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  • 1
    Electronic Resource
    Electronic Resource
    Endogenous control of timing of metamorphosis in megalopae of the shore crab Carcinus maenas (1997)
    Springer
    Marine biology 128 (1997), S. 299-305 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Batches of hundreds of freshly collected megalopae of the shore crab Carcinus maenas (L.) showed persistent circatidal rhythms of moulting to the juvenile crab stage when maintained in constant laboratory conditions. Peaks of moulting occurred around expected times of high tides, with few megalopae moulting at other times. In larvae collected offshore, the highest tidally-timed peak of metamorphosis occurred during the second to fifth expected times of high tide, and metamorphosis of 50% of each batch took about 22 h or longer. In contrast, in larvae collected at the water's edge, 70% metamorphosed during the first expected episode of high tide, within 6 to 8 h after collection. However, although inshore megalopae moulted before offshore ones, the tidal timing of moulting remained unaltered whether megalopae were collected at neaps or springs, from the water's edge or farther offshore, in the presence or absence of natural substratum, and under various light–dark and salinity regimes. Metamorphosis of C. maenas megalopae around the times of high tides may enhance settlement into the upper intertidal zone. Early juveniles of the crab apparently prefer that zone as they are most abundant there and, unlike adults, do not undertake up-and-down-shore migration with tides. The present finding demonstrates, for the first time, endogenous physiological timing of circatidal periodicity in the metamorphic moult of crab megalopae, suggesting that endogenous factors, as well as exogenous ones should be taken into account in considering the process of settlement by crab megalopae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050095
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  • 2
    Electronic Resource
    Electronic Resource
    Chela loss in the shore crab Carcinus maenas (Crustacea: Brachyura) and its effect on mating success (1994)
    Springer
    Marine biology 121 (1994), S. 247-252 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Field and experimental studies were conducted to determine the incidence of chela loss and its effect on mating success in a population of the shore crab Carcinus maenas (Linnaeus, 1758) inhabiting the Menai Straits, North Wales. The study was performed between 1989 and 1993. Male crabs showed a higher degree of chela loss (12.5%) than females (7.9%). In males, frequencies ranged from ∼10% at sizes 50 mm CW (carapace width) up to ∼30% in the largest crabs of 70 to 80 mm CW. The percentage of females with missing chelae appears to be unrelated to size. The most common type of chela loss in the population studied was of a missing crusher chela of right-handed crabs. Red crabs, which are assumed to be in prolonged intermoult, had a much higher degree of chela loss (20.5%) than the green, early intermoult crabs (9.7%). The proportion of red crabs with chela losses increased with size, possibly reflecting an increase in intermoult duration with size. In green crabs, there was no such increase. The proportion of male crabs with missing chelae found in mating pairs in the field was much lower than that found in the adult unpaired population, suggesting that the loss of a chela constitutes a handicap to a male crab when trying to mate. Also, by studying the relative frequencies of different categories of chela loss, it is suggested that the loss of a crusher chela exerts a more deleterious effect than the loss of a cutter. Experiments were performed in the laboratory where pairs in pre-copula were confronted with an additional single male in various combinations of sizes and patten of chela loss. These showed that the loss of a chela constitutes a handicap for a male crab when either competing for or defending a paired pre-moult female. This handicap was estimated to be equivalent to a reduction in size of 7 to 8 mm CW relative to the size of the competitor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346732
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  • 3
    Electronic Resource
    Electronic Resource
    Population characteristics of the deep-sea lobsters Polycheles typhlops and Stereomastis sculpta (Decapoda: Polychelidae) in a bathyal mud community of the Mediterranean Sea (1992)
    Springer
    Marine biology 114 (1992), S. 109-117 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Distribution and abundance as a function of depth, and population parameters such as sex and size structure of the population and aspects of reproductive biology have been studied in the deep-sea polychelid lobsters Polycheles typhlops and Stereomastis sculpta. Samples were taken by otter trawl in the Balearic Sea, a deepsea basin in the northwestern Mediterranean Sea from 1985 to 1989. In both species the largest size classes were dominated by females. In S. sculpta, male and female sizes were very similar. In P. typhlops, ovigerous females and those with external spermatophores were ≥23 and 25 mm in carapace length (CL), respectively; males with external spermatophores were ≥17 mm in CL. In S. sculpta, ovigerous females and those with external spermatophores were ≥24 and ≥19 mm CL, respectively, and males with external spermatophores ≥19 mm CL. Highest densities of P. typhlops occurred along the middle slope at depths between 500 and 1000 m. Only small-sized individuals were found at the deepest depths sampled; some recruitment must therefore occur in waters much deeper than those usually inhabited by the adult population. The sex-ratio was 1:1 in most samples, but in some of the shallowest samples females predominated. The depth distribution range of S. sculpta was 981 to 2253 m: densities clearly increased with increasing depth. There were no apparent variations in size distribution as a function of depth. Since very few adult males and females were captured, the population in the survey area would seem to be comprised mainly of juveniles. As a function of depth, females were numerically dominant only in some of the shallowest samples taken in the distribution range of this species. There is strict habitat partitioning between the two species. In both species, the variation in the sex-ratio as a function of depth suggests differential migration between the sexes, probably related to egg incubation and hatching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350860
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  • 4
    Electronic Resource
    Electronic Resource
    Population structure and growth of Donax trunculus (Bivalvia: Donacidae) in the western Mediterranean (1995)
    Springer
    Marine biology 121 (1995), S. 665-671 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparison of shell growth in Donax trunculus (collected between 1988 and 1990 of Cullera, Spain) has been carried out using an analysis of cohort progression in monthly length frequency distributions, hyaline surface shell growth rings and internal microgrowth bands. In the Mediterranean there are two periods of recruitment of D. trunculus, one in the summer (July to September) and the other in winter (December to February). Clams recruited to the population in winter display a clear cessation in shell growth during the following summer which may possibly be correlated with spawning, whereas individuals of the summer recruited cohort show no growth cessation the following summer and continue to deposit shell during this period. The normally opaque shell of D.trunculus reveals the presence of translucent hyaline growth rings when the shells are backlit by a strong light source, and these have been shown to be laid down in the shell during summer months. Formation of a hyaline ring is accompanied by a narrowing of the microgrowth patterns present in shell sections. Both the hyaline rings and the length frequency distributions have been used to determine the age and growth rate of D. trunculus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349302
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  • 5
    Electronic Resource
    Electronic Resource
    Fishery dynamics of the mantis shrimp Squilla mantis (Crustacea: Stomatopoda) population off the Ebro delta (northwestern Mediterranean)
    Amsterdam : Elsevier
    Fisheries Research 16 (1993), S. 131-145 
    Details
    ISSN: 0165-7836
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0165-7836(93)90048-C
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  • 6
    Electronic Resource
    Electronic Resource
    Analysis of the structure of decapod crustacean assemblages off the Catalan coast (North-West Mediterranean) (1988)
    Springer
    Marine biology 98 (1988), S. 39-49 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We sampled the communities of decapod crustaceans inhabiting the depth zone between 3 and 871 m off the Catalan coast (North-West Mediterranean) from June 1981 to June 1983. The 185 samples comprised 90 species differing widely in their depth distributions. Multivariate analysis revealed four distinct faunistic assemblages, (1) littoral communities over sandy bottoms, (2) shelf communities over terrigenous muds, (3) upper-slope communitics, and (4) lower-slope or bathyal communities. The brachyuran crab Liocarcinus depurator is the most abundant species of the shelf assemblage, although L. vernalis dominates over the shallow sandy bottoms of the shelf. The dominant species of the upper-slope assemblage are nektobenthic species (Solenocera membranacea, Plesionika heterocarpus, Processa canaliculata), pelagic species (Pasiphaea sivado, Sergestes arcticus), and benthic species (Macropipus tuberculatus, Munida intermedia, Nephrops norvegicus). Aristeus antennatus comprise most of the biomass of the lower-slope community, which supports a greater diversity than the other assemblages. The main assemblages appear to be related to different hydrological characteristics, the extent of seasonal fluctuations, and to the changes in sediment structure associated with changes in the steepness of the bottom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392657
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