Acasta turriformis, Yu & Chan & Achituv & Kolbasov, 2017

Yu, Meng-Chen, Chan, Benny K. K., Achituv, Yair & Kolbasov, Gregory A., 2017, Four new sponge-inhabiting barnacles of the genus Acasta (Thoracica: Archaeobalanidae: Acastinae) from the Indo-Pacific, Raffles Bulletin of Zoology 65, pp. 585-615 : 586

Acasta turriformis , new species

( Figs. 1–7 )

Material examined. Four specimens (holotype and paratypes) in the sponge Lissodendoryx (Lissodendoryx) sp. Topsent, 1892, Gongguan , Green Island, Taitung, Taiwan 22°40′47″N 121°29′29″E, SCUBA diving, depth 9 m. The holotype (dry shell compartments, mouth parts and cirri mounted in glycerol on glass slide) and paratype (shell in EtOH) are deposited in the Zoological Museum of Moscow State University under registration numbers Mg –1230 (holotype) and Mg –1231 (paratype). The other paratypes ( ASIZCR000371 and ASIZCR000372 ) are deposited in the Biodiversity Research Museum , Biodiversity Research Center, Academia Sinica, Taiwan .

Diagnosis. Shell white, elongated in height, with long, narrow slits between wall plates; parietes with long longitudinal ribs internally; carinolatus 2 narrow, basis deep, bowlshaped, with crenated margin; scutum without distinct radial striations, articular ridge prominent, pits of adductor and depressor muscles conspicuous; tergum without long beakshaped apex, spur wide, with end almost quadrate; cirri IV and V with developed curved teeth on anterior rami; basidorsal point of penis absent. Embedded in sponge Lissodendoryx (Lissodendoryx) sp. Topsent, 1892.

Description. (Based on holotype). Shell white, elongated, 9.3–10 mm high, 4.1–4.3 mm rostro-carinal basal diameter; tips of wall plates tinged with pale violet; orifice moderately small, toothed, 2.0– 2.7 mm maximum length, 6 long, narrow slits 2.5–3.0 mm high between proximal halves of wall plates ( Fig. 1A, B ). Basis deep, bowl-shaped, 4.0– 4.3 mm high, with growth lines concentric, margin crenated, bottom of basis deformed or with 4 radial grooves ( Fig. 1A, B, E ). Parietes ( Fig. 1C, D ) with small, dense, granulate, external projections and fine growth lines, basal parts thinner, sheath about 1/3 total length, with horizontal striations, inner lamina beneath sheath with long, distinct longitudinal ribs. Radii and alae with summits oblique, radii ~1/2 length of parietes, with fine, oblique, external striations, alae semitransparent. Carinolatus 2 narrow ( Fig. 1A, B, D ), paries ~1/5–1/7 width of carinolatus 1.

Figures

Fig. 1. Acasta turriformis sp. nov., shell, general view and compartments (holotype: A, C–E; paratype: B). A, B, Complete shell, left side (long narrow slits between compartments indicated); C, Rostrum, external surface; D, Carinolatera 1 and 2, internal surface; E, Margin of basis. Abbreviations: ba = basis, ca = carina, cl1 = carinolatus 1, cl2 = carinolatus 2, r = rostrum. Scale bars in µm.

Fig. 2. Acasta turriformis sp. nov., opercular plates (holotype). A, B, Left scutum, internal and external view; C, D, Right scutum, external and internal view; E, F, Left tergum, external and internal view; G, H, Right tergum, internal and external view. Scale bars in µm.

Fig. 3. Acasta turriformis sp. nov., mouth parts (holotype). A, Labrum with mandibular palps; B, Enlarged crests of labrum; C, Mandible; D, E, Maxillules. Scale bars in µm.

Fig. 4. Acasta turriformis sp. nov., cirri (holotype). A, Cirrus IV, basal part; B, Cirrus V, basal part. Scale bars in µm.

Fig. 5. Acasta turriformis sp. nov., mouth parts (SEM, paratype). A, Labrum with mandibular palp; B, Mandibular palp, inner surface; C, Enlarged proximal part of mandibular palp, inner surface; D, E, Mandibles, outer surface; F, Enlarged lower part of mandible, outer surface; G, H, Maxillules, outer and inner surfaces; I, Enlarged lower part of maxillule, inner surface; J, Enlarged lower part of maxillule, outer surface. Abbreviations: lb = labrum, mdp = mandibular palp. Scale bars in µm.

Fig. 6. Acasta turriformis sp. nov., maxillae and penis (SEM, paratype). A, Maxillae, lateral view; B, Distal part of maxilla; C, Serrated setae on proximal part of maxilla; D, Biserrate setae and combs of fine setae in basal part of maxillae; E, Stub setae in upper-lateral part of lower lobe; F, G, Basal and terminal parts of penis; Abbreviations: c2 to c6 = cirri II to cirri VI, pe = penis. Scale bars in µm.

Fig. 7. Acasta turriformis sp. nov., cirri (SEM, paratype). A, Cirrus I; B, Cirrus II; C, Cirrus II, plumose setae on posterior margin of coxa; D, Cirrus II, annuli of posterior ramus; E, Cirrus II, cuticular folders on coxa; F, Cirrus III; G, Cirrus IV; H, Cirrus IV, distal annuli; I, Cirrus IV, basal annuli; J, Cirrus V, basal annuli; K, Cirrus VI, middle annuli. Scale bars in µm.