Treijathana dentata, (Darwin, 1854)

Achituv, Yair & Langsam, Yaacov, 2005, Coral-inhabiting barnacles (Cirripedia; Thoracica; Balanomorpha; Pyrgomatinae) from east of 150 ° W, Journal of Natural History (J. Nat. Hist.) 39 (20), pp. 1705-1717 : 1709-1711

TreIJathana dentata ( Darwin, 1854)

Synonymy

Pyrgoma dentatum Darwin 1854, p 369 –370, Plate 13, Figure 3 a–g.

Saυignium dentatum: Ross and Newman 1973, p 159 , Figure 17h–k.

Treυathana dentatum: Anderson 1992, p 329 , 336, Figures 38L, 39.

Treυathana dentata: Asami and Yamaguchi 1997 , p 13, 14, Figures 1 , 2 .

Material examined

MNHN-Ci 2957 from Montastraea or Faυia sp. MNHN-Scle 20272 (field number TUR 6 c; [ T VI, p 1067]). Eight specimens, shells, opercular valves and broken shells; bases left on original coral. French Polynesia; Tuamotu Archipelago; Tureia Island; NE coast of the atoll; 20 ° 50 9 S, 138 ° 33 9 W, 4 November 1965, coll. Chevalier; MUSEUM II (CEA) Expedition .

MNHN-Ci 2958 and HUJI Cirr-222 from Faυia faυus MNHN-Scle 20275 (field number GAM 43 b; [ T VI, p 1132]). Five specimens; shells, opercular valves and broken shells; bases left on original coral. French Polynesia; Gambier Islands; Tarauru-Roa Island; 23 ° 07 9 S, 134 ° 52 9 W; NW point of outer reef, 17 November 1965, coll. Chevalier; MUSEUM II (CEA) Expedition .

MNHN-Ci 2959 from Faυia sp. MNHN-Scle 20269 (field number MUR 177 c; [ T VIII, p 1619]). French Polynesia; Tuamotu Archipelago ; Moruroa Island, Viviane Bay; 21 ° 53 9 S, 138 ° 54 9 W; depth 2–3 m, 14 April 1969, coll. Chevalier; MUSEUM VI (CEA) Expedition .

MNHN-Ci 2960 from Montastraea curta MNHN-Scle20270 (field number MUR 74 f; [ T V, p 979]). French Polynesia; Tuamotu Archipelago ; Moruroa Island; Giroflée Bay; 21 ° 50 9 S, 138 ° 57 9 W, 22 October 1965, coll. Chevalier; MUSEUM II (CEA) Expedition .

MNHN-Ci 2961 from Montastraea sp. MNHN-Scle 20273 (field number TUR 4 a; [ T VI, p 1059]). One specimen, shell and operculum valves, one tergum missing. French Polynesia; Tuamotu Archipelago ; Tureia Island, Fakamaru; 20 ° 50 9 S, 138 ° 33 9 W, 3 November 1965, coll. Chevalier; MUSEUM II (CEA) Expedition .

MNHN-Ci 2962 from Faυites sp. MNHN-Scle 20274 (field number TUR 11 b; [ T VI, p 1071]). French Polynesia; Tuamotu Archipelago ; Tureia Island; SW side of the lagoon; 20 ° 50 9 S 138 ° 33 9 W, 5 November 1965, coll. Chevalier; MUSEUM II (CEA) Expedition .

MNHN-Ci 2963 from Faυia sp. MNHN-Scle 20289 (field number NUK 20 b; [ T VIII, p 1462–1464]). French Polynesia; Tuamotu Archipelago ; Nukutavake Island, between the village and NE of beginning point of internal reef plate; 19 ° 17 9 S, 138 ° 48 9 W, subtidal to 3 m depth, 23 March 1968; MUSEUM V Expedition .

MNHN-Ci 2964 and HUJI Cirr-221 from Faυia sp.? (alternative determination Montipora curta ). MNHN-Scle 20281 (field number TAI 35 a; [ T X, p 1981]). French Polynesia; Tuamotu Archipelago ; Taiaro Island; 15 ° 46 9 S, 144 ° 37 9 W, exterior reef, sheltered coast, 17 July 1972, coll. Chevalier; MUSEUM VIII Expedition .

MNHN-Ci 2965 from Montastraea curta . MNHN-Scle 20282 (field number TAI 1 ; [ T X, p 1935]). French Polynesia; Tuamotu Archipelago ; Taiaro Island; 15 ° 46 9 S, 144 ° 37 9 W, exterior reef, depth 12.5 m, 10 July 1972, coll. Chevalier; MUSEUM VIII Expedition .

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 Treυathana 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 Treυathana dentata from different corals are genetically different.

Figures

Figure 1. Collection sites of coral-inhabiting barnacles in French Polynesia. Location of Tahiti is marked for reference.

Figure 2. Cantelius tredecimus from Marquesas Islands; Nuku-Hiva Island. (A) Scutum, outer view; (B) scutum, inner view; (C) tergum inner view, tergum is damaged. Scale bars: 1 mm (A, B); 0.5 mm (C).

Figure 3. Treυathana paulayi sample lost, from Gambier Islands; Aukena Island. (A) Shell outer view; (B) shell inner view showing part of basis and interlocking; (C) scutum inner view; (D) scutum outer view; (E) tergum external view; (F) tergum inner view; (G) scutum and tergum attached showing position of internal tooth. Scale bars: 1 mm.