摘要:

Palaemon longirostrisandCrangon crangonlarval and post-larval stages were collected intensively in two 24-h cycles during neap and spring tidal periods in a fixed station located in the mid-Mira estuary (southwest Portugal). In each case, on the previous day, horizontal distribution of larval stages was studied in a series of 20 stations from the mouth of the estuary to near freshwater. Horizontal distribution of the discrete instars of both species were similar, suggesting larval retention. Results from the 24-h cycles indicate a semilunar cycle of larval release activity, and an initial displacement of the larvae from the parental stock, as newly-hatched larvae concentrate in the surface layer of the water column on post-crepuscular ebbing tides. The sequence of larval stages tends to be progressively more dependent of the bottom layers, and the whole larval and post-larval development is accomplished within the estuarine boundaries. Larval release cycles, coupled with duration of development and progressive change in vertical position, induce mutual exclusion of different aged larvae, which may minimise cannibalistic behaviour and competition between larvae with different capabilities.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652634

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Pinnotheridae represents a diverse group of very small crabs associated with other invertebrates. Here we show that, among the brachyurans, pinnotherids display the greatest diversity in numbers of gills and gill grooming appendages, with a continuous spectrum ranging from eight to three gills per branchial chamber, on as many as five to as few as two gill bearing appendages. There is no linear relationship between the reduction of gill numbers and size of the crabs. The reduction of gills took place in both anterior and posterior thoracic regions. Also, unlike other Brachyura, some pinnotherids lack a gill grooming appendage on maxilliped 2. These taxa are characterized by four or fewer gills per branchial chamber. In the interest of clarifying the systematic position of species and genera within the Pinnotheridae, 13 adult characters related to gill formulas, morphology of grooming appendages and setae, and hosts were used with 13 larval characters to determine sister group relationships among 34 taxa. The higher Brachyura served as the outgroup in this phylogenetic analysis. It generated multiple trees from which strict consensus and 50% majority-rule consensus trees were computed. All trees identified the genusPinnothereliaas the most basal taxon, followed byAsthenognathusand the remaining pinnotherids. Members of the Pinnotherinae represent the most derived taxa among pinnotherids. This subfamily formed a separate clade, excluding taxa of the Pinnothereliinae and Asthenognathinae, with the exception ofPinnixaandOpisthopus, respectively. Basal to the Pinnotherinae,XenophthalmusandAnomalifronsformed sister taxa. The cladograms indicate progressive loss of gills, starting with the podobranch on maxilliped 3, followed by the podobranch on maxilliped 2 and pleurobranchs associated with pereiopods 2 and 3. Finally the epipodite of maxilliped 2 was lost.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652635

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Using larval data of zoeae from selected genera of majids, we determined tree topologies, levels of homoplasy, and frequencies of reduction under three different assumptions of character argumentation: ordered reduction events, unordered reduction events, and outgroup comparison. Under each assumption we provided a phylogenetic hypothesis for some majid genera and evaluated the assumption that structural reduction can be assumed a priori as a criterion to infer character transformation polarity in phylogenetic reconstruction of decapods. The results indicate that the a priori assumption of “reduction” as the derived condition is not justified because under this assumption, reduction is not always maintained throughout the resulting phylogenetic hypothesis. Furthermore, we also found that this criterion fails to provide the most parsimonious explanation of the data set. Therefore, we reject the use a “reduction=derived” criterion to infer polarity in phylogenetic reconstruction. Phylogenetic analysis using outgroup comparison provided a phylogenetic hypothesis with a better fit and a lower frequency of reduction events. However, we found that statements of homology may be problematic when the number of larval stages in the outgroup differ from those of the ingroup. To overcome this problem, we suggest that, in the absence of evidence for developmental homology, all larval stages should be considered as potential homologues. Using this approach to homology of larval stages, we provide a new phylogenetic hypothesis for 15 genera of majids based on larval morphology. Within Majidae, representative members of Majinae formed a highly nested monophyletic group with the following topology: ((Jacquinotia+Notomithrax) (Leptomithrax+Maja)). In contrast, the Oregoniinae (Hyas+Chionoecetes) formed a basal monophyletic group. Contrary to established ideas for the monophyly of Inachinae,Macrocheirais basal to the Oregoniinae. Other taxa did not form monophyletic groupings based on classical assignment to subfamilies.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652636

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In the last few years, (bio)chemical and molecular biological studies have shown that several members of the hyperglycemic hormone family are present in different molecular forms.In vivoandin vitrobioassays revealed that some of these isoforms also play a role in the control of reproduction in decapod crustaceans. This communication gives a review of the cytological aspects of the eyestalk X-organ sinus gland complex, responsible for the synthesis, storage and release of these neuropeptides, and the molecular and functional aspects of those members involved in the control of reproduction. Finally, the role of the hyperglycemic hormone family in the regulation of reproduction in the female lobster is described as an example of the (possible) interactions of the members of the hyperglycemic hormone family with other (neuro)endocrine factors in the reproductive process of crustaceans.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652637

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This review deals with the studies which have been conducted for the past 30 years on the endocrine and neuroendocrine regulations in embryos and larvae of crustaceans, mostly in decapods. Y-organs, mandibular organs and the X-organ sinus gland complex of the eyestalks are present in the first post-embryonic instar of most investigated species. Y-organs, the X-organs and the sinus glands have also been located in embryos of a few species. Larval molting appears to be regulated in a way similar to that in adults involving a MIH-ecdysteroid system. Evidence points to a control of metamorphosis through the eyestalks. Experimental evidence points to a neuroendocrine control of changes in pigmentation and of osmoregulation. Progress in the isolation and characterization of the hormones and neurohormones controlling these metabolic changes in adults should help and promote further research on regulation during the embryonic and early postembryonic development.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652638

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652639

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652640

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652623

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor