Ovicides paralithodis (Nemertea,Carcinonemertidae), a new species of symbiotic egg predator of the red king crab Paralithodes camtschaticus (Tilesius, 1815) (Decapoda,Anomura)

Ovicides paralithodis sp. n. is described from the egg mass of the red king crab Paralithodes camtschaticus (Tilesius, 1815) from the Sea of Okhotsk, off Hokkaido, Japan, and Alaska, USA. Among four congeners, Ovicides paralithodis can be distinguished from Ovicides julieae Shields, 2001 and Ovicides davidi Shields and Segonzac, 2007 by having no eyes; from Ovicides jonesi Shields and Segonzac, 2007 by the presence of basophilic, vacuolated glandular lobes in the precerebral region; and from Ovicides jasoni Shields and Segonzac, 2007 by the arrangement of the acidophilic submuscular glands, which are not arranged in a row. Ovicides paralithodis represents the third described species of egg-predatory nemertean from Paralithodes camtschaticus, the second described carcinonemertid species from Japan, and the 21st described species in the family. The intensity of infestations may exceed 24,000 worms per a single egg-bearing pleopod of Paralithodes camtschaticus. A preliminary molecular phylogenetic analysis based on sequences of 28S rRNA and cytochrome c oxidase subunit I genes among selected monostiliferous hoplonemertean species supported the monophyly of Carcinonemertidae, suggesting that within the lineage of the family, evolution of the unique vas deferens, Takakura’s duct, preceded loss of accessory stylets and accessory-stylet pouches.     

Population genetic analysis and origin discrimination of snow crab (Chionoecetes opilio) using microsatellite markers

Major habitats for the snow crab Chionoecetes opilio are mostly found within the northwest Atlantic and North Pacific Oceans. However, the East Sea populations of C. opilio, along with its relative the red snow crab (C. japonicas), are two of the most important commercial crustacean species for fisheries on the east coast of the Korean Peninsula. The East Sea populations of C. opilio are facing declining resources due to overfishing and global climate change. Thus, an analysis of population structure is necessary for future management. Five Korean and one Russian group of C. opilio were analyzed using nine microsatellite markers that were recently developed using next-generation sequencing. No linkage disequilibrium was found between any pair of loci, indicating that the markers were independent. The number of alleles per locus varied from 4 to 18 with a mean of 12, and allelic richness per locus ranged from 4.0 to 17.1 across all populations with a mean of 9.7. The Hardy–Weinberg equilibrium test revealed significant deviation in three out of nine loci in some populations after sequential Bonferroni correction and all of them had higher expected heterozygosity than observed heterozygosity. Null alleles were presumed in four loci, which explained the homozygosity in three loci. The pairwise fixation index (F _ST ) values among the five Korean snow crab populations did not differ significantly, but all of the pairwise F _ST values between each of the Korean snow crab populations and the Russian snow crab population differed significantly. An UPGMA dendrogram revealed clear separation of the Russian snow crab population from the Korean snow crab populations. Assignment tests based on the allele distribution discriminated between Korean and Russian origins with 93 % accuracy. Therefore, the snow crab populations around the Korean Peninsula need to be managed separately from the populations in Bering Sea in global scale resource management. Also, this information can be used for identification of snow crab origin which is problematic in worldwide crab trade.     

Change of carotenoid composition in crabs during embryogenesis

Changes of the qualitative and quantitative compositions of carotenoids are studied at various development stages of the external hard roe, determined based on color differences, for the species C. opilio, P. camtschaticus, and P. platypus. It has been revealed that the major carotenoids of the new egg are astaxanthin and β-carotene. Intermediate products of transformation of β-carotene into astaxanthin are identified: echinenone, canthaxanthine, and phenicoxanthine. The carotenoid content per embryo for the new hard roe of C. opilio (the orange egg) amounted to 22.7 ng, of P. camtschaticus and P. platypus (the violet egg)—to 49.2 and 23.3 ng, respectively. In the hard roe at the later development stage (the brown egg) the carotenoid content was decreased to 13.1 ng in C. opilio and to 20.1 ng in P. camtschaticus. Development of embryos is accompanied by accumulation of esterified carotenoids and a decrease of β-carotene and astaxanthine concentrations in all studied species.     

First observations of temperature tolerances of adult male snow crab (Chionoecetes opilio) from the Barents Sea population and the effects on the fisheries strategy

This study investigates the effects of temperature on the survival, food intake, oxygen consumption and growth during long-term live holding of captive male snow crab (Chionoecetes opilio) (average?=?0.7?kg). The crabs were held at three different temperatures, 3, 6 and 9°C. The trials were done using groups of snow crabs held in nine land-based holding tanks (three replicates per temperature treatment). The results showed that temperature had a significant effect on survival. The survival rate at 3°C (61%) was significantly higher than at 6°C (33%) and at 9°C (28%). Specific oxygen consumption rates of unfed crab at 6°C were significantly higher than at 9°C and 3°C. In summary, the current study shows that the Barents Sea snow crab have a narrow temperature range in which they thrive compared with the Barents Sea red king crab (Paralithodes camtschaticus). Barents Sea snow crab has similar metabolic and physiological attributes to other major snow crab populations. In conditions when ambient temperatures are approximately 6°C, it may prove beneficial for animal welfare and also be financially advantageous to reduce ambient water temperatures in live snow crab holding facilities on boat or on land.     

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.     

Metamorphosis season from megalopa to the first crab stage in snow crab Chionoecetes opilio and red snow crab C. japonicus (Crustacea,Decapoda, Majoidea) in the Sea of Japan,estimated from captive culture

ABSTRACT

Metamorphosis season of megalopae to the first crab stage in snow crab Chionoecetes opilio and red snow crab C. japonicus was inferred by culturing wild-born megalopae collected from the Sea of Japan. Metamorphosis occurred from late June to late July (mainly in July) in snow crab, and from early July to early October (mainly from August to September) in red snow crab. The number of days required from the time of collection to metamorphosis was less than the intermoult period previously reported for snow crab megalopae. However, the developmental period of the megalopae was estimated as substantially longer in red snow crab than in snow crab. Previous studies have shown that the hatching season and the period of the zoeal stage in both two species are similar. These results suggest that a different metamorphosis season between the two species would be due to a difference in their megalopal intermoult period.     

Variations in the Carbon and Nitrogen Isotope Composition of the Crabs <Emphasis Type="Italic">Chionoecetes opilio</Emphasis> (Fabricius, 1788) and <Emphasis Type="Italic">Hyas coarctatus</Emphasis> Leach, 1816 (Crustacea: Decapoda) from the Chukchi Sea

Some regions of the Chukchi Sea shelf are characterized by an unusually high abundance of the benthos. The carbon and nitrogen isotope composition (δ¹³C and δ¹⁵N) of two crab species, Chionoecetes opilio and Hyas coarctatus, which occupy the upper trophic levels in bottom communities in the southern regions influenced by the Anadyr Water (AW) and in the regions exposed to the influence of the Siberian Coastal Current (SCC), was analyzed in order to compare between the trophic characteristics of their benthic communities. It has been found that these two species have similar spatial trends of stable isotope signature variations. As the effect of the productive AW on bottom communities decreases, a substantial depletion of δ¹³C with a simultaneous growth of δ¹⁵N values are observed in crab tissues. The trophic niches of C. opilio and H. coarctatus, which are represented by “isotope” niches as standard ellipse areas in the δ¹³C/δ¹⁵N biplot, significantly overlap in communities of the southern part of the shelf and become completely separated in those of the regions influenced by the SCC. The separation of the isotope niches of C. opilio and H. coarctatus and the simultaneous increase in δ¹⁵N values in both species by more than 3‰ indicate partitioning of the trophic resources between them and elongation of the food chains of both these carnivorous generalists by almost one trophic level in the communities that exist under the influence of less productive waters.     

On the growth of the blue king crab (<Emphasis Type="Italic">Paralithodes platypus</Emphasis>) population in the Peter the Great Bay of the sea of Japan

The causes of the appearance of large blue king crabs (Paralithodes platypus) in Peter the Great Bay for the last decade are discussed. This species is an important commercial resource in the waters of Russian Far Eastern seas, and its general concentrations are related mainly to the sublittoral and upper bathyal zones of the northwestern Bering Sea and the northern Sea of Okhotsk. Until recently, this species has been observed in areas along the continental coast of the northwestern Sea of Japan up to the Peter the Great Bay, where it incidentally showed up in red king crab (P. camtschaticus) and snow crab (Chionoecetes opilio) catches but was also commercially used. This area was considered as the southern periphery of the species range. Since the late 1990s, both male and female blue king crabs have been recorded in trawl and trap catches during research works conducted within the Peter the Great Bay. Since 2002, any commercial catches of shelf crab species are prohibited in the waters south of 47°20′ N because of a dramatic decline in their populations. Since then all the illegally caught crabs, including blue king crabs that are seized live from poachers, are released back into the water in certain places of the bay. In total, at least 29 503 blue king crabs, including egg-bearing females, were released within the period from 2002 to November 2009. At present, the overall blue king crab abundance in Peter the Great Bay, estimated based on the trap catches over an area of 7048 km², is 50500, the abundance of commercial-size males (with a carapace width over 130 mm) is 7500, and the male to female ratio is 1.00: 1.35. The increase in the blue king crab population observed in the bay is the result of the immigration of mature and viable individuals from other areas of its range. After this “uncontrolled introduction” blue king crabs adapted to new conditions, and then began breeding and spreading over the entire area of the bay.     

Epibionts of the red king crab Paralithodes camtschaticus (Tilesius, 1815) in Sayda Inlet of Kola Bay

The species composition of organisms associated with the red king crab Paralithodes camtschaticus (Tilesius, 1815) was investigated in Sayda Inlet of Kola Bay in 2004–2005. Nine fouler species and three symbiotic species were found on the carapaces of the red king crab. Balanus crenatus Bruigere 1789 barnacles were the most abundant fouler species and were found on 14.8% of the crabs. Symbiotic amphipods Ischyrocerus commensalis Chevreux, 1900 were found for one-tenth of all the crabs studied. The mean intensity of the amphipods was significantly greater for September, when the reproduction period of this species occurred. Male and female crabs were hosted with the same intensity. The number of host crabs increased accordingly to the crab size. The proportion of hosted crabs was three-fold less in Sayda Inlet than in the less polluted areas of the Barents Sea.     

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.     

Evidence for a permanent establishment of the snow crab (Chionoecetes opilio) in the Barents Sea

In the Atlantic the snow crab (Chionoecetes opilio) is naturally distributed on the northwestern side, i.e. eastern Canada and west Greenland. Until recently, there have been no observations of snow crab in eastern Atlantic. However, in 1990s single and occasional reports were made of crabs captured in the eastern part of the Barents Sea, presumably introduced through ballast water. Special attention during the annual bottom-trawl surveys in the Barents Sea during February 2004–2006 were given to include recordings of snow crab to evaluate if the introduced species has succeeded to establish a self-sustaining population in this region. Recordings of snow crabs were systematically noted and biological measurements carried out. The results confirm previous Russian observations of snow crabs in the northern region of Gåsebanken. In addition, a significant number of crabs were also found in the central region of the Barents Sea, mainly in deeper waters from 180 to 350 m depth. The sizes ranged from 14 to 136 mm carapace width. All females above 70 mm were berried with fertilised eggs. A major fraction (31% in 2005; 76% in 2006) of the crabs consisted of juveniles below 50 mm CW, providing evidence for successful recruitment. The small-sized crabs were exclusively found in Gåsebanken, identifying the main recruiting area at present for snow crab in the Barents Sea. The results obtained show that the snow crab is now adapted to the northeast Atlantic.     

Limb autotomy patterns in Paralithodes camtschaticus (Tilesius, 1815), an invasive crab, in the coastal Barents Sea

We examined levels of limb injury in the red king crab Paralithodes camtschaticus at 3 sites in the coastal waters of the Barents Sea. High incidences of autotomy were registered at all sites examined averaging 46.6% in Dolgaya Bay (DLB), 42.6% in Yarnyshnaya Bay (YRB) and 45.6% in Dalnezelenetskaya Bay (DZB). These levels were greater than in deep waters of the Barents Sea. Significant inter-annual increases in limb loss rates were observed in DZB. The positive correlation of autotomy frequency with the body size was observed for the females in YRB and DZB. The frequency of autotomy was independent of sex for all sites and size groups except for the crabs with CL > 135 mm in DZB where the females had autotomized limbs more often than the males. The chance of injury was higher for posterior legs. Right-side limbs (especially, claws) were lost more often than left-side limbs. The observed frequency of crabs within limb loss patterns did not differ significantly from the expected levels in P. camtschaticus collected in DLB and in YRB but was significantly different than a frequency expected if limb losses were independent in DZB. Our results suggest that crabs in DZB are more affected by limb-inducing factors than individuals from DLB or YRB. The main factors affecting limb injuries in P. camtschaticus in the coastal Barents Sea are predator pressure (mainly for immature crabs), and illegal fishing and recreational diving (for mature crabs).     

Marine invertebrates of the Sea of Okhotsk as a new source of lypopolysaccharide-binding proteins

Invertebrates from the Sea of Okhotsk were studied as a source of proteins that are capable of binding to lipopolysaccharides (LPSs) of gram-negative bacteria. A DOT analysis using dansyl-labeled LPS that we developed revealed LPS-binding proteins in blood-cell lysates of 21 out of 33 investigated species of invertebrates. Most of the investigated species with positive LPS-binding activity were decapod crustaceans (class Malacostraca, phylum Arthropoda). Hemocyte lysates from the red king crab Paralithodes camtschaticus and the sculptured shrimp Sclerocrangon boreas contained several LPS-binding proteins with different molecular weights. LPS-binding proteins were found for the first time in echinoderms (classes Holothuroidea, Asteroidea, and Echinoidea), sipunculans, and brachiopods.     

Red king crab (<Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis>) fisheries in Russian waters: historical review and present status

The red king crab (Paralithodes camtschaticus) is a highly valued delicacy on the international market and currently contributes significantly to the income from fisheries in the regions where it is harvested. Russian income from red king crab export is $200–250 million per year. We review both the biology and fishery of the two largest populations of this species in Russia, i.e., in western Kamchatka (Sea of Okhotsk) and in the Barents Sea. The latter was established in the mid-1990s after introduction of red king crab to the area in the 1960s. The Barents Sea crabs are larger, grow faster and mature earlier than the crabs from the Sea of Okhotsk owing to more favorable temperature conditions in the Barents Sea. Additionally, we provide fishery information for the Prymorie population of red king crab (Sea of Japan) that remains depressed and closed for commercial fishery at present. Although the fishery period of red king crab in western Kamchatka is much longer than in the Barents Sea (1930–present time vs. 2004–present time), similar patterns were observed for the exploited king crab populations. High annual landings led to a pronounced decrease in population density and total abundance that, in turn, led to closures or some limitations of fisheries. Subsequent rehabilitations of the populations provided an opportunity for reopening of the fisheries and further exploration of red king crab populations under sustainable management. The main reason explaining a decline in red king crab populations both in the North Pacific and in the Barents Sea is high, mainly illegal, fishing pressure. Sustainable harvest strategies for the fisheries could prevent negative scenarios (overfishing) in the future.     

Estimation of foraging on the sea urchin <Emphasis Type="Italic">Strongylocentrotus droebachiensis</Emphasis> (Echinoidea: Echinoida) by the red king crab <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Malacostraca: Decapoda) in coastal waters of the Barents Sea

A new method for the estimation of foraging on the sea urchin Strongylocentrotus droebachiensis (O.F. Müller, 1776) by the red king crab Paralithodes camtschaticus (Tilesius, 1815) is proposed. This method uses the reconstruction of the size, number, and biomass of eaten sea urchins, based on fragments of their teeth and tests from the crab’s digestive tract. Data obtained by this method suggest that in shallow waters of the Barents Sea (Kola Bay, Dal’nezelenetskaya Bay) adult, most often, female and immature crabs predominantly consume juvenile sea urchins. The weight of sea urchins daily eaten by one adult red king crab was 0.2–8.0% of its body weight for sexually mature crabs and 3.0–28.0% for immature specimens. Damage inflicted to the S. droebachiensis population as a result of the crab feeding activity was estimated to be at least 10% of the sea urchin biomass in Dal’nezelenetskaya Inlet and at least 30% in Kola Bay.     

Impact scenario for the invasive red king crab <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Tilesius, 1815) (Reptantia,Lithodidae) on Norwegian,native, epibenthic prey

Large invasive predators like the king crab, Paralithodes camtschaticus, deserve particular attention due to their potential for catastrophic ecological impact on recipient communities. Conspicuous, epibenthic prey species, such as the slow growing commercial scallop Chlamys islandica, are particularly exposed to the risk of local extinction. A research program integrating experiments and field monitoring is attempting to predict and track the impact of invasive king crab on scallop beds and associated fauna along the north Norwegian coast. The claw gape of the crab shows no limitations in handling the flat-bodied scallop. However, the potential impact of the crab on scallop may depend on the availability of other calcified prey associated with scallop beds, such as the sea star, sea urchin, and blue mussel, all species recorded in the diet of P. camtschaticus. To address this issue, a laboratory experiment on foraging behaviour of P. camtschaticus was conducted. The experimental results show that all size classes of red king crab prefer scallops, but small juveniles and medium sized crabs demonstrate active selection for starfish (Asterias rubens) that equals or surpasses the electivity of the large crab. The selection of sea urchin (Strongylocentrotus droebachiensis) and blue mussel (Mytilus edulis) is slightly positive or neutral for the three crab size classes. These results suggest that scallop beds with a rich associated fauna are less vulnerable to red king crabs predation and possibly more resilient than beds with few associated species. Also, crab size distribution is likely relevant for invasion impact, with increasing abundance of small and medium sized crabs being detrimental for alternative calcified prey associated with scallop beds. Successive stages of crab invasion will see an acceleration of scallop mortality rates associated with (i) decreasing availability of alternative prey, due to protracted predation pressure intensified by recruitment of juvenile crabs, and (ii) increased number of large crabs. Estimates of crab density and intake rates suggest that the accelerated loss rates will eventually endanger scallop beds persistence.     

Symbiotic Crab Sestrostoma balssi (Shen, 1932) (Varunidae: Gaeticinae) from Vostok Bay, Sea of Japan: A New Species for the Fauna of Russia

A symbiotic crab Sestrostoma balssi (Shen, 1932) (Varunidae: Gaeticinae) that lives in burrows of the large ghost shrimp Upogebia major (De Haan, 1841) and U. issaeffi (Balss, 1913) (Upogebiidae) was found in Vostok Bay (Peter the Great Bay, Sea of Japan) for the first time. The occurrence of mature and juvenile specimens indicates the existence of a stable population of this species in the investigated region. This finding substantially extends the distribution area of S. balssi in the Sea of Japan.     

Red king crab (<Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis>) in the Barents Sea: A comparative study of introduced and native populations

Red king crab (Paralithodes camtschaticus) was introduced into the Barents Sea in the 1960–1970s. At present, it occurs along the coast from Hammerfest (Northern Norway) to the (northeastern coast of Kola Peninsula). We studied the polymorphism of a mitochondrial gene encoding cytochrome oxidase (COI) and five nuclear microsatellite loci in four samples from the Barents Sea and two donor populations from the Western Kamchatka and Primorye (Russian Pacifics). No decrease in the genetic diversity of the introduced populations was observed. The results of PCA103 locusanalysis but some samples from the Barents Sea significantly differed from the Pacific populations according to the test for population differentiation demonstrated that the sample from Varrangerfjord was highly significantly different from the other five populations. As no significant differences between the other samples were found at this locus. We consider it to be a marker for Varangerfjord population differentiation. Possible reasons of this phenomenon are discussed.     

Two new cryptic and sympatric species of the king crab parasite Briarosaccus (Cirripedia: Rhizocephala) in the North Pacific

Rhizocephalan barnacles have been reported to parasitize a wide range of king crab species (Lithodidae). So far all these parasites have been assigned to a single species, Briarosaccus callosus Boschma, 1930, which is assumed to have a global distribution. Here we investigate Briarosaccus specimens from three different king crab hosts from the fjord systems of Southeastern Alaska: Lithodes aequispinus Benedict, 1895, Paralithodes camtschaticus (Tilesius, 1815), and Paralithodes platypus (Brandt, 1850). Using molecular markers and by morphological comparison we show that Briarosaccus specimens from these three commercial exploited king crabs are in fact morphologically distinct from B. callosus, and further represent two separate species which we describe. The two new species, Briarosaccus auratum n. sp. and B. regalis n. sp., are cryptic by morphological means and were identified as distinct species by the use of genetic markers (COI and 16S). They occur sympatrically, yet no overlap in king crab hosts occurs, with B. auratum n. sp. only found on L. aequispinus, and B. regalis n. sp. as parasite of the two Paralithodes hosts. © 2015 The Authors. Zoological Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London     

Invasion of the Atlantic rock crab (Cancer irroratus) at high latitudes

With the increase in global oceanic trade the establishment of non-indigenous marine organisms has become a major environmental and economic problem worldwide. Recently, the Atlantic rock crab (Cancer irroratus) was reported in Icelandic waters, Eastern North Atlantic. This is the first record of this relatively large crab species outside its natural range, i.e. the east coast of North America. The crab was most likely transferred to Iceland as larvae in ballast water and has successfully established a reproducing population in Icelandic waters. The species is distributed along the southwestern- and western-coast of Iceland. Adult specimens are now common in Faxaflói Bay, Southwest Iceland, but with sporadic occurrences in western and northwestern Icelandic waters. The green crab (Carcinus maenas) and the spider crab (Hyas araneus) are the only native brachyuran decapod species commonly found in its new habitat, but despite its recent colonization the rock crab was the most abundant brachyuran in the areas studied in southwest Iceland. Egg bearing rock crab and green crab females were found from June to October, while egg bearing spider crab females were seen from July to December. In Southwest Iceland both rock crab and green crab larvae were abundant in mid-summer but rare in both spring and autumn, which is opposite of what was observed for the spider crab. The size and abundance of adult crabs, their reproductive conditions, and occurrence of all larval stages, indicate that the Atlantic rock crab has successfully colonized Iceland.