Acasta sulcata Lamarck, 1818

Yu, Meng-Chen, Kolbasov, Gregory A., Hosie, Andrew M., Lee, Tse-Min & Chan, Benny K. K., 2017, Descriptions of four new sponge-inhabiting barnacles (Thoracica: Archaeobalanidae: Acastinae), Zootaxa 4277 (2), pp. 151-198 : 179-187

Acasta sulcata Lamarck, 1818

Figs 25 ̄31

Acasta sulcata Lamarck, 1818: 668 .― Deshayes 1831: 24, fig. 24.― Darwin 1854: 310 ̅311, pl. 9, fig. 2a̅2d.― Borradaile 1903: 442.― Gruvel 1905: 263 ̅264, fig. 294.― Krüger 1911: 56, tab. 1, fig. 9; tab. 4, fig. 40.― Hoek 1913: 233.― Pilsbry 1916: 241.— Hiro 1937a: 451 ̅454, figs 31, 32.― Broch 1947: 6.― Kolosváry 1947: 361.― Utinomi 1958: 309.― Newman and Ross 1976: 54.― Foster 1980: 207 ̅232, tab. 3, fig. 4A.― Ren 1984: 191 ̅193, fig. 5, tab. 3, figs 1̅9.— Jones 1990a: 222, fig. 12.— Jones 1990b: 400, fig. 23. ― Kolbasov 1993: 411, fig. 10.― Liu and Ren 2007: 423 ̅425, fig. 192.― Biccard 2012: 93, pl. 23, figs E, F.

Acasta sulcata anchoris Barnard, 1924: 81 , pl. 1, fig. 16.

Acasta serrata Hiro, 1937b: 64 –66 fig. 12.

Acasta sulcata spinosa Daniel, 1956: 29 ̅30, pl. 8, figs 7̅14.

Material examined. ASIZCR000369, Daping , Yeliou, Wanli, Taiwan (25°12′45.18″N, 121°42′04.29″E, water depth 18̄ 26 m), August 2011, coll. B.K.K. Chan, on host sponge Callyspongia sp.

CEL-SN48-3 data same as for ASIZCR000369.

Diagnosis. Shell white to pale yellow, orifice rather small, with toothed edge. Basis saucer- or cup-shaped, pointed towards central umbo, rim crenate. Shell in adults often with membrane-covered clefts between plates. Externally, scutum with horizontal growth ridges, articular furrow shallow. Spur of tergum broad, square shaped, truncated at end, width slightly more than 1/2 of basal margin. Sheath extending approximately half of parietes, with internal vesicular structure, inner shell surface below sheath with longitudinal ribs. Proximal segments of anterior ramus and basis of cirrus IV with curved teeth.

Description. Shell ( Figs 25 , 26 ) white to pale yellow after extraction from sponge, becoming white (sometimes tinged with reddish patches towards apex) after bleach treatment, orifice rather small, toothed; basis saucer- or cup-shaped, rim strongly crenated. Membrane covered clefts between junctions of parietes often present. Parietes externally smooth, with horizontal growth ridges and few calcareous projections, radii with inclined and horizontal striations; parietes internally ribbed, apices incurved, sheath extending over half of parietes, with vesicular structure, radii and alae with horizontal ridges, both not reaching base; inner and outer edges of alae white, thickened; carinolaterals narrow, about 1/6 of width of laterals ( Figs 25 ĀC, 26ĀL).

Externally, scutum with horizontal growth ridges, without longitudinal striation; 11̄13 teeth on occludent margin, tooth size increasing gradually from apex to base; basal margin slightly concave in middle; articular furrow shallow, articular ridge low, not prominent, not truncated, about ½ of tergal margin; adductor ridge and pit of adductor muscle feebly developed; pit of depressor muscle rudimentary ( Fig. 25 F, G).

Tergum thin, semitransparent; apex beaked; articular ridge short; spur broad, separated from basiscutal angle, truncated, square-shaped, width exceeding 1/2 of basal margin, spur furrow shallow, wide; internally, scutal margin slightly raised, carinal margin perpendicular to basal margin, depressor muscle crests absent ( Fig. 25 H, I).

Counts of cirral segments given in Table 1. Cirrus I, rami unequal ( Fig. 27 A), protopod anterior margin lacking setae, posterior margin with serrulate and plumose setae ( Fig. 27 B), thick serrulate setae on posterior margins of both rami ( Fig. 27 C), serrulate and bifid setae on distal margins of terminal segments of anterior ramus and posterior ramus ( Fig. 27 D, E). Cirrus II, rami unequal, protopod anterior and posterior margins with pappose and plumose setae, respectively ( Fig. 27 F), thick serrulate setae on posterodistal angle of segments of both rami ( Fig. 27 G), distal segments of anterior and posterior rami with bifid and serrulate setae ( Fig. 27 H, I). Cirrus III, rami subequal, protopod anterior and posterior margins with simple and plumose setae, respectively ( Fig. 28 A), serrulate setae along segments ( Fig. 28 B), terminal segments of anterior and posterior rami with serrate and serrulate setae ( Fig. 28 C, D). Cirrus IV, rami unequal, protopod anterior and posterior margins with simple and plumose setae, respectively ( Fig. 28 E), armed with 12 teeth (acute and truncate) on anterior margin of basis ( Fig. 28 F), frontal edge of proximal and intermediate segments of anterior ramus bearing 3 or 4 teeth (acute and truncate) ( Fig. 28 ḠI), intermediate segments with 3 pairs of long simple similar length setae ( Fig. 28 I), terminal segment of anterior and posterior rami with serrate setae ( Fig. 28 J). Cirri V and VI similar, rami subequal, protopod anterior and posterior margins with serrulate and short simple setae, respectively, intermediate segments of rami with 2 pairs long serrulate setae, terminal segments of anterior and posterior rami with serrate setae ( Fig. 29 ĀG). Cirrus V bearing 1 or 2 small teeth at frontal edge of proximal segments of anterior ramus ( Fig. 29 C, D).

Penis finely annulated, gradually tapering to tip ( Fig. 30 H), basidorsal point vestigial ( Fig. 29 J), distal tip with long setae ( Fig. 29 I).

Maxilla bilobed ( Fig. 30 A), inner edge straight, distal end with thick serrulate setae ( Fig. 30 B̄D); outer edge with simple setae, basal portion without setae ( Fig. 30 B). Maxillule cutting edge straight without notch, with 11 large, cuspidate setae ( Fig. 30 E, F), upper margin with 7 or 8 pairs of simple setae ( Fig. 30 G), lower margin with numerous simple setae ( Fig. 30 H). Mandible with 5 teeth, second to fourth bifid, inferior angle blunt with stout, simple setae ( Fig. 31 A, B), upper margin of lateral angle bearsing simple setae ( Fig. 31 C, D). Mandibular palp broadly truncated ( Fig. 31 ĒH), dense serrulate setae terminally and at outer margin ( Fig. 31 E, F), middle region of outer margin concave ( Fig. 31 G). Labrum bilobed, separated by V-shaped notch, 3 small teeth on each side of crest ( Fig. 31 I, J).

Remarks. Morphological characters of our specimens are consistent among the samples collected. Previously, numerous brief descriptions and records of A. sulcata have been provided, but these most likely represent a complex of cryptic species (see Introduction). Even among specimens assigned by Darwin (1854) to his var. a, considerable variation was noted; for example, hooked teeth may or may not be present on the segments and protopod of cirrus IV. Hiro (1937a) described specimens having a recurved tooth on the median segments of the anterior ramus of cirrus V, which are notably lacking in the present specimens as well as in Darwin’s varieties ( Darwin 1854). Our specimens fit the morphology of A. sulcata var. b of Darwin (1854) because of the presence of externally smooth and internally ribbed parietes, with membrane-covered clefts in the shell plates, which are also not mentioned by Hiro (1937a).

The present specimens were extracted from a species of Callyspongia and represent only the second attempt at identifying the host. The first attempt was by Kolbasov (1993), who listed the hosts as belonging to the genus Haliclona and a member of the Myxillidae . Host utilization and specificity is a poorly explored area of sponge–barnacle diversity.

The re-examination of specimens and hosts described in the literature as well as the use of molecular data from recent collections are essential for understanding what constitutes intra- or inter-specific variation. The status of Lamarck’s (1818) and Darwin’s (1854) specimens is currently unknown.

Figures

FIGURE 25. Acasta sulcata. Complete shell, scuta and terga (ASIZCR 000369). A, view from rostrum; B, view from lateral; C, view from carina; D, view from orifice showing the whole shell; E, view from basis; F, external view of scuta; G, internal view of scuta; H, external view of terga; I, internal view of terga. Scale bars = 1 mm.

FIGURE 26. Acasta sulcata disassembled shell showing separated plates and basis after bleach treatment (ASIZCR 000369). A, external view of rostrum; B, internal view of rostrum; C, E, external view of laterals; D, F, internal view of laterals; G, I, external view of carinolaterals; H, J, internal view of carinolaterals; K, external view of carina; L, internal view of carina; M, external view of basis; N, internal view of basis. Scale bar = 1 mm.

FIGURE 27. Acasta sulcata. Cirri I (A ̅ E) and II (F ̅ I) (ASIZCR 000369). A, rami of cirrus I (basal part broken); B, protopod and posterior ramus (anterior ramus broken); C, intermediate segments of anterior ramus; D, serrulate setae on anterior ramus; E, bifid setae on posterior ramus; F, cirrus II, pappose and plumose setae enlarged in rectangle area; G, intermediate segments of posterior ramus; H, bifid and serrulate setae on posterior ramus; I, bifid and serrulate setae on anterior ramus. Scale bars in µm.

FIGURE 28. Acasta sulcata. Cirri III (A ̅ D) and IV (E ̅ J) (ASIZCR 000369). A, cirrus III, simple and plumose setae enlarged in rectangle area; B, intermediate segments of posterior ramus; C, serrate and serrulate setae on anterior ramus; D, serrate and serrulate setae on posterior ramus; E, cirrus IV, plumose setae enlarged in rectangle area; F, 12 teeth on basis; G, H, teeth on anterior ramus; I, intermediate segments of anterior ramus; J, serrate setae on terminal segments of anterior and posterior rami. Scale bars in µm.

FIGURE 29. Acasta sulcata. Cirri V (A ̅ D), VI (E ̅ G) and penis (H ̅ J) (ASIZCR 000369). A, Cirrus V; B, serrate setae on anterior ramus; C, sharp denticles on anterior ramus enlarged in rectangle area; D, 3 pairs of setae and denticles on intermediate segments; E, Cirrus VI; F, terminal segment of posterior ramus with serrate setae enlarged in rectangle area; G, 3 pairs of setae on intermediate segments; H, penis; I, long setae on tip; J, vestigial basidorsal point of penis. Scale bars in µm.

FIGURE 30. Acasta sulcata. Maxillae (A ̅ D) and maxillule (E ̅ H) (ASIZCR 000369). A, maxillae; B, outer edge; C and D, inner edge; E, maxillule; F, straight cutting margin showing 11 cuspidate setae; G, upper half of cutting edge; H, lower half of cutting edge. Scale bars in µm.

FIGURE 31. Acasta sulcata. Mandible (A ̅ D), mandibular palp (E ̅ H) and labrum (I, J) (ASIZCR 000369). A, mandible; B, lower margin and inferior angle; C, upper half of blade with bifid second tooth; D, upper margin; E, mandibular palp; F, serrulate setae distal; G, outer margin; H, basal part; I, labrum; J, teeth on labrum. Scale bars in µm.