Hyas Coarctatus Research Articles

Temporal and spatial dynamics of the invasive red king crab and native brachyuran and anomuran larvae in Norwegian waters

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 29:1-16 (2020) - DOI: https://doi.org/10.3354/ab00720 Temporal and spatial dynamics of the invasive red king crab and native brachyuran and anomuran larvae in Norwegian waters Helena Kling Michelsen*, Einar Magnus Nilssen, Torstein Pedersen, Camilla Svensen Department of Arctic and Marine Biology, UiT The Arctic University of Norway, 9019 Tromsø, Norway *Corresponding author: helena.k.michelsen@gmail.com ABSTRACT: This study investigates the temporal and spatial patterns of larval stages of the invasive red king crab Paralithodes camtschaticus (RKC) and co-existing native brachyurans and anomurans in a Norwegian fjord. It is one of few field studies describing the larval stage of native and invasive brachyurans and anomurans in the southern Barents Sea. Larvae were collected at 6 to 18 stations at roughly 1 to 2 mo intervals over a 1.5-yr period. To help explain timing in hatch of RKC larvae, the reproductive state of females was determined. The first larval stage of RKC was found in higher abundances in shallow bays, reflecting the spawning migrations of reproducing females. RKC was the first species among anomurans and brachyurans to release their larvae in Norwegian waters, and due to an extended larval release (January-May) their larvae occurred for the longest period of time in the water column. The native boreo-Arctic Pagurus pubescens and Hyas araneus released their larvae early in the year, starting in March. In contrast, larvae of the native boreal Pagurus bernhardus, Hyas coarctatus and Munida sp. were observed later in spring and summer. The combination of protracted hatching, high fecundity and high adult abundance of RKC are likely strong contributing factors to the species’ successful establishment in the southern Barents Sea and could favour the dispersal of RKC south along the Norwegian coast and potentially north into Arctic shelf areas. KEY WORDS: Paralithodes camtschaticus · Zoea · Pagurus · Hyas · Munida · Barents Sea · Biogeography · Invasive species Full text in pdf format Supplementary material NextCite this article as: Michelsen HK, Nilssen EM, Pedersen T, Svensen C (2020) Temporal and spatial dynamics of the invasive red king crab and native brachyuran and anomuran larvae in Norwegian waters. Aquat Biol 29:1-16. https://doi.org/10.3354/ab00720 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 29. Online publication date: January 16, 2020 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2020 Inter-Research.

Особенности питания керчака-яока Myoxocephalus jaok (Cuvier, 1829) (Cottidae) и его место в трофической системе прикамчатских вод

По материалам 1978–2008 гг. (975 желудков обработано количественно-весовым методом, около 2 тыс. желудков вскрыто и проанализировано в полевых условиях) рассмотрены особенности питания керчака-яока Myoxocephalus jaok в прикамчатских водах Охотского, Берингова морей и Тихого океана и предпринята попытка выяснить место этого вида рогатковых в трофической системе данного района. Показано, что керчак-яок характеризуется широким спектром питания (свыше 100 кормовых объектов), однако наибольшее значение в его рационе имеют рыбы (в среднем 64,1 % массы пищи) и десятиногие раки (32,2 %). Основу первых составляют камбалы Pleuronectidae (24,3 % массы пищи), минтай Theragra chalcogramma (14,4 %), тихоокеанская песчанка Ammodytes hexapterus (9,5 %) и рогатковые Cottidae (5,6 %); вторых ― крабы семейства Majidae (22,4 %) (главным образом краб-стригун Chionoecetes opilio (14,2 %) и краб-паук Hyas coarctatus (8,1 %)), а также крабы семейства Atelecyclidae (4,7 %) (преимущественно пятиугольный волосатый краб Telmessus cheiragonus (4,5 %)) и креветки семейства Crangonidae (3,1 %). Рассмотрены сезонные, локальные, межгодовые и возрастные изменения состава пищи керчака-яока. Установлено, что этот вид является факультативным хищником-засадчиком; ему свойственна высокая пластичность питания, дающая возможность использовать значительный набор пищевых компонентов. В трофической системе прикамчатских вод выделены звенья, формирующие биомассу керчака-яока.

Variations in the Carbon and Nitrogen Isotope Composition of the Crabs Chionoecetes opilio (Fabricius, 1788) and Hyas coarctatus 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.

Size-frequency distribution, growth, and mortality of snow crab (Chionoecetes opilio) and arctic lyre crab (Hyas coarctatus) in the chukchi sea from 2009 to 2013

The snow crab Chionoecetes opilio and Arctic lyre crab Hyas coarctatus are prominent members of the Chukchi Sea epifaunal community. A better understanding of their life history will aid in determining their role in this ecosystem in light of the changing climate and resource development. In this study, the size frequency distribution, growth, and mortality of these two crab species was examined in 2009, 2010, 2012, and 2013 to determine temporal and spatial patterns within the eastern Chukchi Sea, and to identify potential environmental drivers of the observed patterns. Temporally, the mean size of both sexes of C. opilio and H. coarctatus decreased significantly from 2009 to 2013, with the number of rare maximum sized organisms decreasing significantly to near absence in the latter two study years. Spatially, the mean size of male and female crabs of both species showed a latitudinal trend, decreasing from south to north in the investigation area. Growth of both sexes of C. opilio and H. coarctatus was linear over the sampled size range, and mortality was highest in the latter two study years. Life history features of both species related to different environmental parameters in different years, ranging from temperature, the sediment carbon to nitrogen ratio of the organic content, and sediment grain size distribution. Likely explanations for the observed temporal and spatial variability are ontogenetic migrations of mature crabs to warmer areas possibly due to cooler water temperatures in the latter two study years, or interannual fluctuations, which have been reported for C. opilio populations in other areas where successful waves of recruitment were estimated to occur in eight year intervals. Further research is suggested to determine if the spatial and temporal patterns found in this study are part of the natural variability in this system or if they are an indication of long-term trends.

Size frequency distributions of key epibenthic organisms in the eastern Chukchi Sea and their correlations with environmental parameters

Epibenthic communities play a key role in ecosystem functioning in Arctic shelf Seas, such as in the Chukchi Sea in the Pacific Arctic. These communities, however, are patchily distributed and are influenced by various environmental parameters. Along with taxonomic composition, another community aspect that may vary spatially and be influenced by the environment is the distribution of organism sizes. This study presents the first size frequency distributions of nine epifaunal taxa that were determined to be dominant in the eastern Chukchi Sea in July/August 2009 and 2010, including male, female and gravid Chionoecetes opilio and Hyas coarctatus crabs, the gastropods Neptunea spp., Plicifusus spp., Colus spp., and Cryptonatica spp., and the echinoderms Gorgonocephalus spp., Leptasterias spp., and Echinarachnius parma. Some abundant taxa exhibited a wide range of sizes (i.e. C. opilio, Neptunea spp., and Leptasterias spp.), while others had a much smaller size range (i.e. Cryptonatica spp. and E. parma). We also found that size distributions of these taxa correlated with various combinations of the environmental parameters that have been shown to be important in structuring the general distribution patterns for the epibenthic invertebrate communities in the study area, including percent total sediment organic carbon, sediment chlorophyll a, temperature, latitude, sediment grain size 2 and 4phi, pH, and dissolved oxygen. Our findings present benchmark information that is needed to detect future alterations in body-size frequency distributions that are likely to happen in response to the predicted climate and environmental changes in the Chukchi Sea region.

Seasonal dynamics of the density of the crab larvae (Decapoda: Brachyura et Anomura) in Minonosok Bay of Pos’eta Bay (Peter the Great Bay, Sea of Japan)

As the materials for this project, we used data on the distribution of the larvae of the Asian paddle crab Charybdis japonicus (A. Milne-Edwards, 1861); the spider crabs Hyas coarctatus ursinus (=Hyas ursinus) (Rathbun, 1924), Pugettia quadridens (de Haan, 1839), and Pisoides bidentatus (H. Milne-Edwards, 1873); the samurai crab Paradorippe granulata (=Dorippe granulata) (de Haan, 1841); the pea crab Pinnixa rathbuni (Sakai, 1934); and the porcelain crab Pachycheles stevensii (Stimpson, 1858) in Minonosok Bay of Pos’eta Bay obtained during 2000–2002 and in 2004. The planktonic samples were collected from the last third of May to September. The greatest density of the larvae was observed in May, mid-June, late June-early July, and late July-early August. The greatest densities of the crab larvae and the decapod larvae ranged from 20.4 to 48.2 and from 88.4 to 245.3 specimens/m3. The schedule of the crab larvae’s occurrence in the plankton is provided for the first time. The distribution of the density showed pronounced patchiness.

Molecular detection of Hematodinium sp. in Northeast Pacific Chionoecetes spp. and evidence of two species in the Northern Hemisphere

Hematodinium is a genus of parasitic dinoflagellates that infects crustaceans worldwide including Tanner crabs Chionoecetes bairdi and snow crabs C. opilio in the Northeast Pacific Ocean. The present study describes the optimization of a PCR-based assay for the detection and monitoring of Hematodinium sp. in snow and Tanner crabs. Two fragments, 1682 and 187 bp, were amplified from the 18S ribosomal DNA region of the parasite. The assay performed well in 6 additional decapod species (1 lobster and 5 crabs) infected with Hematodinium spp., suggesting that it could be used to detect Hematodinium spp. in other decapods. We also report Hematodinium spp. infections in the majid crab, Hyas coarctatus, and the lithodid crab, Lithodes couesi. Sequencing of 18S rDNA and the adjacent internal transcribed spacer 1 (ITS1) region of Hematodinium spp. isolated from 7 host species in the present study revealed the presence of 2 Hematodinium clades, one in the blue crab Callinectes sapidus and a second in all other host species. The ITS1 sequences of the 2 clades could not be aligned, but showed a conserved secondary structure that may be related to a functional diversification during a host switch. Comparison of our data with 18S and ITS1 sequence data available in GenBank placed the north Pacific Hematodinium sp. in a clade separate from the Hematodinium sp. infecting the portunoids, C. sapidus, Liocarcinus depurator and Scylla serrata, and within a second clade that infected all other decapod hosts located in the North Pacific and North Atlantic Oceans.

Spatial distribution of the crab larvae (Decapoda: Anomura et Brachyura) in Possyet Bay (Peter the Great Bay of the Sea of Japan) in 2000–2001

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.

Spatial linkages between decapod planktonic and benthic adult stages in a Newfoundland fjordic system

The relative importance of predatory decapod crustaceans in sedimentary communities depends on the spatial variability in their abundance and composition. At the scale of a fjord, such spatial patterns could be related to sill-mediated larval supply. This study examines larval and adult distributions of abundant predatory decapods at six representative sites in a sub-arctic Newfoundland fjord during three consecutive summers. Adult snow crab (Chionoecetes opilio) and toad crab (Hyas coarctatus, H. araneus) characterized outer areas of the fjord, whereas pandalid shrimp (Pandalus montagui) dominated inner areas, and rock crab (Cancer irroratus) showed only minor spatial differences. Multivariate analysis and nonparametric comparisons of larval abundance and composition suggest that the sill separating inner and outer areas of the fjord results in differences in larval supply that correspond to adult abundances for at least two of the species analyzed here: snow crab and pandalid shrimp. Although larval abundance was not related to adult distribution when all zoeal stages were considered, correspondence between larval and adult patterns emerged when only late stages (zoeae II) were included in the multivariate analyses. Nonparametric comparisons supported these results, indicating significant differences in larval abundance inside and outside the sill for corresponding species and stages. Our results suggest that larval supply may play a critical role in establishing adult spatial patterns at the scale of the entire fjord for some species, but a less relevant role at the finer scale represented by the sites and habitats located at each side of the sill.

Growth to maturity of juveniles of the spider crabs Hyas coarctatus Leach and Inachus dorsettensis (Pennant) (Brachyura: Majidae)

Specimens of the spider crabs Hyas coarctatus and Inachus dorsettensis were reared in the laboratory under ambient temperature conditions. Individuals were retained until they had undergone two moults, or moulted to the terminal instar: they were then replaced by fresh specimens. The percentage increment was recorded for each moult, and the duration for each intermoult period. Both intermoult period and percentage increment either declined with increasing temperature or showed no response. The effect of body size on these variables tended to reflect that expected in species with determinate growth—intermoult period generally increased with size, whereas percentage increment remained unchanged. Percentage increment was compared between juvenile moults and the puberty moult in both this and earlier studies. In males, the puberty moult increment was smaller than juvenile increments, and this is tentatively related to the diversion of resources to the large puberty increase in chelar size. In females, the puberty moult increment was either larger or smaller, dependant on whether the ovaries matured after or before the puberty moult, respectively—again a reflection of resource allocation. Growth curves constructed from the laboratory data were compared with those based on field studies. These analyses emphasised that seasonal constraints in natural populations could compromise predictions from laboratory experiments.

ONTOGENY OF FEMALE PRIMARY SEXUAL CHARACTERS IN THE MAJID CRABS CHIONOECETES OPILIO AND HYAS COARCTATUS

ABSTRACT To investigate the development of primary sexual characters in the family Majidae, the spermathecae, ovaries, and oviducts of juvenile female Chionoecetes opilio and Hyas coarctatus were examined, using histology, histochemistry, and electron microscopy, and compared to those of mature females. Females were divided into 3 developmental categories, with corresponding size ranges, based on anatomical criteria: immature, premature, and mature. Immature crabs were still temporally remote from the terminal molt, had white ovaries, and the spermatheca presented a thin tissule separation between the dorsal and ventral regions. No stratified glandular epithelium was present; only a columnar epithelium lined the lumen. This epithelium tested slightly positive for amine-containing substances. Premature females were temporally close to terminal molt, had orange ovaries, and retained the tissule separation between the dorsal and ventral regions of the spermatheca. In addition, they presented a stratified glandular epithelium which developed beneath the columnar epithelium lining the lumen. The latter degenerated and sloughed into the lumen as the former developed. Mature females had undergone the terminal molt, and were examined both prior to and following egg extrusion. No trace remained of the columnar epithelium which was present in the preceding two categories. In mature females which had extruded eggs, the tissule separation between dorsal and ventral regions of the spermatheca was also absent. Neutral mucopolysaccharides dominated in the secretions of the dorsal glandular epithelium of both types of mature female. These results establish the primary sexual characters in female C. opilio and H. coarctatus, and also document the sequence of aquisition of these characters.

Reproductive investment in two spider crabs with different breeding strategies

Reproductive investment was studied in Irish Sea populations of the spider crabs Hyas coarctatus and Inachus dorsettensis. The species are similar in that reproduction is restricted to the terminal instar, but differ in that H. coarctatus produces a single brood per year, whilst I. dorsettensis produces several. In relation to body weight, egg number (and brood weight) was higher in H. coarctatus. In I. dorsettensis, the first brood produced after maturity had a much lower egg number than subsequent broods. Energy content of broods in relation to energy content of females displayed similar trends, with means of 35 and 32% in Hyas and Inachus, respectively. However, the annual investment in reproduction was higher in Inachus. Possible explanations for an apparently suboptimal reproductive strategy in Hyas are discussed.

Unsaturated hydrocarbons in muscle and hepatopancreas of two crab species, Chionoecetes opilio and Hyas coarctatus

Polycyclic aromatic hydrocarbon (PAH) contaminants and biogenic unsaturated hydrocarbons were identified in muscle and hepatopancreas of two crab species, collected nearshore and offshore the island of Newfoundland. A correlation was made between the compounds present in hepatopancreas and in surface sediments collected from Conception Bay, Newfoundland. The bioaccumulation of unsaturated compounds differed slightly with species, while a large variation was noticed between tissues. Relatively greater levels of fluorescing compounds (PAC) were present in hepatopancreas than in muscle of the spider crab ( Hyas coarctatus) or snow crab ( Chionoecetes opilio), while a larger number of PAH was also present in that tissue. The unsaturated hydrocarbons fraction separated from the hepatopancreas extracts was quantified in terms of gravimetry, by ultraviolet/fluorescence (uv/f, four standards), gas chromatography-mass spectrometry (GC-MS) analysis of a series of 25 PAC (GC-MS-SIM), as well as by the analysis of the predominant compounds (GC-MS-TIC). Results obtained by gravimetry were highest (20 μg g −1, dry wt), levels of total fluorescing compounds (uv/f, 1.1 μg g −1, in terms of chrysene units), of four unsaturated biogenic hydrocarbons (< 10 μg g −1) and of detectable parental and alkylated PAH (0.67 μg g −1) were relatively lower. As could be expected, these various concentrations in hepatopancreas samples were not equivalent, but reasonably complementary.

Size Distribution in Spider Crab Populations: Spatial and Temporal Variation

The size distribution of the spider crabs Hyas coarctatus and Inachus dorsettensis was investigated in several areas close to the Isle of Man. Samples were collected in 1958-1959 and again in 1988-1990. One area was sampled during both periods. On both occasions each species displayed clear differences between areas in the size distribution of the terminal instar. This is attributed to variation in the size at which the terminal pubertal molt occurred; the contributions of genetic and environmental factors to this variation are discussed. In prepubertal specimens males exceeded females, but females predominated among postpubertal crabs. This swing in sex ratio is discussed. In the area sampled in both periods, the abundance of each species declined to about a fifth of that recorded 30 years ago. This is considered a result of heavy scallop dredging throughout that interval. An expected decrease in the size of the terminal instar was not observed, and, in fact, an increase occurred in Inachus dorsettensis. Possible explanations are considered.

SIZE DISTRIBUTION IN SPIDER CRAB POPULATIONS– SPATIAL AND TEMPORAL VARIATION

The size distribution of the spider crabs Hyas coarctatus and Inachus dorsettensis was investigated in several areas close to the Isle of Man. Samples were collected in 1958-1959 and again in 1988-1990. One area was sampled during both periods. On both occasions each species displayed clear differences between areas in the size distribution of the terminal instar. This is attributed to variation in the size at which the terminal pubertal molt occurred; the contributions of genetic and environmental factors to this variation are discussed. In prepubertal specimens males exceeded females, but females predominated among postpubertal crabs. This swing in sex ratio is discussed. In the area sampled in both periods, the abundance of each species declined to about a fifth of that recorded 30 years ago. This is considered a result of heavy scallop dredging throughout that interval. An expected decrease in the size of the terminal instar was not observed, and, in fact, an increase occurred in Inachus dorsettensis. Possible explanations are considered.

Larval development of Canadian Atlantic oregoniid crabs (Brachyura: Majidae), with emphasis on Hyas coarctatus alutaceus Brandt, 1851, and a comparison with Atlantic and Pacific conspecifics

Larval development of Hyas coarctatus alutaceus Brandt, 1851, consisting of two zoeal stages followed by a megalopa, is described for the first time from larvae of known parentage. Mean duration of the first and second zoeal stages was 41 and 30 days at ambient temperature (3–12 °C) and 30 and 36 days at 9 °C, respectively. First megalopae appeared after 69 and 62 days post-hatching at ambient temperature and 9 °C, respectively. For comparison, all larval stages of Hyas araneus, Hyas coarctatus coarctatus, and Chionoecetes opilio were also cultured from local populations. Zoeae of all these species were found to be very similar. Larvae of H. c. alutaceus were significantly larger than those of H. c. coarctatus, surpassing even those of H. araneus. Laboratory-reared and wild-caught larvae from different geographic areas were also compared. Characters potentially useful in the interspecific and subspecific differentiation of zoeae are presented. These include (i) relative dimensions of the carapace, spinules on carapace spines, setae on antennal exopodites, lateral abdominal spines relative to abdominal somites, spines on the telson furca, and dorsolateral spines on abdominal somite 3; (ii) presence or absence of spinules on lateral abdominal spines and knobs on eyestalks; (iii) setation of appendages; and (iv) pigmentation. Megalopae are also compared morphometrically and meristically. Larvae vary more than appeared previously. A key for the identification of larval stages of C. opilio and Hyas spp. is provided.

Larval development and survival in seven decapod species (Crustacea) in relation to laboratory diet

Three species of phytoplankton diatoms, Biddulphia sinensis, Thalassiiosira rotula and Skeletonema costatum, were tested for suitability as food for larvae of one anomuran and six brachyuran species, Pagurus bernhardus (Paguridae), Cancer pagurus (Cancridae), Hyas coarctatus, Hyas araneus (Majidae), Carcinus maenas, Ltocarcinus holsatus and Necora puber (Portunidae). Rates of development and survival were used as criteria for nutritional value of the test food, compared with those in a starved and an Artemia-fed control group. In all cases, larvae fed with algae survived longer than in the starved control. The developmental success seems to depend on food particle size. Larvae moulted most successfully when fed with Biddulphia sinensis, the largest diatom tested, and only occasionally when fed with Skeletonema costatum, the smallest species tested. The larvae of H. coarctatus were the only species which developed to the first crab instar when fed with phytoplankton ( B. sinensis). The larvae developed most successfully when fed with Artemia nauplii. With the exception of L. holsatus and N. puber, all tested species developed to the first juvenile instar when fed with Artemia sp.

Laboratory growth of the larvae of six British crabs

The larvae of six species of crabs — Cancer pagurus Linnaeus, Hyas coarctatus Leach, Inachus dorsettensis (Pennant), I. leptochirus Leach, Liocartinus depurator (Linnaeus), and Pilumnus hirtellus (Linnaeus) — were reared under laboratory conditions. The conditions of light, salinity and feeding were controlled, and the temperature was constant at either 15 or 20 ° C. Large numbers were reared in isolation, and the survival, size, and duration of each instar recorded. Survival was good through the zoeal instars, variable to the megalopa, whilst only Inachus dorsettensis showed good survival to the first crab instar. Survival was better at 20 than at 15 °C. Intermoult duration increased with instar number, and was greatly extended at the lower temperature. Moult increment was slightly reduced at the higher temperature, and had a mean value of 21.5% for the whole study. The range of size variation within an instar showed no consistent patterns of change within the larval series.

Distribution and Association of Larval Crabs (Decapoda: Brachyura) on the Scotian Shelf

Thirty-five taxa of neustonic larval Brachyura were distinguished and identified to stage of development in 3055 samples from the Scotian Shelf taken from north of Cape Breton to Georges Bank. A maximum of 17 species of larvae was taken in a single tow, with a norm of about 4 per tow. The most abundant species, collected in all stages of development, were the indigenous Chionoecetes opilio, Hyas araneus and Hyas coarctatus, Cancer borealis and Cancer irroratus, and Carcinus maenas. Biomass was dominated by the Hyas and Cancer species. Distributions of the three Majidae species indicated that larvae drift southwest along the shelf, and that they are indigenously derived. Twenty-six expatriate species occurred as megalopas only, predominantly offshore. Reciprocal averaging and factor analysis showed that there was considerable separation of the indigenous and expatriate larval species, but did not reveal strong relationships to environmental variables or ecological gradients. Recurrent group analysis indicated that community structure was weak and variable, but confirmed the virtual separation into indigenous and expatriate associations. An examination of co-occurrences of indigenous and expatriate species by stage of development showed strong patterns. We suggest that concurrent analysis of larval lobster and larval crab distribution patterns on the Scotian Shelf could indicate recruitment origin of lobsters (Homarus americanus).

Growth and respiration during the larval development of Hyas coarctatus (Decapoda: Majidae)

The spider crab Hyas coarctatus Leach was reared in the laboratory from hatching to metamorphosis, and growth and respiration were measured in all larval stages at regular intervals of time. Growth, measured as dry weight (W), carbon (C), nitrogen (N), hydrogen (H), and energy (E; calculated from C), can be described in the zoeal stages by a power function, and as a non-linear (quadratic) regression equation of time (t; days) in the megalopa. C, H, and E showed higher growth rates than W or N during the zoeal stages, suggesting accumulation mainly of lipids rather than protein. Respiration (R; expressed as μg O2h-1 individual-1) increased as a linear function of t in the zoeal stages. From this simple relationship and the above power function for increase in W, equations describing the relationships between R and W and between QO 2 (μg O2h-1 mg-1), t, and W were derived for zoeal development. Both R and QO 2 first decreased during megalopa postmoult, then increased for a short period, before decreasing again toward metamorphosis. No descriptive models were proposed for these changes in the ultimate larval stage. The total amount of energy lost by zoeal respiration was less than their net gain by body growth, whereas the megalopa respired almost 14 times the amount of energy eventually gained. This means that net growth efficiency is far lower in the megalopa than in the zoeal stages of H. coarctatus.