Euraphia depressa (Poli, 1795)

Pochai, Ashitapol, Kingtong, Sutin, Sukparangsi, Woranop & Khachonpisitsak, Salinee, 2017, The diversity of acorn barnacles (Cirripedia, Balanomorpha) across Thailand's coasts: The Andaman Sea and the Gulf of Thailand, Zoosystematics and Evolution 93 (1), pp. 13-34 : 14-16

Euraphia depressa (Poli, 1795) Figure 3 ; Tables 2, 3

Chthamalus depressus Poli, 1791

Chthamalus stellatus var. depressus : Darwin 1854.

Euraphia depressa : Utinomi (1959); Southward (1964).

Non-type material examined.

Gulf of Thailand: 2 specimens, Chon Buri province, Mueang Chon Buri district, Khao Sam Muk beach, 05.VII.2016, W. Sukparangsi (BUU16.CM.ED01-02) .

Description.

Peduncle absent; body length 3-10 mm; base membranous. Shell light brown-yellowish brown with 6 plates (1 carina, 2 carinal latus, 2 latus and 1 rostrum), shell flatted and thin-walled; parietes symmetrical and solid, external surface of shell without ribbed, inner surface of parietes smooth and light brown and white with small horizontal striations around aperture, parietes separable, suture distinct and easily parted; orifice rhomboidal. Opercular plates symmetrical, tergum smaller than scutum, scutum and tergum separable jointing between tergum and scutum with slightly sinous. Scutum triangular with slightly curved basal margin, external surface with shallow and horizontal striations from occludent margin to tergal margin, occludent margin of scutum without teeth, tergal margin slightly sinous from interior view; tergum with 2-3 lateral depressor crests. Mandible with 3 teeth, lower margin pectinated with 8 setae, three large setae at the edge; labrum with obvious teeth; caudal appendage absent.

Distribution.

In previous records, Euraphia depressa was found to inhabit along Mediteranean localities, including Spain (Punta Carnero, Punta de la Chullera, Malago, Salobrena and Calpe), France (Cap Bear, La Couronne, and Cassis), Italy (Pegli and Lido), Greece (Amnisso), the Black Sea and Suez canal ( Utinomi 1959; Southward 1964; Achituv and Safriel 1980; Crisp 1981). In this study, the presence of Euraphia depressa in Khao Sam Muk station (Chon Buri) in Thailand was unexpected as it was previously unrecorded along Thailand’s coastal areas. They were found along rocky shores exposed to heavy wave action inhabiting sheltered crevices of the rocky platform and high shore. The abundance of Euraphia depressa is much less than that of the cosmopolitan barnacle Amphibalanus amphitrite in the same area of observation.

Remarks.

Euraphia depressa (Poli, 1795) was the reassigned name from Chthamalus depressus (Poli, 1795). According to Southward (1964), Euraphia depressa can be distinguished from Chthamalus stellatus , based on the shell morphology showing smooth unribbed shell on the external surface from younger specimens to more adult stage and the operculum characters, showing joints between tergum and scutum without sinous or slightly sinous, and smaller tergum. In addition, a barnacle of the genus Euraphia is distinguished from the genus Chthamalus based on the number of teeth on mandible and as described in Southward (1964) our specimens have mandible with three large teeth and three large setae on the lower edge (Figure 3F & G ) and lacking of caudal appendages, leading to species identification of our specimens as Euraphia depressa . However, the number of setae at the pectinated margin of mandible in our specimens is different. Only small 5 setae after larger three setae were found in our specimens while up to 12 setae were mentioned in Southward (1964).

Figures

Figure 3. Euraphia depressa collected from Khao Sam Muk beach, Chon Buri (BUU 16. CH. ED 01). A. Dorsal and ventral view of external shell, B. External (left panel) and internal (right panel) view of tergum (upper panel) and scutum (lower panel), C. External (upper panel) and internal (lower panel) view of shell plates, D-G. Light microscopy on mouthparts, D. Labrum, E. Close up on the teeth of the labrum, F. Mandible with three large teeth, G. Close up on the pectinated lower margin of mandible. D-G. Scale bars in µm. Abbreviations: c, carina; cl, carinal latus; l, latus; r, rostrum.