The deep-sea chiton Nierstraszella (Mollusca: Polyplacophora: Lepidopleurida) in the Indo-West Pacific: taxonomy, morphology and a bizarre ectosymbiont

This study investigated the taxonomy and distribution of the deep-sea polyplacophoran mollusc Nierstraszella Sirenko, 1992 in the Indo-West Pacific, based on a collection of 516 specimens collected in the Philippines and Solomon Islands. Although seven species names have historically been proposed in this group of chitons, all have been considered as synonyms of the monotypic N. lineata (Nierstrasz, 1905). Morphological examination of this new material reveals the presence of two species. N. lineata is distinct from N. andamanica (Smith, 1906), based on morphological characters given in the original species description and very distinctly different morphology of aesthete pores in the shell surface. Furthermore, populations of N. andamanica in the Philippines and Solomon Islands are locally colonized with the epibiotic (ectoparasitic) bryozoan Pseudobathyalozoon profundum d'Hondt, 2006. These bryozoans attach ventrally to the girdle of the host chiton and the erect zooids feed within the pallial cavity, among the chiton's gills.

Deep-sea chitons from sunken wood in the West Pacific (Mollusca: Polyplacophora: Lepidopleurida): taxonomy, distribution, and seven new species

Natural deposits of sunken wood provide an important habitat for deep-sea invertebrates. Deep-sea chitons in the primitive order Lepidopleurida are typically collected rarely and as single specimens. However, these animals have been recovered in large densities associated with sunken wood in the tropical West Pacific, in groups of up to 50 individuals. Four deep- sea expeditions in the West Pacific, to the Philippines, Solomon Islands, and Vanuatu, recovered a large number of poly- placophorans. We have examined the morphology as well as the range and distribution of these species, based on the larg- est collection ever examined (more than 1300 individuals). These species show potentially adapted characters associated with exploitation of sunken wood as habitat, such as protruding caps on sensory shell pores (aesthetes) and large interseg- mental bristles with potential sensory function. In this study we investigated the twenty-two species recovered, including seven newly described here (Leptochiton consimilis n. sp., L. angustidens n. sp., L. dykei n. sp., L. samadiae n. sp., L. longisetosus n. sp., L. clarki n. sp., L. schwabei n. sp.), and provide the first identification key to the 34 lepidopleuran chitons known from sunken wood worldwide.

Taxonomy and phylogeny of Osmundea (Rhodomelaceae, Rhodophyta) in Atlantic Europe

Two species of Osmundea Stackhouse (Rhodomelaceae, Rhodophyta) that occur in Atlantic Europe have been confused under the names Osmundea ramosissima (Oeder) Athanasiadis and Osmundea truncata (Kutzing) Nam et Maggs, regarded until now as a synonym of O. ramosissima, An epitype from its type locality (Stavanger, Norway) is selected for Osmundea ramosissima Athanasiadis, recognized here as a valid name for Fucus ramosissimus Oeder, nom. illeg. Details of vegetative and reproductive morphology of O. ramosissima are reported, based on material from France, the British Isles, and Helgoland. Osmundea ramosissima resembles other species of Osmundea in its vegetative axial segments with two pericentral cells and one trichoblast, spermatangial development from apical and epidermal cells (filament type), the formation of five pericentral cells in the procarp-bearing segment of the female trichoblast, and tetrasporangial production from random epidermal cells. Among the species of Osmundea, O. ramosissima is most similar to O. truncata. Both species have discoid holdfasts, secondary pit connections between epidermal cells, and cup-shaped spermatangial pits. They differ in that: (a) O. ramosissima lacks lenticular wail thickenings and refractive needle-like inclusions in medullary cells, both of which are present in O. truncata; (b) O. ramosissima has branched spermatangial filaments that terminate in a cluster of several cells, whereas in O. truncata the unbranched spermatangial filaments have a single large terminal sterile cell; and (c) cystocarps of O. ramosissima lack protuberant ostioles but ostioles are remarkably protuberant in o. truncata. Phylogenetic analyses of rbcL sequences of Laurencia obtusa (Hudson) Lamouroux and all five Atlantic European species of Osmundea, including the type species, strongly support the generic status of Osmundea. Osmundea ramosissima and O. truncata are closely related (5.2% sequence divergence) and form a well-supported clade sister to a clade consisting of O. pinnatifida (Hudson) Stack-house, O. osmunda Stackhouse and O. hybrida (A. P. de Candolle) Nam. The formation of secondary pit connections between epidermal cells is a synapomorphy for the O. ramosissima + O. truncata clade. The close relationship between species with cup-shaped spermatangial pits (Osmundea hybrida) and urn-shaped pits (Osmundea pinnatifida and Osmundea osmunda) shows that spermatangial pit shape is not an important phylogenetic character. Parsimony analysis of a morphological data set also supports the genus Osmundea but conflicts with the molecular trees in infrageneric relationships, placing O. hybrida basal within the Osmundea clade and grouping O. osmunda and O. pinnatifida but not O. truncata and O. ramosissima. A key to Osmundea species is presented.

Molecular Phylogenies Support Homoplasy of Multiple Morphological Characters Used in the Taxonomy of Heteroscleromorpha (Porifera: Demospongiae)

Sponge classification has long been based mainly on morphocladistic analyses but is now being greatly challenged by more than 12 years of accumulated analyses of molecular data analyses. The current study used phylogenetic hypotheses based on sequence data from 18S rRNA, 28S rRNA, and the CO1 barcoding fragment, combined with morphology to justify the resurrection of the order Axinellida Lévi, 1953. Axinellida occupies a key position in different morphologically derived topologies. The abandonment of Axinellida and the establishment of Halichondrida Vosmaer, 1887 sensu lato to contain Halichondriidae Gray, 1867, Axinellidae Carter, 1875, Bubaridae Topsent, 1894, Heteroxyidae Dendy, 1905, and a new family Dictyonellidae van Soest et al., 1990 was based on the conclusion that an axially condensed skeleton evolved independently in separate lineages in preference to the less parsimonious assumption that asters (star-shaped spicules), acanthostyles (club-shaped spicules with spines), and sigmata (C-shaped spicules) each evolved more than once. Our new molecular trees are congruent and contrast with the earlier, morphologically based, trees. The results show that axially condensed skeletons, asters, acanthostyles, and sigmata are all homoplasious characters. The unrecognized homoplasious nature of these characters explains much of the incongruence between molecular-based and morphology-based phylogenies. We use the molecular trees presented here as a basis for re-interpreting the morphological characters within Heteroscleromorpha. The implications for the classification of Heteroscleromorpha are discussed and a new order Biemnida ord. nov. is erected.