Tetranchyroderma korynetum, 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 : 61-63

Tetranchyroderma korynetum new species [Tet krnt]

Figure 6 A–C

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

Diagnosis: Adult Lt 300 Μm; PhJIn at U42. Head end rounded, with prominent sensorial knobs; trunk narrows in the fore and hind pharyngeal regions, broadens gradually to the anal region, then narrows to the caudal base; caudal pedicles short naked, with a concave margin between, indenting medially to U98. Epidermis fully covered with relatively large pentancres. Glands small, 7–8 per side. TbA 5 per side, tubes inserting directly on the body, 1 short and 1 long pair medially, and 3 more laterally; TbVL 16 per side, 1 in the fore pharyngeal region, 1 between pharyngeal pores and PhJIn, and the others with increasing size and spacing along the trunk, with 1 of these inserting behind the anus; TbL per se /TbV/TbD absent; TbP 2 per side on the caudal pedicles, forming the fused ‘two fingers’ typical of the family, lacking the ‘thumb’ and a cirratum-like element inserting between the ‘fingers’, but with 3 additional tubes in the interpeduncular space. Locomotor ciliature: a single field covers the ventral body surface. Mouth subterminal, nearly as wide as the fore end of the body, oral hood reaches to U09; buccal cavity non-cuticularized; pharynx has basal pharyngeal pores; intestine broadest in front, narrowing to the rear; anus at U88. Testis is on left as seen from below; vas deferens opens into the rear of the caudal organ near the anus; developing egg(s) not seen; oblong caudal organ lies above the anus; frontal organ is a small sphere.

Description: Adult Lt 300 Μm; LPh 127 Μm to PhJIn at U42 ( Fig. 6 A, B). Body compact as an adult, ventrally flattened, dorsally vaulted; head end rounded, with prominent sensorial knobs that are asymmetrical front to rear; trunk narrows in the fore and hind pharyngeal regions, broadens gradually to the anal region, then narrows to the caudal base; caudal pedicles short (L 8 Μm) naked, with a concave margin separating the two groups, indenting medially to U98. Widths along pharynx/PhJIn/midgut/anus/caudal base and locations along the length of the body are as follows: 43,36,38,31/33/42/16 Μm at U06,U11,U20,U29/U42/U85/U95, respectively. Glands 7–8 per side (3–5 Μm diam.) are scattered along the sides in columns.

Cuticular Armature: Realtively large pentancres fully cover the dorsal, lateral and ventrolateral epidermis; ancres ( Fig. 6 C; W and H 5 Μm) are smaller on the middle of the oral hood than elsewhere on the body. They are absent from the fore part of the oral hood and caudum.

Adhesive tubes: TbA 5 per side (L 6–9 Μm), the tubes inserting directly on the postoral body surface at U10-U12, the most medial occurring behind the others and pointing forward, then the longest tube and finally a set of three, pointing more and more obliquely forward; TbVL 16 per side (L 6–10 Μm), with 1 in the fore pharyngeal region at U 10, 1 in the hind pharyngeal region between pharyngeal pores and PhJIn, and 14 of varying size and spacing that increases rearward along the trunk, with 1 of these inserting behind the anus; TbL per se /TbV/TbD are absent; TbP 2 per side on the caudal pedicles, forming the fused ‘two fingers’ typical of the family, (L terminal tubes 5–6 Μm), but lacking the ‘thumb’ and a cirratum-like element inserting between the ‘fingers,’ but with 3 additional tubes in the interpedicular space.

Ciliation: Short cilia (L 5–6 Μm) insert on scallops along the dorsal border of the oral hood; shorter ones (L 2–3 Μm) insert on finger-like projections (L 2–3 Μm) along the ventral border of the oral hood; stout vibratile sensory cilia (L 10–12 Μm) occur in two rows on the dorsal oral hood in front of the initial pentancres, with other vibratile cilia (L 10–12 Μm) on either side of the oral hood on lateral and ventral surfaces; other cilia (L 14–20 Μm) occur along the dorsolateral body surfaces, numbering perhaps 5–6 per side; other columns have not been seen. Ventral locomotor ciliature forms a single field of transverse rows beneath the body, extending from U12 to the anus at U88.

Digestive tract: Mouth subterminal, nearly as broad as the fore end of the body, width 36 Μm, the oral hood extending from its tip 19 Μm rearward to U09; non-cuticularized buccal cavity narrows quickly; pharynx has basal pharyngeal pores at U37; intestine is broadest in front, narrowing gradually to the rear; anus is at U88.

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; developing egg(s) not seen; oblong caudal organ (15 x 20 Μm) lies above the anus; frontal organ is a sphere (7 Μm diam.).

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 m water depth.

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

Remarks: The description of Tetranchyroderma korynetum n. sp. is taken from a single specimen (WDH video #1529, a holotype, ICZN Articles 73.1.2). T. korynetum n. sp. is unusual among pentancrous macrodasyids in having prominent sensorial organs that are highly asymmetrical.

Etymology: The species is named for the golf club-like sensorial organs borne laterally on the head (Greek: korynetes) club-bearer.

Taxonomic affinities: Tetranchyroderma korynetum n. sp. alone has pentancres and prominent sensorial organs that are asymmetrical front to rear, without having dorsal cephalic tentacles, TbD or TbV. T. hystrix Remane, 1926 is a species from Northern Europe with prominent symmetrical sensorial organs that also lacks cephalic tentacles, TbD and TbV; it is also pentancrous as listed by Todaro 2002: key to species in the genus, p. 562; see Hummon & Todaro 2010).

Figures

FIGURE 6. Tetranchyroderma korynetum n. sp. A—dorsal, B—ventral views of an adult (Lt = 300 µm, LPh = 127 µm), and C—a pentancre with a separate scalebar, from Spiaggia d'Ischia Porto, Isola d’Ischia, Italy, dorsal with glands and the cuticular armature of pentancres shown on the right side; ventral with cuticular armature of pentancres shown on the left side, along with digestive and reproductive tracts, adhesive tubes and the ventral locomotor ciliary band.