A combined approach to the phylogeny of Cephalopoda (Mollusca)

Abstract

Cephalopoda represents a highly diverse group of molluscs, ranging in habitat from coastal regions to deep benthic waters. While cephalopods remain at the forefront of modern biology, in providing insight into fields such as neurobiology and population genetics, little is known about the relationships within the group. This study provides a comprehensive phylogenetic analysis of Cephalopoda (Mollusca) using a combination of molecular and morphological data. Four loci (three nuclear 18S rRNA, fragments of 28S rRNA and histone H3 and one mitochondrial cytochrome c oxidase subunit I) were combined with 101 morphological characters to test the relationships of 60 species of cephalopods, with emphasis within Decabrachia (squids and cuttlefishes). Individual and combined data sets were analyzed using the direct optimization method, with parsimony as the optimality criterion. Analyses were repeated for 12 different parameter sets accounting for a range of indel/change and transversion/transition cost ratios. Most analyses support the monophyly of Cephalopoda, Nautiloidea, Coleoidea and Decabrachia, however, the monophyly of Octobrachia was refuted due to the lack of support for a Cirroctopoda + Octopoda group. When analyzing all molecular evidence in combination and for total evidence analyses, Vampyromorpha formed the sister group to Decabrachia under the majority of parameters, while morphological data and some individual data sets supported a sister relationship between Vampyromorpha and Octobrachia. Within Decabrachia, a relationship between the sepioids Idiosepiida, Sepiida, Sepiolida and the teuthid Loliginidae was supported. Spirulida fell within the teuthid group in most analyses, further rendering Teuthida paraphyletic. Relationships within Decabrachia and specifically Oegopsida were found to be highly parameter‐dependent. © The Willi Hennig Society 2004.

Evidence for a clade composed of molluscs with serially repeated structures: Monoplacophorans are related to chitons

“…Taxon sampling was carefully designed following original and published work on the internal phylogeny of chitons, bivalves, cephalopods, gastropods, and scaphopods (15,16,(36)(37)(38). Outgroups were selected among other spiralian protostomes (lophotrochozoans) (39).…”

“…Molecular data were obtained from ethanolpreserved specimens following standard protocols for molluscan samples (15,37,38,40). Monoplacophoran DNA samples were extracted from the half specimen preserved in 96% EtOH.…”

Evolution of Nacre: Biochemistry and Proteomics of the Shell Organic Matrix of the Cephalopod Nautilus macromphalus

“…The choice of this model is dictated by the basal position of the genus Nautilus in the diverse phylogenetic trees of the class Cephalopoda. [21] It is the representative of the order Nautiloida, the most ancient lineage of the extant cephalopods [22] and the only one to have conserved an external calcified shell with a A C H T U N G T R E N N U N G nacroprismatic texture, truly A C H T U N G T R E N N U N G homologous to that of bivalve or gastropod. Furthermore, although the nautilus has been the focus of several ultrastructural [5,[23][24][25][26] and biochemical investigations into the bulk shell matrix, [9,[27][28][29] only a few papers have dealt with the detailed characterization of its shell proteins, [30][31][32] and only three short N-terminal sequences are so far available.…”

The scaphopod foot is ventral: more evidence from the anatomy ofRhabdus rectius(Carpenter, 1864) (Dentaliida: Rhabdidae)

“…This is a trait that unifies scaphopods with cephalopods and gastropods (Ponder and Lindberg 1997;Lindgren et al 2004). In scaphopods the anus is above the mouth, although it is directed ventrally (cf.…”