title: Does the kinorhynch have a hydrophobic body surface? Measurement of the wettability of a meiobenthic metazoan.
abstract: The body surface of aquatic invertebrates is generally thought to be hydrophilic to prevent the attachment of air bubbles. In contrast, some interstitial invertebrates, such as kinorhynchs and some crustaceans, have a hydrophobic body surface: they are often trapped at the water surface when the sediment in which they reside is mixed with air and water. Here, we directly measured the wettability of the body surface of the kinorhynchEchinoderes komatsui, using a microscopic contact angle meter. The intact body surface of live specimens was not hydrophobic, but the anterior part was less hydrophilic. Furthermore, washing with seawater significantly decreased the wettability of the body surface, but a hydrophilic surface was recovered after a 1 h incubation in seawater. We believe that the hydrophobic cuticle of the kinorhynch has a hydrophilic coat that is readily exfoliated by disturbance. Ultrastructural observations supported the presence of a mucus-like coating on the cuticle. Regulation of wettability is crucial to survival in shallow, fluctuating habitats for microscopic organisms and may also contribute to expansion of the dispersal range of these animals.
authors.affiliation: Department of Life Science and Applied Chemistry , Graduate School of Engineering , Nagoya Institute of Technology, Nagoya, Aichi 466-8555 , Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ishii
authors.affiliation: Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan; Museum für Naturkunde Berlin, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, 10115 Berlin, Germany.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamasaki
authors.affiliation: Department of Chemistry, Biology and Marine Science, Faculty of Science , University of the Ryukyus , Nishihara, Okinawa 903-0213 , Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Uozumi
authors.affiliation: Department of Chemistry, Biology and Marine Science, Faculty of Science , University of the Ryukyus , Nishihara, Okinawa 903-0213 , Japan.
authors.forename: Euichi
authors.identifier: 0000-0001-7002-4524
authors.initials: E
authors.lastname: Hirose
keywords: contact angle; hydrophilic coat; hydrophobic cuticle; interstitial habitat; meiobenthos; wettability