Hematodinium sp. infection of red Paralithodes camtschaticus and blue Paralithodes platypus king crabs from the Sea of Okhotsk, Russia

A disease caused by a parasitic dinoflagellate of the genus Hematodinium was identified in red, Paralithodes camtschaticus, and blue, Paralithodes platypus, king crabs from the north-east region of the Sea of Okhotsk, Russia, during annual stock surveys. No carapace color change was observed even in heavily infected crabs, but diseased crabs possessed creamy-yellow hemolymph, which was visible through the arthrodial membranes of the abdomen and appendages. Several stages of the parasite’s life history, including trophonts, plasmodia, sporonts and macrodinospores, were observed in tissues of infected king crabs. Numerous parasite cells were observed in the lumina of the myocardium, the gills, the connective tissue of antennal glands and the sinuses of nerve ganglia, eyestalks and gastrointestinal tract of king crabs with gross signs of infection. Based on sequencing of the 18S rDNA, it appears that the Hematodinium sp. found in red and blue king crabs is identical or closely related to Hematodinium sp. isolated from crabs of the genera Chionoecetes and Lithodes. Observed prevalences were 0.33% in sublegal male red king crabs, 0.18% in female red king crabs, 0.34% in sublegal male blue king crabs and 0.31% in female blue king crabs.     

Observations on the histopathology of a systemic ciliate (Paranophrys sp.?) disease in the Dungeness crab, Cancer magister

Infections of the hemolymph of crabs by ciliates have been known for almost a century. Originally placed in the genus Anophrys, these crab-parasitizing ciliates have been recently transferred to the genus Paranophrys. Infections were long thought to be confined to the hemolymph in living crabs, with death caused by consumption of all hemocytes. Histological examination of heavily infected, but living, Dungeness crabs demonstrate that the ciliates actively invade and probably consume many tissues of the host prior to death rather than saprophytically feeding on the decomposing tissues subsequent to death as previously reported.     

Respiratory,cardiovascular, and hemolymph acid‐base changes in the amphibious crab,Cardisoma guanhumi,during immersion and emersion

The cardiorespiratory and hemolymph acid base status of bimodal breathing crabs, Cardisoma guanhumi, was monitored during the transition from breathing air to breathing water. Upon immersion, oxygen uptake (MO₂) decreased by half. Ventilatory frequency (fsc) increased more than 5 fold, causing a decrease in hemolymph carbon dioxide partial pressure (PCO₂). This was nearly fully compensated for by a gradual decrease in hemolymph bicarbonate concentration ([HCO₃ ^‐]) over 96 hours post‐immersion. After one to two weeks of immersion, when crabs were removed from the water, oxygen uptake initially increased, but eventually returned to the initial immersed value. Heart rate was unchanged but fsc slowed dramatically. The decreased ventilation resulted in a buildup of hemolymph PCO₂, causing a respiratory acidosis that was slowly compensated for by increased hemolymph [HCO₃ ^‐]. C. guanhumi appears to be a truly amphibious crab with respiratory and acid‐base adaptations found in both fully aquatic and fully terrestrial species.     

Estimation of total hemolymph volume in the horseshoe crab Limulus polyphemus

Biomedical companies extract blood from the horseshoe crab, Limulus polyphemus, for the production of Limulus Amebocyte Lysate, used worldwide for detecting endotoxins in injectable solutions and medical devices. Despite the extensive use of horseshoe crabs by the biomedical industry, total hemolymph volume for this species is not known. The hemolymph volume of 60 adult horseshoe crabs was estimated using an inulin dilution technique. Blood volume of the horseshoe crab represented as a percentage of wet body weight was 25?±?2.2% for males and 25?±?5.1% (mean?±?SD) for females. Relationships between hemolymph volume and weight (p?=?0.0026, r ²?=?0.8762), hemolymph volume and prosomal width (p?<?0.0001), and hemolymph volume and inter-ocular width (p?<?0.0001) were observed. No significant differences were observed between males and females. The relationship of animal size and hemolymph volume can be used to predict how much blood can be drawn from horseshoe crabs used by the biomedical industry, and can be of further use in future bleeding mortality studies.     

Methyl farnesoate binding proteins in tissues of the spider crab, Libinia emarginata

Methyl farnesoate (MF) binding proteins (MFBPs) were found in the ovaries, testes, accessory glands, and hemolymph of the spider crab Libinia emarginata, by photoaffinity labeling the tissues in vitro with tritiated farnesyl diazomethyl ketone ([3H]-FDK). Specificity was demonstrated by competitive displacement of [3H]-FDK with MF. SDS-PAGE followed by fluorography revealed several labeled proteins in the hemolymph and testes with molecular masses ranging from 29 to 116 kDa, and two in the ovary that were 97 and 70 kDa. Tissues from reproductive animals bound twice as much label per gram weight compared to those that were from non-reproductive crabs.     

A method for continuous in vivo measurement of hemolymph conductivity in crabs

A miniaturized conductivity measuring device has been developed to monitor in vivo hemolymph conductivity in crabs. The device measures the conductivity by means of implanted platinum electrodes, and transmits the data via radiotelemetry to a receiving station through 6 ft of water. Crabs used in these investigations survived the insertion of the conductivity probe and appeared to behave and feed normally for up to one week with the probe in position. Blue crabs, Callinectes sapidus Rathbun, which were acclimated to either 5 or 35 ‰ were abruptly transferred to 35 and 5 ‰, respectively and the rate of change of hemolymph conductivity sucessfully monitored. The time required for the conductivity (ionic composition) change in the hemolymph of the crabs after transfer varied from 12 to 16 h for crabs transferred from 35 to 5 ‰ to less than an hour when the change was from 5 to 35 ‰.     

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.     

Walking speed and area utilization of red king crab (<Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis>) introduced to the Barents Sea coastal ecosystem

The red king crab (Paralithodes camtschaticus) was introduced in the Barents Sea in the 1960s and soon established a viable population. Proper management and exploitation of the Barents Sea king crab stock require better understanding of the spatial dynamics at different scales. This study examines the small-scale movement patterns of seven adult male crabs tracked for a period of up to one month from mid July to mid August at 150 m depth in a semi-enclosed fjord on the Russo-Norwegian border. The crabs were tagged with acoustic transmitters and their movements monitored with an acoustic positioning system. Low walking speeds (<0.01 m s⁻¹) were most frequent but the crabs could move at a maximum speed of 0.15 m s⁻¹ and walk an actual distance of up to 270 m over a period of one hour. However, the crabs usually moved within a relatively restricted area with mean hourly longest rectilinear distance varying from 26 to 64 m. The crabs alternated between periods of low and high activity, which could reflect feeding in and movements between food patches. The lack of a diel activity rhythm may be due to high light levels during the polar summer night, or a chemically mediated food search strategy.     

Chemical host detection and differential attraction in a parasitic pea crab infecting two echinoids

Mechanisms of host detection and host choice are important for mobile parasites or symbionts that frequently move among host individuals. The parasitic pea crab Dissodactylus primitivus is an ectoparasite exploiting asymmetrically two spatangoid echinoid hosts, Meoma ventricosa and Plagiobrissus grandis. The entire life cycle takes place on M. ventricosa, while only adults colonize P. grandis, the host where female's fecundity is the greatest. Dissodactylus primitivus frequently exhibits host-switching, a behaviour that raises the question of host detection. To test if adult crabs are able to detect potential hosts and are attracted to the host where their fitness is greater, crab olfactory responses were investigated using a Y-tube. We first showed that D. primitivus are attracted by olfactory cues of M. ventricosa, versus those of a non-host echinoid species, Clypeaster rosaceus sharing the same habitat. This attractiveness was not due to a yellowish water-soluble substance secreted by the host. We then showed that the chemical attraction to the two hosts was different according to the origin of the crabs. Crabs coming from M. ventricosa were more attracted to this host than to P. grandis, a pattern compatible with an imprinting phenomenon. However, crabs collected from P. grandis were equally attracted to both host species, as if imprinting was lost after host change. We propose that the pattern of D. primitivus host detection could be intermediate between the behaviour of specialist and generalist symbionts.     

Biological features of a puzzling symbiotic association between the hermit crab Dardanus insignis and the porcellanid crab Porcellana Sayana (Crustacea)

The symbiotic lifestyle is widespread among porcellanid crabs, which maintain ecological and co-evolutionary associations with annelid polychaetes, poriferans, cnidarians, echinoderms, gastropod mollusks, and other crustaceans such as shrimps and hermit crabs, among others. We investigated the ecological association between the hermit crab Dardanus insignis and the porcellanid Porcellana sayana, in southeastern Brazil. Porcellanid crabs, hermit crabs, and available shells were collected monthly from July 2001 to June 2003, with a shrimp boat equipped with two double-rig trawl nets. The majority of P. sayana specimens were collected in shells occupied by D. insignis (96.6%); a few were found in empty shells (3.4%). The catch of both symbionts and hosts increased with increasing depth, with the highest occurrence at 35 m. The P. sayana crabs of various sizes could be found solitary or forming aggregations of up to 14 individuals per host, showing no sex or size segregation. In spite of the high diversity of shell species occupied by the hermit crabs and also available in the field, only a few of them were also utilized by P. sayana. The majority (93%) of shells utilized by P. sayana also hosted other symbiont species, constituting the basis of extensive symbiotic complexes. Thus, the ecological relationship between D. insignis and P. sayana may be classified as a non-obligate and non-specific symbiosis that may also involve other facultative organisms such as sea anemones.     

A systemic microbial disease in the Dungeness crab,Cancer magister,caused by a Chlamydia-like organism

A Chlamydia-like agent was diagnosed in Dungeness crabs, Cancer magister, collected from Willapa Bay and northern Puget Sound, Washington. Over a 5-year period, infected crabs were found during the months of December through March. Infection by the organism is systemic, resulting in greatly hypertrophied cells with appressed nuclei. Unlike Chlamydia or other Chlamydia-like organisms, the present microbe has a great affinity for connective tissue or connective tissue cells rather than epithelial cells. Transmission electron microscopy revealed the presence of several developmental stages that are similar to chlamydial stages, in addition to what appear to be slightly altered or aberrant stages.     

红树林湿地相手蟹科动物摄食生态研究进展

相手蟹科物种是红树林湿地的主要底栖动物类群,在生态系统中起着重要的作用。我国大陆地区目前已记录的相手蟹科物种数量为12种,低于其它红树林地区(国内常用的采样方法会造成螃蟹物种数量和密度的低估),其中褶痕相手蟹(Sesarma plicata)、无齿相手蟹(S.deaani)和双齿相手蟹(S.bidens)等是常见种。红树植物叶片是相手蟹科动物的主要食物来源,相手蟹科动物通过地表摄食和洞穴贮存的形为消耗了大量的红树植物凋落叶,使这些凋落叶的有机质和营养元素得以保留在生态系统内,在凋落叶的周转和物质归还方面起到重要的作用。它们同时也摄食红树植物的繁殖体并且对不同物种的繁殖体具有摄食偏好,这可能对一些红树物种的植被更新能力和红树植被群落结构产生影响。相手蟹科动物对不同物种和不同状态的红树叶片也存在摄食偏好,通常对腐烂的叶片摄食偏好较强;螃蟹的摄食偏好与叶片的营养成份、粗纤维和单宁含量以及C/N比等性质有关;但在恶劣的野外环境下,螃蟹则会表现出随机性摄食。目前关于相手蟹科动物生态学作用的认识仍不充分,例如它们的种群大小和对凋落物的转化作用等,有待于进一步研究。     

Bacterial Flora of the Hemolymph of the Blue Crab, Callinectes sapidus: Numerical Taxonomy

Bacteria isolated from the hemolymph of normal blue crabs were found to be predominantly Vibrio sp., Pseudomonas sp., Acinetobacter sp., Bacillus sp., Flavobacterium sp., and coliforms. Vibrio parahaemolyticus, a cosmopolitan facultative pathogen widely implicated in outbreaks of gastroenteritis related to the consumption of improperly processed seafood, was present in crabs collected between the months of May to November and was identified in up to 21% of the hemolymphs sampled.     

Detrimental effects of Ulva lactuca (L.) exudates and low oxygen on estuarine crab larvae

Conventional theory postulates that associations between marine macrophytes and animals are generally positive. This paper presents evidence, however, that a common species of green macroalga, Ulva lactuca (L.), is detrimental to estuarine invertebrates due to the production of toxic exudates and low oxygen tensions which occur in the seaweed beds at night. Bioassays of the responses of zoeae of five species of estuarine crabs (Callinectes sapidus Rathbun, Carcinus maenas L., Eurypanopeus depressus Smith, Neopanope texana savi Smith and Rhithropanopeus harissii Gould), using water in which Ulva lactuca was cultured for 24 h, produced 100% mortality after 22 days. No crabs survived the molt into megalopa. Hypoxic water, 0.5 ± 0.3 ppm oxygen, caused a decline in larval activity (movement), but there was no mortality over an 8-h period, Ulva-water purged to 0.4 ± 0.1 ppm oxygen caused 100% mortality in 13–40 min. These synergistic effects could be critical in estuaries where dense U. lactuca beds cause periods of low dissolved oxygen. We hypothesize larval recruitment may be limited in such systems, particularly in areas where flushing is poor.     

Histopathological Changes Associated with Shell Disease in the Red King Crab <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Tilesius, 1815)

Histopathological changes have been revealed associated with shell disease in the red king crab, Paralithodes camtschaticus. The changes in the gills, esophagus, stomach, hepatopancreas, heart, and antennal glands of the crabs are described.     

Biennial reproduction with embryonic diapause in Lopholithodes foraminatus (Anomura: Lithodidae) from British Columbia waters

Abstract. A paucity of data on the reproductive cycle of crabs in the family Lithodidae inhibits both the development of management strategies and the formulation of hypotheses regarding the evolution of lithodid life histories. Life‐history parameters of Lopholithodes foraminatus from British Columbia, Canada, were investigated based on 26 females maintained in the laboratory and supplementary observations on other living and preserved animals. The rate of embryonic development was determined by measuring the percentage area occupied by yolk in lateral views of eggs removed from brooding females throughout development. Females of L. foraminatus exhibited biennial reproduction including an 18‐month brooding period. Females molted, mated, and extruded eggs in mid‐summer, and did not release larvae until late winter or early spring of the second year after fertilization. Embryogenesis included a 12‐month diapause at the gastrula stage. Females released larvae over a mean interval of 69 d, the longest reported for any lithodid. While the development stage of embryos was observed to be heterogeneous within a brood, no spatial gradient in development rate was observed, calling into question the oxygen limitation hypothesis of extended hatching. Biennial reproduction of individuals of L. foraminatus may be a consequence of a relatively low‐quality habitat. Relative to annual reproduction, biennial reproduction halves the potential rate of increase of a population and increases vulnerability to overharvesting, suggesting that L. foraminatus is not a good candidate for commercial exploitation. The adaptive value of embryonic diapause is uncertain and warrants further research.     

The ectosymbiont crab Dissodactylus mellitae-sand dollar Mellita isometra relationship

The presence of the ectosymbiont Dissodactylus mellitae on Mellita isometra was studied at Tybee Island in Georgia. The number of crabs found on sand dollars, stage of maturity, sex, numbers of eggs, and size of eggs produced by crabs were noted. The test diameter of sand dollars, and the number and diameter of eggs produced were also noted. Infestation rates of crabs on sand dollars varied over time. The maximum number of crabs found on a sand dollar was 10. The three types of population dispersion, random, uniform, and clumped, were observed for crabs on sand dollars throughout the sampling period. Clumped or gregarious settling was observed when juvenile crabs were abundant, uniform and random distribution when mature crabs were abundant. Female crabs were significantly larger than male crabs, with carapace width of the largest mature female crab being 4.6 mm and the largest male 3.1 mm. Crabs produced between 80 and 300 eggs from 0.188 to 0.291 mm in diameter. Bigger crabs produced significantly more eggs than smaller crabs. Sand dollar sizes were 50-110 mm, with a mode between 60 and 70 mm. The effect of crab burden on egg production in the sand dollar was time-dependent. The presence of crabs on sand dollars correlated with total egg production of sand dollars in May, the peak of the spawning season, with sand dollars carrying one or two crabs having a lower egg production than those without crabs. Overall, variation in egg size was attributed to variation among females followed by variation between seasons and crab burden.     

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.     

Infection Status of Freshwater Crabs and Crayfish with Metacercariae of Paragonimus westermani in Korea

The present study investigated the infection status of Paragonimus westermani metacercariae in freshwater crabs (n = 363) and crayfish (n = 31) from October 2007 to October 2008 using the crush method. All of the freshwater crabs, Eriocheir japonicus, were negative for P. westermani metacercariae while 10 (32.3%) of the 31 examined crayfish were positive. The 10 positive crayfish were caught in Haenam, Jeollanam-do, and there were 8-59 (mean 28.4) metacrcariae per infected crayfish. These results suggest that P. westermani metacerariae are still transmitted by crayfish enzootically in southern Korea, and that freshwater crabs may transmit metacercariae only on rare occasions.