Tetranchyroderma corallium, 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 : 26-27

Tetranchyroderma corallium sp. n. Figure 13

Tetranchyroderma EgyF Hummon (2009) [E Med & Red Seas Database]

Diagnosis:

Adult Lt 332 µm; PhJIn at U29. Body short, robust; head end truncated, without pestle organs, tentacles or lobes; lacking any neck; trunk broadening through out the pharyngeal region, then even more along the fore-gut, before narrowing gradually to the caudal base; cirrata 6 per side of nearly similar lengths, dorsolateral at U10, U30, U45, U62, U79 and U96; caudal pedicles medium, borne on fleshy lobes, with a broad concave margin separating the two lobes, incising medially to U94. Glands 6 per side (3-8 µm diameter) in lateral columns at U15-U79. Epidermis covered with pentancres twice as long as wide, with the center tine 20% longer than the others, though ancres are smaller fore and aft; ancres occur in 55-60 rows of 15-17 ancres each, extending onto the rear of the oral hood and onto the caudal lobes. TbA 7 per side forming 3 rows of 2, 3 and 2 tubes, all projecting obliquely forward, tubes inserting directly on the postoral body surface at U05-U07; TbVL 18 per side, 1 at U08, a group of 11 at U25-U71, 1 at U80, and a group of 5 at U86-U95; TbV 3 per side, 1 at U65 and 2 at U72; TbDL 4 per side (L 17-19 µm) at at U13, U47, U64 and U80; TbL/D per se absent; TbP 3 per side on the caudal pedicles, forming the fused 'two fingers and a thumb’ typical of the family, supplemented by the last of the dorsal cirrata, with 5 additional tubes in the space between the peduncles. Locomotor ciliature: a single field that covers the entire ventral surface from TbA to the anus. Mouth subterminal, as broad as the fore end of the body, lightly cuticularized buccal cavity, pharynx with inconspicuous basal pores; intestine narrows fore to aft, anus ventral at U91. Hermaphroditic; testis on left side as seen from below; vas deferens opens in front of the anus; developing ovum occurs above the hind-gut; caudal organ ovoid and thick-walled; frontal organ spherical, hyaline, bearing active sperm, partly embedded in the rear of the ovum.

Description:

Adult Lt 280-332 µm; LPh 85-80 µm to PhJIn at U30-U29 (Fig. 13). Body short, robust, ventrally flattened, dorsally vaulted; head end truncated, without pestle organs, tentacles or lobes; lacking any neck, broadening through out the pharyngeal region, then even more along the fore-gut, before narrowing gently to the caudal base; cirrata 6 per side of nearly similar lengths (L 16-22 µm), dorsolateral at U10, U30, U45, U62, U79 and U96, the last one homologous with the cirratum that is so often associated with the pedicles; caudal pedicles medium (L 17 µm), borne on fleshy lobes, with a broad concave margin separating the two lobes, incising medially to U94. Widths at mouth /rear pharynx /mid-gut /caudal base, and locations along the length of the body are as follows: 26 /49 /53 /32 µm at U01 /U29 /U48 /U96, respectively. Glands 6 per side (3-8 µm diameter) scattered in lateral columns at U15-U79.

Cuticular armature: Epidermis armored with pentancres (L 5, W 2 µm), much taller than wide, the central tine 20% longer (L 6 µm) than the other four (Fig. 13 B); ancres of similar size over much of the body, but are smaller fore and aft; ancres cover dorsal and lateral surfaces in some 55-60 rows of 15-17 ancres each, extending onto the rear of the oral hood and onto the caudal lobes.

Adhesive tubes: TbA 7 per side (L 4-6 µm), forming three rows of 2 (medial), 3 (lateral) and 2 (smaller, behind the lateral) tubes, all projecting obliquely forward and all inserting directly on the postoral body surface at U05-U07; TbVL 18 per side (L 4-10 µm), 1 at U08, inserting just behind the TbA, a group of 11 at U25-U71, 1 at U80, and a group of 5 at U86-U95, the first tube being shorter than the others; TbV 3 per side (L 7-9 µm), 1 at U65 and a row of 2 at U72; TbDL 4 per side (L 7-10 µm) at U13, U47, U64 and U80; TbL/D per se 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 4-5 µm, L tube on the inner margin 6 µm), supplemented by the last of the dorsal cirrata, with 5 additional tubes (L 8-9 µm) in the space between the peduncles.

Ciliation: Short sensory cilia occur around the ventral oral opening (L 4 µm), with a number on the oral hood (L 7-8 µm), 1 longer per side (L 36 µm) being quite active, as well as numerous cilia laterally (L 5-12 µm); other cilia (L 12-20 µm) occur regularly along the lateral, dorsolateral and dorsal body surfaces, numbering 12-13 each. Ventral locomotor ciliature forms a single field of transverse rows from TbA to anus, lying between the TbVL columns; individual cilia are 6-8 µm in length.

Digestive tract: Mouth subterminal, as broad as the fore end of the body (23 µm width); oral hood extends from U00 to U04; buccal cavity is lightly cuticularized; pharynx has inconspicuous basal pharyngeal pores; intestine narrows gradually front to rear; anus is ventral at U91.

Reproductive tract: Hermaphroditic, testis on right side as seen from above (left side as seen from below); vas deferens appears to open into the caudal organ in front of the anus; the developing ovum (up to 49 × 22 µm) occurs above the hind-gut; caudal organ ovoid (14 µm outer diameter) is thick-walled, except where the vas deferens enters; frontal organ spherical and hyaline, bearing active sperm, partly embedded in the rear of the ovum.

Ecology:

Sparse in frequency of occurrence (fewer than 10% of samples), rare to scarce in abundance (fewer than 1% to 5% of a sample); littoral in medium fine to medium, medium sorted coralline sand at low water neap to low water spring, 0-10 cm depth; sublittoral in fine to medium-fine, well to medium sorted coralline sand at 1.5-3 m water depth (sometimes in very fine to very coarse, very poorly sorted coralline sand at 14 m water depth, between coral platforms).

Geographical distribution:

RED SEA:EGYPT {Sharm el-Arab Inside, Wadi 'Araba [video], Marsa Bareika N, ^Middle Garden (27°54'N, 34°21'E) [2-videos]}.

Remarks:

There are three sequences of Tetranchyroderma corallium sp. n., all are from the upper Red Sea of Egypt. These are available as MPEG 2 (and MPEG 1) from Hummon (2009) #1519 a mature adult of Lt=332 µm (LPh=110 µm) from the Wadi 'Araba, Egypt; #1518 a mature Lectotype adult of Lt=280 µm (LPh=85 µm), collected in July 1994 from Middle Garden, off Ras Mohamed National Park, S. Sinai, Egypt; and #1516 a subadult of Lt=156 µm (LPh=79 µm) also from Middle Garden.

Etymology:

The species is named with reference to the coralline-calcareous sediment in which it was always found.

Taxonomic affinities:

Tetranchyroderma corallium sp. n. is the only small species in the genus without pestle organs, tentacles or lobes, a PhJIn at U29-U33, 6 cirrata of similar size and spacing per side, and pentancres twice as long as wide, with a more elongate central tine, which also has TbA 7 per side in three rows of 2, 3 and 2 tubes; TbVL 17 per side, solitary tubes at U08 and U80, and two groups of 11 at U25-U71 and 5 at U86-U95; TbV 3 per side, 1 at U65 and 2 at U72; TbDL 4 per side at U13, U47, U64 and U80; TbP 3 per side as 'two fingers and a thumb’ on small pedicles supplemented by the last of the dorsal cirrata, and 5 additional tubes in the space between pedicles. There are only two pentancrous species, whose central tine is longer than the other tines: Tetranchyroderma polyacanthus (Remane, 1926) and Tetranchyroderma tanymesathrum Hummon, Todaro, Balsamo & Tongiorgi, 1996, neither of which have the TbD or TbV that are present in Tetranchyroderma corallium sp. n.