Phylogeny of the family Aglajidae (Pilsbry, 1895) (Heterobranchia: Cephalaspidea) inferred from mtDNA and nDNA.

The family Aglajidae includes several species of benthic, carnivorous cephalaspidean sea slugs, which generally lack a radula, have an internal shell, a posterior shield with short to moderate caudal lobes, and sensory cilia present on the head. The present study reports a phylogenetic analysis of the Aglajidae based on the mitochondrial genes 16S and CO1 and the nuclear gene H3, including 160 specimens of 54 species, that confirms the monophyly of Aglajidae as well as most taxonomically established genera, with some exceptions. Although support values are low for some clades, the analysis recovered the following clades within the Aglajidae: Odontoglaja, Nakamigawaia, and Melanochlamys. Chelidonura appears to be paraphyletic and the monophyly of a Chelidonura-Navanax-Aglaja clade is strongly supported in the Bayesian analysis, plus three of the four individual gene trees (COI, COI without 3rd codon positions, 16S and H3). However, the relatively low levels of support in the maximum likelihood analyses prevent us from proposing the synonymization of Navanax and Aglaja with Chelidonura. Melanochlamys is the sister clade of Chelidonura+Aglaja+Navanax. Odontoglaja is basal to the rest of the Aglajidae, confirming previous hypotheses on the loss of the radula in Aglajidae. Nakamigawaia and Melanochlamys are monophyletic, and should be maintained as valid. The monophyly of Philinopsis is strongly supported in the Bayesian analysis and in three of the four individual gene trees. Further research on this group is necessary to further affirm the monophyly of Chelidonura+Aglaja+Navanax and Philinopsis. Based on the results of this phylogenetic analysis, a reclassification of the taxonomy of Aglajidae is probably necessary. Additional genes should provide more information and probably fully resolve this situation. The present molecular study (including ABGD species delineation analyses) suggests the existence of previously undetected species complexes that require additional study to determine the extent of undocumented biodiversity.

Color pattern variation in a shallow-water species of opisthobranch mollusc.

The color pattern of benthic opisthobranch sea slugs (Mollusca: Gastropoda) appears to play an important defensive role, and numerous species seem to have aposematic (warning) colorations. Color pattern is an important trait for opisthobranch identification-this conclusion is based on the assumption that most species have limited color variation. For those species in which color variation is recognized, the reasons for the variation remain unknown. In this paper we study Philinopsis pusa, a benthic putative species of opisthobranch sea slug with a broad range of color pattern. Lighter individuals appear to be camouflaged on the white sand environment in which the animals are typically found, whereas darker individuals appear conspicuously different from their background. Because of its broad color variation, P. pusa has been subdivided into different species. Animals were collected and observed in the Bahamas during a 6-year span. The color pattern of the specimens was subjectively classified into five phenotypic classes. Two mitochondrial genes (16S, CO1) were sequenced from 41 specimens. The association between color pattern, body length, burrowing escaping behavior, and the genetic structure of the population was investigated. We found two genetically distinct groups in the target population but no significant association between color pattern and genetic structure. Additionally, there was no significant association between color pattern and ontogeny or defensive behavior in these organisms. The present paper suggests that general assumptions on the biological and evolutionary role of color in opisthobranchs need to be carefully evaluated.