The Parasitic Fauna of Common Species of Hermit Crabs of Vostok Bay (Sea of Japan)

The parasitic fauna of common species of hermit crabs was investigated in Vostok Bay (the northwestern Sea of Japan). Pagurus proximus and Areopaguristes hirsutimanus had no parasites. The average prevalence of rhizocephalan infestation in other five species of hermit crabs ranged from 5.67 to 20.83%. The prevalence of the isopod Parapseudione lata on hermit crabs did not exceed 1%, the prevalence of infestation with the isopod Athelges takanoshimensis was significantly higher, reaching 14.58% in Pagurus middendorffii. Parasitism by the isopod P. lata on the hermit crabs Pagurus minutus and P. ochotensis, as well as parasitism by the rhizocephalan Peltogaster reticulata on P. minutus were recorded for the first time. Several variants of simultaneous infestation with two parasitic species were found. The decline in the abundance of P. middendorffii accompanied by the high prevalence of parasites, primarily the colonial rhizocephalan Peltogasterella gracilis, suggests that parasite invasion may play a more significant role in regulating the abundance of hermit crabs than was previously assumed.     

Aerial respiration in the semaphore crab,Heloecius cordiformis,with or without branchial water

• 1.1. Semaphore crabs (Heloecius cordiformis) are active in air at low tide. Their branchial chambers are lined with a vascular epithelium and are expanded above the gills (five pairs) to form air cavities which could function as lungs. Water is continuously circulated over the gills.
• 2.2. The relative contribution made by the gills and lungs to gas exchange in semaphore crabs active in air and circulating branchial water, was determined by measuring oxygen consumption (at 25°C) in crabs with and without branchial water, and in crabs with their lungs subsequently occluded.
• 3.3. Activity levels and VO₂ were unaffected by the absence of branchial water.
• 4.4. With their lungs occluded, VO₂ dropped (on average) by 61% in crabs with branchial water (i.e. gills still functional) and by 81% in crabs without branchial water (gill function impaired).
• 5.5. It is concluded that semaphore crabs are obligate air breathers while active on land, despite carrying water within their branchial chambers. Lung development and gill reduction in land crabs is discussed briefly in relation to “terrestriality”.

     

The bitter crab syndrome in commercial crabs in the Western part of the Bering and Chukchi Seas

We studied the distribution of the “bitter-crab” syndrome, a disease caused by the parasitic dinoflagellate Hematodinium sp., in eight commercial species of crabs in the west of the Bering and Chukchi seas. The crabs (25 388 individuals) were sampled during bottom trawl surveys of July?September 2010 and October?November 2012. The disease was first identified visually by a color change of the exoskeleton and the hemolymph of the animals and then using microscope analysis of hemolymph samples. Infestation was detected in crabs of three species, Chionoecetes opilio, C. bairdi, and Paralithodes platypus. The prevalence of the disease (the percent of infected individuals relative to all of those examined) in C. bairdi and P. platypus was very low, 0.1 and 0.3%, respectively. Infestation was widespread among C. opilio, its peak in the Bering Sea was in the fall. The average prevalence of the crab disease in different areas of the Bering Sea ranged from 0.8 to 10.8%. A high rate of crab infection was recorded in the Korfa Bay. In the Chukchi Sea, the average prevalence was 2%. Infestation by Hematodinium sp. was not revealed in the deep-sea snow crabs Chionoecetes tanneri and C. angulatus, and in three species of lithodid crabs, Paralithodes camtschaticus, P. brevipes, and Lithodes couesi. This can be explained by the small sample volume and/or ecology of these species, since the disease was registered in other areas in four of them.     

Host location and selection by the symbiotic sargassum crab <Emphasis Type="Italic">Portunus sayi</Emphasis>: the role of chemical,visual and tactile cues

The Sargassum community consists of a unique and diverse assemblage of symbiotic fauna critical to pelagic food chains. Associated symbionts presumably have adaptations to assist in finding Sargassum. In situ scattered Sargassum patches accumulate as they are pushed toward the shoreline (via wind, waves, currents or tides) and are frequently less than 1 m apart and in depths of 10 cm or less as the patches approach the shoreline Crabs, and other symbiotic fauna, must relocate to another patch that is seaward in direction or likely perish as their current patch will likely become beached. This study investigated sensory cues used for host location and selection by the Sargassum crab, Portunus sayi. Chemical detection trials were conducted with a two-chamber choice apparatus with Sargassum spp. and Thalassia testudinum as habitat source odors. Visual detection trials (devoid of chemical cues) and habitat selection trials were conducted in which crabs were given a choice between hosts. Results showed that P. sayi responded to chemicals from Sargassum spp. Crabs visually located host habitats but did not visually distinguish between different hosts. In host selection trials, crabs selected Sargassum spp. over artificial Sargassum and T. testudinum. These results suggest that crabs isolated from Sargassum likely use chemoreception; within visual proximity of a potential patch, crabs likely use both chemical and visual information.     

Concerning the problem of carcinophilia of <Emphasis Type="Italic">Careproctus</Emphasis> species (Scorpaeniformes: Liparidae) in the North Kurils

Along the east coast of North Kurils, the egg deposits of Careproctus snailfishes (Scorpaeniformes: Liparidae) were revealed in the gill cavity of 9.9% of all golden king crabs, mostly in individuals with carapace of 61–80 mm width (61.6%). The number of Careproctus eggs in the gill cavity of crabs increased with the increase of the carapace width. In fact, 97.0% of the crabs had such egg deposits only at one side of their carapaces. Most of the egg deposits, apparently, belonged to C. cypsellurus and C. furcellus. The number of crabs with egg deposits was related to the number of post-molt individuals. Evidently, egg depositing by Careproctus snailfishes out of the gill cavity of crabs is a rather widespread phenomenon.     

Variations in response to environmental hypoxia of different colour forms of the shore crab,Carcinus maenas

• 1.1. The oxygen consumption of red and green Carcinus in normoxic and hypoxic sea water was determined, using an oxygen electrode in a sealed respirometer.
• 2.2. The red crabs had significantly higher “excited” oxygen uptake rates and a lower ability to compensate for hypoxia than the green crabs.
• 3.3. Red Carcinus display an emersion response to declining oxygen at lower oxygen tensions than the green crabs.
• 4.4. Mortality of red crabs exposed to prolonged anoxia was much greater.
• 5.5. The relationship of these findings to the zonation of the two colour forms on the shore is discussed.

     

Hemolymph osmo-ionic concentrations in terrestrial crabs following desiccation

• 1.1. The hemolymph osmotic, Na⁺ K⁺, Ca⁺⁺ and Mg⁺⁺ concentrations were determined for both sexes in crabs from mangrove Ucides cordatus and Goniopsis cruentata and supralittoral Ocypode quadrala after aerial desiccation, for 10 hr.
• 2.2. There was no difference between sexes in the two mangrove crabs, but in O. quadrata the females were the most significantly affected (P < 0.01).
• 3.3. Hemolymph osmotic Na⁺, Ca⁺⁺ and Mg⁺⁺ concentrations increased significantly in desiccated ghost crabs, while K ⁺ concentration was not significantly changed. In the two mangrove crabs, only hemolymph Ca⁺⁺ concentration increased significantly, after desiccation.
• 4.4. The short time desiccation is suggested to be a device to study the steps of osmo-ionic regulation in terrestrial crabs.

     

Effect of eyestalk ablation on oxygen consumption of callinectes similis exposed to salinity changes

• 1.1. The effect of eyestalk ablation on preadults of Callinectes similis exposed to a constant salinity (30%.) and to simulated tidal changes in salinity (30-11 to 30%.) were measured.
• 2.2. In constant salinity, crabs showed a persistent respiratory rhythm, with a maximum oxygen consumption during the day. Under these conditions, ablation significantly increased the respiratory rate but not the rhythm.
• 3.3. In variable salinities, the highest respiratory rates occurred in salinities of 11 and 16%. during the night. In these crabs, ablation of eyestalks and subsequent injection of eyestalk extracts did not alter the respiration rate rhythm.
• 4.4. The circadian rhythm is controlled by the periodicity of environmental changes instead of the influence of eyestalk hormones.
• 5.5. Regulation of metabolism in C. similis associated with osmoregulation involves other neurosecretory organs.

     

Extraction of hermit crabs from their shells by white-faced capuchin monkeys (<Emphasis Type="Italic">Cebus capucinus</Emphasis>)

We observed two capuchin monkeys (Cebus capucinus) feeding on hermit crabs (Coenobita compressus) on the coast, and the tactics they used to extract this well-protected prey. The observations took place during the dry season at Playa Escondida beach, Puntarenas, Costa Rica. The capuchins descended from trees at the back edge of the beach to capture passing hermit crabs. Both capuchins extracted the hermit crabs from their protective shells by holding the shell with one hand and pulling the crab out with the other. Even though this was accomplished within seconds, the extraction of hermit crabs from their shells did not appear to be a straightforward task. Once the capuchins succeeded in pulling the crabs out of their shells, they consumed the soft abdomen and discarded the rest of the crab's body. To our knowledge, the consumption of hermit crabs has not been previously reported for any capuchin monkey (Cebus or Sapajus). Our observations provide a new example of extractive foraging by capuchins, and thus an additional natural context for which fine motor skills (which are highly developed in capuchins) are necessary.     

Estuarine fouling communities are dominated by nonindigenous species in the presence of an invasive crab

Interactions between anthropogenic disturbances and introduced and native species can shift ecological communities, potentially leading to the successful establishment of additional invaders. Since its discovery in New Jersey in 1988, the Asian shore crab (Hemigrapsus sanguineus) has continued to expand its range, invading estuarine and coastal habitats in eastern North America. In estuarine environments, H. sanguineus occupies similar habitats to native, panopeid mud crabs. These crabs, and a variety of fouling organisms (both NIS and native), often inhabit man-made substrates (like piers and riprap) and anthropogenic debris. In a series of in situ experiments at a closed dock in southwestern Long Island (New York, USA), we documented the impacts of these native and introduced crabs on hard-substrate fouling communities. We found that while the presence of native mud crabs did not significantly influence the succession of fouling communities compared to caged and uncaged controls, the presence of introduced H. sanguineus reduced the biomass of native tunicates (particularly Molgula manhattensis), relative to caged controls. Moreover, the presence of H. sanguineus favored fouling communities dominated by introduced tunicates (especially Botrylloides violaceous and Diplosoma listerianum). Altogether, our results suggest that H. sanguineus could help facilitate introduced fouling tunicates in the region, particularly in locations where additional solid substrates have created novel habitats.     

Negotiation or aggression during shell fights of the hermit crab Pagurus bernhardus?

Shell fighting behaviour of the hermit crab Pagurus bernhardus was investigated. Analysis of fights between crabs in which there was little or no asymmetry in potential benefit for the two crabs from a shell exchange suggested that the duration of the fight increased as the potential benefit increased. Further experiments indicated that a naked crab was capable of evicting a housed crab by a process of direct aggression. Analysis of fights in which there was a slight asymmetry in potential gains from shell exchange indicated that the result of the fight was primarily determined by the large of the two crabs. These results are contrary to the proposal of Hazlett (1978) that the interactions represent a process of negotiation rather than aggression.     

Parasitism of the rhizocephalan <Emphasis Type="Italic">Briarosaccus callosus</Emphasis> on the crab <Emphasis Type="Italic">Paralomis verrilli</Emphasis> (Crustacea: Lithodidae) in the waters of southeast Sakhalin

The crab Paralomis verrilli in the waters of southeast Sakhalin is infected by the parasitic rhizocephalan barnacle Briarosaccus callosus. The prevalence of parasitic infection was on the average 4.36% (6.29% for females, 3.28% for males) and varied between samples from none up to 14.9%. The degree of prevalence was not related to the average carapace width and the sex ratio of crabs in samples. Sterilization of female P. verrilli was caused by the B. callosus infestation or its consequences. No more than two parasite externae per crab were found. Crabs with two externae made up 5.6% of all infected specimens. The infestation of crab hosts with two B. callosus externae negatively influenced the growth of the externae. A positive relationship was found between the width of the crab carapace and the length of the parasitic externae. The survival rate of P. verrilli with either one or two parasite B. callosus externae did not differ substantially. The proportion of crabs with externae and those with “scars” (12.2% in our case) can be taken as the index of survival of the parasitized crabs.     

Effects of the complete replacement of fish oil with linseed oil on growth,fatty acid composition,and protein expression in the Chinese mitten crab (<Emphasis Type="Italic">Eriocheir sinensis</Emphasis>)

Background

The finite marine resources make it difficult for us to obtain enough fish oil (FO) used in aquatic feeds. Another sustainable ingredients should be found to substitute FO. The effects of replacing FO with vegetable oil have been studied in a variety of crustaceans, but most studies have focused on the phenotypic effects. Little is known about the mechanisms of the effects.

Methods

To understand the molecular responses during the replacement of FO in Eriocheir sinensis, we investigated the effects of feeding FO or linseed oil (LO) on growth performance, digestive enzyme activity, fatty acid composition and protein expression in E. sinensis. Twenty-four juvenile crabs were fed diets containing FO or LO for 112 days. Weight, carapace length and width were recorded. Fatty acid composition of the diets and the hepatopancreas and protein expression in the hepatopancreas were analyzed.

Results

Growth performance and molting interval were unchanged by diet. Crabs fed FO and LO had same activity of lipase and amylase, but comparing with crabs fed LO, crabs fed FO had higher trypsin activity and lower pepsin activity. Hepatopancreas fatty acid composition changed to reflect the fatty acid composition of the diets. In total, 194 proteins were differentially expressed in the hepatopancreas between the diets. Expression of heat shock proteins was higher in crabs fed LO. Expression of fatty acid synthase, long-chain fatty acid transport protein 4, acyl-CoA delta-9 desaturase, and fatty acid-binding protein 1, was higher in crabs fed FO.

Conclusions

The substitution of FO with LO didn’t have any effects on the growth and molting of mitten crab, but could significantly decrease the ability of mitten crab to cope with stress. The high content of HUFAs in the hepatopancreas of mitten crab fed FO is due to the high abundance of the proteins relative to the transport of the HUFAs. These findings provide a reason of the high content of EPA and DHA in crabs fed with FO, and provide new information for the replacement of FO in diets of mitten crab.

     

Assessment of antioxidant defense system responses in the hepatopancreas of the freshwater crab Sinopotamon henanense exposed to lead

Lead (Pb) is a common pollutant in aquatic ecosystems, which produces a wide range of toxic biochemical effects in different organisms. The aim of the present study was to explore the mechanisms of acute toxicity and antioxidant defenses in freshwater crab Sinopotamon henanense induced by Pb. Hepatopancreas was collected from S. henanense exposed for 96 h to Pb (0, 9.188, 18.375, 36.75, 73.5, and 147 mg/l). Oxidative stress was examined using a suite of assays in crabs, including contents of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), activities of antioxidative enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), and glutathione system-related parameters such as glutathione (GSH), glutathione S-transferase (GST), and glutathione reductase (GR). A dose-dependent increase of H₂O₂ and MDA was observed in the crabs after Pb exposure, while antioxidative enzymes activities were suppressed significantly (P < 0.05) at higher concentrations of Pb. The ratios of CAT/SOD, GPx/SOD, and GR/GPx were also suppressed. Our results suggested that acute exposure of Pb causes lipid peroxidation and harmful lessened antioxidant defenses of crabs. The above parameters were evaluated as potential biomarkers for Pb pollution monitoring and health assessment of crabs which is also important for the aquaculture of crabs.     

Apparent and real variability in the presence and metal contents of metallothioneins in the crab Carcinus maenas including the effects of isolation procedure and metal induction

• 1.1. Reducing conditions must be maintained throughout the procedure of isolating metallothioneins from crabs. Dithiothreitol is preferred to 2-mercaptoethanol for long-term protection.
• 2.2. Two metallothioneins (10,100 and 4100 mol. wt, respectively) in the hepatopancreas of the crab Carcinus maenas showed great variability between individual crabs as to their presence and to their contents of Zn, Cu and Cd.
• 3.3. The 10,100 mol. wt metallothionein was induced in the laboratory by exposure to Cu and Cd, and variably by Zn-exposure. Laboratory induction did not raise significantly the total metal content of 0.88 ± 1.13 g atoms/mol protein of this metallothionein in crabs from the Firth of Clyde, Scotland.
• 4.4. The 4100 mol. wt metallothionein was not induced in the laboratory by exposure to Cu, Cd or Zn. This metallothionein in crabs from the Firth of Clyde, Scotland, contained 0.27 ± 0.34 g atoms of total Cu, Cd and Zn per mole of protein.

     

A review on fisheries and conservation status of Asian horseshoe crabs

Horseshoe crabs are the only extant xiphosurans and are believed to be morphologically unchanged for more than 200 million years. Of the four extant species namely, Limulus polyphemus, Tachypleus tridentatus, Tapinauchenius gigas and Carcinoscorpius rotundicauda, the latter three are found in Asian waters. Recent evidences showed that Asian horseshoe crabs are facing serious threats such as degradation of their spawning grounds and habitat, environmental pollution, overexploitation as a culinary delicacy and biomedical bleeding practices. Baseline data on the distribution and existing population of the wild horseshoe crabs remain poorly known in several Asian regions. Several studies have clearly revealed that pressure due to over-fishing of wild stock has increased tremendously in the last decade. Due to an increase in demand for Tachypleus Amebocyte Lysate (TAL) analogous to Limulus Amebocyte Lysate (LAL) in the United States, there is an urgent need to comprehensively address their fishing and conservation measures in the Asian region. This review addresses the overall studies on three species of Asian horseshoe crabs in relation to their fishing practices, local exploitation of their wild stock either for human consumption (or) by biomedical industries. The authors have structured the discussion on an international scale to address the existing problems in fishing and conservation of horseshoe crabs. Since no specific regulatory force or legislative protection act or a policy to preserve their natural stock are available to this date, this paper strongly recommends representative countries to include horseshoe crabs under their wildlife protection act to avoid further unsustainable exploitation of their wild populations.     

Comparative Burrow Architectures of Resident Fiddler Crabs (Ocypodidae) in Indian Sundarban Mangroves to Assess Their Suitability as Bioturbating Agents

Excavation of burrows by fiddler crabs (genus Uca) is an important component in mangrove ecosystem functioning. This bioturbation activity can be measured by analysing the burrow architecture of these crabs. The aim of the present study is to describe and evaluate inter specific differences in the burrow morphologies of four species of fiddler crabs (Uca rosea, Uca triangularis, Uca dussumieri and Uca vocans) using polyester resin casts of the burrows. For each of the species, sex and carapace width (CW; mm) were determined for all the individuals. Three burrow morphological characters viz. burrow diameter (BD; mm), total burrow depth (TBD; mm) and burrow volume (BV; cm³) were considered during the study. Density of each species throughout the year was also assessed. For all the species BD and BV were higher in case of males compared to the females and they showed significant positive correlation with the CW of the burrow inhabitants. The amount of sediment excavated by each crab was evaluated in terms of BV. Among all the studied species, U. rosea was established as the most potent bioturbative candidate in the studied mangrove due to their greater density and moderate ability to excavate burrow.     

Induction of the intrinsic apoptotic pathway via a new antimitotic agent in an esophageal carcinoma cell line

Background

2-Ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16) is a unique, in silico-designed compound with possible anticancer properties, which were identified in our laboratory. This compound is capable of interfering with microtubule dynamics and is believed to have potential carbonic anhydrase IX inhibiting activity.In this study, it was investigated whether ESE-16 is capable of inducing apoptosis in vitro in the esophageal carcinoma SNO cell line via the intrinsic pathway at a concentration of 0.2 μM with an exposure time of 24 hours.

Results

Qualitative results were obtained via light microscopy, transmission electron microscopy and confocal microscopy. Results showed hallmarks of apoptosis in the ESE-16-treated cells. In addition, data revealed an increase in the number of ESE-16-treated cells blocked in metaphase. Cell death via apoptosis in the ESE-16-treated cells was confirmed by studying the internal ultrastructure of the cells via transmission electron microscopy, while confocal microscopy revealed abnormal spindle formation and condensed chromatin in ESE-16-treated cells, thus confirming metaphase block.Quantitative results were obtained via flow cytometry and spectrophotometry. Cell death via apoptosis in ESE-16-treated cells was quantitatively confirmed by the Annexin V-FITC apoptosis detection assay. Flow cytometry and spectrophotometry revealed dissipation of mitochondrial membrane potential and an increase in superoxide levels in the ESE-16-treated cells when compared to the relevant controls. Both initiator caspase 9 and effector caspase 3 activities were increased, which demonstrates that ESE-16 causes cell death in a caspase-dependent manner.

Conclusions

This was the first in vitro study conducted to investigate the action mechanism of ESE-16 on an esophageal carcinoma cell line. The results provided valuable information on the action mechanism of this potential anticancer agent. It can be concluded that the novel in silico-designed compound exerts an anti-proliferative effect on the esophageal carcinoma SNO cell line by disrupting microtubule function resulting in metaphase block. This culminates in apoptotic cell death via the intrinsic apoptotic pathway. This research provided cellular targets warranting in vivo assessment of ESE-16’s potential as an anticancer agent.

     

Adenosine monophosphate-activated protein kinase from the mud crab, <Emphasis Type="Italic">Scylla paramamosain</Emphasis>: cDNA cloning and profiles under cold stress

Adenosine monophosphate-activated protein kinase (AMPK), an important energy sensor, is crucial for organism survival under adverse conditions. In this study, the roles of this gene under cold stress in a warm-water mud crab, Scylla paramamosain was investigated. The full-length cDNA (SpAMPK) was 1884 bp and its open reading frame of 1566 bp was isolated and characterized. The expressions of SpAMPK detected by quantitative real-time PCR (qRT-PCR) in various tissues revealed that the highest expression was in the hepatopancreas. The profiles of SpAMPK gene in the hepatopancreas, chela muscle and gill were detected when the subadult crabs were exposed to the four temperature conditions of 10, 15, 20 and 25^°C. The results showed that the expression patterns of SpAMPK mRNA in the three tissues were significantly higher when crabs were exposed to 15^°C than the other three temperature treatments, while at 10^°C treatment, the SpAMPK mRNA was lowest among the four temperature treatments. These findings suggested that the high expression of SpAMPK mRNA might initiate ATP-producing pathways to generate energy to cope with cold stress at 15^°C treatment, which was slightly below the range of optimum temperatures; while treatment at 10^°C, far lower than optima, the low expression of SpAMPK mRNA could reduce the energy expenditure and thus induce the crabs into cold anesthesia. The results of SpAMPK in this study might contribute to the understanding of the molecular mechanism of acclimation to cold hardiness in S. paramamosain.     

Potential impact of the Asian shore crab <Emphasis Type="Italic">Hemigrapsus sanguineus</Emphasis> on native northeast Pacific crabs

Asian shore crabs (Hemigrapsus sanguineus De Haan) are a dominant invasive species in the northwest Atlantic, where recent evidence suggests that they have been introduced multiple times from their native range of Japan and Korea. Despite favorable environmental conditions and a high level of shipping traffic across the Pacific, this crab has not become established in the northeast Pacific. This may be due to interactions with the native shore crab assemblage, which previous studies have found to outcompete juvenile H. sanguineus for shelter. The present study used a combination of feeding and behavioral experiments to quantify the feeding behavior of native crabs (Pachygrapsus crassipes, Hemigrapsus nudus, Hemigrapsus oregonensis) with and without the presence of H. sanguineus. H. sanguineus ate more than the native crabs combined at both 7 and 13 °C. Crabs in the mixed treatment which included all four species ate less than expected, indicating that at least one species reduced its feeding rate. However, time-lapse photography revealed similar amounts of time feeding in both treatments for all 4 species, suggesting that there were changes in feeding intensity when all crabs were together. The high feeding rates but lack of a competitive advantage for H. sanguineus make it an unlikely but potentially impactful invader in the northeast Pacific.