Antennulary sensory organs in cyprids of Octolasmis and Lepas (Crustacea: Thecostraca: Cirripedia: Thoracica): A scanning electron microscopic study

Abstract

Cypris larvae of the pedunculate barnacles Octolasmis angulata (Poecilasmatidae), Lepas australis, L. pectinata, and Dosima fascicularis (Lepadidae) were studied with scanning electron microscopy, focusing on the sensory setae and the attachment disc on the antennules. The antennules of O. angulata did not exhibit any remarkable trait, but carry the same number of setae as seen in most other thoracicans. The third segment is bell-shaped and quite distinct from the second and its attachment disc is surrounded by a skirt. We found several potential synapomorphies in antennulary morphology between cyprids of the lepadid species but none of them were shared with the cyprids of Octolasmis; the list of unique lepadid characters includes: one additional, preaxial seta on the second segment; multiple similar (up to eight) postaxial setae (PS3) on the third segment, unlike all other thoracicans, where there is only a single PS3; the third segment consists almost entirely of the attachment disc, which is distended and surrounded by two parallel rows of radial setae; on the fourth segment the terminal seta E is diminutive. We found no traits in cyprids of Octolasmis that seem to be adaptations to their attachment site within the branchial chamber of swimming crabs and, in particular, no similarities with cyprids of rhizocephalan barnacles, many of which also attach in the gill chamber. The synapomorphies between cyprids of the lepadid species may be adaptations to their life in the neuston.

Cypris morphology in the barnacles Ibla and Paralepas (Crustacea: Cirripedia Thoracica) implications for cirripede evolution

“…The morphology and setation of the fourth segment vary even more extensively than that of the third (Nott and Foster, 1969;Clare and Nott, 1994;Kolbasov et al, 1999;Blomsterberg et al, 2004), but only a couple of studies have suggested schemes for the homology of its setation across all Cirripedia (Høeg and Rybakov, 1996;Kolbasov and Høeg, 2007). From the few well-studied thoracicans it seems that the fourth segment carries a basic set of four subterminal and five terminal setae as seen here in Ibla.…”

“…The postaxial disc seta and the axial disc seta were formerly called ''organs'' (see Moyse et al, 1995) but are nothing but ordinary setae. Within the Thoracica, the Lepadidae (but not the closely related Poecilasmatidae) are apomorphic in having up to eight ps3 setae (Blomsterberg et al, 2004). The Rhizocephala also differ significantly in having, in the ground pattern, the ps3 seta elaborated as a large aesthetasc, whereas no other cirripede cyprids carry aesthetascs on the third segment.…”

“…The gross anatomy of the cyprid is very similar in all cirripedes, but it sports a host of characters at the ultrastructural level that can provide important phylogenetic information. The lattice organs in the shield (carapace) were the first larval features used for a phylogenetic analysis of all Cirripedia, including the parasitic Rhizocephala (Jensen et al, 1994a,b;Høeg and Kolbasov, 2002;Buckeridge and Newman, 2006), but the diversity of antennular sensory organs and the morphology of the thorax and abdomen-telson also provide important character sets (Elfimov, 1995;Moyse et al, 1995;Kolbasov et al, 1999;Høeg and Kolbasov, 2002;Blomsterberg et al, 2004;Høeg et al, 2004a).…”

Harvest locations of goose barnacles can be successfully discriminated using trace elemental signatures

“…As a consequence most studies applying TES to crustaceans have used the whole body634, integrating the elements contained in the soft tissues to minimize the potential resetting of the signature. However, in goose barnacles, the shell plates are not shed during the molt; rather they are maintained and increase in size, being accreted at the periphery over time49, consequently preserving imprinted TES over their lifespan. With this in mind, the present work aimed to develop and validate a tool for tracing the origin of goose barnacles using shell plates.…”

Morphometric and molecular identification of individual barnacle cyprids from wild plankton: an approach to detecting fouling and invasive barnacle species

“…In fouling studies, it is essential to know which larvae are present in the plankton, because there is no certainty that all cyprids behave like the few model species, eg Amphibalanus amphitrite, used in settlement assays in the laboratory (eg Chaw et al 2011;Chen et al 2011;De Gregoris et al 2011;Maruzzo et al 2011). The diversity of cyprid sensory armature now known to exist in cirripedes may well indicate similar differences in their settlement biology, such as substratum preference and response to settlement factors (Moyse et al 1995;Blomsterberg et al 2004;Bielecki et al 2009). Furthermore, reliable identification of cyprids in the plankton could serve as early warning of unwanted marine immigrant species that could pose new problems as biofoulers.…”