Lithodid Crabs Research Articles

Epibiotic Communities of Common Crab Species in the Coastal Barents Sea: Biodiversity and Infestation Patterns

Crabs are important ecosystem engineers in marine habitats worldwide. Based on long-term data, we analyzed the species composition and infestation indices of epibionts and symbionts colonizing the great spider crab, Hyas araneus, and two lithodid crabs—the northern stone crab, Lithodes maja, and the red king crab, Paralithodes camtschaticus—in the coastal zone of the Barents Sea. The epibiotic communities found on great spider crabs were closer to northern stone crabs (33%) compared to red king crabs (25%). The prevalence of mobile symbionts (amphipods, Ischyrocerus, and polychaetes, Harmothoe) and common epibionts, such as barnacles and hydrozoans, was low on great spider crabs and high on the body and in the gills of lithodid crabs. Epiphytes were abundant on great spider crabs but not present on both species of lithodid crabs. Egg symbionts found on H. araneus and P. camtschaticus do not affect their local populations. Differences in the fouling communities found on the three crab species are associated with host size range, surface properties of their carapaces, and behavior patterns.

Movements of a potential fishery resource, porcupine crab (Neolithodes grimaldii) in Northern Davis Strait, Eastern Canadian Arctic

Climate change is positioning deep-sea lithodid crab species to expand their distributions. In Canada's Eastern Arctic, there is additional interest in the lithodid crab, Neolithodes grimaldii, (or porcupine crab) as a potential fisheries resource, as high biomass has been observed through incidental bycatch in the Greenland halibut (Reinhardtius hippoglossoides) fishery. This study aimed to advance our knowledge of the biology of the porcupine crab by addressing undescribed aspects of the crabs' spatiotemporal distribution. We administered pop-up archival tags (mrPATs and miniPATs) on 18 porcupine crabs and tracked their movements in Davis Strait at ~900 m depth. The tags were programmed to release sequentially, providing the location of a crab every six days across the study period (July–October 2018). Of the 18 tags, 17 (94%) successfully reported locations and six of those (35%) popped-off on the programmed date. A systematic method was established to estimate the most accurate final location of each crab, considering error introduced by tag drift (horizontal and vertical) and by satellite location accuracy. Six crabs (35%) moved between 3.1 and 33 km away from the deployment site over the course of 19 - 66 days, while the rest remained highly site attached moving <1 km. Crabs moved in a southern direction away from the deployment site; however, the broad range of this directional movement (113.6° – 283.7°), provides little support for coordinated group movement. Crabs also remained within a narrow depth and thermal range for the study period. To our knowledge, this study is the first to administer pop-up archival tags on porcupine crabs revealing a new technique to investigate their spatiotemporal movements. We propose further telemetry work to support the development of an offshore porcupine crab fishery in the Canadian Arctic.

Effects of fishery practices on fecundity of two lithodid crab species of commercial interest in Southern South America

The fishery of Lithodes santolla is the second most productive lithodid crab fishery in the world and in southernmost South America is considered a mixed fishery due to its co-occurrence with Paralomis granulosa. Fishing takes place in Argentina and Chile, where regulations restrict to land only males larger than a legal size, but with variable fishing seasons. All females and small males must be returned to water. Both species have long periods of embryogenesis. Individual fishers operate on a small geographic scale, following lithodid crabs which are typically confined to channels, fjords or straits. Therefore females can be fished and discarded on multiple occasions throughout egg-bearing period. We studied the effect of the fishing practices on the fecundity of L. santolla and P. granulosa. First, we experimentally evaluated the effect of seven repeated return-to-water simulations in different conditions: aerial exposition or aerial exposition followed by a free fall (FF) or ramp. Secondly and only in L. santolla, we tested the effect on the egg-loss of different stocking densities followed by a FF return-to-water. Finally, we estimated the fecundity at the beginning and at the end of the egg-bearing period in females of L. santolla. The FF produced a high egg-loss and did not increase with the trial repetitions in L. santolla. Female P. granulosa showed a similar egg-loss pattern for all treatments, and overall lost fewer eggs than female L. santolla. In P. granulosa except for the FF, the trial repetition produced an increase in the egg-loss. In L. santolla there was no effect on the egg-loss due to stocking densities. Based on the field studies, fecundity of L. santolla decreased during the egg-bearing period. This study demonstrated the effects of repetitive fishing events on the fecundity in two lithodid species of commercial interest.

Temperature effects on larval development in the lithodid crab Lithodes maja

Physiological adaptations enabling tolerance of low temperature, as well as adaptations in larval development, are thought to be critical to the global radiation of deep-water lineages of lithodine crabs. However, global climate change is warming the oceans, potentially impacting the biogeographic distributions of these large predatory crabs. To date, larval thermal scope has only been explored in a few deep-water lineage lithodines. We assessed larval development parameters in the northern stone crab Lithodes maja at temperatures ranging from 1 °C to 15 °C. We examined larval survival, duration of development, energetic reserve utilisation, and respiration rate. L. maja larvae displayed a narrow thermal tolerance window and metamorphosed successfully at 6 °C only. Differential uses of energetic reserves among temperatures during development in L. maja support the interpretation of a narrow larval thermal scope and indicate that 6 °C is the optimum temperature for development in this species. Consequently, continued ocean warming is likely to force biogeographic range shifts in L. maja.

A new host for Hematodinium infection among lithodid crabs from the Sea of Okhotsk.

A disease caused by parasitic dinoflagellates of the genus Hematodinium has been found in the soft crab Hapalogaster grebnitzkii from the Sea of Okhotsk, which is considered a new host for this agent among lithodid crabs. This report provides macro- and micromorphological descriptions (using light and transmission electron microscopy) of the disease, as well as molecular identification of Hematodinium sp. from soft crabs, based on 18S RNA sequence data.

Climate change and the threat of novel marine predators in Antarctica

AbstractHistorically low temperatures have severely limited skeleton‐breaking predation on the Antarctic shelf, facilitating the evolution of a benthic fauna poorly defended against durophagy. Now, rapid warming of the Southern Ocean is restructuring Antarctic marine ecosystems as conditions become favorable for range expansions. Populations of the lithodid crab Paralomis birsteini currently inhabit some areas of the continental slope off Antarctica. They could potentially expand along the slope and upward to the outer continental shelf, where temperatures are no longer prohibitively low. We identified two sites inhabited by different densities of lithodids in the slope environment along the western Antarctic Peninsula. Analysis of the gut contents of P. birsteini trapped on the slope revealed them to be opportunistic invertivores. The abundances of three commonly eaten, eurybathic taxa—ophiuroids, echinoids, and gastropods—were negatively associated with P. birsteini off Marguerite Bay, where lithodid densities averaged 4280 ind/km2 at depths of 1100–1499 m (range 3440–5010 ind/km2), but not off Anvers Island, where lithodid densities were lower, averaging 2060 ind/km2 at these depths (range 660–3270 ind/km2). Higher abundances of lithodids appear to exert a negative effect on invertebrate distribution on the slope. Lateral or vertical range expansions of P. birsteini at sufficient densities could substantially reduce populations of their benthic prey off Antarctica, potentially exacerbating the direct impacts of rising temperatures on the distribution and diversity of the contemporary shelf benthos.

Metabolic costs imposed by hydrostatic pressure constrain bathymetric range in the lithodid crab Lithodes maja.

The changing climate is shifting the distributions of marine species, yet the potential for shifts in depth distributions is virtually unexplored. Hydrostatic pressure is proposed to contribute to a physiological bottleneck constraining depth range extension in shallow-water taxa. However, bathymetric limitation by hydrostatic pressure remains undemonstrated, and the mechanism limiting hyperbaric tolerance remains hypothetical. Here, we assess the effects of hydrostatic pressure in the lithodid crab Lithodes maja (bathymetric range 4-790 m depth, approximately equivalent to 0.1 to 7.9 MPa hydrostatic pressure). Heart rate decreased with increasing hydrostatic pressure, and was significantly lower at ≥10.0 MPa than at 0.1 MPa. Oxygen consumption increased with increasing hydrostatic pressure to 12.5 MPa, before decreasing as hydrostatic pressure increased to 20.0 MPa; oxygen consumption was significantly higher at 7.5-17.5 MPa than at 0.1 MPa. Increases in expression of genes associated with neurotransmission, metabolism and stress were observed between 7.5 and 12.5 MPa. We suggest that hyperbaric tolerance in Lmaja may be oxygen-limited by hyperbaric effects on heart rate and metabolic rate, but that Lmaja's bathymetric range is limited by metabolic costs imposed by the effects of high hydrostatic pressure. These results advocate including hydrostatic pressure in a complex model of environmental tolerance, where energy limitation constrains biogeographic range, and facilitate the incorporation of hydrostatic pressure into the broader metabolic framework for ecology and evolution. Such an approach is crucial for accurately projecting biogeographic responses to changing climate, and for understanding the ecology and evolution of life at depth.

Symbiosis between the holothurianScotoplanessp. A and the lithodid crabNeolithodes diomedeaeon a featureless bathyal sediment plain

Vulnerability to predation may be high for many megafaunal taxa in deep-sea sedimentary habitats where physical heterogeneity is low. During ROV observations in a bathyal sediment plain off Central California, juveniles of the lithodid crab Neolithodes diomedeae were frequently observed on or under the holothurian (sea cucumber) Scotoplanes sp. A, and are hypothesized to benefit from this association as a nursery or refugium from predation. Ninety-six percent (n = 574 of 599) of the juvenile N. diomedeae observed (density varied from 0.02–0.75/m2 among sites and seasons) in the study area were associated with Scotoplanes sp. A. Of the 2596 Scotoplanes sp. A observed (density varied from 0.48 to 25.90/m2), 22% were attended by at least one juvenile crab, and rarely two crabs (n = 4). Solitary N. diomedeae were rarely observed. This decapod–holothurian symbiosis appears to be largely commensal, with juvenile crabs (carapace width = 0.03–0.31 × holothurian length) observed on or beneath Scotoplanes sp. A in a habitat with few refugia from epibenthic predators. Other hypotheses may explain or enhance the potential benefits of the association for N. diomedeae, such as elevated food availability due to the activities of Scotoplanes sp. A. The relationship may be mutualistic if there is a benefit for the holothurian, including the removal of epizoic parasites. Ultimately, the nursery or other effects on the population dynamics of N. diomedeae may be minimal in low-relief, sediment-dominated habitats, as very few sub-adult crabs were observed in the study area and were likely consumed upon outgrowing their refugia. While sedimentary habitats may be a sink for N. diomedeae populations, growth of juvenile crabs during their association with Scotoplanes sp. A should increase energy flow to its predator populations. This association has not been reported previously but may be expected in sediment-dominated habitats where these species overlap.

Reproductive Parasitism between Distant Phyla: Molecular Identification of Snailfish (Liparidae) Egg Masses in the Gill Cavities of King Crabs (Lithodidae)

Snailfishes of the genus Careproctus deposit egg masses inside the gill cavity of lithodid crabs. Previous attempts to identify the species depositing the eggs have been inconclusive because of the difficulties in identifying snailfish eggs and larvae. For this study, samples were collected from egg masses found in crabs in the commercial fishery and during benthic trawl survey work. Egg masses were found in Lithodes aequispinus (Golden King Crab) and, for the first time, in L. couesi (Scarlet King Crab). Mitochondrial DNA from the cytochrome c oxidase subunit I (COI) region was amplified from embryos and sequenced. Comparison of COI sequences from eggs to COI sequences from positively identified adult voucher specimens yielded identifications of 75 egg masses to species. A total of 38 egg masses were identified as Careproctus melanurus; 29 as C. colletti; seven as C. furcellus; and one as C. simus. Each egg mass contained eggs from only one species, and there was no indication of multiple maternal parent...

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.

Marine litter in submarine canyons of the Bay of Biscay

Marine litter is a matter of increasing concern worldwide, from shallow seas to the open ocean and from beaches to the deep-seafloor. Indeed, the deep sea may be the ultimate repository of a large proportion of litter in the ocean.We used footage acquired with a Remotely Operated Vehicle (ROV) and a towed camera to investigate the distribution and composition of litter in the submarine canyons of the Bay of Biscay. This bay contains many submarine canyons housing Vulnerable Marine Ecosystems (VMEs) such as scleractinian coral habitats. VMEs are considered to be important for fish and they increase the local biodiversity. The objectives of the study were to investigate and discuss: (i) litter density, (ii) the principal sources of litter, (iii) the influence of environmental factors on the distribution of litter, and (iv) the impact of litter on benthic communities.Litter was found in all 15 canyons and at three sites on the edge of the continental shelf/canyon, in 25 of 29 dives. The Belle-île and Arcachon Canyons contained the largest amounts of litter, up to 12.6 and 9.5 items per 100 images respectively. Plastic items were the most abundant (42%), followed by fishing-related items (16%). The litter had both a maritime and a terrestrial origin. The main sources could be linked to fishing activities, major shipping lanes and river discharges. Litter appeared to accumulate at water depths of 801–1100m and 1401–1700m. In the deeper of these two depth ranges, litter accumulated on a geologically structured area, accounting for its high frequency at this depth. A larger number of images taken in areas of coral in the shallower of these two depth ranges may account for the high frequency of litter detection at this depth. A larger number of litter items, including plastic objects in particular, were observed on geological structures and in coral areas than on areas of bare substratum. The distribution of fishing-related items was similar for the various types of relief. Litter items were mostly colonised by scleractinian corals and hydroids. Several fish species and a lithodid crab seemed to associate with the accumulated litter.This extensive study showed litter to be widely distributed in the submarine canyons of the Bay of Biscay. These findings increase our understanding of the distribution of litter, its composition and accumulation and its impact on benthic communities.

The effect of temperature on the evolution of per offspring investment in a globally distributed family of marine invertebrates (Crustacea: Decapoda: Lithodidae).

Within the marine environment, per offspring investment (POI) is associated with modes in larval development; an increase in POI has often been described with a decrease in temperature, as evidenced along latitudinal clines. However, the environmental drivers of POI remain largely hypothetical and have not yet been tested within an evolutionary context. Here, we test the hypothesis that developmental temperature is linked to POI within a globally distributed and diverse family of benthic crustaceans, the Lithodidae, also known as stone or king crab. To do this, we examine variations in egg diameter—a proven corollary of POI—within the Lithodidae. Based on a rare case of well-construed phylogeny, we test the relationship between egg diameter and two aspects of the maternal physical environment: water depth and temperature. We observe a significant relationship between decreasing environmental temperature and an increase in POI within genera of lithodid crabs, and independent of depth. There is a clear correlation of high levels in POI with a decrease in temperature in lithodid crab genera currently inhabiting the deep sea, all of which follow a food-independent (lecithotrophic) mode of larval development. In contrast, lithodid genera thriving in the warmer waters of shallow (continental shelf) seas follow a feeding (planktotrophic) mode in larval development. We conclude that temperature is an important factor governing POI, and discuss its importance in the evolution of larval lecithotrophy in marine invertebrates.Electronic supplementary materialThe online version of this article (doi:10.1007/s00227-015-2776-8) contains supplementary material, which is available to authorized users.

First records of Lithodes longispina Sakai, 1971 (Crustacea: Decapoda: Anomura: Lithodidae) from southwestern Taiwan, including a site in the vicinity of a cold seep.

Lithodid crabs (Lithodidae Samouelle, 1819), commonly known as king crabs, are frequent targets of commercial fishing worldwide with most of them living in deep water (Sakai 1971; Ahyong et al. 2010). Lithodes Latreille, 1806, is the second largest genus of lithodid crabs, currently including 29 species worldwide (Ahyong 2010). In Taiwanese waters, however, only two species, L. turritus Ortmann, 1892, and L. formosae Ahyong & Chan, 2010, have been reported (Wu et al. 1998; Ahyong & Chan 2010; Ahyong et al. 2010). We report herein the discovery of L. longispina Sakai, 1971, previously known reliably only from Japan (Sakai 1971; Ikeda 1998; Ahyong 2010), from off southwestern Taiwan, including a specimen collected in the vicinity of a cold seep.

Deep water marine lobsters and lithodids (Crustacea: Decapoda) from Mauritania (NW Africa) collected by the Spanish Maurit surveys

Deep water marine lobsters and lithodids (Crustacea: Decapoda) from Mauritania (NW Africa) collected by the Spanish Maurit surveys

First 3D reconstruction of the rhizocephalan root system using MicroCT

Parasitic barnacles (Cirripedia: Rhizocephala) are highly specialized parasites of crustaceans. Instead of an alimentary tract for feeding they utilize a system of roots, which infiltrates the body of their hosts to absorb nutrients. Using X-ray micro computer tomography (MicroCT) and computer-aided 3D-reconstruction, we document the spatial organization of this root system, the interna, inside the intact host and also demonstrate its use for morphological examinations of the parasites reproductive part, the externa. This is the first 3D visualization of the unique root system of the Rhizocephala in situ, showing how it is related to the inner organs of the host. We investigated the interna from different parasitic barnacles of the family Peltogastridae, which are parasitic on anomuran crustaceans. Rhizocephalan parasites of pagurid hermit crabs and lithodid crabs were analysed in this study.

Methane seep ecosystem functions and services from a recently discovered southern California seep

AbstractThe recent discovery of a methane seep with diverse microhabitats and abundant groundfish in the San Diego Trough (1020 m) off the coast of Del Mar, California raised questions about the role of seep ecosystem functions and services in relation to continental margins. We used multicorer and ROV grab samples and an ROV survey to characterize macrofaunal structure, diversity, and trophic patterns in soft sediments and authigenic carbonates; seep microhabitats and taxa observed; and the abundance and spatial patterns of fishery‐relevant species. Biogenic microhabitats near the Del Mar Seep included microbially precipitated carbonate boulders, bacterial mats, vesicomyid clam beds, frenulate and ampharetid beds, vestimentiferan tubeworm clumps, and fields of Bathysiphon filiformis tubes. Macrofaunal abundance increased and mean faunal δ13C signatures decreased in multicorer samples nearer the seep, suggesting that chemosynthetic production enhanced animal densities outside the seep center. Polychaetes dominated sediments, and ampharetids became especially abundant near microbial mats, while gastropods, hydroids, and sponges dominated carbonate rocks. A wide range of stable isotopic signatures reflected the diversity of microhabitats, and methane‐derived carbon was the most prevalent source of nutrition for several taxa, especially those associated with carbonates. Megafaunal species living near the seep included longspine thornyhead (Sebastolobus altivelis), Pacific dover sole (Microstomus pacificus), and lithodid crabs (Paralomis verrilli), which represent targets for demersal fisheries. Sebastolobus altivelis was especially abundant (6.5–8.2 fish·100 m−2) and appeared to aggregate near the most active seep microhabitats. The Del Mar Methane Seep, like many others along the world's continental margins, exhibits diverse ecosystem functions and enhances regional diversity. Seeps such as this one may also contribute ecosystem services if they provide habitat for fishery species, export production to support margin food webs, and serve as sinks for methane‐derived carbon.

Discovery of a recent, natural whale fall on the continental slope off Anvers Island, western Antarctic Peninsula

Whale falls provide a substantial, nutrient-rich resource for species in areas of the ocean that may otherwise be largely devoid of food. We report the discovery of a natural whale fall at 1430m depth in the cold waters of the continental slope off the western Antarctic Peninsula. This is the highest-latitude whale fall reported to date. The section of the carcass we observed—the tail fluke—was more complete than any previously reported natural whale fall from the deep sea and in the early stages of decomposition. We estimate the entire cetacean to measure 5–8m in length. The flesh remained almost intact on the carcass but the skin was missing from the entire section except for the end of the fluke, clearly exposing blubber and soft tissue. The absence of skin indicates rapid and Homogeneous loss. The dominant macrofauna present were crustaceans, including most prominently the lithodid crab Paralomis birsteini, and zoarcid fish typical of the ‘mobile-scavenger’ successional stage. The density of mobile macrofauna was greatest on the carcass and declined to background levels within 100m, indicating that they were attracted to the whale fall. This whale fall offers an important opportunity to examine the decomposition of a carcass under deep-sea conditions at polar latitudes.

Methane-carbon flow into the benthic food web at cold seeps--a case study from the Costa Rica subduction zone.

Cold seep ecosystems can support enormous biomasses of free-living and symbiotic chemoautotrophic organisms that get their energy from the oxidation of methane or sulfide. Most of this biomass derives from animals that are associated with bacterial symbionts, which are able to metabolize the chemical resources provided by the seeping fluids. Often these systems also harbor dense accumulations of non-symbiotic megafauna, which can be relevant in exporting chemosynthetically fixed carbon from seeps to the surrounding deep sea. Here we investigated the carbon sources of lithodid crabs (Paralomis sp.) feeding on thiotrophic bacterial mats at an active mud volcano at the Costa Rica subduction zone. To evaluate the dietary carbon source of the crabs, we compared the microbial community in stomach contents with surface sediments covered by microbial mats. The stomach content analyses revealed a dominance of epsilonproteobacterial 16S rRNA gene sequences related to the free-living and epibiotic sulfur oxidiser Sulfurovum sp. We also found Sulfurovum sp. as well as members of the genera Arcobacter and Sulfurimonas in mat-covered surface sediments where Epsilonproteobacteria were highly abundant constituting 10% of total cells. Furthermore, we detected substantial amounts of bacterial fatty acids such as i-C15∶0 and C17∶1ω6c with stable carbon isotope compositions as low as −53‰ in the stomach and muscle tissue. These results indicate that the white microbial mats at Mound 12 are comprised of Epsilonproteobacteria and that microbial mat-derived carbon provides an important contribution to the crab's nutrition. In addition, our lipid analyses also suggest that the crabs feed on other 13C-depleted organic matter sources, possibly symbiotic megafauna as well as on photosynthetic carbon sources such as sedimentary detritus.

Antarctic crabs: invasion or endurance?

Recent scientific interest following the “discovery” of lithodid crabs around Antarctica has centred on a hypothesis that these crabs might be poised to invade the Antarctic shelf if the recent warming trend continues, potentially decimating its native fauna. This “invasion hypothesis” suggests that decapod crabs were driven out of Antarctica 40–15 million years ago and are only now returning as “warm” enough habitats become available. The hypothesis is based on a geographically and spatially poor fossil record of a different group of crabs (Brachyura), and examination of relatively few Recent lithodid samples from the Antarctic slope. In this paper, we examine the existing lithodid fossil record and present the distribution and biogeographic patterns derived from over 16,000 records of Recent Southern Hemisphere crabs and lobsters. Globally, the lithodid fossil record consists of only two known specimens, neither of which comes from the Antarctic. Recent records show that 22 species of crabs and lobsters have been reported from the Southern Ocean, with 12 species found south of 60°S. All are restricted to waters warmer than 0°C, with their Antarctic distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW). Currently, CDW extends further and shallower onto the West Antarctic shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that West Antarctic shelf could have been available for colonisation during the last 9,000 years. Distribution patterns, species richness, and levels of endemism all suggest that, rather than becoming extinct and recently re-invading from outside Antarctica, the lithodid crabs have likely persisted, and even radiated, on or near to Antarctic slope. We conclude there is no evidence for a modern-day “crab invasion”. We recommend a repeated targeted lithodid sampling program along the West Antarctic shelf to fully test the validity of the “invasion hypothesis”.

Carcinophyly of fish of the genus Careproctus (Scorpaeniformes: Liparidae) in waters of southeastern Sakhalin (Sea of Okhotsk)

In waters of southeastern Sakhalin (Sea of Okhotsk), clutches of snailfishes of the genus Careproctus containing eggs at different stages of development or prolarvae were found on gills of the largest individuals (mainly in males) of three species of crabs (Lithodidae)-Paralomis verrilli (clutches were found in 1.4% of individuals), P. multispina (0.8%), and Lithodes covesi (11.6%). With an increase in the carapace width of lithodid crabs, the amount of eggs of snailfishes deposited in them and their diameter increase. More frequently, clutches are located from the left side of the carapace of crabs. Two-side clutches occur in larger individuals of crabs. No direct relationship between the presence of clutches of snailfishes on gills of lithodid crabs with necrosis or reduction of gills was revealed. The form of relations between lithodid crabs and Careproctus snailfishes was defined as “lodging” with different degree of impact on the host.