Erimacrus Research Articles

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

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

Gender identification of the horsehair crab, Erimacrus isenbeckii (Brandt, 1848), by image recognition with a deep neural network

Appearance-based gender identification of the horsehair crab [Erimacrus isenbeckii (Brandt, 1848)] is important for preventing indiscriminate fishing of female crabs. Although their gender is easily identified by visual observation of their abdomen because of a difference in the forms of their sex organs, most of the crabs settle with their shell side upward when placed on a floor, making visual gender identification difficult. Our objective is to use deep learning to identify the gender of the horsehair crab on the basis of images of their shell and abdomen sides. Deep learning was applied to a photograph of 60 males and 60 females captured in Funka Bay, Southern Hokkaido, Japan. The deep learning algorithms used the AlexNet, VGG-16, and ResNet-50 convolutional neural networks. The VGG-16 network achieved high accuracy. Heatmaps were enhanced near the forms of the sex organs in the abdomen side (F-1 measure: 98%). The bottom of the shell was enhanced in the heatmap of a male; by contrast, the upper part of the shell was enhanced in the heatmap of a female (F-1 measure: 95%). The image recognition of the shell side based on a deep learning algorithm enabled more precise gender identification than could be achieved by human-eye inspection.

New data on biology and captures of <i>Erimacrus isenbeckii</i> (Decapoda: Cheiragonidae) in the Shelikhov Bay (northern Okhotsk Sea)

New data on biology of hair crab Erimacrus isenbeckii are presented and ecological and geographical variability of this species is discussed. Molting, growth, sex and size structure of the crab are considered on the data collected in the Shelikhov Bay of the Okhotsk Sea in September-October, 2022. The male : female ratio of E. isenbeckii in the trap catches was 14 : 1. Gender differences in their age, weight, and carapace width were not significant (p < 0.05). The maximum size of E. isenbeckii in the Shelikhov Bay was 104 mm that is less the size values at the western coast of Kamchatka, southward from Kamchatka, and in the Aniva Bay of Sakhalin Island, and much smaller the crabs from the waters of Hokkaido Island and Alaska Peninsula. Rather high portion of the males on the 3rd intermolting stage was detected (57 %). The age composition of males varied significantly in dependence on stage of molting (p < 0.05). A freshly molted female on the 1st intermolting stage with an unoccluded genital opening was caught together with its exuvia. After molting, within the crab trap, it had increased the width of carapace in 6 mm. This new information could be used in monitoring of the E. isenbeckii population in the Shelikhov Bay.

Morphometric approaches reveal sexual differences in the carapace shape of the horsehair crab, Erimacrus isenbeckii (Brandt, 1848)

Morphometric approaches reveal sexual differences in the carapace shape of the horsehair crab, Erimacrus isenbeckii (Brandt, 1848)

Larval survival, development and growth in the horsehair crab, Erimacrus isenbeckii , cultured under different photoperiod conditions

Larval sinking causes larval mass mortality during seed production in the horsehair crab, Erimacrus isenbeckii. Under normal light conditions, horsehair crab larvae generally show negative phototactic behaviour and sink in their rearing seawater. It has been proposed that culturing larvae in the dark may prevent larval sinking. Herein, we examined the effect of photoperiods on horsehair crab larval survival and development to facilitate the development of larval rearing techniques that prevent sinking. Newly hatched larvae were reared with Artemia to the first crab stage in 2-L beakers under five photoperiods: 0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D. Larvae survived and molted to the first crab stage under all tested photoperiod conditions. The survival rate improved with increasing light period, whereas the developmental period for each larval stage decreased with increasing light period. Longer light periods increased the carapace length at the first crab stage. Our results suggest that larvae could be cultured to the first crab stage in large-scale tanks under constant darkness. However, significantly improved larval performance under longer photoperiodic conditions indicates a need for developing alternative culture techniques to control larval behaviour in the seed production tank.

Effect of Light Environment on the Sinking Phenomenon and the Development of Larvae of the Horsehair Crab Erimacrus isenbeckii in Rearing Tanks

Effect of Light Environment on the Sinking Phenomenon and the Development of Larvae of the Horsehair Crab Erimacrus isenbeckii in Rearing Tanks

Effects of Supplementation of Rearing Water with Diatom Thalassiosira sp. and Dietary n-3 Highly Unsaturated Fatty Acids on the Survival and Developmental Period of Horsehair Crab Erimacrus isenbeckii Zoeae

Effects of Supplementation of Rearing Water with Diatom Thalassiosira sp. and Dietary n-3 Highly Unsaturated Fatty Acids on the Survival and Developmental Period of Horsehair Crab Erimacrus isenbeckii Zoeae

Structural Elucidation of the Neutral Glycosphingolipids, Mono-, Di-, Tri- and Tetraglycosylceramides from the Marine Crab Erimacrus isenbeckii

The neutral glycosphingolipids, mono-, di-, tri- and tetraglycosylceramides (GL-1, GL-2, GL-3, GL-4a and GL-4b), were identified from whole tissues of the marine crab Erimacrus isenbeckii by successive column chromatography with ion exchange Sephadex (QAE-Sephadex), magnesium silicate (Florisil) and silicic acid (Iatrobeads) resins. Through component analysis, sugar analysis, methylation studies, exoglycosidase cleavage, and various chromatographic and spectrometric techniques, their structures were proposed to be as follows: GL-1, Glcβ1-1Cer; GL-2, Manβ1-4Glcβ1-1Cer; GL-3, Galβ1-3Manβ1-4Glcβ1-1Cer; and GL-4a and GL-4b, Gal3Meα1-4Galβ1-3Manβ1-4Glcβ1-1Cer. The main molecular species of the aliphatic moiety in each purified glycolipid were 18:0, 22:0, 22:1-d14:1 (fatty acid-sphingoid) and 18:0-d16:1 for GL-1; 18:0-d16:1 and 22:1-d14:1, d16:1 for GL-2; 22:1, 24:1-d16:1 for GL-3; 22:1, 24:1-d16:1 for GL-4a; and h22:1, h24:1-d16:1 for GL-4b, respectively. By immunological detection, an arthro-series glycosphingolipid (At3Cer; GlcNAcβ1-3Manβ1-4Glcβ1-1Cer) was also detected as a minor component. The characteristic arthro-series glycosphingolipid has been observed in most animals belonging to the phylum Arthropoda.

飼育したケガニ幼生の走光性，鉛直分布，体密度と外部形態の発育に伴う変化

ケガニの種苗生産では，幼生の沈降死現象が問題視されている。沈降死防除技術を開発する基礎として，幼生の走光性，鉛直分布，体密度，外部形態を調べた。ふ化ゾエアは正の走光性を示し，以後は負の走光性が強くなった。特に，620 nm 以上の長波長で負の反応が強かった。ふ化当日の幼生は縦型容器内で浮遊したが，以後は沈降した。幼生の体密度は海水比重より大きく，沈下抵抗に関わる体の突起状部位は発育に伴い縮小した。ケガニ幼生は明条件下では沈降しやすいことから，暗条件や長波長を利用した飼育方法を検討する必要性を指摘した。

Effects of n-3 highly unsaturated fatty acid content in Artemia on survival and development of laboratory-reared horsehair crab Erimacrus isenbeckii larvae

The effect of varying levels of dietary n-3 highly unsaturated fatty acid (HUFA) content in Artemia sp. on survival, the number of days required to reach each larval stage, and the growth and morphogenesis of larvae of the horsehair crab Erimacrus isenbeckii were examined. Artemia enriched with materials of six types [condensed Nannochloropsis sp., ethyl oleate, two enrichment levels of eicosapentaenoic acid (EPA), and those of docosahexaenoic acid], and unenriched Artemia were fed to larvae. Newly hatched larvae were reared in groups of 50 individuals in two 2-l beakers until they reached the first crab stage. No significant difference was found in survival rate, growth, or morphogenesis of larvae, but fewer days tended to be required to reach the first crab stage in the group enriched with high EPA compared to the other groups. Results show that, although the amount of n-3 HUFA in unenriched Artemia might meet the demands of horsehair crab larvae for their survival, growth, and morphogenesis, Artemia should be enriched with high EPA to improve the rate of larval development.

Individual variations of the phospholipid compositions of the organs of arthropods, echinoderms, and tunicates from peter the Great Bay of the Sea of Japan

Individual variations in the phospholipid compositions of the organs of marine invertebrates were investigated in the representatives of three phyla: Arthropoda [decapods: Paralithodes camtschaticus (Tilesius, 1815) and Erimacrus isenbeckii (Brandt, 1848)]; Echinodermata [starfishes: Distolasterias nipon (Doderlein, 1902) and Evasterias echinosoma Fisher, 1926]; and Tunicata [ascidians: Halocynthia aurantium (Pallas, 1787), H. roretzi (Drasche, 1884), and Styela clava Herdman, 1881]. The specificity of individual phospholipid variation was shown to be related to the systematic status and functional properties of the organs of marine invertebrates. Phosphatidylcholine and phosphatidylethanolamine were the least variable. Low variation of phospholipid composition was found in the liver, legs, and gills of decapods; in the liver of starfishes; and in the gonads and skin-muscular and gill sacs of ascidians. The contents of ceramide aminoethylphosphonate (CAEP) and phosphatidylglycerol (PG) showed the highest variation. These phospholipids were found but not in all individuals or organs studied. After 7 days of starvation, CAEP completely disappeared from the organs of the animals; thus, we suggest its exogenous origin.

ケガニ幼生の生残，発育および摂餌に及ぼす塩分の影響

ケガニ幼生の生残，発育および摂餌に及ぼす塩分の影響

Diet and some ecological features of the most widespread commercial crab species in the northwestern Sea of Japan in early spring

Results of the study of feeding habits of the commercial crab species Chionoecetes opilio, Ch. japonicus, Paralithodes platypus, P. camtschaticus, and Erimacrus isenbeckii in early spring 2009 are presented. The composition, distribution, and quantitative characteristics of benthos in the areas of sampling are analyzed. The generalized pattern of distribution of the considered crabs is shown with the maximum and mean densities. These crabs were found to consume at least three to four single portions of food during 10–12 hours of daylight. The lowest feeding intensity was observed in the opilio snow crab in March and April. Cannibalism proved to be typical for all the studied crab species in the spring. It was most developed in the deepwater red snow crab, in whose diet representatives of the same species constituted a one-third share. It was also noted that the diet of the studied crabs included a major proportion of crabs and shrimps, which was unusual for the feeding habits of the same species in other Far Eastern seas.

The period of occurrence, density, and distribution of larvae of three commercial crab species in Peter the Great Bay, Sea of Japan

Based on materials from plankton surveys carried out in 2004–2009, the period of occurrence, density, and distribution of larvae of three commercial species of crabs in the Peter the Great bay and adjacent areas of Sea of Japan were studied. The larvae of the horsehair crab Erimacrus isenbeckii (Brandt, 1848) occurred in the plankton from mid-March to early June, within the range of water temperature from −1 to 10.8°C. The larvae of the helmet crab Telmessus cheiragonus (Tilesius, 1812) appeared in the plankton in mid-April and occurred to the end of June within the temperature range from 2.8 to 13.0°C. The larvae of the snow crab Chionoecetes opilio (O. Fabricius, 1788) appeared in the plankton in mid-April as well, but some individuals sporadically occurred until early August. All the species of crabs produced one generation of larvae for their reproduction season. The terms of larval stay in plankton depended on water temperature and the duration of the pelagic period increased in colder years. In that area, the larvae of C. opilio were the most abundant (up to 41 ind./m3) and the zoea density of horsehair and helmet crabs was significantly lower (no more than 2 ind./m3). The larvae of C. opilio occurred over the entire area of the Peter the Great bay; the greatest aggregations of their early stages were observed in its southwestern open part. The maximum density of E. isenbeckii zoea was recorded in the south of the Amursky bay and in the Posyet bay. Individual larvae of T. cheiragonus occurred in the Posyet bay and in the southern part of the Amursky and Ussuriisky bays. The late-stage larvae of all crab species were concentrated in areas of the coastal circulation.

Hemocyanin-derived phenoloxidase activity with broad temperature stability extending into the cold environment in hemocytes of the hair crab Erimacrus isenbeckii

Phenoloxidase (PO) activity is a major component of the innate immune response in arthropods. In this study, we characterized PO activity from the hair crab Erimacrus isenbeckii, which inhabits very cold regions (2.4-3.4°C) of the Bering Sea. Hemocyte lysate supernatant (HLS) prepared from E. isenbeckii was inactive HLS until activated by nonspecific agents such as sodium dodecyl sulfate and trypsin, and elicitors such as lipopolysaccharide and lipoteichoic acid from the cell wall constituent of bacteria. The PO activity was maximal at 4°C, decreased slightly at temperatures up to 60°C, and fell rapidly at 80°C. Both L-DOPA and catechol were efficient substrates for the PO (EC 1.10.3.1), with K(m) values of 0.96 and 1.15mM, respectively, whereas tyrosine and hydroquinone were not. We isolated a protein fraction from HLS as a hexamer of 75kDa units with 216.7-fold higher PO activity than that of the HLS. The N-terminal amino acid analysis of an isolated protein revealed 80% sequence identity to hemocyanins from other crabs. These results suggest that cold-adapted hemocyanin-derived PO activity is important to the survival of these crabs. This is the first report of a crab PO activity with broad temperature stability extending into the cold environment.

Early zoeal stages of edible crab Erimacrus isenbeckii (Brandt, 1848) (Crustacea: Decapoda: Brachyura: Cheiragonidae) and a comparison with other cheiragonid zoeae

Ovigerous crabs of Erimacrus isenbeckii were collected from the northeastern coast of South Korea and their larvae were reared in the laboratory. Two zoeal stages were described and illustrated in detail. The first zoeal characteristics between the present material and Sasaki and Mihara's (1993: J Crust Biol. 13:511–522) were different especially in the setations of the endopods of the maxillipeds. The zoea of Erimacrus isenbeckii strongly resembled those of two Telmessus species in the Cheiragonidae, but the former could be distinguished from the latter by having spinulate carapace spines, a lateral process on the abdominal somite 3, and longer lateral spines on the telson fork.

Thematic Review Series: Sphingolipids. Biodiversity of sphingoid bases (“sphingosines”) and related amino alcohols

“Sphingosin” was first described by J. L. W. Thudichum in 1884 and structurally characterized as 2S,3R,4E-2-aminooctadec-4-ene-1,3-diol in 1947 by Herb Carter, who also proposed the designation of “lipides derived from sphingosine as sphingolipides.” This category of amino alcohols is now known to encompass hundreds of compounds that are referred to as sphingoid bases and sphingoid base-like compounds, which vary in chain length, number, position, and stereochemistry of double bonds, hydroxyl groups, and other functionalities. Some have especially intriguing features, such as the tail-to-tail combination of two sphingoid bases in the α,ω-sphingoids produced by sponges. Most of these compounds participate in cell structure and regulation, and some (such as the fumonisins) disrupt normal sphingolipid metabolism and cause plant and animal disease. Many of the naturally occurring and synthetic sphingoid bases are cytotoxic for cancer cells and pathogenic microorganisms or have other potentially useful bioactivities; hence, they offer promise as pharmaceutical leads. This thematic review gives an overview of the biodiversity of the backbones of sphingolipids and the broader field of naturally occurring and synthetic sphingoid base-like compounds.

Genetic Variation and Population Structure of Hair Crab (Erimacrus isenbeckii ) in Japan Inferred from Mitochondrial DNA Sequence Analysis

Genetic variation and population structure of hair crab (Erimacrus isenbeckii) were examined using nucleotide sequence analysis of 580 base pairs (bp) in the 3' portion of the mitochondrial cytochrome c oxidase subunit I gene (COI) of 20 samples collected from 16 locales in Japan (the Hokkaido and Honshu Islands) and one in Korea. A total of 27 haplotypes was defined by 23 variable nucleotide sites in the examined COI region. Pairwise population F (ST) estimates and neighbor-joining tree inferred distinct genetic differentiation between the representative samples from the Pacific Ocean off the Eastern Hokkaido Island and the Sea of Japan, while others were intermediate between these two groups. AMOVA also showed a weak but significant differentiation among these three groups. The present results suggest a moderate population structure of hair crab, probably influenced by high gene flow between regional populations due to sea current dependent larval dispersal of this species.

A Novel Lectin Isolated from the Hemolymph of the Marine Hair Crab Erimacrus isenbeckii

A lectin that induces hemagglutination activity in mouse and rabbit erythrocytes has been purified from the hemolymph of the marine hair crab Erimacrus isenbeckii. The results of SDS-PAGE, gel-filtration, affinity and anion-exchange chromatography indicate that this lectin, designated EIL (E. isenbeckii lectin), was successfully purified as a single protein, and comprises a mixture of a major (90%) dimeric and a minor (10%) oligomeric protein with a molecular mass of 116 kDa, with covalent linking between two subunits of 62 and 54 kDa. The activity was maximal at pH 5.6-8.0 and at temperatures below 50 degrees C. The N-terminal amino acid sequences were determined, and these differed greatly from those of other reported lectins from invertebrates, vertebrates, or plants. EIL binds with high specificities to both the O-acetylsialic acid and mannose that are present in bacterial pathogens, which suggests that EIL can act as a defense protein against infection in this crab.

Molecular Cloning of Tropomyosins Identified as Allergens in Six Species of Crustaceans

Although tropomyosin is known to be a major allergen of crustaceans, its structural information is limited to only five species. In this study, tropomyosin was confirmed to be a major allergen in six species of crustaceans (black tiger prawn, kuruma prawn, pink shrimp, king crab, snow crab, and horsehair crab) by immunoblotting. Then, the amino acid sequences of tropomyosins from these crustaceans were elucidated by a cDNA cloning technique. Sequence data for crustacean tropomyosins including the obtained results reveal that fast tropomyosins are contained in shrimps (or prawns) and lobsters, slow tropomyosins in crabs, and both tropomyosins in crayfishes and hermit crabs. Although fast and slow tropomyosins share a high sequence identity (about 90%) with each other, significant differences are observed in specific regions between both tropomyosins.