Tetranchyroderma sinaiensis, 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 : 30-32

Tetranchyroderma sinaiensis sp. n. Figure 15

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

Diagnosis:

Adult Lt 423 µm; PhJIn at U34. Body of medium length, narrow; head end rounded, without pestle organs, tentacles or lobes; neck indistinct along the rear pharynx, trunk broadening slightly in the mid-body, before narrowing gently to the caudal base; caudal pedicles short, borne on short lobes, with a wide concave margin separating the two lobes, incising medially to U97. Glands 8 per side, small, scattered in lateral columns. Epidermis covered with tetrancres of similar size, slightly smaller fore and aft; ancres occur in 45-50 rows of 9-10 ancres each, excluding the entire oral hood, but extending onto the base of the caudal lobes. TbA 7 per side forming arcs radiating from forward to outward, tubes inserting directly on the postoral body surface at U03-U05; TbVL 43 per side, 1 at U06, a group of 36 at U25-U80, 1 at U89, and a group of 5 at U93-U97; TbV 5 per side in a transverse row at U85; TbDL 9 per side, of two sizes, 7 (short) subequally spaced at U10-U90, and 2 (long) at U86 and U93; TbL/D per se absent; TbP 5 per side on the caudal pedicles, forming the fused 'two fingers and a thumb’ typical of the family, supplemented by a cirrata-like structure projecting from between the ‘fingers,’ with 5 additional tubes in the space between the peduncles. Locomotor ciliature: a single field that covers the entire ventral surface at U04-U96. Mouth subterminal, as broad as the fore end of the body; buccal cavity lightly cuticularized; pharynx, broad throughout, has inconspicuous basal pores; intestine narrows fore to aft, anus is ventral at U94. Hermaphroditic; testis on left side as seen from below; vas deferens appears to open in front of the anus; developing ovum occurs above the hindgut; caudal organ is longitudinally ovoid and thick-walled, with an interior of refractive material and a central canal in the fore half; frontal organ is ovoid, hyaline and bi-layered, bearing active sperm, and partly embedded in the rear of the ovum.

Description:

Adult Lt 423 µm (others Lt 241-410); LPh 146 µm (others LPh 95-141) to PhJIn at U34 (others PhJIn at U39-U34) (Fig. 15). Body of medium length, narrow, ventrally flattened, dorsally vaulted; head end rounded, without pestle organs, tentacles or lobes; neck indistinct along the rear pharynx, trunk broadening slightly in the mid-body, before narrowing gently to the caudal base; caudal pedicles short (L 11 µm) borne on short lobes, with a wide concave margin separating the two lobes, incising medially to U97. Widths at mouth /rear pharynx /mid-gut /caudal base, and locations along the length of the body are as follows: 21 /36 /49 /27 µm at U02 /U25 /U61 /U97, respectively. Glands 8 per side (4-6 µm diameter) scattered in lateral columns at U08-U90.

Cuticular armature: Epidermis armored with tetrancres, taller than wide (L 6, W 3 µm), of much the same size over much of the body, slightly smaller fore and aft; ancres cover dorsal surface in some 45-50 rows of 9-10 ancres each, being absent from the oral hood, but extending onto the base of the caudal lobes.

Adhesive tubes: TbA 7 per side (L 3-5 µm), forming arcs radiating from directly forward to obliquely outward, the medial-most being smaller than the other 6 and set slightly to the rear of the arc, all tubes inserting directly on the postoral body surface at U03-U05. TbVL 43 per side, 1 at U06 (L 8 µm), just behind the TbA, a group of 36 at U25-U80 (L 10-12 µm), 1 at U89 (L 10 µm), and a group of 5 at U93-U97 (L 10-12 µm); TbV 5 per side (L 11-12 µm) in a transverse row at U85; TbDL 9 per side, of two sizes, 7 (L 6-8 µm) subequally spaced at U10, U28, U44, U55, U65, U75 and U90, and 2 (L 17-19 µm) at U86 and U93; 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 7 µm, L tube on the inner margin 4 µm), supplemented by a blind cirrata-like structure projecting dorsoposteriorly from between the ‘fingers,’ with 5 additional tubes (L 5 µm) in the space between the peduncles 3 on one side and 2 on the other.

Ciliation: Short sensory cilia surround the oral opening (L 2-4 µm), with a number on the oral hood and several laterally (L 15-24 µm), the longer ones being vibratile; other cilia occur regularly along the lateral (L 8-11 µm) and dorsolateral (L 14-17 µm) body surfaces, numbering 23 each. Ventral locomotor ciliature forms a single field of transverse rows from TbA to anus, lying between the TbVL columns, the field narrowing from anus to caudal base; individual cilia are 6-8 µm in length.

Digestive tract: Mouth subterminal, as broad as the fore end of the body (15 µm width); oral hood extends from U00 to U02; buccal cavity lightly cuticularized; pharynx, broad throughout, has inconspicuous basal pores; intestine narrows gradually front to rear and bends around the reproductive organs in the hind-gut region; anus is ventral at U94.

Reproductive tract: Hermaphroditic, testis on right side as seen from above (left side as seen from below); vas deferens opens in front of the anus; developing ovum (up to 48 × 32 µm) occurs above the hindgut; caudal organ, large, longitudinally ovoid and thick-walled (43 × 12 µm), has an anterior protuberance, a concentric circular pore in the rear, an interior of refractive material, and a central canal in the fore half; frontal organ, ovoid, hyaline and bi-layered, bears active sperm, and is partly embedded in the rear of the ovum.

Ecology:

Common in frequency of occurrence (30-60% of samples), scarce to prevalent in abundance (3% to greater than 30% of a sample, occasionally a co- [cdom] or dominant [dom]); sublittoral in very fine to medium, well to medium sorted sand at 0.5-10 m water depth (sometimes in very fine-very to coarse, poorly to very poorly sorted sand at 2-15 m water depth, amid fringing corals or between coral platforms, of both healthy and unhealthy corals, or at 1.5 m water depth at the base of a seagrass bed).

Geographical distribution:

RED SEA:EGYPT {Abu Ramada 1 [video], Abu Ramada 2 [dom], Abu Ramada 3, Marsa Bareika N [dom], Daghashland [video], Far Garden [2-videos], Giftun Island SE [video], Main Beach Ras Mohamed NP [cdom], Moon Beach, Moon Valley, ^ Na’ama Bay S (27°53'N, 34°19'E) [3-videos], Nabq S [video], Ras Nasrani, Ras Qanti [video], Tareef el-Reeh S [dom]}; ISRAEL: {Coral Beach M2, M3, M4 & M5, Princess Hotel [video], Snuba DS [video]}.

Remarks:

There are 12 video sequences of Tetranchyroderma sinaiensis sp. n., all from the upper Red Sea in Egypt and Israel. Five of these are available as MPEG 2 (and MPEG 1) from Hummon (2009): #1505 a mature Lectotype adult of Lt=423 µm (LPh=146 µm), collected in July 1994 from Na’ama Bay, S. Sinai, Egypt; #1504 a mature adult of Lt=410 µm (LPh=141 µm) from Giftun Island SE, near Hurghada, Egypt; #1508 a mature adult of Lt=371 µm (LPh=110 µm) from Ras Qanti, S. Sinai, Egypt; #1506 a mature adult of Lt=241 µm (LPh=95 µm) also from Na’ama Bay; and #1509 a juvenile of Lt=154 µm (LPh=73 µm) from Far Garden, S. Sinai, Egypt.

Etymology:

Sinaiensis (pronounced ‘sinaiënsis’ with a dieresis over the ‘e’ to indicate that it is to be pronounced separately from the diphthong ‘ai’) is named after the geographical region, the Sinai Peninsula, in which it was first found.

Taxonomic affinities:

Tetranchyroderma sinaiensis sp. n. is the only species of medium length in the genus without pestle organs, tentacles or lobes, a PhJIn at U39-U34, and tetrancres, which also has TbA 7 per side; TbVL 43 per side, two solitary tubes at U06 and U89, and two groups of 36 at U25-U80 and 5 at U93-U97; TbV 5 in a row on either side at U85, TbDL 9 per side, of two sizes, 7 short at U10-U90, and 2 long at U86 and U93, TbP 3 per side as 'two fingers and a thumb’ on small pedicles with a blind cirrata-like structure inserting between the ‘fingers’ and 5 additional tubes in the space between pedicles, but lacking TbL/D per se. Tetranchyroderma pachysomum Hummon, Todaro & Tongiorgi, 1993 is the only other species in the genus that has tetrancres, TbD and TbV, but it is a short, squat animal, with differing numbers and arrangements of adhesive tubes than in Tetranchyroderma sinaiensis sp. n.