Bernard Sainte-Marie

Delivery and Storage of Sperm at First Mating of Female Chionoecetes opilio (Brachyura: Majidae) in Relation to Size and Morphometric Maturity of Male Parent

ABSTRACT Virgin female Chionoecetes opilio were paired with males, in a noncompetitive laboratory setting, less than 12 h after molting to maturity. The quantity of sperm that females received and stored was measured as ejaculate weight and number of sperm cells. Females copulated 1-4 times prior to spawning; the first and second intromissions lasted an average of 34.4 and 37.7 min, respectively. On the whole, the weight of ejaculate and number of sperm cells did not differ between the left and right spermathecae. The number of sperm cells received or stored in spermathecae was independent of male and female carapace widths. Morphometrically mature (large claw) males transmitted an estimated 10.8 x 106 sperm cells to each spermatheca, and an estimated 2.1 x 106 sperm cells from each spermatheca were used to fertilize the first egg clutch (≈ 70 sperm cells per oocyte). Females did not extrude eggs when fewer than 1.9 x 105 sperm cells were delivered to at least one spermatheca, resulting in a ratio of <7 sperm cells per oocyte. A median of 10.2 x 106 and 8.7 x 106 sperm cells were stored per spermatheca by females that extruded eggs after mating with morphometrically immature (small claw) and morphometrically mature males, respectively. The ratio of number of sperm cells to ejaculate weight was significantly greater in stored ejaculates from morphometrically immature males than in those from morphometrically mature males. Both male morphs mated successively with 5 different females over a period of 14-33 days, with no significant change in the weight of ejaculate or the number of sperm cells stored by females after spawning.

Pattern and causes of a temperature-dependent gradient of size at terminal moult in snow crab (Chionoecetes opilio) along West Greenland

Geographic variation in size of male and female snow crabs (Chionoecetes opilio) was investigated along the west coast of Greenland to test the hypothesis that size at terminal molt (=adulthood) is temperature dependent. A total of 81,490 snow crabs were collected in small-mesh traps in Disko Bay (68–69°N) and six sites near Sisimiut (66–67°N) in May and June from 2000 to 2005. Average bottom temperature over the study period ranged from −0.8 to 3.2°C across the sampling sites. Mean carapace width was positively correlated with temperature in both sexes, a pattern often described as a converse Jame’s cline. We infer that temperature per se is the causative factor and discount season length, food availability or density as ultimate causes of the cline. Temperature effects on body size of crabs apparently result from a change in the number of instars before terminal molt. This interpretation is supported by size frequency analysis showing that in general crabs were larger at instar in a colder than in a warmer site. We briefly discuss the implications of our findings for population reproductive potential and the effectiveness of a fixed legal size limit in protecting some adult males from exploitation at different temperature regimes.

Longevity and Change in Shell Condition of Adult Male Snow Crab Chionoecetes opilio Inferred from Dactyl Wear and Mark-Recapture Data

Abstract Postmolt longevity and changes in the shell condition and body integrity of male snow crab Chionoecetes opilio after their terminal molt were assessed through a mark-recapture experiment and population censuses in a commercially unfished locality of eastern Canada. The experiment explored the value of dactyl wear as a quantitative measure and shell condition (SC; measured on a five-stage scale) as a relative index of shell age. Males were recaptured up to 6 years after release. Much of the extensive variation in observed dactyl wear was explained by time at liberty (Δt) and male size, and the extent of change in SC was positively correlated with Δt. The conservative wear-based estimate of male longevity was 7.7 years, a value 1-3 years greater than previously estimated. Dactyl wear and recapture data confirmed that SC is a relative, albeit rough, index of shell age. Shell hardness was positively correlated with male size and peaked in stage 3 about 3.5 years after the terminal molt. The number of...

OBSERVATIONS ON THE GROWTH OF THE SCULPTURED SHRIMP SCLEROCRANGON BOREAS (DECAPODA: CARIDEA)

Abstract Little is known of the growth of the sculptured shrimp Sclerocrangon boreas, a remarkable member of arctic and subarctic marine shelf communities. We determined the length-weight relationship, abdomen allometry, and size structure of shrimp in a population of the Gulf of Saint Lawrence, eastern Canada. We also reared shrimp for up to 3.5 years to measure their growth. The presence of very small immature females in the wild population indicates that the sculptured shrimp is not obligatorily a protandric hermaphrodite, if at all. Females grow faster, reach a greater size, and live longer than males. Males may be ≥ 4 years old at 17 mm cephalothorax length (CL) and females ≥ 6 years old at 29 mm CL. Ovigerous females have a broader abdomen with longer pleopod setae than similarly-sized immature females. After releasing their progeny, some females may molt and grow in length but revert to a condition of narrow abdomen and short pleopod setae, and then molt again to a condition of broad abdomen with long pleopod setae. This finding and demographic data suggest that some females are alternate-year spawners. Other females did not molt for ≥ 2 years and may spawn in successive years.

Interspecific activity of the sex pheromone of the European shore crab (Carcinus maenas)

The recent identification of uridine diphosphate (UDP) as the female sex-pheromone in the European shore crab Carcinus maenas demonstrated not only the link between moult and pheromone production, but also how it may have evolved from a ‘simple’ metabolic byproduct. Consequently, it is expected to be present in other moulting crustaceans, thus raising issues involving species specificity of the female pheromone. Bioassays were conducted using synthetic pheromone (UDP, 10 –3 –10 –4 M) to examine if it induced sexual behaviour in other crustacean species that are neither closely related nor occur in the same ecosystem. The snow crab, Chionoecetes opilio , and the yellowline arrow crab, Stenorhynchus seticornis , both belonging to a different superfamily (Majoidea) and occurring in different habitats than C. maneas (Portunoidea), displayed significant sexual behaviour towards UDP treated objects ( p < 0.005). These and other examples demonstrate that the female sex-pheromone UDP is not species-specific but is present and active in some other decapod crustaceans.

Effect of temperature on development rate of larvae from cold-water American lobster (Homarus americanus)

The duration of the larval phase of the American lobster influences the distance larvae drift, and thus the potential settlement and recruitment patterns of lobsters to local populations and fisheries. The duration of larval stages is influenced by temperature, with warmer temperatures resulting in faster development and shorter stage duration. The quantitative relationship between temperature and duration of larval stages has been previously investigated, but only for lobsters originating from relatively warm-water regions. We examined the effects of temperature on stage duration for lobster larvae originating from a cold-water region, the northern shore of the Gaspe Peninsula in the northern Gulf of St. Lawrence, Canada. We reared larvae individually using a new experimental apparatus with automated movement of culture containers to facilitate water exchange. We compared observed duration of larval stages for these cold-water source larvae to durations in previous studies that used warmer-water source larvae. We observed 38% shorter development times at the coldest temperature used (10°C) and 47, 50, and 100% longer development times at warmer temperatures (14, 18 and 22°C, respectively) than at the same temperatures in previous studies of warm-water larvae, suggesting potential geographic variation in the functional relationship between temperature and larval development time. Given these results, future research should examine this question in more detail, to enhance understanding of lobster ecology and population dynamics across the species’ range.

Tissue specificity and ontogeny of lactate dehydrogenase in snow crab, Chionoecetes opilio (Brachyura, Majidae)

Abstract In the snow crab, Chionoecetes opilio (Brachyura: Majidae), LDH is present in rive isozymic forms, as revealed by the rive coloration zones in zymograms. This is characteristic of a tetrameric LDH enzyme formed by the random association between two distinct sub-units. Isozymes of C. opilio LDH show tissue specificity. No LDH activity is detected in the hepatopancreas. The LDH-B∗ locus is expressed in all other tissues examined, except the eye, in which LDH-A∗ is the only locus detected. Both loci are expressed in nervous, midgut and leg muscle tissues, the last showing individual variability. At least among males, the LDH-B∗ locus is expressed in leg muscle tissue at every developmental stage, while LDH-A∗ locus expression is initiated only in the VII th post-larval stage, just before the onset of gametogenesis. Results suggest that LDH sub-units in C. opilio have distinct physiological roles. This is very well known in vertebrates, but is virtually undocumented in invertebrates.

Behavior, Growth and Survival of Stage V Lobsters (Homarus Americanus) in Relation to Shelter Availability and Lobster Density

The effects of 2 levels of shelter availability (8 or 32 shelters) and of 3 levels of intraspecific density (5, 15, or 30 individuals per 0.5 m 2) on the behavior, survival and growth of stage V lobsters over a period of h 25 days were examined through controlled laboratory experiments. Dominance interactions were apparent in all treatments and only certain lobsters gained access to shelter in the medium- and high-density treatments. Lobsters spent more than 95% of their time in shelter when possible, and expressed significantly greater fidelity to one shelter in the 8-shelter treatment compared to the 32-shelter treatment. Shelter availability and lobster density had no effect on the incidence of molting or on the mean size of lobsters at experiments end. The proportion of injured lobsters was independent of shelter availability, but was positively related to density. Lobsters were most likely to die after having molted and percent mortality was significantly greater at low density and in the 32-shelter treatment than in other treatments, probably due to a stronger and more consistent dominance hierarchy. Overall, the findings suggest that settlers may interact, that the frequency and intensity of interactions may be modified by relative shelter availability and lobster density, and that such interactions may contribute to determine a cohorts fate.

Vertical distribution of snow crab (Chionoecetes opilio) pelagic stages in the Gulf of St. Lawrence (Canada) and effect of temperature on development and survival

Knowledge of the vertical distribution, thermal habitat, and growth of the larvae of the cold stenothermic snow crab (Chionoecetes opilio) is incomplete and inconsistent. This study explored aspects of the vertical distribution and development rate of larvae from eastern Canada. In the Gulf of St. Lawrence (GSL), during 2002, the mean vertical positions of the snow crab zoeae I and II larvae were recorded within and above the permanent thermocline and in close association with the depth of strong density discontinuities in the stratified water column. No statistically significant differences were detected between nighttime and daytime vertical positions. The water temperatures at the centre of the larvae distributions were 2–3 C in late May in the colder northern GSL and 7–8 C in June in the warmer southern GSL. Data from the literature and from a rearing experiment in 2014 were used to develop functions linking development and survival to water temperature. Assuming the snow crab larvae remain in the upper mixed layer until final metamorphosis, development may last 2.2–4 months depending on hatch time and location. Development would be prolonged by several weeks if premolt megalopae move into and reside in the deeper, colder waters as appears to be the case. A relative survival index suggests that optimum temperature for development is around 10.8 C, 9.5 C, and 8.7 C for snow crab zoea I, zoea II, and megalopa, respectively. These results should contribute to modelling efforts that aim to evaluate the extent of larval drift and location of potential settlement areas, as well as the potential impact of climate change on snow crab in the North Atlantic.