be the most influential functional species for this hyper-arid ecosystem due to their abundance, size, bioturbation potential and niche specificity for the intertidal zone. The limited number of species within the arid mangrove system emphasised the biogeographic pressure and inherent importance of the few active bioengineering species present and adapted to the harsh conditions, indicating that the dominant crabs within the biotope are directly related to the successful evolutionary establishment of these hyperarid mangroves. The study highlights important implications for future forest management strategies of the only forest ecosystem that tolerates the extremes of the southwestern Persian-Arabian Gulf area.

The population and mortality characteristics of mangrove crab (Scylla serrata) in the mangrove ecosystem of Tarakan City, Indonesia

Abstract. Indarjo A, Salim G, Zein M, Septian D, Bija S. 2020. The population and mortality characteristics of mangrove crab (Scylla serrata) in the mangrove ecosystem of Tarakan City, Indonesia. Biodiversitas 21: 3856-3866. The mangrove crab is an iconic species of Tarakan City and is often is used as a souvenir. However, the high demand for this species can cause its population to decline. This study aimed to characterize the mangrove crab (Scylla serrata) population in the mangrove ecosystem of Tarakan City, North Kalimantan, Indonesia. This study was designed using a quantitative descriptive method with a case study model. The samples of mangrove crabs were obtained from 6 different stations using a purposive sampling method. The mangrove crab specimens were caught using 35-50 units of crab traps known as the ambau brackets. The primary data included carapace length, carapace width, carapace thickness, sex, and the total weight of each mangrove crab specimen. The results showed that male mangrove crabs have positive allometric growth when the condition index was fat. However, female crabs exhibited negative allometric growth when the condition index was thin. The Von Bertalanffy growth model analysis showed that the maximum carapace length of male mangrove crab in the mangrove ecosystem of Tarakan City was approximately 11.1118 cm for 189 days, while the female length was 9.6474 cm for 80 days. The total mortality value of male and female crabs was 120.01% and 154.94%, the mortality due to fishing was 84.69% and 135.75%, and natural mortality was 35.32% and 19.2%, respectively. The estimated rate of exploitation of both male and female crabs was 70.57% and 87.61%, respectively. The exploitation of S. serrata in the mangrove ecosystem of Tarakan City was evident, hence, conservation efforts are urgently required.