title: 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.
authors.affiliation: Akkeshi Marine Station, Field Science Center for Northern Biosphere, Hokkaido Univesity, Aikappu, Akkeshi, Hokkaido 088-1113, Japan.|Atmosphere and Ocean Research Institute, the University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Yorisue
authors.affiliation: Research Center for Biodiversity, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Benny K K
authors.initials: BK
authors.lastname: Chan
authors.affiliation: School of Marine Biosciences, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0373, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kado
authors.affiliation: Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Atmosphere and Ocean Research Institute, the University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Inoue
authors.affiliation: Atmosphere and Ocean Research Institute, the University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan.
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Kojima
authors.affiliation: Marine Biology Section, Department of Biology, University of Copenhagen, Universitetsparken 4, DK-2100, Copenhagen, Denmark.
authors.forename: Jens T
authors.initials: JT
authors.lastname: Høeg
mesh_terms: D000818:Animals; D005075:Biological Evolution; D017753:Ecosystem; D007814:Larva / Q000033:anatomy & histology; D011984:Sensory Receptor Cells / Q000166:cytology*; D013045:Species Specificity; D001468:Thoracica / Q000033:anatomy & histology*
keywords: hydrothermal vent; larval development; scanning electron microscopy; seep; settlement