TL;DR: Two new records for decapod larval forms in pelagic environments off oceanic islands in the western tropical Atlantic are reported, and detailed diagnoses and images of these larvae are provided.
Abstract: The current biogeographic and taxonomic knowledge on decapod larvae in tropical oceans is still very incomplete, in spite of their huge ecological and socio-economic importance. The present study reports two new records for decapod larval forms in pelagic environments off oceanic islands in the western tropical Atlantic, and provides detailed diagnoses and images of these larvae. Samples were taken from July 2010 to November 2014 using neuston, bongo and WP-2 nets at three localities: St. Peter and St. Paul’s Archipelago (SPSP), Rocas Atoll (RA) and Fernando de Noronha Archipelago (FN). The larval forms Cerataspis monstrosa (Gray, 1828) and Amphionides reynaudii (H. Milne Edwards, 1832) were recorded around these areas, constituting the first record for these oceanic islands. Out of 121 samples analyzed, one specimen of C. monstrosa (Mysis II) was found off FN, and 20 specimens of A. reynaudii in nine distinct stages (Mysis II, IV, VI, VII, VIII, IX, X, XI, XII) were found off SPSP, RA and FN.
TL;DR: Evidence is presented that the single representative of the crustacean order Amphionidacea is a decapod shrimp and not a distinct order, and it is proposed to treat Amphionides reynaudii as incertae sedis within Caridea, rather than a separate family.
Abstract: We present evidence that the single representative of the crustacean order Amphionidacea is a decapod shrimp and not a distinct order. After reviewing available morphological evidence, it is concluded that Amphionides is a larval form, but with an as yet unknown parentage. Although the most likely adult form is in the family Pandalidae, the limited molecular data available cannot fully resolve its affinity. We therefore propose to treat Amphionides reynaudii as incertae sedis within Caridea, rather than a separate family. In view of the large scale, tropical and subtropical distribution of the taxon, the possibility is discussed that Amphionides is more likely to be a composite taxon at generic level, rather than larvae of a single shrimp species.