Alternate Title

Morphological Features of Taxonomical Value for the Identification of Three Western Atlantic Penaeid Shrimp Genera (Decopoda: Penaeidae)

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Rostra, telsons and patterns of sternal spines were examined for Western Atlantic penaeid shrimps Metapenaeopsis, Rimapenaeus and Farfantepenaeus to facilitate the identification of postlarval and juvenile stages and clarify the patterns of sternal spines previously proposed as a useful tool for identifying penaeid postlarvae at the generic level. Examination of the telsons and rostra from closely related Metapenaeopsis and Rimapenaeus species indicated that at the postlarval stages these morphological features are very similar in shape and size. Regarding the sternal spines, Metapenaeopsis spp. bear a pair on the second thoracic plate, while Rimapenaeus spp. lack thoracic spines. The different pattern of thoracic spines provides a useful tool for distinguishing taxa of these two closely related genera. A comparison of the sternal spine patterns of Western Atlantic Metapenaeopsis and Rimapenaeus species with that described for Indo-Pacific species indicated that patterns are different at the generic level. The sternal spines in Farfantepenaeus postlarvae also showed variable patterns among species. Most Farfantepenaeus duorarum postlarvae bear one spine on the fourth thoracic plate while Farfantepenaeus aztecus bear one spine on the fourth plate and one on the fifth. These results demonstrate that patterns of sternal spines could be useful to discriminate closely related taxa, but patterns at the generic level are more variable than had previously been described.

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