Acasta undulaterga, Yu & Kolbasov & Hosie & Lee & Chan, 2017

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 : 187-194

publication ID	https://doi.org/ 10.11646/zootaxa.4277.2.1
publication LSID	lsid:zoobank.org:pub:9DFC7355-BA9C-43CE-9E39-8AC770624AA1
DOI	https://doi.org/10.5281/zenodo.6027911
persistent identifier	https://treatment.plazi.org/id/9B78EFED-49E2-4AEE-A067-02BF8F99A1C0
taxon LSID	lsid:zoobank.org:act:9B78EFED-49E2-4AEE-A067-02BF8F99A1C0
treatment provided by	Plazi
scientific name	Acasta undulaterga
status	sp. nov.

Treatment

Acasta undulaterga sp. nov.

Figs 32 View FIGURE 32 ̄38

Material examined. Holotype: ASIZCR000370, Longdong, Gongliao, New Taipei City, Taiwan (25°06′50.27″N, 121°55′13.40″E, water depth 17m), July 2011, coll. J.H.Y. Yu, on host sponge Jaspis splendens (de Laubenfels, 1954) . GoogleMaps

Paratype: CEL-SNE47-5—data same as for holotype.

Diagnosis. Shell white to pale yellow, tinged pinkish towards apex. Basis pentagonal, saucer-shaped, with 4 indistinct and shallow radial furrows extending from center to the crenate basal rim. Scutum strongly latticed, articular furrow distinct, articular ridge prominent, short. Tergum beaked, apex tinged with red, spur long, truncated, width about 1/3 of basal margin, basal margin deeply concave at spur base. Feeble armament of curved teeth on anterior ramus of cirrus IV.

Description. Shell white to pale yellow after extraction from sponge, becoming white and semitransparent (sometimes tinged with reddish patches towards apex) after bleach treatment ( Figs 32 View FIGURE 32 ĀD, 33ĀL). Basis pentagonal, saucer-shaped, with 4 external radial shallow furrows extending from center to crenate basal rim ( Fig. 33 View FIGURE 33 M, N). Parietes externally smooth with fine growth ridges; internally with longitudinal basal ribs not reaching sheath; sheath with horizontal striations; radii with inclined and horizontal striations; alae with horizontal striations, not reaching to base ( Fig. 33 View FIGURE 33 ĀL). Carinolaterals small, axe-shaped, about 1/5 of width of laterals ( Fig. 33 View FIGURE 33 G, H, I, J). Carina longest, with incurved apex ( Figs 32 View FIGURE 32 ĀD, 33K, L).

Scutum ( Fig. 32 View FIGURE 32 ĒF) externally latticed by strong growth and longitudinal ridges with prominent teeth on occludent margin. Basal margin slightly concave at basioccludent angle, basiscutal angle rounded. Internal surface smooth, with rudimentary adductor ridge, articular furrow distinct, articular ridge prominent, short, about 1/2 of length of tergal margin, adductor and depressor pits absent. Tergum ( Fig. 32 View FIGURE 32 G, H) thin, fragile, apex beaked, tinged with red, with fine growth ridges, spur narrow, truncated, width about 1/3 of basal margin, distinctly separated from basiscutal angle, spur furrow wide, shallow, basal margin deeply concave at spur base; internally scutal margin raised, articular ridge short, reddish, crests of depressor muscles absent.

Counts of cirral segments given in Table 1. Cirrus I with rami unequal, posterior margin with serrulate and plumose setae ( Fig. 34 View FIGURE 34 A), simple and bifid setae on distal margin of terminal segments of anterior and posterior rami, respectively ( Fig. 34 View FIGURE 34 B, C). Cirrus II rami unequal, protopod anterior and posterior margins with plumose and pappose setae, respectively ( Fig. 34 View FIGURE 34 D), terminal segments of anterior and posterior rami with bifid setae ( Fig. 34 View FIGURE 34 E, F). Cirrus III, rami subequal; protopod anterior and posterior margins with simple and plumose setae, respectively ( Fig. 34 View FIGURE 34 G), terminal segments of anterior and posterior rami with serrate and serrulate setae ( Fig. 34 View FIGURE 34 H, I), anterior and posterior rami with small, sharp denticles on intermediate segments ( Fig. 34 View FIGURE 34 J). Cirrus IV, rami unequal, protopod anterior and posterior margins with serrulate and plumose setae, respectively ( Fig. 35 View FIGURE 35 A), anterior margin of basis armed with few denticles ( Fig. 35 View FIGURE 35 B), proximal segments of anterior ramus bearing 1 curved tooth and upturned spines/denticles on anterior margin ( Fig. 35 View FIGURE 35 C̄E), intermediate segments with 2 pairs of long and short, serrulate setae ( Fig. 35 View FIGURE 35 F), terminal segments of anterior and posterior rami with simple and serrulate setae ( Fig. 35 View FIGURE 35 ḠH). Cirrus V, protopod anterior and posterior margins with serrulate and few short simple setae, respectively ( Fig. 36 View FIGURE 36 A), intermediate segments of both rami with 2 pairs of long and 1 pair of short serrulate setae, terminal segments of anterior and posterior rami with serrulate setae ( Fig. 36 View FIGURE 36 ĀC). Cirrus VI with rami unequal, protopod with few short simple and anterior serrulate setae ( Fig. 36 View FIGURE 36 D), intermediate segments with 2 pairs of long and 1 pair of short serrulate setae, terminal segments of anterior and posterior rami with serrulate setae ( Fig. 36 View FIGURE 36 D̄F). Penis finely annulated, without basidorsal point, gradually tapering to tip ( Fig. 36 View FIGURE 36 G), tip broken ( Fig. 36 View FIGURE 36 H).

Maxilla bilobed, oblong ( Fig. 37 View FIGURE 37 A), distal lobe with serrulate setae ( Fig. 37 View FIGURE 37 B), outer edge without long setae, inner edge straight, basal lobe with serrulate setae ( Fig. 37 View FIGURE 37 C, D). Maxillule cutting margin straight, without notch, with 8 large cuspidate setae, upper and lower pairs largest ( Fig. 37 View FIGURE 37 E, F), upper margin with 5 pairs of simple setae, lower margin with numerous simple setae ( Fig. 37 View FIGURE 37 G, H). Mandible with 5 teeth ( Fig. 38 View FIGURE 38 A), second bifid ( Fig. 38 View FIGURE 38 B), inferior angle with 3 denticles and stout setae, lower margin bearing simple setae ( Fig. 38 View FIGURE 38 C). Mandibular palp broadly truncated ( Fig. 38 View FIGURE 38 D), outer margin distinctly concave ( Fig. 38 View FIGURE 38 E), with dense serrulate setae ( Fig. 38 View FIGURE 38 G), basal margin with prominent process ( Fig. 38 View FIGURE 38 F). Labrum bilobed, with deep, V-shaped notch ( Fig. 38 View FIGURE 38 H), 3 small teeth on each crest ( Fig. 38 View FIGURE 38 I).

Remarks. In our specimens, the morphological characters are consistent between the holotype and paratype. Although this species shares some morphological characters with A. sulcata , including a basis with a crenate rim and a beaked tergum with a truncated spur, it differs from A. sulcata in having i) a completely, strongly latticed scutum, ii) a narrower spur of the tergum, and iii) a deeply concave basal margin of the tergum at the base of the spur. From the 34 extant species of Acasta , only two ( Acasta japonica Pilsbry, 1911 and Acasta newmani Van Syoc & Winther, 1999 ) are characterized by the possession of a latticed scutum. However, the present new species may be easily distinguished from A. japonica and A. newmani by the longer and narrower tergal spur and the deeply concave basal margin of the tergum. The latticed scutum is characteristic of several species of the genera Archiacasta , Neoacasta and Pectinoacasta . The new species differs from species of the genus Archiacasta in having a saucer-shaped calcareous basis, the internal longitudinal ribs of the shell plates, and the teeth on cirrus IV. It also differs from Neoacasta in having internal longitudinal ribs of the shell plates and recurved teeth on cirrus IV, and by the absence of six internal ribs on the basis. It differs from Pectinoacasta due to the absence of a latticed or longitudinally striated tergum. On the basis of these differences, these specimens are described as a new species.