Reproductive strategy of two deep-sea scalpellid barnacles (Crustacea: Cirripedia: Thoracica) associated with decapods a
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ORIGINAL ARTICLE
Reproductive strategy of two deep-sea scalpellid barnacles (Crustacea: Cirripedia: Thoracica) associated with decapods and pycnogonids and the first description of a penis in scalpellid dwarf males Lene Buhl-Mortensen & Jens T. Høeg
Received: 26 October 2012 / Accepted: 7 April 2013 # Gesellschaft für Biologische Systematik 2013
Abstract We investigated the sexual system in two pedunculate barnacles of the family Scalpellidae. Both inhabit deep water and are attached to mobile arthropod hosts. Verum brachiumcancri was attached to the majid crab Rochinia hertwigi, and Weltnerium nymphocola to the pycnogonidan sea spider Boreonymphon rubrum. Both barnacles have separate sexes and females almost always carry two dwarf males that are almost fully embedded in a pair of symmetrically situated receptacles inside the rim of the mantle cavity. The dwarf males of V. brachiumcancri have a complex penile structure extending into the female mantle cavity. This is the first time a copulatory structure has been described in detail for a dwarf male of a scalpellid barnacle. Both species lack free nauplii and their larvae are released as cyprids; the brood size is small. This is probably an adaptation for settling close to the parent population. We compare reproductive strategies among scalpellids and suggest that the present males are highly specialized and that the females are allocating resources to few offspring. Keywords Cyprid . Dwarf male . Penis . Reproductive strategy . Settlement . Larval biology
L. Buhl-Mortensen (*) Benthic Habitat Research Group, Institute of Marine Research, P.B. 1870, Nordnes, 5817 Bergen, Norway e-mail: [email protected] J. T. Høeg Marine Biology Section, Department of Biology, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen, Denmark
Introduction All scalpellids are pedunculate suspension-feeding barnacles with the upper part of the body (the capitulum) covered with shell plates. They range extensively in size, are found from shallow water to the deep sea, and can attach to a variety of substrata, from rock surfaces to various sorts of plants and animals. In addition to a wide range in size and habitat, members of this species-rich family (~281 species) also exhibit a range of sexual systems, rendering them eminently suited for ecological and evolutionary studies (Svane 1986; Buhl-Mortensen and Høeg 2006; Spremberg et al. 2012). In the Scalpellidae, larval development can comprise the usual cirripede series of nauplii followed by a cyprid, or larvae can be released at the cypris stage, thus abbreviating life in the plankton and limiting capacity for dispersal. The sexual system of the Scalpellidae ranges from pure hermaphroditism through androdioecy (hermaphrodites and males) to dioecy (separate sexes) (BuhlMortensen and Høeg 2006; Kelly and Sanford 2010; Yusa et al. 2011) but, wherever found, the males are always minute dwarf males that are permanently attached to their partner. Most previous studies on scalpellids have been either taxonomic, describing the female/
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