Cephalodasys saegailus, 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 : 7-9

Cephalodasys saegailus sp. n. Figure 3

Cephalodasys EgyA of Hummon (2009) [E Med & Red Sea Database]; Todaro et al. (2003: Appx. 1).

Diagnosis:

Adult Lt to 517 µm (perhaps reaching 600 µm); PhJIn at U38. Head pyriform, with a broad circumcephalic band of cilia at U02-U07, separated from the rest of the body by a long gradual neck constriction; trunk medium, broadest at the mid-body, caudum slightly flaired. Epidermis finely granular, without glands. TbA 4 per side, borne on fleshy hands; TbVL 10 per side, inserted regularly from U24 to U66, three along the rear pharynx, the others along the fore- and midgut; TbV 2 per side amid the TbVL series at U44 and U49; TbP 18 of varying lengths (12 longer, 6 shorter), inserting on the rear of 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 broadly cylindrical; pharyngeal pores basal; intestine broadest at the rear mid-body and narrowing behind; anus ventral at U92. Hermaphroditic; possibly protandric, testes begin at the PhJIn, vasa deferentia run rearward, but termini not seen; female system not seen, nor were frontal or caudal organs.

Description:

Adult Lt 492-517 µm; LPh 191-196 µm to PhJIn at U39-U38 (Fig. 3). Body transparent, strap-shaped, dorsoventrally flattened, but vaulted dorsally; head pyriform, truncated apically, with a broad circumcephalic band of cilia at U02-U07, separated from the rest of the body by a long gradual neck constriction; trunk of medium width, sides of body broadest at the mid-body, and then narrowing behind to a rounded, slightly flaired caudum. Widths of head /neck /rear pharynx /midtrunk /caudal base /caudal flair, and locations along the length of the body are as follows: 43 /31 /36 /55 /36 /38 µm at U08 /U10 /U31 /U63 /U89 /U92, respectively. Cuticle is flexible; epidermis is finely granular; glands are lacking.

Adhesive tubes:TbA 4 per side (L 6-8 µm), thick, borne on broad fleshy asymmetrical hands that insert at U11-U12; TbVL 10 per side (L 10-16 µm), insert regularly from U24 to U66, three along the rear pharynx, the others along the fore- and midgut; TbV 2 per side (L 8-9 µm) occur amidst the TbVL series at U44 and U49; TbL/TbD absent; TbP 18 of varying lengths insert in more than one row around the rear of the rounded caudum, mostly projecting rearward (longer ones, L 8-10 µm, as # 1-2, 4, 6, 8-9 from either side, and shorter ones, L 5-7 µm, as # 3, 5, 7 from either side).

Ciliation: Three sensory hairs (L 7-15 µm) project forward on either side of the mouth and others (L 10-20 µm) project obliquely from the head; a broad band of cephalic cilia (L 15-20 µm) covers the head and joins the locomotor ciliature ventrally; 18-20 sensory hairs each occur regularly in lateral (L 4-6 µm), dorsolateral (L 10-14 µm) and dorsal (L 14-20 µm) columns along each side of the trunk. Ventral locomotor ciliature forms two longitudinal bands of short (L 4-6 µm), scattered cilia that follow the lateral body contours 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 terminal, but slightly inclined to the ventral surface, medium in width (10 µm diameter); buccal cavity semi-cylindrical, lightly cuticularized, having ca. 8 short longitudinal ridges set dorsally in the oral opening; pharynx of medium breadth, narrowest just before the well-developed, basal pharyngeal pores; intestine broad in front, narrowing behind; anus ventral at U92.

Reproductive tract: Hermaphroditic, probably protandrous; testes begin at the PhJIn (U34), with vasa deferentia continuing rearward past U50, but termini not seen; female system was not yet developed; frontal organ and caudal organ not seen.

Ecology: Sparse in frequency of occurrence (fewer than 10% of samples), scarce in abundance (3-5% of a sample); sublittoral in very fine to fine, well to medium-well sorted sand at 3 m water depth.

Geographical distribution:

MED:EGYPT {Marsa Matruh [3-vid], ^Sidi Abd al-Rahman [vid]}.

Remarks:

There are four video sequences of Cephalodasys saegialus sp. n., all from the eastern Mediterranean Sea in Egypt. These are available as MPEG 2 (and MPEG 1) from Hummon (2009): #755 a mature adult Lectotype of Lt=517 µm (LPh=196 µm), collected in June 1994 from Sidi Abd al-Rahman, Egypt; #754 a mature adult of Lt=492 µm (LPh=191 µm) from Marsa Matruh, Egypt; #753 a subadult of Lt=369 µm (LPh=158 µm) also from Marsa Matruh; and the other #752 a subadult of Lt=193 µm (LPh=95 µm) again from Marsa Matruh. Cephalodasys saegialus feeds on a diversity of diatoms. The largest specimen seen was a young adult and can be expected to reach a longer length, perhaps 600 µm.

Etymology:

Saegailus (Greek: sos + aigialos = meaning 'safe shore’) refers to its shallow sublittoral habitat along the southern Mediterranean being sheltered from the west wind (zephyr).

Taxonomic affinities:

Cephalodasys saegialus sp. n. is the only species in the genus that has the following combination of characters: a pyriform head, with a transverse band of cephalic cilia, and PhJIn at U39-U38, with TbA 4 per side; TbVL 10 per side at U24-U66, with three along the rear pharynx, the others along the fore- and midgut; TbV 2 per side, amidst the TbVL at U44 & U49; TbL per se /D absent; and TbP 18, of varying sizes, insert in more than one row around the rear of the caudum, with testes but neither ova nor accessory sex organs seen. Cephalodasys saegialus belongs in the group of species that have pyriform heads, but is unique in having an extended gap between TbL and TbP and in having TbV, compared with 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).