Darwiniella angularis, Chen, Yi-Yang, Lin, Hsiu-Chin & Chan, Benny K. K., 2012

Chen, Yi-Yang, Lin, Hsiu-Chin & Chan, Benny K. K., 2012, Description of a new species of coral-inhabiting barnacle, Darwiniella angularis sp. n. (Cirripedia, Pyrgomatidae) from Taiwan, ZooKeys 214, pp. 43-74 : 45-47

Darwiniella angularis sp. n. Figures 2-9

Material examined.

HOLOTYPE. NMNS-6878-001, Lobster Cave, Siaoliouciou Island, Taiwan (22°20'N, 120°23'E), August 2010, coll. B.K.K. Chan, on host coral Astreopora sp. PARATYPES. ASIZCR000202, Turtle Tail, Turtle Island, Taiwan (24°50'N, 121°56'E), October 2010, coll. B.K.K. Chan, on coral host Cyphastrea chalcidicum ( Forskål, 1775). ASIZCR000204, data same as ASIZCR000202. CEL-RYU-13-2 and CEL-RYU-13-3 data same as holotype. CEL-TI-1-7, CEL-TI-5-6, and CEL-TI-9-10 data same as paratype ASIZCR000202.

Diagnosis.

Scutum triangular, rostral tooth and obvious adductor plate present, basal margin of adductor plate forming obvious angle. Tergum trapezoid, spur triangular, medial furrow curved.

Description.

(Type specimen: 6 mm in basal diameter, rostro-carinal diameter to 5.2 mm). Shell plates fully fused, purple, oval, externally surface with about 24 strip-like projections radiating from subcentral orifice to shell plate margin (Fig. 2A). Bases of shell with about 27 internal ribs radiating from rim of inner operculum (Fig. 2B). Orifice oval, long, narrow, about 1/3 length of rostro-carinal diameter.

Scutum and tergum white, fused without junctions (consistent through 3 specimens, Fig. 2 C–H). Scutum triangular, width equal to height, occludent margin slightly curved, rostral tooth basally, 15 teeth along ventral surface of occludent margin, tooth size increasing gradually from apex to base. Ventral view with oval-shaped adductor muscle scar (Fig. 2D, F, H). Dorsal view with obvious adductor plate, convex, extending below basal margin of scutum, plate about 3/5 height of scutum, basal margin with obvious angle (Fig. 2C, E, G). Dorsal surface with horizontal striations, striations with row of small pores.

Tergum trapezoid, lateral depressor muscle crests present. Spur triangular, blunt, curved, height reaching more than 1/2 height of tergum, basal margin not obvious due to curved spur. Dorsal surface with medial furrow, curving from basal margin towards the carinal margin (Fig. 2C, E, G). Dorsal surface with horizontal striations, striations with row of small pores.

Maxilla bilobed (Fig. 3A), serrulate setae distally (Fig. 3C) and along inferior margin (Fig. 3B). Maxillule cutting edge straight, without notch, bearing row of 7 large and 3 smaller setae (Fig. 3D). Region close to cutting edge with dense fine simple setae (Fig. 3F), anterior and posterior margins with long simple setae (Fig. 3E). Mandible with 4 or 5 teeth, excluding inferior angle (inconsistent in 4 specimens, Fig. 4A, D, F, H). Second, third and fourth teeth bidentate (Fig. 4B), the first 3 teeth occupying most of length of cutting edge. Lateral surface, lower margin and cutting edge of mandible bearing simple setae. Lower margin short, about 1/16 length of mandible, inferior angle ending in blunt angle with dense, fine setae (Fig. 4C, E, G). Mandibular palp rectangular, elongated (Fig. 5A), bearing serrulate setae distally (Fig. 5C) and inferior margin (Fig. 5B). Labrum bilobed, V-shaped notch between lobes, no or 2 sharp teeth on each side of notch (inconsistent in three specimens, Fig. 5D, G, H).

Cirrus I with rami unequal, anterior ramus long, slender, 14-segmented, posterior ramus 6-segmented (Figs 6A, 7A), bearing serrulate setae (Fig. 7B, C, D). Cirrus II with rami subequal, both 7-segmented (Figs 6B, 7E), bearing serrulate setae (Fig. 7F, G, H). Cirrus III with rami subequal, anterior ramus 8-segmented, posterior ramus 7-segmented (Figs 6C, 8A), bearing serrulate setae (Fig. 8B, C, D). Cirri IV–VI long, slender, rami equal. Cirrus IV with anterior ramus16-segmented, posterior 15-segmented, Cirrus V (anterior 21-segmented, posterior 19-segmented), Cirrus VI (anterior 22-segmented, posterior 21-segmented) (Figs 6D, E, F, 8E, 9A, D). Intermediate segments of Cirri IV–VI with 4 pairs of serrulate setae (Figs 8F, 9C, F), distal pair longest, proximal pair shortest.

Penis long (1.9 times length of Cirrus VI), annulated, some dark spots present, scattered short simple setae (Fig. 9G). Pedicel with basidorsal point (Fig. 9G, H), apex bearing short simple setae (Fig. 9I).

Distribution.

At present only recorded from Taiwan.

Etymology.

The name angularis denotes the presences of the obvious adductor plate angle, which is a diagnostic character of this species.

Remarks.

External shell morphology and arthropodal characters of Darwiniella angularis sp. n. are similar to Darwiniella conjugatum . However, Darwiniella angularis has an obvious adductor plate angle, whereas that of Darwiniella conjugatum is less obvious (see description below). Darwiniella conjugatum also has a sharper spur angle than Darwiniella angularis - mean ± 1 SD of the spur angle (from 10 specimens) reaching 23.6 ± 4.8o in Darwiniella conjugatum and 32 ± 4.6o in Darwiniella angularis , which is significantly different between the two species using the t-test (t value: -4.3, df = 18, p <0.05).