Ontogenetic changes in the relative growth of males and females of the spider crab Maja squinado were analyzed and related to their reproductive (maturity) status in order to define criteria to assign individuals to each growth phase. The sampling was carried out in two different areas of southern Galician waters, northwestern Spain, in shallow water (�10 m) with mixed rocky-sandy bottoms (juvenile and postpubertal adult areas) and deep water (�20 m) with soft bottoms (adult habitat). A Principal Component Analysis (PCA) of morphometric variables and a nonhierarchic K-means cluster of PCA scores differentiated two morphometric groups defined as juvenile and adult phases. A significant change in allometry of cheliped size was detected in juvenile males with a break point at a 109-mm carapace length (CL). This point may indicate a change in the relative growth of juveniles, separating the immature and adolescent phases. Histological analysis of a subsample of males showed that sperm were present in most adolescent crabs, but not in immature crabs. Bivariate morphometric linear discriminant functions allow for the identification of juvenile and adult males (classified previously by K-means cluster) with over 99% correct classification using CL and the length or height of the right cheliped. Carapace length at the onset of sexual maturity was estimated to be 132.7 mm (50% of adult males), although in a broad range, 112-165 mm, the size of juveniles and adults overlap. The life history of male spider crabs shows 3 phases differentiated by the relative growth rate of chelipeds separated by two 2 critical molts: prepubertal molt (immature-adolescent) determines a slight increase in allometry, and pubertal or terminal molt (adolescent-adult) determines an increase in the relative size and allometry of chelipeds and the onset of functional maturity. Females showed only 2 phases separated by the terminal molt. Growth of chelipeds in females showed no changes in allometry and was similar to juvenile males. Juvenile females presented a smaller relative width and a higher allometry of the abdomen with regard to adult females. Unlike juvenile females with a flat abdomen, adult females with a domed abdomen have well-developed pleopods, gonads, and seminal receptacles. Carapace length at the onset of sexual maturity was estimated to be 130.4 mm (50% of adult females). The range of overlap of the size of juveniles and adults (114-143 mm) was smaller than in males.
Cañás, L., Stransky, C., Schlickeisen, J., Sampedro, M. P., and Fariña, A. C. 2012. Use of the otolith shape analysis in stock identification of anglerfish (Lophius piscatorius) in the Northeast Atlantic. – ICES Journal of Marine Science, 69: 250–256. The geographical variability in the anglerfish Lophius piscatorius otolith shape was investigated to examine biological evidence for the current separation into Northern and Southern stocks of L. piscatorius established in the Southwest European waters (Southern Shelf area) by the International Council for the Exploration of the Sea (ICES). In all, 629 otoliths of L. piscatorius (12–90 cm total length) from commercial fishing and research surveys were collected in two consecutive years, 2008 and 2009. The otolith shape was compared between stocks for differences in univariate descriptors using non-parametric analysis of covariance, as well as elliptical Fourier shape descriptors, through a metric multidimensional scaling and a linear discriminant analysis (LDA). The differences found in the otolith shape between Northern and Southern stocks were not large enough to hold the current status of L. piscatorius regarding stock definition in the Southern Shelf area, although homogeneous mixing between both stocks is not expected as there were significant differences between three univariate descriptors and the LDA was significant. These results are in agreement with the previous L. piscatorius stock identification studies (genetics, body morphology, and migratory behaviour), which do not support the current separation of these stocks but found substructures within the area.
Over the course of the moult cycle of Maja squinado, the spider crab changes in the hardness and colour of the carapace were assessed and used as methods to identify the intermoult stage in each individual. This intermoult staging was later verified by means of the microscopic observation of the maxilla. These staging techniques made it possible for the prompt identification of the principal intermoult stages—postmoult, intermoult and premoult. In 90% of the cases analysed, there was a correlation between the presence of an underlying carapace and a pink colour of the abdominal vein in crabs in advanced premoult stages.The seasonality of the moult was studied based on the number of specimens in the postmoult stage. There were two main moulting periods—the first occurring in April, and the second, longer period was between July and November. A hypothetical growth model was established and growth rates were determined by length–frequency distribution analyses. Three groups of juveniles and one group of adults were identified. The adults were only found among the population between July and October. In both males and females, the moult increment rate was lower in terminal moults (mean=22%) than in juvenile or prepubertal moults (mean=27%).
Two anglerfish species, Lophius piscatorius and Lophius budegassa, caught off the north and northwest coast of Spain in 2007, were examined for parasite infections. Four parasite taxa were chosen for study, i.e., Anisakis larvae Type I (sensu Berland, 1961), Hysterothylacium rigidum (Nematoda), Spraguea lophii (Microsporidia), and Chondracanthus lophii (Copepoda). Prevalence, intensity, and abundance were determined and related to host size and sex. The abundance of Anisakis larvae Type I significantly increased with size in both anglerfish species, and C. lophii was also more abundant in larger L. piscatorius specimens. The abundance of H. rigidum and the prevalence of S. lophii were unrelated to host size. The infestation with the parasites studied was not affected by host sex.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.