Acanthodasys flabellicaudus, Hummon, William D. & Todaro, Antonio, 2009

Hummon, William D. & Todaro, Antonio, 2009, Italian marine Gastrotricha: VI. Seven new species of Macrodasyida, Zootaxa 2278, pp. 47-68 : 53-56

Acanthodasys flabellicaudus new species [Acd fvcd]

Figure 3 A–E

Acanthodasys sp. B ( Todaro, Hummon, Balsamo, Fregni & Tongiorgi 2001: p. 122); ( Hummon 2001 – 2009: W Med Database)

Diagnosis: Adult Lt 592 Μm; PhJIn at U27. Head end nearly squared off; trunk broadens somewhat in the pharyngeal region, becomes obesely broad in the mid-intestinal region, then narrows in two stages to the rounded caudum. Glands 30–32 per side, most dense behind the anus. Epidermis is covered with small T-shaped uniancres, similar both dorsally and ventrally, having no intervening cuticular elements; only the ciliated patches of locomotor cilia are free of uniancres. TbA 5 per side, inserting directly on the body, projecting forward to diagonally outward; TbVL 12 per side, 9 at U18-U57, with 3 at the rear of the pharynx, and 6 in the fore intestinal region, the remaining 3 at U73, U90 and U94, the final 2 being in the postanal region; TbDL 3 per side, asymmetrically placed at U29-U59; TbL per se /TbV absent; TbP 6, longer medially than laterally, occur on the rounded rear of the caudum. Locomotor ciliature: a field of ciliary patches, interspersed with the ventral uniancres. Mouth terminal, as broad as the fore end of the body, rim bears a corona of cilia; non-cuticularized buccal cavity narrows quickly; narrow pharynx has inconspicuous basal pharyngeal pores; intestine broadest in the middle, narrowing gradually fore to aft; anus at U89. Hermaphroditic; testes are bilateral in this subfamily, beginning just behind the PhJIn, with vasa deferentia continuing rearward before joining medially at U73 and leading rearward to an irregularly shaped longitudinal caudal organ with a medial canal and some glandular material; a developing egg and 2 germinal vesicles occur in the mid-intestinal region; a spherical frontal organ is hyaline and bears motile sperm; another spherical structure bearing small round objects occurs between the germinal vesicles and the frontal organ; a dorsal rosette occurs in the fore-intestinal region at U38.

Description: Adult Lt 592 Μm; LPh 158 Μm to PhJIn at U27 ( Fig. 3 A, B). Body long as an adult, ventrally flattened, dorsally vaulted; head end nearly squared off; trunk broadens somewhat in the pharyngeal region, becomes obesely broad in the mid-intestinal region, then narrows in two stages to the rounded caudum. Widths at and just behind mouth/PhJIn/mid-intestine/anus/caudum and locations along the length of the body are as follows: 44,40/62/92/40/15 Μm at U01,U02/U27/U60/U89/U97, respectively. Glands 30–32 per side (2–4 Μm diam.) are scattered in lateral and dorsal columns, most densely clustered behind the anus.

Cuticular Armature: Epidermis is covered with small T-shaped uniancres ( Fig. 3 E), of similar size ventrally and dorsally (L 8 Μm), having no intervening cuticular elements. Only the ciliated patches of locomotor cilia are free of uniancres.

Adhesive tubes: TbA 5 per side (L 5–7 Μm), in a broad, shallow arc, inserting directly on the postoral body surface at U02-U03 and project forward to diagonally outward; TbVL 12 per side (L 12–14 Μm), with 9 at U18-U57, most symmetrically placed, 0 of these in the fore pharyngeal and 3 in the rear pharyngeal regions, and 6 in the fore intestinal region, the remaining 3 occurring symmetrically at U73, U90 and U94, the final 2 being in the postanal region; TbDL 3 per side, asymmetrically placed at U29-U59; TbL per se /TbV are absent; TbP 6 (L 14–17 Μm), longer medially than laterally, occur on the rounded rear of the caudum.

Ciliation: Mouth rim bears a corona of cilia (L 8–12 Μm); sensory hairs arise in lateral columns on either side of the body (L 6–10 Μm), numbering c. 45 each. Ventral locomotor ciliature forms a field of ciliary patches (cilia L 10 Μm), interspersed with the ventral uniancres ( Fig. 3 D).

Digestive tract: Mouth terminal, as broad as the fore end of the body, width 39 Μm; non-cuticularized buccal cavity narrows quickly; narrow pharynx has inconspicuous basal pharyngeal pores; intestine is broadest in the middle, narrowing gradually to the rear; anus is at U89.

Reproductive tract: Testes are bilateral in this subfamily, beginning just behind the PhJIn, with vasa deferentia continuing rearward before joining medially at U73 and leading rearward in the hind-intestinal region to a longitudinally oriented caudal organ of irregular shape that has a medial canal, followed to the rear by some glandular material; a developing egg (39 x 52 Μm) and 2 germinal vesicles occur in the mid-intestinal region; a spherical frontal organ occurs that is hyaline and bears a cell-like structure and some motile sperm; another spherical structure with a dozen small round objects occurs between the germinal vesicles and the frontal organ; a dorsal rosette occurs in the fore-intestinal region at U38.

Ecology: Sparse in frequency of occurrence (less than 10% of samples), scarce in abundance (3–5 % of a sample); sublittoral in fine, medium-well sorted, clean sand, 5.0 m water depth, 0–10 cm depth.

Geographical distribution: MED: EUROPE: ITALY: Campania Archipelago { Isola d’Ischia: Spiaggia degli Inglesi^ 40°,45’N/13°,56’E [2-videos]}

Remarks: The description of Acanthodasys flabellicaudus n. sp. is taken from two specimens, both from the same location. One (WDH video #9, Fig. 3 A,B, a holotype, ICZN Article 73.1.1) is a mature adult. The other (WDH video #10, Fig. 3 C,D, a paratype, ICZN Article 72.4.5) is a subadult: Lt 428 Μm; LPh 152 Μm, with TbA 4 or 5 per side, TbVL 7 per side, TbD 3 per side, and TbP 6 per side.

Etymology: The species is named after the small fan-shaped (Latin flabellum) array of rear (Latin cauda) adhesive tubes.

Taxonomic affinities: There are currently eight described species of Acanthodasys , including: Acanthodasys flabellicaudus n. sp., the latter being the only species having a rounded rather than a furcated caudum, together with TbA 5 per side, TbDL 3 per side, and T-shaped uniancres of similar size dorsally and ventrally, with no additional elements in between.

Figures

FIGURE 3. Acanthodasys flabellicaudus n. sp. A—dorsal and B—ventral views of an adult (Lt = 592 µm, LPh = 158 µm); C—dorsal and D—ventral views of a subadult (Lt = 428 µm, LPh = 152 µm), both from Spiaggia degli Inglesi, Isola d’Ischia, Italy, dorsal with glands, adhesive tubes and the cuticular armature of uniancres (shown only on the left side as seen from below, (A) or just glands and tubes (C); ventral with digestive and reproductive tracts, and adhesive tubes (B) or with cuticular armature of uniancres shown on the side, along with digestive tract, adhesive tubes and the ventral locomotor ciliary patches (D). E—a uniancre with its separate scalebar.