Tetranchyroderma hyponiglarum, 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 : 59-61

Tetranchyroderma hyponiglarum new species [Tet hpng]

Figure 5 A–C

Tetranchyroderma sp. AC ( Todaro, Hummon, Balsamo, Fregni & Tongiorgi 2001: p. 128); ( Hummon 2001 – 2009: W Med Database)

Diagnosis: Adult Lt 504 Μm; PhJIn at U28. Head end rounded, without tentacles or sensorial knobs; body narrowest at the PhJIn, broadest in the anal region, then narrowing to the broad caudal base; caudal pedicles medium, with a concave medial border indenting to U95. Epidermis fully covered with small tetrancres. Glands small, 16 per side, with a cluster of 8 in the rump region. TbA 4 per side, form a stepped transverse row, tubes inserting directly on the body, the most medial separated from the 3 more lateral by a small gap; TbL 13 per side, 1 in the fore pharyngeal region, the others regularly spaced and of similar size occur along the intestine at U31- U85, with 2 inserting behind the anus; TbV occur as a solitary tube or a fan of 3 tubes with a common base; TbD absent; TbP 3 per side on the caudal pedicles, forming the fused ‘two fingers and a thumb’ typical of the family, with a cirratum-like element inserting between the ‘fingers’, with 3 more tubes in the interpeduncular space (total 5). Locomotor ciliature: a single field covers the ventral body surface. Mouth subterminal, narrower than the fore end of the body, oral hood reaches only to U02; buccal cavity non-cuticularized; pharynx has basal pharyngeal pores; intestine broadest in the middle, narrowing to the rear; anus at U91. Testis is on left as seen from below; vas deferens opens into the rear of the bibulbed caudal organ in front of the anus; developing egg occurs in the rear mid-gut region; round frontal organ bears small spheres, and was without sperm.

Description: Adult Lt 504 Μm; LPh 140 Μm to PhJIn at U28 ( Fig. 5 A, B). Body elongate as an adult, ventrally flattened, dorsally vaulted; head end rounded, without tentacles or sensorial knobs; trunk narrows in the PhJIn region, broadens gradually to the anal region, then narrows to the broad caudal base; caudal pedicles medium (L 25 Μm) naked, with a concave margin separating the two groups, indenting medially to U95. Widths behind mouth/PhJIn/midgut/anus/caudal base and locations along the length of the body are as follows: 42/38/ 51/59/48 Μm at U04/U28/U60/U85/U97, respectively. Glands 16 per side (5–10 Μm diam.) are scattered along the sides in lateral and dorsal columns, with a cluster of 8 lying just before the caudal base.

Cuticular Armature: Small tetrancres fully cover the dorsal, lateral and ventrolateral epidermis; ancres ( Fig. 5 C; W 2–3 Μm, H 3–5 Μm) are smaller in the fore body than in the mid- and hindbody. They are absent from the oral hood and caudum.

Adhesive tubes: TbA 4 per side (L 10–12 Μm), forming a stepped transverse row, the tubes inserting directly on the postoral body surface at U03-U04, the most medial occurring behind the others and pointing forward, and after a small separation the 3 more lateral pointing obliquely forward; TbL 13 per side (L 12–26 Μm), with 1 in the fore pharyngeal region at U10, none in the hind pharyngeal region, 10 of varying size and irregular spacing in the intestinal region at U31-U85, and 2 inserting behind the anus; TbV occur as a solitary tube or a fan of 3 tubes with a common base (L 18–24 Μm) at U78; TbD are absent; TbP 3 per side on the caudal pedicles, forming the fused ‘two fingers and a thumb’ typical of the family, (L terminal tubes 10–11 Μm, L tube on the inner margin also 10 Μm), with a cirratum-like element inserting between the ‘fingers,’ and with 3 additional tubes in the interpedicular space for a total of 5.

Ciliation: Short sensory cilia (L 4 Μm) surround the entire oral opening, with longer vibratile cilia (L 16– 18 Μm) on each side of the oral hood; other hairs (L 14 Μm) occur regularly along the lateral body surfaces, numbering 28–30 per side; other columns have not been seen. Ventral locomotor ciliature forms a single field of transverse rows beneath the body, extending from U04 to the anus at U92; individual cilia are 10–12 Μm in length.

Digestive tract: Mouth subterminal, narrower than the fore end of the body, width 15 Μm, the oral hood extending from its tip 10 Μm rearward to U02; non-cuticularized buccal cavity narrows quickly; pharynx has basal pharyngeal pores at U25; intestine is broadest in the mid-body, narrowing gradually to the rear; anus is at U91.

Reproductive tract: Testis is on the left side as seen from below; vas deferens opens into the rear of the caudal organ near the anus; a developing egg occurs in the mid-gut region on the opposite side (largest 25 x 41 Μm); bibulbous caudal organ (ca. 16 x 40 Μm), with a hollow fore bulb, lies in front of the anus; frontal organ is a round cluster (ca. 20 Μm diam.) of spheres (3 Μm diam.), no sperm being seen.

Ecology: Sparse in frequency of occurrence (less than 10% of samples), rare in abundance (less than 1% of a sample); sublittoral in fine, medium-well sorted sand at 1.5–5.0 m water depth.

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

Remarks: The description of Tetranchyroderma hyponiglarum n. sp. is taken from a single specimen, one of only two found, (WDH video #1521, a holotype, ICZN Article 73.1.2). T. hyponiglarum n. sp. is unusual among macrodasyids in being broader in the rear body than in the fore body.

Etymology: The species is named for the adhesive tubes that lie beneath the trunk (Greek: hypo) under, beneath (Greek: niglaros) small pipe, whistle.

Taxonomic affinities: Tetranchyroderma hyponiglarum n. sp. and the two species to be described below bring the total in this genus into the upper-60s. With this species, there are 4 that are tetrancrous and have TbV, only 3 of which have been described ( Todaro 2002: key to species in the genus, p. 561). T. hyponiglarum alone has but one group of TbV, fewer than 15 TbL per side with 1 in the fore pharyngeal and 0 in the rear pharyngeal regions, and only 4 TbA per side. T. sp. 5 of Valbonesi & Luporini (1984: p. 20, Fig. 9) is closest in overall body shape, being broadest in the rear, but has 0 of 11 TbL in the fore pharyngeal and 3 in the rear pharyngeal regions, while it has 7 TbA per side.

Figures

FIGURE 5. Tetranchyroderma hyponiglarum n. sp. A—dorsal, B—ventral views of an adult (Lt = 704 µm, LPh = 130 µm), and C—a tetrancre with a separate scalebar, from Spiaggia d'Ischia Porto, Isola d’Ischia, Italy, dorsal with glands and the cuticular armature of tetrancres shown on the right side; ventral with cuticular armature of tetrancres shown on the left side, along with digestive and reproductive tracts, adhesive tubes and the ventral locomotor ciliary band.