On the morphology of antennular sensory and attachment organs in cypris larvae of the deep‐sea vent/seep barnacles, Ashinkailepas and Neoverruca

Abstract

Barnacle cypris larvae show high morphological variation in the organs used in search of and attaching to a substratum. This variation may represent adaptation to the habitat of the species. Here, we studied SEM level morphologies of cypris antennular sensory and attachment organs in a deep-sea vent endemic species (Neoverruca sp.) and a vent/seep inhabiting species (Ashinkailepas seepiophila). We compare them with three species from other environments. The antennular morphologies of Neoverruca sp. and A. seepiophila were similar, which is consistent with recent molecular studies showing a close relationship of the two species. The setation pattern of the antennules was very conservative among species from various environments. In contrast, striking differences were observed in the structure of the attachment organ (the third antennular segment). Neoverruca sp. and A. seepiophila had no velum or a skirt surrounding the attachment disc on the third segment, while other cirripede cyprids almost always have either of these structures. In addition, both cyprids of A. seepiophila and Neoverruca sp. had the attachment disc angled toward the substratum, whereas it faces distally in cyprids from hard bottom inhabiting barnacles. We suggest that both velum/skirt and the angle of the attachment disc play an important role, when the antennules are contacting the substratum during surface exploration. Differences in attachment organ structures may be highly adaptive, enabling cirripede species to enter new habitats during evolution.

Biochemistry of Barnacle Adhesion: An Updated Review

“…Cyprid attachment discs are flat and covered by a carpet of cuticular villi (Figures 2B,C). Among species, they vary markedly in outlines (e.g., circular or elliptical), perimeter structures (e.g., velum or skirt), tilting angles relative to the long axis of the antennule, and microvilli density (Bielecki et al, 2009;Brickner and Hoeg, 2010;Al-Yahya et al, 2016;Yorisue et al, 2016). During surface exploration, the two attachment discs attach and detach from the surface alternatively, allowing the cyprid to "walk" bipedally on the surface.…”

Towards a barnacle tree of life: integrating diverse phylogenetic efforts into a comprehensive hypothesis of thecostracan evolution

“…This is especially problematic with morphological characters as very different characters have been used at the higher taxonomic ranks compared to lower ranks, and in some groups (e.g., parasitic barnacles) it is impossible to determine character homology. Within Thecostraca, larval characters are the only ones that can be compared across all taxa, but compiling and coding such information is cumbersome and time consuming, especially for rare and hard to sample species (e.g., Yorisue et al, 2016). Similarly, genetic data sets are also hard to combine since experts tend to use different (sometimes completely different) sets of genetic markers.…”

Peer Review #2 of "Towards a barnacle tree of life: integrating diverse phylogenetic efforts into a comprehensive hypothesis of thecostracan evolution (v0.1)"

“…Within Thecostraca, larval characters are the only ones that can be compared across all taxa, but compiling and coding such information is cumbersome and time consuming, especially for rare and hard to sample species (e.g. Yorisue et al, 2016). Similarly, genetic data sets are also hard to combine since experts tend to use different (sometimes completely different) sets of genetic markers.…”