Spider Crab Research Articles

The effects of trophic transfer and environmental factors on microplastic uptake by plaice, Pleuronectes plastessa, and spider crab, Maja squinado

Microplastic pollution is apparent throughout the marine environment from deep ocean sediments to coastal habitats. Most of this is believed to originate on land, although marine activities, such as fishing and shipping, also contribute to the release and redistribution of microplastic. The relative importance of these maritime plastic sources, the manner by which they are distributed in the environment, and their effect on uptake by marine organisms are yet to be fully quantified. In this study, the relative impact of fishing activities on microplastic uptake by demersal fish and crustaceans was explored. Local fishing intensity, proximity to land and mean water velocity are compared to microplastic uptake in plaice, Pleuronectes platessa, and spider crab, Maja squinado, from the Celtic Sea. Observations were also made of microplastic contamination in ingested sand eels, Ammodytes tobianus, to establish a potential route of trophic transfer. This study is the first to identify microplastic contamination in spider crab and to document trophic transfer in the wild. Individuals were sampled from sites of varied fishing intensity in the Celtic Sea, and their stomach contents examined for the presence of microplastic. Contamination was observed in 50% of P. platessa, 42.4% of M. squinado, and 44.4% of A. tobianus. Locations of highest plastic abundance varied between P. platessa and M. squinado, indicating that different factors influence the uptake of microplastic in these two taxa. No significant link was observed between fishing effort and microplastic abundance; however, proximity to land was linked to increased abundance in M. squinado and Observations of whole prey demonstrate ongoing trophic transfer from A. tobianus to P. platessa. The lack of significant difference in microplastic abundance between predator and prey suggests that microplastic is not retained by P. platessa.

Total mercury levels in crustacean species from Italian fishery

ABSTRACTThis study investigated mercury contamination levels in eight commercially valuable crustacean species caught off the Central Adriatic and Tyrrhenian coasts of Italy. Total mercury levels were measured by Thermal Decomposition-Amalgamation-Atomic Absorption Spectrophotometry. Results showed a high variability among species with values ranging from 0.070 to 1.24 (mg kg−1 wet weight). The lowest mercury levels were detected in caramote prawn (Penaeus kerathurus), warty crab (Eriphia verrucosa) and European spider crab (Maja squinado), decapods living in shallow waters. Levels exceeding the limits established by the European Commission were found in species living in close contact with bottom sediments: deepwater rose shrimp (Parapenaeus longirostris), blue and red shrimp (Aristeus antennatus) and Norway lobster (Nephrops norvegicus). For shrimps, the inter-individual variability observed was mostly related to the body size, indicating the accumulation of mercury with age. An estimation of the human intake of mercury associated to the consumption of the crustaceans sampled and its comparison with the Tolerable Weekly Intake are provided.

Crab spiders impact floral-signal evolution indirectly through removal of florivores

The puzzling diversity of flowers is primarily shaped by selection and evolutionary change caused by the plant’s interaction with animals. The contribution of individual animal species to net selection, however, may vary depending on the network of interacting organisms. Here we document that in the buckler mustard, Biscutella laevigata, the crab spider Thomisus onustus reduces bee visits to flowers but also benefits plants by feeding on florivores. Uninfested plants experience a trade-off between pollinator and spider attraction as both bees and crab spiders are attracted by the floral volatile β-ocimene. This trade-off is reduced by the induced emission of β-ocimene after florivore infestation, which is stronger in plant populations where crab spiders are present than where they are absent, suggesting that plants are locally adapted to the presence of crab spiders. Our study demonstrates the context-dependence of selection and shows how crab spiders impact on floral evolution.

Changing oviposition times of the crab spider Misumena vatia (Thomisidae) correlate with climate change

The crab spider Misumena vatia (Clerck, 1757) (Thomisidae) is an important sit-and-wait predator at flowers visited by nectar or pollen-seeking insects. Typically, female M. vatia molt into their adult stage when many insect-attracting flowers come into bloom, and the spiders quickly gain weight leading up to oviposition. Between 1979 and 2010, the first spider ovipositions shifted one month earlier, from late July to late June, at my study site in coastal Maine, USA, in accordance with a concurrent temperature increase of ca. 0.44°C and a lengthening growing season. Flowering times of the spiders' most important hunting site, common milkweed Asclepias syriaca, as well as recruitment dates of their most important prey, bumblebees Bombus spp., to flowering milkweed, advanced as well. The shift in spider oviposition times increased the feasibility of second broods, though I found no successful second broods in the field, and the success of such broods would be problematic because of heavy overwintering losses. Differing rates of change of spider, milkweed and bumblebee activity indicated decreasing synchrony among these species; in particular, lessening future hunting opportunities for the spiders.

There and back again: More on the taxonomy of the crab spiders genus Epicadus (Thomisidae: Stephanopinae).

The Neotropical crab spider genera Tobias Simon, 1895 and Epicadus Simon, 1895 comprise species with remarkable somatic morphology and confounding taxonomic history. The results of our recent cladistic analysis corroborate and extend preceding taxonomic assumptions in showing that Tobias is a junior synonym of Epicadus. In the present paper the six species recently transferred from Tobias to Epicadus are redescribed. Two new species are described based on both males and females: Epicadus dimidiaster sp. nov. and Epicadus tigrinus sp. nov.; the male of Epicadus granulatus Banks, 1909 is described for the first time. The diagnosis of the genus is revised, an identification key is provided, and information on geographical distribution is updated. Epicadus now comprises eleven species.

Effects of domestic effluent discharges on mangrove crab physiology: Integrated energetic, osmoregulatory and redox balances of a key engineer species

Mangroves are increasingly used as biofiltering systems of (pre-treated) domestic effluents. However, these wastewater discharges may affect local macrofauna. This laboratory study investigates the effects of wastewater exposure on the mangrove spider crab Neosarmatium meinerti, a key engineering species which is known to be affected by waste waters in effluent-impacted areas. These effects were quantified by monitoring biological markers of physiological state, namely oxygen consumption, the branchial cavity ventilation rate, gill physiology and morphology, and osmoregulatory and redox balance. Adults acclimated to clean seawater (SW, 32 ppt) and freshwater (FW, ∼0 ppt) were compared to crabs exposed to wastewater for 5 h (WW, ∼0 ppt). Spider crabs exposed to WW increased their ventilation and whole-animal respiration rates by 2- and 3-fold respectively, while isolated gill respiration increased in the animals exposed to FW (from 0.5 to 2.3 and 1.1 nmol O2 min−1 mg DW−1 for anterior and posterior gills, respectively) but was not modified in WW-exposed individuals. WW exposure also impaired crab osmoregulatory capacity; an 80 mOsm kg−1 decrease was observed compared to FW, likely due to decreased branchial NKA activity. ROS production (DCF fluorescence in hemolymph), antioxidant defenses (superoxide dismutase and catalase activities) and oxidative damage (malondialdehyde concentration) responses varied according to animal gender. Overall, this study demonstrates that specific physiological parameters must be considered when focusing on crabs with bimodal breathing capacities. We conclude that spider crabs exposed to WW face osmoregulatory imbalances due to functional and morphological gill remodeling, which must rapidly exhaust energy reserves. These physiological disruptions could explain the ecological changes observed in the field.

Application of Miniature Heart Rate Data Loggers for Use in Large Free-Moving Decapod Crustaceans: Method Development and Validation.

Cardiovascular responses of decapod crustaceans to environmental challenges have received extensive attention. However, nearly all of these studies have been restricted to lab-based experiments; here we describe a methodology that will enable measurement of heart rate (HR) in free-moving decapods in the field. Data storage tag heart rate and temperature loggers (DST micro-HRT; Star-Oddi) were used to record electrocardiograms (ECG) and HR in large decapod crustaceans. These loggers were originally designed for use in vertebrates and must be surgically implanted in the body cavity near the heart in order to function. We adapted these loggers for external use in large decapod crustaceans. The method involved abrading the carapace directly above the heart and placing the electrodes of the logger directly on top of the dermal tissue. The logger was then secured in place with periphery wax. This method negated some of the more intricate operations used for vertebrates. The rapid setup time of approximately 5 min suggested that animals could be easily instrumented in the field and without the use of anesthetic. The logger was calibrated by simultaneously measuring the HR changes of a West Indian spider crab Mithrax spinosissimus with a pulsed-Doppler flowmeter. The data gathered with the two methods showed a tight correlation during an increase in temperature. The loggers were also successfully implanted in a variety of other large species of aquatic and terrestrial decapods. The data obtained showed that the method works in a broad range of species, under different experimental conditions. In each case, the loggers comprised less than 1% of the body mass and would be suitable for use in animals >300 g. All animals survived the attachment procedures and were feeding and active after removal of the loggers. Nearly all previous cardiac measurements on decapods have been carried out in controlled laboratory settings. The use of these loggers will make significant advances in measuring HR in unrestrained, undisturbed animals in their natural environment during extended periods of time and has the potential to lead to novel findings.

Differentially expressed genes in gonads of the spider crab Maja brachydactyla

Differentially expressed genes in gonads of the spider crab Maja brachydactyla

Influence of the male size and storage time in the spermatheca on the sperm quality of the spider crab Maja brachydactyla (Balss, 1922)

Influence of the male size and storage time in the spermatheca on the sperm quality of the spider crab Maja brachydactyla (Balss, 1922)

A new large oregoniid spider crab of the genus Pleistacantha Miers, 1879, from the Bay of Bengal, India (Crustacea, Brachyura, Majoidea).

A new species of deep-water oregoniid spider crab of the genus Pleistacantha Miers, 1879, is described from the Indian Ocean. The species is distinct in possessing a prominently inflated carapace in which the median parts of the branchial regions almost meet. It can also be distinguished from its closest congeners, P. moseleyi (Miers, 1885), P. pungens (Wood-Mason, in Wood-Mason & Alcock, 1891), and P. ori Ahyong & Ng, 2007, in its more elongate and less spinose chelipeds and ambulatory legs, shorter third maxilliped, trapezoidal male pleon and a male first gonopod which is relatively stout with a short subdistal dorsal papilla.

Species-specific crab predation on the hydrozoan clinging jellyfish Gonionemus sp. (Cnidaria, Hydrozoa), subsequent crab mortality, and possible ecological consequences.

Here we report a unique trophic interaction between the cryptogenic and sometimes highly toxic hydrozoan clinging jellyfish Gonionemus sp. and the spider crab Libinia dubia. We assessed species–specific predation on the Gonionemus medusae by crabs found in eelgrass meadows in Massachusetts, USA. The native spider crab species L. dubia consumed Gonionemus medusae, often enthusiastically, but the invasive green crab Carcinus maenus avoided consumption in all trials. One out of two blue crabs (Callinectes sapidus) also consumed Gonionemus, but this species was too rare in our study system to evaluate further. Libinia crabs could consume up to 30 jellyfish, which was the maximum jellyfish density treatment in our experiments, over a 24-hour period. Gonionemus consumption was associated with Libinia mortality. Spider crab mortality increased with Gonionemus consumption, and 100% of spider crabs tested died within 24 h of consuming jellyfish in our maximum jellyfish density containers. As the numbers of Gonionemus medusae used in our experiments likely underestimate the number of medusae that could be encountered by spider crabs over a 24-hour period in the field, we expect that Gonionemus may be having a negative effect on natural Libinia populations. Furthermore, given that Libinia overlaps in habitat and resource use with Carcinus, which avoids Gonionemus consumption, Carcinus populations could be indirectly benefiting from this unusual crab–jellyfish trophic relationship.

A new species of Angaeus from Malaysia with possible affinity to related genera within Stephanopinae (Araneae: Thomisidae).

The crab spider genus Angaeus Thorell, 1881 currently contains 10 described species (Benjamin 2013; WSC 2017). All species of the genus are restricted to tropical Asia. The aim of this correspondence is to illustrate and describe a new species of the genus characterized by a number of features previously found in the genera Angaeus, Borboropactus Simon, 1884, Epidius Thorell, 1877 and Geraesta Simon, 1889. The most unusual feature is the elongated tibia of the male palp that was previously thought to be diagnostic of Epidius (Figs 1, 2, 8; character 1 in Benjamin 2011; Benjamin 2017). However, the new species lacks tibial macrosetae (Figs 1, 2, 8) and lacks a flexibly attached MA, both also being characteristics of Epidius (characters 2 and 18 in Benjamin 2011). Furthermore, this new species differs considerably in general appearance from all known species of Epidius.

Field evidence challenges the often-presumed relationship between early male maturation and female-biased sexual size dimorphism.

Female‐biased sexual size dimorphism (SSD) is often considered an epiphenomenon of selection for the increased mating opportunities provided by early male maturation (i.e., protandry). Empirical evidence of the adaptive significance of protandry remains nonetheless fairly scarce. We use field data collected throughout the reproductive season of an SSD crab spider, Mecaphesa celer, to test two hypotheses: Protandry provides fitness benefits to males, leading to female‐biased SSD, or protandry is an indirect consequence of selection for small male size/large female size. Using field‐collected data, we modeled the probability of mating success for females and males according to their timing of maturation. We found that males matured earlier than females and the proportion of virgin females decreased abruptly early in the season, but unexpectedly increased afterward. Timing of female maturation was not related to clutch size, but large females tended to have more offspring than small females. Timing of female and male maturation was inversely related to size at adulthood, as early‐maturing individuals were larger than late‐maturing ones, suggesting that both sexes exhibit some plasticity in their developmental trajectories. Such plasticity indicates that protandry could co‐occur with any degree and direction of SSD. Our calculation of the probability of mating success along the season shows multiple male maturation time points with similar predicted mating success. This suggests that males follow multiple strategies with equal success, trading‐off access to virgin females with intensity of male–male competition. Our results challenge classic hypotheses linking protandry and female‐biased SSD, and emphasize the importance of directly testing the often‐assumed relationships between co‐occurring animal traits.

Deep-sea spider crabs of the families Epialtidae MacLeay, 1838 and Inachidae MacLeay, 1838, from the South China Sea, with descriptions of two new species (Decapoda, Brachyura, Majoidea)

Recent expeditions (NANHAI 2014, DONGSHA 2014 and ZHONGSHA 2015) conducted in deep waters of the South China Sea obtained interesting material of various spider crabs (Majoidea) including several new records for the area, and two new species of epialtids of the genera Oxypleurodon Miers, 1885 and Stegopleurodon Richer de Forges & Ng, 2009. Two poorly known species, previously only known from their types, Rochinia strangeri Serène & Lohavanijaya, 1973 and R. kagoshimensis (Rathbun, 1932) comb. nov., are redescribed, refigured, and their taxonomy discussed.

Oxidative stability of the hemolymph in different crustacean species

The aim of this study was to determine interspecies and gender differences in the lipid metabolism and hemolymph oxidation stability in intermoult period of the European spider crab (M. squinado), the warty crab (E. verrucosa) and the European spiny lobster (P. elephas). In hemolymph samples activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and paraoxonase 1 (PON 1), as well as hemolymph cholesterol, triacylglycerol and non-esterified fatty acid (NEFA) concentrations were determined. The hemolymph of M. squinado showed the highest levels of SOD activity, cholesterol and triacylglycerol and the lowest levels of PON 1 activity compared to values determined in the hemolymph of E. verrucosa and P. elephas. Gender differences were determined only in M. squinado samples. Males had significantly higher activity of PON 1 and lower NEFA values compared to females. M. squinado hemolymph lipid metabolism and oxidation stability in intermoult period could be attributed to their biological, metabolic characteristics and environmental conditions in which these species live.

Redescription of Bomis larvata L. Koch, 1874 with the description of a new Australian species

All known species of Bomis are very small—spiders in this genus belong to the smallest crab spiders known. The type species, Bomis larvata L. Koch, 1874, is distributed in Australia. Three more species of the genus have been described from India. This paper is a redescription of B. larvata accompanied by a description of Bomis hippoponoi n. sp. from Australia.

Ultrastructure of spermatozoa of spider crabs, family Mithracidae (Crustacea, Decapoda, Brachyura): Integrative analyses based on morphological and molecular data.

Recent studies based on morphological and molecular data provide a new perspective concerning taxonomic aspects of the brachyuran family Mithracidae. These studies proposed a series of nominal changes and indicated that the family is actually represented by a different number and representatives of genera than previously thought. Here, we provide a comparative description of the ultrastructure of spermatozoa and spermatophores of some species of Mithracidae in a phylogenetic context. The ultrastructure of the spermatozoa and spermatophore was observed by scanning and transmission electron microscopy. The most informative morphological characters analysed were thickness of the operculum, shape of the perforatorial chamber and shape and thickness of the inner acrosomal zone. As a framework, we used a topology based on a phylogenetic analysis using mitochondrial data obtained here and from previous studies. Our results indicate that closely related species share a series of morphological characteristics of the spermatozoa. A thick operculum, for example, is a feature observed in species of the genera Amphithrax, Teleophrys, and Omalacantha in contrast to the slender operculum observed in Mithraculus and Mithrax. Amphithrax and Teleophrys have a rhomboid perforatorial chamber, while Mithraculus, Mithrax, and Omalacantha show a wider, deltoid morphology. Furthermore, our results are in agreement with recently proposed taxonomic changes including the separation of the genera Mithrax (previously Damithrax), Amphithrax (previously Mithrax) and Mithraculus, and the synonymy of Mithrax caribbaeus with Mithrax hispidus. Overall, the spermiotaxonomy of these species of Mithracidae represent a novel set of data that corroborates the most recent taxonomic revision of the family and can be used in future taxonomic and phylogenetic studies within this family.

Two new species of the genus Oxytate from China (Araneae: Thomisidae)

Two new crab spider species from China are diagnosed, described and illustrated: Oxytate bicornis sp. nov. from Jiangxi and Oxytate palmata sp. nov. from Guangxi. The total number of the known species of Oxytate from China rises to 13 with the addition of two new species described in the present paper.

The morphology of the male and female reproductive system in two species of spider crabs (Decapoda: Brachyura: Majoidea) and the issue of the velum in majoid reproduction

The reproductive system of spider crabs (Majoidea) has raised considerable interest due to the complexity of female sperm storage organs. In several majoid species, the seminal receptacle has been described as being divided into a dorsal storage chamber and a ventral fertilization chamber separated by a muscular velum. The velum is supposed to control the amount of sperm used for fertilization and to play an important role in sperm competition. Here, we present a study on the reproductive systems of the two majoid species, Mithraculus sculptus (Lamarck, 1818) and Stenorhynchus seticornis (Herbst, 1788) using various morphological techniques such as μCT scans and 3D-reconstructions, complemented by paraffin histology. The male gonopods of the herein investigated species are similar in their general morphology and in the presence and distribution of setae. The tubular first gonopod holding the ejaculatory canal is much longer than the short and stout second gonopod, which is supposed to function as a piston in the transport of sperm into the female ducts. The female reproductive system of M. sculptus and S. seticornis conforms to that of other Eubrachyura in possessing paired ovaries, oviducts, seminal receptacles, vaginae, and vulvae. Based on our 3D-reconstructions we demonstrate that there is no division of the seminal receptacle into two chambers separated by a velum. In contrast to this, we observed a spatially restricted invagination of the seminal receptacle. A comparison of our data with those of previous studies, allows for the conclusion that the invagination of the seminal receptacle may have been misinterpreted and mistaken for a velum by other authors. Thus, the division of the seminal receptacle into two chambers separated by a velum is a character which needs to be re-evaluated.

Profile Analysis on the Ornamental Marine Yellow-Arrow Spider Crab Stenorhynchus debilis (Smith 1871) into Experimental Studies for Live Management and Cultivation in Laboratory

Ornamental marine species from the tropical west American coast are poorly known although many of them are being commercialized since a while ago. For example, yellow-arrow spider crabs, Stenorhynchus debilis (Brachyura: Inachidea), are frequently found for sale in web-based stores and as tenants into domestic aquaria. Therefore, the interest in studying the species’ requirements for management in land-based conditions is pertinent. This paper examines S. debilis as experimental actor. Specimens were collected along May to August 2015 into cultivation artifacts designed for pearl oysters farming at La Paz bay, Gulf of California. Five experiments were prepared towards two main objectives viewing at the practical framework of ornamental marine species: (1) Find the species’ profile into selected tests. Data included: anesthetic therapies, acute responses to temperature and salinity, special effects (food and feeding, density, sex-ratio, size, shelters, and handling in general), and notes concerning ovigerous females, eggs and larvae, and (2) Evaluate outputs seeking explanations for growth, survival and performances as a function of tropical-temperate and small-crab criteria. Our results agreed with expected bio-benchmarks overall, so did as to consistency of highlights regarding compatibility in domestic aquaria, and species-dependent aspects. Nevertheless, growth happened in a diet experiment even if only one crab out of the 24 under test displayed an incomplete –deadly—molt. A triangular-like Size Index was assessed, finding that two of the three food types tested had promoted better performance. Finally, this paper may contribute with some updates for the still incomplete mosaic of knowledge about ornamental marine crabs.