Larval Morphology of the Snapping Shrimp Alpheus angulosus (Decapoda, Caridea) Supports Taxonomic Separation From the Alpheus armillatus Species Complex

The genus Alpheus Fabricius, 1798 is the second most speciose among caridean shrimps; however, its larval development remains poorly understood, with only about 10% of species having their first larval stages described. Within the Alpheus armillatus H. Milne Edwards, 1837 species complex, recent taxonomic rearrangements have emphasized the need for integrative studies to differentiate cryptic species. Following this direction, this study described and illustrated the first two larval stages (zoea I and zoea II) of A. angulosus McClure, 2002, based on specimens collected in two distinct localities in the state of Alagoas, Northeastern Brazil. Morphological descriptions were conducted using light microscopy and camera lucida , following standard setal classification systems. Partial sequence of the 16S rRNA gene of one parental female was analysed, providing molecular support for species identification. Our results showed that zoea I of A. angulosus can be distinguished from other members of the A. armillatus complex which have larval morphology described ( A. brasileiro Anker 2012 and A. carlae Anker 2012) by specific setal counts on the maxillule, maxilla and maxillipeds. This study highlights the relevance of larval morphology as complementary information for decapod taxonomy and suggests that the differences observed in A. angulosus warrant further integrative taxonomic revision.