Coral‐inhabiting barnacles (Cirripedia; Thoracica; Balanomorpha; Pyrgomatinae) from east of 150°W

The absence of coral‐inhabiting barnacles in the eastern Pacific has been generally accepted. Examination of corals collected on seven islands of French Polynesia, presently found in the collection of the Muséum national d'Histoire naturelle, Paris, revealed the presence of four known species of coral‐inhabiting barnacles, Cantellius tredecimus, Trevathana dentata, T. paulayi, and Neotrevathana elongata, and two new species, Trevathana tureiae and Savignium tuamotum. The present report extends the distribution of the pyrgomatines further east and south of their previously documented distribution.


Introduction
The subfamily Pyrgomatinae accommodates the Indo-Pacific coral-inhabiting barnacles. Gruvel (1912, p 350) reported Trevathana (Pyrgoma) dentata from Gambier, French Polynesia, in the collection of the Muséum national d'Histoire naturelle, Paris (MNHN). For nearly a century this was the only report of coral-inhabiting barnacles east of the Line Islands (Ross and Newman 2002). A comprehensive geographic distribution of the coralinhabiting barnacles was first compiled by Ross and Newman (1973), who presented distribution maps and noted that in the Pacific, pyrgomatines are absent east of 160uW longitude, with the exception of the single record of Pyrgoma east of 150uW (Gruvel 1912). Since this publication, more papers compiling data on the distribution of coral barnacles, based on literature records and various collections, have been published but with no mention of these barnacles east of 160uW (Ogawa and Matsuzuki 1992). In their analysis of coral barnacles, Ross and Newman (2002), referred only to the single case mentioned by Gruvel (1912). The absence of coral-inhabiting barnacles in the eastern Pacific has been generally accepted, and supported by the absence of barnacles from the well-studied Hawaiian corals. Recent examination of corals in the MNHN revealed that the apparent absence of these barnacles from east of 160uW is due to the lack of examination of material from this region. In the present paper, we report the occurrence of four known species of pyrgomatines, Cantellius tredecimus, Trevathana dentata, T. paulayi, and Neotrevathana elongata and describe two new species, Trevathana tureiae and Savignium tuamotum. The specimens were collected from 11 coral samples collected on seven islands of French Polynesia by Jean-Pierre Chevalier. This extends the distribution of pyrgomatines further east and south than their previously recorded distribution.

Material
The corals used for the present study form a part of the ''Chevalier collection'' in the Muséum national d'Histoire naturelle, Paris, France (MNHN). All corals were collected and determined by Jean Pierre Chevalier. The coral number in the coral collection and field number given by Chevalier are presented. Details are taken from Chevalier's notebooks kept at the MNHN and references to the notebooks are given in square brackets; the number of the note book is given in roman numbers, pages in arabic numbers. Localities are presented on the map of French Polynesia (Figure 1).

Methods
The wall plates and opercular valves were removed from the coral, immersed for about 2 h in household bleach, then rinsed in tap water followed by distilled water. The specimens were examined under the dissecting microscope, adhering chitin was removed using needles and fine forceps and then dried on a small hot plate at 80uC. Dried samples were mounted on brass stubs, coated with gold, and examined with a JEOL scanning electron microscope at 25 kV. Images were copied and stored using Autobeam software.
Barnacle material is deposited in the crustacean collection of the MNHN, and the corals are found in the coral collection of the MNHN. Two sub-samples are kept in the zoological collection of the Hebrew University of Jerusalem, Israel (HUJI).   longitudinal ridges slightly sulcate separated by narrower grooves; ridges with a series of coarse parallel growth lines. Opercular valves white; scutum triangular, growth ridges on outer surface coarse, crossed by fine striae, ridges forming teeth on occludent margin; adductor ridge, adductor pit and rostral tooth absent; articular ridge about three-quarters length of tergal margin; pit for lateral depressor at basi-tergal angle.

Distribution
Singapore, Indonesia, Great Barrier Reef, French Polynesia.

Remarks
Cantelius tredecimus was described by Kolosváry (1947) from Tridactphyllia lactuca from Singapore. Ogawa and Matsuzaki (1992) mentioned this species only from unidentified Montipora, which agrees with the present findings. Achituv (unpublished) surveyed the coral collection of the Museum of Natural History, Leiden, The Netherlands, which is based mainly on corals from Indonesia and found C. tredecimus on 20 species of corals from 13 genera, including Montipora.

Description
Wall oval, with radial ribs, rostro-carinal diameter to 5 mm. Reddish purple, the area between the two rostral radial ribs white, orifice oval. Scutum transversally elongated, growth lines distinct, short broad articular ridge, no occludent ledge. Tergum nearly quadrangular, no external furrow, indistinct spur, internal tooth blunt.

Distribution
Guam, French Polynesia.

Remarks
Trevathana paulayi was recently described by Asami and Yamaguchi (2001). This species is distinguished from Trevathana dentata by the reddish purple colour of its shell, the lack of occludent ledge on the scutum and the lack of internal tooth in the tergum. The type location of T. paulayi is Guam. It was not reported from other localities and the present report indicates that this species is found only in the eastern Pacific. Ross and Newman (2002) noted that the restricted distribution of some pyrgomatines might be an artefact due to lack of information. However, examination of the rich coral collection from Indonesia in the Museum of Natural History in Leiden, The Netherlands (Y. Achituv, unpublished), did not reveal any specimen of Trevathana paulayi supporting the hypothesis that this barnacle is restricted to the eastern Pacific.

Description
Shell colour variable, white, pale pink to red-purple; form concrescent, oval, maximum carino rostral diameter 6 mm, lateral diameter 4 mm; radiating ribs carrying rows of fingerlike projections, maximum four per row. Shell tubiferous, number of radiating tubes equal to number of ribs. Ridges white, primary radial ridges reaching the orifice, secondary ridges reaching halfway from margins to orifice, five to six projections on primary ridges; ridges ending at margins as studs that interlock to basis. Shell internally pink to white, with concentric growth lines. Orifice oval, one-third of carino rostral diameter. Basis embedded in host coral, white, tapering.
Scutum elongated, total length from (and including) tergal tooth 2.5-3 times maximal width. Basal margins sinusoidal; adductor pit distinct; adductor ridge extending beyond basal margin; tergal tooth width about half width of tergal margin. Small protuberances on inner side of tergal tooth. Growth lines on outer surface; oblique, shallow furrow running from middle of tergal margin to middle of basal margin; additional furrow running from middle of tergal margin to basi-occludent angle. Tergum triangular; growth lines on outer surface; spur short with shallow furrow. Groove running from middle of scutal margin to basi-carinal apex. Inner tooth pointed, located on internal side of spur, perpendicular to basal margin reaching middle of scutal margin. Growth lines inside depression for articulation of tergal tooth.

Distribution
Red Sea, Mauritius, Persian Gulf, Indian Ocean, Andaman Sea, Bay of Bengal, Singapore, Indonesia, Papua New Guinea, Great Barrier Reef, Philippines, Palau Is., Taiwan, Hong Kong, Japan, Niue Islands, Fiji, French Polynesia.

Remarks
Darwin (1854) described three varieties of Pyrgoma dentatum. The diagnostic differences between the varieties are mainly based on shape and position of the internal tergal tooth. Examination of the present material as well as material from other localities reveals that there are more ''varieties'' of Trevathana dentata. We also noticed that there are additional differences between the ''varieties'': the nature of the external radial ridges of the shell differ in specimens collected from different corals. The ratio between the width and length of the shell may also differ, as well as the shape of the tergal tooth of the scutum. We found that in some cases it was difficult to refer the opercular valves from various barnacles to any of Darwin's varieties. Examination of the cirri and mouth appendages of T. dentata from different corals revealed differences that might justify their separation to different species (Mokady et al. 1999), suggesting that Darwin's varieties of T. dentata and other undescribed ''varieties'' present a group of related species. Recently, Southward and Newman (2003) emphasized the importance of the ''arthropodal characters'', cirral appendages and trophi, in the separation of closely related species. Mokady et al. (1999) also showed that Trevathana dentata from different corals are genetically different.

Diagnosis
Shell fused, oval, scutum transversally elongated more than four times as long as wide, adductor ridge missing deep adductor ridge, tergum triangular, spur distinct, no inner tooth.

Description
Shell white; fused, flat, oval, rostro-carinal diameter 3 mm; coral skeleton covering most of concentric growth ridges. Scutum and tergum white, separate. Scutum transversally elongate, four times longer than wide, rounded tooth projecting at tergal margin. Outer surface with growth ridges, closed furrow nearly parallel to occludent margin. Inner surface adductor ridge absent, adductor pit deep, elongated; lateral depressor muscle pit elongated, shallow. Tergum triangular, externally with growth ridges, internally with shallow depression accommodating scutal tooth; growth lines inside depression. Spur low, inwardly projecting, teeth absent.

Etymology
The specific name has been derived from the locality where this species was found, Tureia Island.

Remarks
The description and separation of this species is based on the form of the opercular valves. The shell is similar to those of other species of Trevathana and it is impossible to separate the species on this basis. The scutum and tergum are similar to those of Trevathana dentata, the characters that separate this species from T. dentata are the scutum without an adductor ridge. The tergum has spurs that project inward perpendicular to the inner surface of the tergum and does not carry the internal tooth of the tergum. The revised diagnosis of Trevathana (Asami and Yamaguchi 2001) indicates the presence of an internal spur tooth. The dominant features of the opercular valves of Trevathana are the elongated scutum with prominent rounded tooth projecting at tergal margin that join the tergum, and the triangular tergum. We suggest that the diagnosis of the genus should be amended and would not include the presence of internal tooth of the tergal tooth, this character is specific to Trevathana dentata, a sister species to Trevathana tureiae. On the basis of these differences we suggest that they will be assigned to a new species.

Description
Wall oval, with radial ribs, rostro-carinal diameter to 5 mm. White or pink orifice large oval. Inner surface with growth lines, growth line pear shape with pointed end directed to rostrum, blunt end carinal. Scutum and tergum fused, transversally elongated, no suture between scutal and tergal parts of opercular valves. Opercular valves curved inward, apex pointed. Basal margins sinusoidal, short broad articular ridge, no occludent ledge. Indistinct spur, internal tooth blunt, directed inward, located on basal margins on tergal part of valve. Growth lines on outer surface, no external furrow.

Distribution
Red Sea, Japan, French Polynesia.

Description
Shell white; fused, flat, oval, rostro-carinal diameter 4 mm. Scutum and tergum white, separate. Scutum transversally elongate, about three times longer than wide; externally concave due to basal margins curved upward forming shallow trough along basal margin; growth ridges prominent, mainly at basal margin, growth ridges along basal margins arching towards occludent margin; oblique, long, narrow furrow from middle of tergal margins to middle of occludent margin. Tergal margins with low wide articulation tooth, growth lines on tooth; adductor ridge prominent, projecting beyond basal margins; adductor pit prominent; adductor ridge and basal margins flaring.
Tergum quadrangular; growth line highly eroded, more distinct at scutal margins; spur absent, articular ridge distinct, furrow with growth lines; internally concave resulting from elevation of articular ridge and carinal margins; crests for depressor muscle absent.

Etymology
The specific name has been derived from the locality where this species was found, Tuamotu Archipelago Island.

Remarks
The genus Savignium was resurrected by Ross and Newman (1973) to accommodate the pyrgomatine barnacles with a fused, oval shell and a transverslly elongated scutum. Originally, this genus included four species. Anderson (1992Anderson ( , 1993 erected two new genera: Trevathana that contains the Darwin varieties of T. dentata; and Wanella, which contains W. milleporae Darwin. Anderson (1992) suggested that Savignium contained two species, S. crenatum with separate opercular plates and S. elongatum with calcified opercular valves. Subsequently, Ross (1999) allocated S. elongatum to a new genus, Neotrevathana. Therefore Savignium contain only one species, S. crenatum. In Savignium, the articular ledge of the scutum is wide and occupies the whole tergal margin, the adductor ridge is developed and projects beyond the basal margins. The material from French Polynesia clearly show these characters but the tergum is different from that of S. crenatum, therefore, we deduce that our material is a new species of Savignium. Ross and Newman (2002) noted that the greatest number of genera of pyrgomatines occur in Australia, followed by Japan. They believe that this pattern of distribution represents a collecting bias and does not reflect the real distribution of this group. Our report on the occurrence of four known species of pyrgomatines and two new species in French Polynesia, based on the examination of a limited number of corals, supports the notion of Ross and Newman that the rarity of pyrgomatines in the south-east Pacific is due to inadequate collecting rather than absence of this group from this region. Examination of more corals from areas as yet unstudied may reveal the presence of more pyrgomatines species and change our knowledge of the biogeography of this group. Combined with a study of the distribution of the host corals this information will also shed light on species specificity and the coevolution of these groups.