Cephalodasys dolichosomus, Hummon, William D., 2011

Hummon, William D., 2011, Marine Gastrotricha of the Near East: 1. Fourteen new species of Macrodasyida and a redescription of Dactylopodola agadasys Hochberg, 2003, ZooKeys 94, pp. 1-59 : 5-7

Cephalodasys dolichosomus sp. n. Figure 2

Cephalodasys EgyB Hummon (2009) [E Med & Red Sea Database].

Diagnosis:

Adult Lt to 772 µm; PhJIn at U28. Head small, pyriform, with a broad circumcephalic band of cilia at U02-U05, separated from the rest of the body by a long gradual neck constriction; trunk narrow, bowed outward along the mid-gut, caudum slightly flaired. Epidermis finely granular, without glands. TbA 4 per side, borne on fleshy hands; TbVL 6 per side, with 5 inserted regularly from U27 to U51 and the 6th at U72, one in the rear pharyngeal region, the others in the fore- and midgut region; TbP 10-12, inserting on the rounded caudum. Locomotor ciliature: 2 longitudinal bands, separate from one another, but uniting with cilia of the transverse cephalic band in front, and joining together behind the anus. Mouth terminal, of medium diameter; buccal cavity cylindrical; pharyngeal pores basal; intestine broadest at the rear mid-gut, narrowing behind; anus ventral at U95. Hermaphroditic; testes begin at the PhJIn, vasa deferentia run rearward, but termini not seen; a column of eggs lies along the mid-gut, developing front to rear; frontal and caudal organs not seen.

Description:

Adult Lt 615-772 µm; LPh 205-215 µm to PhJIn at U33-U28 (Fig. 2). Body transparent, strap-shaped, dorsoventrally flattened, but vaulted dorsally; head small, pyriform, truncated apically, with a broad circumcephalic band of cilia at U02-U05, separated from the rest of the body by a long gradual neck constriction; trunk narrow, bowed slightly outward along the mid-gut, and then narrowing again to a rounded, slightly flaired caudum. Widths of head /neck /trunk /caudal base /caudal flair, and locations along the length of the body are as follows: 44 /32 /63 /24 /28 µm at U05 /U07 /U54 /U95 /U96, respectively. Cuticle is flexible, epidermis finely granular, but lacking glands.

Adhesive tubes:TbA 4 per side (L 8-9 µm), borne on broad fleshy hands that insert at U08; TbVL 6 per side (L 15-18 µm), 5 inserted regularly from U27 to U51 and the 6th at U72, one between pharyngeal pores and PhJIn, the others in the fore- and midgut region; TbP 16 total (L 7-10 µm), inserting in a single row about the flaired caudum.

Ciliation:A number of cilia insert on each side of the head (L 9-18 µm); a broad transverse band of cephalic cilia (L 18-20 µm) covers the broadest part of the head from U02 to U05 and joins the locomotor ciliature ventrally; some 30-32 sensory hairs occur in lateral (L 9-12 µm) and dorsolateral (L 18-20 µm) columns along either side of the trunk at U06-U96. Ventral locomotor ciliature forms two longitudinal bands of short (L 9-12 µm), scattered cilia that follow the lateral body contours beneath the entire length of the body, separate medially beneath the head and pharynx, but converging behind the anus and merging into a single band onto the caudum.

Digestive tract: Mouth is terminal, of medium width (6 µm diameter); buccal cavity nearly cylindrical, lined with cuticule of medium thickness; pharynx narrows toward the rear, but with basal pharyngeal pores showing dorsolateraly; intestine broadest in the rear mid-gut region, narrowing behind; anus is ventral at U95.

Reproductive tract: Hermaphroditic; testes begin at the PhJIn, vasa differentia lead rearward past U50, but termini not seen; ovary solitary, lying above the foregut on the right side, with a column of multiple ova developing toward the rear, reaching 115 × 40 µm in size; frontal and caudal organs not seen.

Ecology: Occasional in frequency of occurrence (10-30% of samples), scarce to prevalent in abundance (3% to more than 30% of a sample, the latter often a sub- [sdom] or co-dominant [cdom]); littoral in fine, well sorted sand to very fine-very coarse, poorly-extremely poorly sorted, clean to detrital sand at 0-10 cm depth, mean low water to extreme low water; mostly sublittoral in very fine to medium, well to medium sorted, clean silicious or coralline sands, sometimes mixed with shell and/or coral gravel, at 0.5-8 m water depth.

Geographical distribution:

Red Sea:EGYPT: {23km south of Ein Sukhna, Marsa Bareika N [sdom], ^Main Beach Ras Mohamed NP [cdom] (27°44'N, 34°12'E) [4-videos], Na’ama Bay N [sdom], Sharm el-Sheikh [3-videos], Ras Sudr [sdom]}; ISRAEL: {Coral Beach M5 [2-videos]}.

Remarks:

There are nine video sequences of Cephalodasys dolichosomus sp. n., all from the upper Red Sea in Egypt and Israel. Three of these are available as MPEG 2 (and MPEG 1) from Hummon (2009): #744 a mature adult Lectotype of Lt=772 µm (LPh=178 µm), collected in July 1994 from Main Beach, Ras Mohamed NP, S. Sinai, Egypt; #1917 a mature adult of Lt=763 µm (LPh=172 µm) from Coral Reserve, Eilat, Israel; and the other, #742 a subadult of Lt=186 µm (LPh=93 µm) from Sharm el-Sheikh, S. Sinai, Egypt. Cephalodasys dolichosomus can occupy a variety of sediments, but its greatest numbers occur sublittorally in finer, well sorted sands; it is unusual among the genus in having so many of its findings as co- or sub-dominant abundances.

Etymology:

Dolichosoma (Greek: dolichos + soma = meaning 'long body’) refers to the overall length of the animal, enhanced by the relative slenderness of its silhouette.

Taxonomic affinities:

When mature, Cephalodasys dolichosomus sp. n. is the longest, thinnest member of the genus, the only species in the genus that has the following combination of characters: a small pyriform head, with a transverse band of cephalic cilia, a PhJIn at U28, which also has TbA 4 per side; TbVL 6 per side (5 at U27-U51 and a 6th at U72); and TbP 16 total, borne on a flaired caudum; TbL per se /D/V absent; and ova developing fore to aft, though accessory sex organs were not seen. Cephalodasys dolichosomus belongs in the group of species that have pyriform heads, but is longer, thinner and with fewer TbL than other species with which it might be compared, namely Cephalodasys cambriensis (Boaden, 1963); Cephalodasys littoralis Renaud-Debyser, 1964; Cephalodasys pacificus Schmidt, 1974; and Cephalodasys turbanelloides (Boaden, 1960).