Abstract While oyster farms and sea otters (Enhydra lutris) coexist in some locations, sustaining these farms and growing interest in their expansion necessitate a comprehensive evaluation of potential interactions. We assessed sea otter interactions with oyster farms through behavioral observations of otters in oyster farms, adjacent non‐farm areas (controls), or bays with no farming activity (references) in southcentral Alaska in 2022–2023. Behavioral observations, conducted through scan surveys, captured sea otter activities (e.g., resting, grooming, swimming, and foraging). Targeted foraging observations tracked foraging success and prey (species and count). We hypothesized that sea otters preferentially used oyster farms for foraging and resting activities compared to non‐farm areas. Contrary to our hypothesis, sea otter activities showed no significant difference in foraging or resting behaviors between oyster farms and controls. Similarly, foraging behavior, including success and prey diversity, did not differ among areas. The dominant prey items in our study included clams (e.g., butter clam [Saxidomus gigantea]), crabs (e.g., helmet crab [Telmessus cheiragonus], red rock crab [Cancer productus]), and mussels (e.g., Pacific blue mussel [Mytilus trossulus]). Notably, there were no observations of farmed oysters being consumed by sea otters. There was strong evidence of differences in the average number of prey consumed per sea otter per dive between the control and reference areas, with the control area averaging 2.6 prey items per dive (SD = 3.6) compared to 4.8 prey items per dive (SD = 7.3) in the reference area. These differences may be attributed to variations in prey biomass and environmental conditions. Our observations indicate that there are no discernible differences in overall sea otter activity or foraging behavior in the presence of oyster farms.

Mating individuals of the helmet crab Telmessus cheiragonus were found during scuba diving in Taui Bay, Sea of Okhotsk, in September 2024. Mating occurred within depths 0.6–10 m and at a water temperature of 8–9°C. The largest crab aggregations were observed at a depth of 2.5–2.8 m in the macrophyte zone. The minimum carapace width in functionally mature males was 84 mm; in females, it was 48 mm. The ratio of females to males found during the study was 1:1.8 in general.

Evaluation of the molting stage of crustaceans is essential for studying their mating behavior because of molt-dependent changes in their behavior. For example, in species in which females mate just after molting, sexually mature premolt females are ready for courtship and postmolt females are ready for copulation. Non-invasive methods of evaluating molt stage are essential in studies of molt-dependent mating behavior so that normal behavior is not disrupted by the evaluation itself. The goal of the present study was to establish a non-invasive evaluation method for the helmet crab Telmessus cheiragonus, which is a model species for research on crustacean sex pheromones. We have identified morphological and behavioral indicators of molt stage. A morphological indicator of molt stage was a change in the color of the edge of telson and sixth abdominal segment, from a dark line to red in premolt animals to white in postmolt animals, which can be observed with the naked eye. A behavioral indicator of molt stage was that premolt females tended to fold their walking legs and chelae to adopt a precopulatory guarded position during artificial handling, whereas late postmolt stage females with developed ovaries and early premolt females in an early molting stage did not show this behavior. These non-invasive morphological and behavioral characteristics are useful indicators of the premolt stage of sexually mature female helmet crabs.

N-acetylglucosamino-1,5-lactone (NAGL) is a molting biomarker in the blue crab Callinectes sapidus The concentration of this compound in urine is highest at the premolt stage. Since sexually mature premolt females release sex pheromone in their urine, NAGL is a candidate sex pheromone molecule in C. sapidus This compound has not been reported in other species. In the present study, we quantified the concentration of NAGL in the urine of the helmet crab Telmessus cheiragonus, using nuclear magnetic resonance spectroscopy, and found that the concentration increases toward the day of molting and decreases after molting. However, the total amount of NAGL collected from individual animals was greatest two to five days after molting, because the amount of urine collected was the lowest at the premolt stage, and it increased after molting. The highest median concentration of NAGL in T. cheiragonas was 29 μmol l(-1), which is 75% of the highest concentration reported in C. sapidus This is the first report of NAGL as a molting biomarker in a species other than C. sapidus We assume that NAGL is part of a pheromone bouquet in these two species.

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.

The analysis of the data obtained during the plankton surveys in Possyet Bay (Peter the Great Bay of the Sea of Japan) in 2000–2001 is presented. The larvae of eight crab species were registered in the plankton: the red king crab Paralithodes camtschaticus (Tilesius, 1815), the snow (opilio) crab Chionoecetes opilio (Fabricius, 1780), the Arctic lyre crab Hyas coarctatus ursinus (Leach, 1815), the kelp crab Pugettia quadridens (de Haan, 1839), the helmet crab Telmessus cheiragonus (Tilesius, 1815), the Japanese swimming crab Charybdis japonica (A. Milne-Edwards, 1861), the pea crab Pinnixa rathbuni (Sakai, 1934), and the porcelain crab Pachycheles stevensii (Stimpson, 1858). These species belonged to six families: Lithodidae, Atelecyclidae, Majidae, Portunidae, Porcellanidae, and Pinnotheridae. The role of the variability of some of the hydrological factors in the meroplankton larvae development was studied. In May, the crab larvae were found mostly in the open part of the bay. In June, they were transported by the current to the northern part of the bay. In July, they spread uniformly in all the bay areas; however, patchiness was observed. The maximal population density of the crab larvae was registered for July and varied from 6.8 to 23.3 ind. m−3. The crab larvae appeared in the plankton in 2000 and 2001 earlier than for the average season.

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 37:241-251 (2008) - DOI: https://doi.org/10.3354/cr00769 Effects of cold winters and climate on the temporal variability of an epibenthic community in the German Bight Hermann Neumann1,*, Siegfried Ehrich2, Ingrid Kröncke1 1Senckenberg Institute, Department for Marine Research, Südstrand 40, 26382 Wilhelmshaven, Germany 2Johann Heinrich von Thünen Institute, Institute for Sea Fisheries, Palmaille 9, 22767 Hamburg, Germany *Email: hneumann@senckenberg.de ABSTRACT: Benthic epifauna was sampled in an area of 10 × 10 nautical miles in the German Bight. Samples were collected in January and July/August from 1998 to 2007 with a standard 2 m beam trawl. The epibenthic communities were severely affected by the cold winter in 1995–1996, which also resulted in high abundance and biomass of the opportunistic brittle star Ophiura albida, in connection with low diversity observed at the beginning of our study period. In the following years winter bottom temperature increased simultaneously with the decrease of O. albida and the increase in abundance and biomass of other species. It appears that these changes were caused by trophic interactions as well as mild winters, which resulted in lower mortality, higher reproduction and higher food supply for benthic fauna due to enhanced primary production. Additionally diversity increased and species such as Astropecten irregularis, Corystes cassivelaunus, Crangon crangon and Crangon allmanni revealed distinct seasonal patterns caused by migration, mortality and reproduction cycles. The changes in community structure are discussed in relation to the general warming trend of the North Sea, which is linked to a phase of continuously increasing North Atlantic Oscillation Index (NAOI) since the late 1980s. We found evidence that climatic variability influenced recruitment success, mortality and migration patterns of epifaunal species. KEY WORDS: Epifauna · North Sea · Temperature · Climate · NAOI · Cold winter · Mild winter · Succession Full text in pdf format PreviousNextCite this article as: Neumann H, Ehrich S, Kröncke I (2008) Effects of cold winters and climate on the temporal variability of an epibenthic community in the German Bight. Clim Res 37:241-251. https://doi.org/10.3354/cr00769 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 37, No. 2-3. Online publication date: October 16, 2008 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2008 Inter-Research.

The effects of preventing female helmet crabs, Telmessus cheiragonus from mating during one breeding season on egg production and egg viability were assessed by investigating the egg clutches of the females isolated from males. A total of 38 females and 18 males were collected in April before the mating peak in 1996 and 1997 in the sublittoral zones of Usujiri, southern Hokkaido, Japan. Eighteen females were held together with 18 males (mating group) and 20 females were isolated from males (non-mating group) during about 7 months of captivity. Subsequently, 11 females of the mating group molted, copulated and produced an egg clutch, and 10 females of the non-mating group molted and spawned without mating. Egg clutch weight and egg diameter did not differ significantly between these two groups. There was also no significant difference in the percentage of viable eggs in an egg clutch between the groups. These results show that preventing female T. cheiragonous from mating during one breeding season has no effect on either clutch size or % viable eggs in a clutch. Sperm storage over one mating season in this species may be advantageous because it allows multiparous females, especially larger ones which could molt and copulate less frequently, to ensure their eggs will be fertilized.

The Belliidae are a small family of crabs whose relationships with other families are enigmatic and whose composition is controversial. It is by no means certain whether their genera form a monophyletic group. One member of this family is Heterozius rotundifrons, a New Zealand endemic crab that lives in the intertidal zone, sheltering under rocks. In the present study the mating behaviour of this species was examined under laboratory conditions. Mating and moulting are closely linked because H. rotundifrons females only mate immediately after moulting. Females remain attractive to males for almost 3 days. A female-derived water-borne pheromone seems to be the basis of this attraction. Prior to moulting males guard females for up to 5 days. During the female moult some males were observed to assist the female. During copulation both males and females exhibited an unusual limb quivering behaviour and afterwards males guarded the females for 10.5 h, which was extended to 37 h when other males were present. Field studies showed that females moulted during early spring over a period of 1 month. Throughout the year very few females moulted, suggesting that there may be intense competition for mates during the early spring. At all times the operational sex ratio was biased in favour of males. In terms of the evolution of reproductive characters among the Belliidae, Atelecyclidae, Cheiragonidae and Corystidae, H. rotundifrons occupies an intermediate position between the ancestral condition and that seen in Corystes cassivelaunus.

Sexually competent females of Telmessus cheiragonus (helmet crab) release two pheromones that elicit grasping and copulation behaviors in males (Kamio et al., 2000, 2002, 2003). Our study aimed to use behavioral and electrophysiological techniques to identify the site of reception of these sex pheromones. In behavioral experiments, either the inner or the outer flagella of the antennules were ablated bilaterally from male crabs, and responses of male crabs to female odor were examined. When the inner flagella were surgically ablated, the sexual response (i.e., grasping and copulation behavior) of male crabs was not significantly changed relative to control animals that had their second antennae ablated. In contrast, the sexual response was significantly reduced when the outer flagella of the antennules were ablated, suggesting that the outer flagellum is the receptor organ that detects the sex pheromones. In electrophysiological experiments, urine, which in females contains the pheromone that elicits grasping behavior by males but does not contain the pheromone eliciting copulation, whose release site is not known, was tested. Female and male urine as well as shrimp extract evoked phasic responses of chemosensory afferents innervating aesthetasc sensilla on the outer flagellum of male crabs. The response of the afferents had significantly higher magnitude and lower threshold when female urine was applied. Thus, behavioral and electrophysiological observations suggest that in male helmet crabs, the outer flagellum of the antennule is the chemosensory organ that detects female sex pheromone.

Abstract Between November 2000 and May 2002, epibenthos was sampled monthly with a 2-m beam trawl at three stations along a transect from the southern German Bight towards the northeastern part of the Dogger Bank (North Sea) in order to investigate the seasonal variability of the epibenthic communities. The stations were chosen to reflect a gradient in the hydrigraphic regime, organic matter supply, and fishing effort. The epibenthic community of the southern German Bight was characterized by high biomass and abundance, dominated by Asterias rubens and Ophiura albida. In contrast, at the northern stations in the Oyster Ground and at the Dogger Bank, epibenthic biomass and abundance were substantially lower and the dominant species were mainly crustaceans such as Corystes cassivelaunus, Liocarcinus holsatus, and Pagurus bernhardus. In terms of seasonal variability, mean abundance and biomass in the southern German Bight showed highest values in the summer months and lowest values in the winter months. A similar pattern, but less distinct, was observed in the Oyster Ground. But at the Dogger Bank the pattern was different, with highest abundance and biomass values in the winter months. The differences in spatial and temporal patterns are discussed in relation to differences in temperature, thermal stratification and fishing effort at the three study sites.

: To clarify the annual testicular maturation cycle in the helmet crab Telmessus cheiragonus, seasonal histological changes of the testis and occurrence of grasping pairs and recently copulated females with fresh sperm plugs were investigated. The testis was composed of seminiferous ducts with many testicular lobules. Development of the lobules was divided into six stages (spermatogonia proliferation, first spermatocyte, reduction division, spermatid, spermiogenesis and free sperm stage) based on the spermatogenic phase of the germ cells in each lobule. The mean percentage of the lobules during each stage was calculated every 1–3 months. Developed lobules occurred with a high percentage throughout the year except in June when developing lobules predominated. Grasping pairs and females with fresh sperm plugs were collected during April–July with a peak in May–June. These results suggest that the males have testis with many developing lobules in June when they are active for mating. Newly formed spermatozoa may be stored in the testis and the vas deferens until the next mating season after June, as the spermatozoa may not have an opportunity to fertilize eggs until the next season and there is no sign of spermatozoa absorption in the testis.

While the benthic infauna of the North Sea has been studied intensively over the past decades, few studies have focused on the larger mobile epifauna. Studies carried out to date have described the distribution of epifaunal communities over the whole of the North Sea, but variability within the identified communities, which occurs on a much smaller scale, has so far remained unstudied. This is the first study to describe seasonal and annual variability of an epifaunal assemblage in the German Bight area, where environmental conditions are highly variable. The benthic community was sampled with a 2 m beam trawl from 1998 to 2001. The echinoderms Ophiura albida and Asterias rubens and the crustacean Pagurus bernhardus were the dominant species caught throughout the study period. Overall the species composition of the catches was relatively consistent, while abundances of dominant species fluctuated considerably between sampling periods. Differences between sampling periods were not only influenced by the abundances of dominant species, but also by less dominant species such as Ophiura ophiura, Astropecten irregularis, Corystes cassivelaunus, Crangon crangon and Aphorrahis pespelicani. The abundances of these species varied annually and seasonally in the assemblage. Clear differences between summer and winter in the species composition, abundance and biomass were identified. Annual and seasonal changes were most likely linked to migratory movements of epifauna into and out of the area under investigation. Temporal changes in species composition and abundance correlated best with water temperatures, while the spatial distribution of the total biomass over the whole sampling period was correlated with sediment characteristics. Anthropogenic influences such as fishing activity and chronic large-scale eutrophication are thought to have influenced the community on a long-term basis, but have been considered unlikely causes for the short-term variability described by this study.

The mating behaviour of the helmet crab, Telmessus cheiragonus, was observed in the laboratory to obtain information of its fishery management and seed production. Females always moulted before copulation and all moulting females copulated with their mates, while males performed precopulatory guarding before their mates moulted. The average duration of precopulatory guarding was 11.8±5.0 SD days. Sex ratios in experimental tanks did not influence the first guarding duration of male but diminished the female's guarded duration under female-biased treatment. Competition among males for females was observed; larger males appeared to have a competitive advantage. Males started copulation in 41.2±10.9 SD min after females moulted and the copulation lasted for 110.6±6.6 SD min. Postcopulatory guarding duration was 4.0±6.6 SD h. Small males tended not to guard and to copulate with females larger than themselves. Common features and differences in mating behaviour between T. cheiragonus and Erimacrus isenbeckii is discussed.

Annual reproductive cycle of the helmet crab Telmessus cheiragonus was investigated based on the histological observations of the ovary and the gonadosomatic indices (GSI = ovarian weight x 100 / body weight). The ovarian maturity was divided into five phases (Phase I-V). Minimum mature size of female was 36.0 mm in carapace length. The annual reproductive cycle in the adult females (more than 36.0 mm carapace length) consisted of the incubating period (October-March) and the maturing period (April-September). During the incubating period, the ovarian maturity was Phase I-II (mean GSI±SD = 3.8±4.7 %) when most of the females were ovigerous. During the maturing period, the ovarian maturity increased to Phase V (GSI ≤ 21.6 %) when the females seemed to be frequently copulating, because the soft shell adult females, which could copulate, occurred with highest frequency. The spawning of most females seemed to occur at the end of the maturing period. These results suggest that the ovarian maturation cycle requires one year, and during the incubation period ovaries are immature.

Abstract A new reliable bioassay method has been developed for detection of female sex pheromone(s) of the helmet crab Telmessus cheiragonus using artificial sponges based on the grasping behavior of male crabs. The seawater, male urine, and pre- and postmolt female urine were tested for pheromonal activity which resulted in the detection of activity only in urine from pre- and postmolt females.

A combination of characters, not individually unique, possessed by the corystid,Corystes cassivelaunus, and the two cancrids,Platepistoma nanum andCancer pagurus, defines a corystoid-type of spermatozoon: the basally bulbous, anteriorly narrowing perforatorium, the extent of this almost to the plasma membrane through a widely perforate operculum, and the simple inner acrosome zone, lacking an acrosome ray zone. The sperm of the two cancrids are closely similar, that of the corystid differing, for instance, in the less pointed, and less tapered, form of the perforatorium. This relative uniformity of spermatozoal ultrastructure in the cancrid+corystid assemblage so far investigated supports inclusion of the two families in the superfamily Corystoidea by Guinot (1978). The combination of perforation of the operculum and absence of an acrosome ray zone (at least in a clearly recognizable form) are features of the Potamidae which possibly indicate that the latter family, modified for a freshwater existence, is related to the cancrid+corystid assemblage. Some elongation of the centrioles, apparent at least inCorystes, may be a further link with potamids in which they are greatly elongated. The coenospermial spermatophores of cancridoids are a notable difference from the cleistospermia of potamids; but the latter is probably an apomorphic modification for fertilization biology.

Abstract During an investigation into the occurrence of various crab species in the Oban (West of Scotland) area, Iphitime cuenoti was found infesting the branchial cavity of Liocarcinus puber, L. corrugatus, L. depurator, Carcinus mamas, Cancer pagurus, Hyas araneus and Macropodia longirostris caught within, or on the sandy mud below, the Laminaria forest. The same crab species obtained from sandy habitats, and crabs peculiar to such a habitat (Portumnus latipes, Liocarcinus holsatus and Corystes cassivelaunus) did not harbour the polychaetes. Three or more worms were commonly found in each Liocarcinus host, the highest number recorded, in L. puber, comprising 9 adult and at least 98 juveniles, the latter being found between the gill lamellae. Over 90% of both L. puber and L. corrugatus were infested, 35% of L. depuratot, but less than 10% of any of the other species. The largest worms (up to 80 mm alcohol-preserved length) were found in L. puber and L. corrugatus. Worms were found to have either simple or slightly bifurcate branchiae, or multifurcate branchiae. Worms with simple branchiae rarely reached 40 mm in length, usually possessed jaws which exceeded 700 μm in length, and were never found to contain eggs. These are regarded as putative males, and histological evidence from three specimens confirms this suggestion. Only Iphitime with multifurcate branchiae were found to contain eggs, and were also the largest worms, but their jaw length was very variable, ranging from 0-1030 μm with little or no relationship to the length of the worm. The smallest worms, 3 mm in length, were found between the gill lamellae throughout the year, but mainly from December to August. In multiple infestations there appeared to be one dominant female which probably inhibited maturation of companion worms, and it is postulated that once this female vacates, there is a sequential maturation and spawning of subordinate worms. The greatest number of mature worms, and the largest worms, occurred during October and November, but because of the extended larval settlement period it is a matter of debate whether the worm is an annual, or has a more extended lifetime. Iphitime paguri was found occupying the apical whorl of4.6% of Buccinum undatum shells and 2.6% of Neptunea antiqua shells occupied by the hermit crab Eupagurus bernhardus. The worm is very fragile and, being rare, there is insufficient data to define its biology. The longest worm was 50 mm (alcohol- preserved length) and the largest jaw length 760 μm; there appeared to be an inverse relationship between length of worm and jaw size, and no worm over 25 mm had jaws larger than 250 μm. All ovigerous worms had small jaws. Nereis fucata was found in 2.6% of Neptunea antiqua and 7.1% of Buccinum undatum shells occupied by the hermit crab. It was not found associated with Iphitime paguri.

INTRODUCTIONThe food and feeding habits of rays (genus Raja) have received more attention than other aspects of their biology. Being nocturnal feeders (Bigelow & Schroeder, 1953), they have been thought to locate food by smell rather than by sight (Steven, 1930, 1947). More recently, the ability of the electric receptors to detect even weak action potentials has been linked with food foraging (Kalmijn, 1966). Wilson (1953) observed that the behaviour of Raja while apprehending prey was similar to that of Torpedo spp. The functional advantages of a ventral mouth as an adaptation to bottom feeding have been stressed by Alexander (1970).Day (1880–1884) recorded that rays ate molluscs, crustaceans and fish. That the young of Raja clavata, R. montagui (as R. maculata), R. naevus and R. brachyura feed on crustaceans was observed by Clark (1922). Steven (1930, 1932, 1947) confirmed this in a wider age sample of the same species, adding that juveniles which ate amphipods and crangonids later changed to Upogebia, Portunus and Corystes cassivelaunus, whereas the adults were highly piscivorous and sometimes cannibalistic. Both Clark and Steven obtained their fish close to Plymouth. Lazzareto (1964) and du Buit (1969), largely corroborating the above, included polychaetes in the list of food items but specified no differentiation according to size.Holden & Tucker (1974), recording only presence or absence of food items, studied R. clavata, R. brachyura, R. montagui and R. naevus from a much wider area.

Abstract An account is given of a preliminary study of epizoites occurring on the pycnogonid Phoxichilidium tubulariae Lebour and the caprellid Caprella linearis (L.) from the southern North Sea; and on the burrowing crab Corystes cassivelaunus (Pennant) from the Solway Firth. Each of these species appears to be associated with a distinctive and restricted epizoic fauna dominated respectively by ciliate and suctorian protozoans; hydroids (Campanularidae) and the anascan bryozoan Electra pilosa (L.); the hydroid Gonothyraea loveni (Allman) and the barnacle Balanus crenatus (Bruguière). These faunas are described in terms of their species-composition and distribution; and the three host species compared with reference to the habitats that they offer for exploitation. The ecological significance of invertebrates, particularly vagile forms, as habitats for sessile organisms is discussed in terms of their effects upon distribution and dispersal. The factors responsible for variations between the composition of epizoic faunas, and also the effects that these communities exert upon the host species are reviewed.