Weltneria acanthostoma, Kolbasov, Gregory A., Chan, Benny K. K. & Cheng, Yu-Rong, 2017

Kolbasov, Gregory A., Chan, Benny K. K. & Cheng, Yu-Rong, 2017, Weltneria acanthostoma sp. nov., a burrowing barnacle (Cirripedia: Acrothoracica) from the deep-waters of the South China Sea, Zootaxa 4290 (3), pp. 591-599 : 592-597

Weltneria acanthostoma sp. nov.

Figures 1–4

Type material. One female (holotype) in the dead part of a colony of the scleractinian Madrepora oculata ; collected by deep-sea Warén dredge at Stn DW 4100, 15°04.3820’ N, 116°31.1860’ E, depth 534 m, hard rocky bottom; Blue Ridge Seamount , Nan-Hai 2014 expedition, 01.01.2014; fixed in absolute ethanol. The holotype (BRMAST-Cir-001) is deposited in the Biodiversity Research Museum, Academia Sinica, Taiwan .

Diagnosis. Weltneria having opercular bars with outer and inner rows of simple hooked teeth and hooked posterior processes; mantle sac without conspicuous teeth; lateral bars absent; attachment disk without calcareous formation.

Description. Female large, ~ 5.75 mm height (from bottom of attachment disc to apex of opercular bars). Mantle white-brown in ethanol with brown coloration at basal part ( Fig. 1 A); mantle sac lacking conspicuous mantle teeth, except simple sharp teeth along posterior margin of aperture; dense setae in posterior and lateral parts of opercular area; mantle micro-sculpture of tiny, hardly visible, simple, bifid and trifid teeth scattered over rear and lateral sides of mantle sac, and multifid ctenoid scales of opercular area; lateral bars and orificial knob absent; group of embryos at attachment area ( Figs 1 A, B, 2A, B). Operculum wide, oval shaped; opercular bars massive, ~ 2.0 mm long, slightly sinusoid, with sharp, hooked posterior processes; outer/lateral and inner / occludent margins with 5 and 4 conspicuous simple hooked teeth, respectively, larger teeth situated on small hillock approximately at middle of opercular bar on both lateral and occludent margins; surface of opercular bars covered with dense, tiny, blunt knobs and sharp denticles, tiny bifid teeth along occludent margin ( Figs 1 A, B, 2A, B). Typical comb collar in posterior part of aperture. Attachment disk chitinous, drop-shaped, ~ 3.6 mm long, with distinct growth lines (15), upper/older quarter dark colored, lower part semitransparent, no calcareous formation/inclusions inside ( Figs 1 A, C, 2A, C).

Labrum saddle-shaped, bullate, with elongated (130 µm) triangular upper part of anterior crest developed, 110 µm high; triangular dorsal process forming twin peaks; conspicuous setae and multifid ctenoid scales on posterior edge of crest and dorsal process; lateral lower margins of crest with tiny, sharp denticles surrounding mouth opening ( Figs 2 F, 3A). Mandible with 3 main teeth excluding inferior angle; first upper tooth largest, separated from lower teeth; inferior angle beneath third tooth with differing morphology on left and right mandibles, bearing 4 or 7 sharp denticles respectively, lateral surfaces in lower half of blade with dense, short setae ( Figs 3 B, C, 4A– D). Distal part of mandibular palp trapezoid, elongated, with row of 14–15 long setae along upper outer margin and tip ( Figs 3 A, B, 4A). Maxillule with 2 small notches, 2 large and 2 small cuspidate setae above upper notch; 2 middle setae and 1 small cuspidate seta between upper and lower notches; bundle of 6 sharp, small setae in lower part of cutting edge; lateral surfaces of blade with dense, thin setae ( Figs 3 D, E, 4E–G). Maxilla bilobed, with larger bean-shaped and smaller oval lobes bearing dense, long setae in upper parts ( Figs 3 F, 4H).

Mouth cirri ~ 830 µm long, with short rami about 1/5 of total length of mouth appendage; coxa curved, elongated, ~ 500 µm long, without setae; basis quadrangular with 3 setae in upper part of outer margin ( Figs 2 D, 3G). Anterior (internal) ramus 4-segmented, twice as long as posterior (external) 2-segmented ramus; both rami with dense, long, plumose setae.

First and second pairs of terminal cirri short; first pair 3 times and second pair 2 times shorter than posterior 3– 5 pairs; annuli with typical setation. Cirral counts as follows:

I II III IV V VI

2–3 10–15 20–27 33–39 40–43 50–54

Caudal appendages two-joined, basal joint with 5 short, distal setae, tip of terminal joint with 5 plumose, long setae ( Figs 1 D, 2E).

Dwarf male(s) not found.

Comparison. The new species, Weltneria acanthostoma , is similar to its congeners, W. exargilla and Weltneria hessleri Newman, 1971 , by the presence of the simple, conspicuous teeth of the opercular bars. W. acanthostoma differs from W. hessleri in having hooked posterior processes and the larger curved teeth of the opercular bars. The opercular bars of W. exargilla have straight margins and a greater number (13–18) of curved, equally sized teeth, whereas those of W. acanthostoma are slightly sinusoid, with a lesser number (4 and 5) of curved teeth of different sizes. Both W. exargilla and W. hessleri possess calcareous formations in the basal area, which is absent in W. acanthostoma . These species were both described from the Atlantic— W. exargilla in the Bay of Biscay and W. hessleri from the Bermuda Islands. Weltneria spinosa and Weltneria tomlinsoni Zevina, 1991 also have hooked posterior processes of the opercular bars, with the opercular bars armed with distinct, conspicuous, bifid teeth in W. spinosa and lacking teeth in W. tomlinsoni .

Etymology. The specific name acanthostoma is from the Greek akanthos (ἄκανθΟς) meaning thorn, and stoma (στόΜα) meaning mouth, referring to the conspicuous hooked teeth on the opercular bars.

Figures

FIGURE 1. Weltneria acanthostoma sp. nov., general appearance (light microscopy). (A) General view, lateral side, part of mantle from rear side enlarged in rectangular area. (B) Opercular area, lateral view, parts of opercular bar with tiny bifid teeth and posterior margin of aperture with simple mantle teeth enlarged in rectangular areas. (C) Attachment disk separated from mantle sac, frontal view. (D) Posterior part of thorax with bases of terminal cirri and caudal appendages. Abbreviations: ad — attachment disk, ca — caudal appendages, ob — opercular bars, oc — oral / mouth cone, tc — terminal cirri. Scale bars in µm.

FIGURE 2. Weltneria acanthostoma sp. nov., general morphology. (A) General view, lateral side. (B) Opercular area, lateral view. (C) Attachment disk separated from mantle sac, frontal view. (D) Mouth cirrus. (E) Caudal appendage. (F) Labrum, lateral view. Abbreviations: ad — attachment disk, ba — basis, co — coxa, em — embryos, er — external / posterior ramus, ir — internal / anterior ramus, mdp — mandibular palp, ob — opercular bars, oc — oral / mouth cone, tc — terminal cirri. Scale bars in µm.

FIGURE 3. Weltneria acanthostoma sp. nov., mouth parts (light microscopy). (A) Labrum, lateral view. (B, C) Mandibles. (D, E) Maxillules. (F) Maxillae. (G) Mouth cirrus. Abbreviations: ba — basis, co — coxa, dpl — dorsal process of labrum, er — external / posterior ramus, ir — internal / anterior ramus, mdp — mandibular palp, oes — oesophagus. Scale bars in µm.

FIGURE 4. Weltneria acanthostoma sp. nov., mouthparts. (A, C) Mandibles. (B, D) Inferior angle of mandibles. (E) Maxillule. (F, G) Cutting edge of maxillules. (H) Maxillae. Scale bars in µm.