Cantellius sextus ( Hiro, 1938 )

Achituv, Yair, Tsang, Ling Ming & Chan, Benny Kwok Kan, 2009, A new species of Cantellius and a redescription of C. sextus (Hiro, 1938) (Cirripedia, Balanomorpha Pyrgomatidae) from the elephant skin coral, Pachyseris speciosa (Dana, 1846) (Scleractinia, Agariciidae) from Taiwan, Zootaxa 2022, pp. 15-28 : 21-24

Cantellius sextus ( Hiro, 1938)

Figs 4–6

Pyrgoma (Creusia) spinolosa var. 6 subvar. 3. - Darwin, 1854: 379, figs 6n-6q Materials examined. ASIZCR 2006-2008, Dong-Qing-Wan, Lanyu Island, Taiwan (22°01’, 121°32’), 5–10 m, coll. B.K.K. Chan.

Diagnosis. Wall with approximately 23 internal ribs ( Fig. 4 A, B); basal margin of scutum longer than tergal margin ( Fig. 4 C), adductor plate extending beyond basal margin ( Fig. 4 D). Tergum with broad spur, external spur furrow shallow; spur length approximately 1/2 length of scutal margin ( Fig. 4 F, G).

Description. Parietes (shell): Slightly projecting above the coral surface covered by coral skeleton overlying external ribs, number of ribs indistinct. Rostro-carinal diameter to 4 mm; wall of 4 parietes, approximately 23 internal radial ribs radiating from central orifice, some secondary ribs reaching 1/2 way between wall circumference and orifice ( Fig. 4 A, B). Tubes between sheath and parietes largely filled ( Fig. 4 B). Orifice oval, 1/5 of rostro-carinal diameter ( Fig. 4 A). Sheath pigmented, orange, with concentric growth ridges extending less than 1/2way down internal surface of parietes. Carina wider than rostrum.

Opercular valves white, thin. Scutum ( Fig. 4 C, D) triangular, externally growth ridges coarse, crossed by fine striae, alternate ridges forming teeth on occludent margin (and on tergal margins). Length of tergal margins approximately 2/3 occludent margin. Tergal portion of scutum strongly inflected. Apical angle approximately 60°, approximately 13–16 rows of pits at apical angle forming honeycomb-like surface ( Fig 4 E). Basal margins sinusoidal. Internally adductor plate extending beyond basal margin forming conspicuous basal ledge ( Fig. 4 C). Basi-occuludent angle with distinct rostral tooth, pit of lateral depressor muscle small ( Fig 4 D).

Tergum ( Fig. 4 F, G) with blunt spur, spur width approximately 1/2 tergal width, external furrow shallow, open from apex to spur base, angle between spur and basal margin obtuse. Pits similar to those on scutum, at apex, forming honeycomb-like surface. Sinusoidal fine growth ridges on tergum surface. Tergal wing height approximately1/2 tergal length (including spur). Internally small pits for tergal depressor muscle ( Fig. 4 F).

Trophi: Labrum with deep V-shaped notch ( Fig 5 A, B), 2 large teeth on each side of notch ( Fig. 5 d, F). Mandible quadridentoid, teeth simple; lower margin straight, without setae or spines ( Fig. 5 D, F).

Setae on surface of mandible serrulate with short setules ( Fig. 5 E). Maxillule without obvious notch, approximately 9 strong spines ( Fig 5 G), serrulate setae with short setules at base of spines ( Fig 5 H). Mandibular palp and maxilla bearing serrulate setae with short, sparse setules ( Fig. 5 I–L).

Cirri: Cirrus I with rami unequal, exopodite longer than endopod, 9 and 5 articles, respectively ( Fig. 6 A); exopodite bearing thin, serrulate setae with sparse setules ( Fig. 6 B, D, G), endopodite bearing thick, serrulate setae with dense, short setules ( Fig. 6 B). Protopodite bearing plumose setae with sparse setules ( Fig. 6 C). Cirrus II with exopodite and endopodite similar lengths, 7–8 articles ( Fig. 6 E). Rami bearing serrate, bidentate setae ( Fig. 6 F). Protopod bearing serrulate setae with fine setules ( Fig. 6 J). Cirrus III with exopodite and endopodite similar lengths, approximately 10 articles ( Fig. 6 H), rami bearing serrate setae with 3 rows of setules ( Fig. 6 E). Protopod bearing plumose setae with long, loose setules ( Fig. 6 G, I). Cirrus IV–VI similar, rami subequal, articles bearing 3–4 pairs of serrulate setae with short setules ( Fig. 6 K, L).

Figures

FIGURE 4. Cantellius sextus. Hard parts. A) Inner view of parietes under SEM; B) inner view of one of the paries; C) scutum, outer view; D) scutum, inner view; E) apical end of scutum showing honeycomb-like structure; F) tergum, outer view; and G) tergum, inner view.

FIGURE 5. Cantellius sextus. Trophi. A) Labrum, general view; B) labrum, showing sharp, deep notch; C) large teeth on the edge of labrum; D) mandible, general view; E) serrulate setae on the side of mandible; F) lower margin of mandible; G) maxillule, general view; H) serrulate setae on maxillule; I) mandibulatory palp; J) serrulate setae on mandibulatory palp; K) maxilla; and L) serrulate setae on maxilla. Scale bar in μm.

FIGURE 6. Cantellius sextus. Cirri. A) Cirrus I, general view; B) serrulate setae on endopod of cirrus I; C) serrulate setae on exopod of cirrus I; D) plumose setae on rami of cirrus I; E) cirrus II, overview; F) bidentate serrate setae on rami of cirrus II; G) serrulate setae on rami of cirrus III; H) cirrus III, general view; I) serrate setae on rami of cirrus III; J) plumose setae with long, loose setae on protopod of cirrus III; K) cirrus IV, general view; L) serrulate setae on rami of cirrus IV. Cirrus V and VI not shown as they are similar to cirrus IV. Scale bar in μm.