Chamaesipho

Abstract: The larval stages of the acorn barnacles Chamaesipho columna, Chamaesipho brunnea, Elminius plicatus, Elminius modestus, Balanus trigonus, and Tetraclita purpurascens are described from larvae reared in the laboratory. A key and a table are included for separating larval stages and species. Skeletonema costatum appears to have a wide application as a food in the rearing of larvae of the Balanidae. The two Chamaesipho species show typical chthamalid characters of hispid antennal setae and unilobed labrum. The similarity between the larvae of Elminius plicatus and Tetraclita purpurascens supports the classification of E. plicatus as a tetraclitid.

Abstract: Euraphia devaneyi new species (of the hernbeli-group) is described from Easter Island. Rehderella belyaevi (Zevina and Kurshakova) new genus is given a supplementary description and its range extended from Easter Island to Pitcairn Island. Consideration of the pleisomorphies and apomorphies of R. belyaevi and related genera necessitates recognition of the Notochthamalinae, a new subfamily of South Pacific species with card setae on some or all of the anterior cirri. Diagnoses are given for Notochtharnalus new genus, for N. scabrosus from South America, Nesochtharnalus new genus, for N. intertextus from widespread west Pacific localities, and Charnaesipho Darwin containing three species from New Zealand and Australia. Both chthamalids of Easter Island are peripheral Polynesian endemics, and the historical biogeography of this in connection with such young islands is discussed. Chthamalid barnacles are characteristic of rocky shores all round the world. Twenty-five species have been assigned to the genus Chthamalus or the closely related genus Euraphia (Newman and Ross, 1976; Dando and Southward, 1980). The distinction between Chthamalus and Euraphia has rested primarily on the nature ofthe mandible; quadridentoid with a combed lower margin in the former and tridentoid with a pectinate lower angle in the latter. Difficulties with this were raised by Pope (1965), particularly with Euraphia intertextus (Darwin) in which characters other than the mandible relate it to Chamaesipho columna (Spengler) which has a quadridentoid mandible. Our attention was refocused on this and related matters when we examined barnacles from Easter Island. The commonest barnacle on the basalt shores there is a chthamalid described and named Chthamalus belyaevi by Zevina and Kurshakova (1973). It has a Chthamalus-like mandible yet is tridentoid, and shows clear shell relationships with E. intertexta of the tropical western Pacific as well as with Chthamalus scabrosus Darwin and Chamaesipho spp. of southeast and southwest shores of the South Pacific respectively. It is our conclusion that the Chthamalus-Euraphia dichotomy for the bulk of the six-plated chthamalid barnacles is not now adequate. The barnacle fauna of Easter Island is meager. Only three shore species are known: a new species of Euraphia described herein, the chthamalid C. belyaevi here given a supplementary description and generically redefined, and a Tesseropora of small size and similar to specimens that have been collected from Norfolk Island and the Hawaiian Islands, and also reminiscent of T. atlantica from Bermuda and the Azores in the Atlantic Ocean (Newman and Ross, 1977). Two stalked barnacles are known: Lepas anserifera Linnaeus was collected on floating debris (BAF, pers. obs.) and Temnaspis cf. hawaiensis (Pilsbry) was shown as commensal on the mouthparts of the lobster Panulirus pascuensis Reed by Holthuis (1972). This paper pays particular attention to the two Easter Island chthamalids, considers their relationship to other chthamalids of the South Pacific Ocean, and