Macrodasys macrurus
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Ordo: Macrodasyida
Familia: Macrodasyidae
Genus: Macrodasys
Name
Macrodasys macrurus Hummon, 2011 sp. n. – Wikispecies link – ZooBank link – Pensoft Profile
- Macrodasys EgyE Hummon (2009)[1] [E Med & Red Seas Database].
Diagnosis:
Adult Lt being described 590 µm; PhJIn at U36. Head ovoid, with a narrow band of circumcephalic cilia at U02 and pestle organs at U03; trunk broad throughout, narrowing gradually along the rear intestinal region to the long caudum. Glands inconspicuous. TbA 11 per side, in arcs that insert directly on the body; TbL 4–5 per side, with 1–2 along the fore and 0 along the rear pharynx, 3 in the rear intestinal region, and 0 behind the anus; TbD 4 per side, of similar size and spacing, in the rear half of the body from U53 to U75; TbV 17 per side, nearly even in size and spacing, with 3 along the rear pharynx, the remainder in the intestinal region, and 0 behind the anus; TbP 7 per side symmetrically along the long caudum. Locomotor ciliature: a single field from the TbA to the tip of the caudum, unciliated in spots surrounding ventral openings. Mouth terminal, of narrow width; shallow buccal cavity is lightly cuticularized, expanding with depth; pharyngeal pores sub-basal; intestine broadest in front, narrowing quickly along the mid- to hind-gut, then bending around the caudal organ; anus ventral at U83. Hermaphroditic; testes begin just before the PhJIn, vasa differentia join beneath the frontal organ; ova develop rear to front; frontal organ elongate ovate, its nozzle in close contact with the ovum, with a beak-like cavity lying on the left that has a ventral pore and an accessory chamber behind; short, thick caudal organ has spiral muscles throughout, except for the rearmost glandular sac, the fore half appearing glandular, the rear half bearing an internal canal; caudal organ barely overlapping the accessory cell of the frontal organ.
Description:
Adult being described Lt 590 µm (others Lt 477–620); LPh 192 µm (others LPh 195–203) to PhJIn at U36 (others PhJIn at U33–U41) (Fig. 7). Body medium in length as an adult, ventrally flattened, dorsally vaulted; head ovoid, bearing a narrow band of circumcephalic cilia at U02 and pestle organs at U03; trunk broad throughout, narrowing gradually along the rear intestinal region to the long caudum. Widths at pestle organs /PhJIn /trunk /anus /caudum, and locations along the length of the body are as follows: 45 /51 /58 /24 /11–7 µm at U03 /U36 /U47 /U83 /U85–U98, respectively. Glands not conspicuous.
Adhesive tubes: TbA 11 per side (L 7–9 µm), in arcs that insert directly on the postoral body surface at U02 and project from forward to obliquely outward; TbL 4–5, of similar size, with 1–2 along the fore and 0 along the rear pharynx, 3 in the rear intestinal region, and 0 behind the anal aperture; TbD 4 per side, of similar size and spacing, all in the rear half of the body from U53 to U75; TbV 17 per side, nearly even in size and spacing (L 8–12 µm), with 3 along the rear pharynx, the remainder in the intestinal region, and 0 behind the anus; TbP 7 per side (L 9–10 µm) symmetrically along the caudum.
Ciliation: Sensory hairs (L 16–20 µm) occur on either side of the mouth and on the head; a band of cilia surrounds the forehead (L 13–15 µm) at U02; other sensory hairs arise in four columns on either side of the body: lower ventrolateral (L 9–12 µm), upper ventrolateral (L 9–12 µm), lateral (L 12–14 µm) and dorsolateral (L 20–24 µm), with about 30–32, 30–32, 28 and 24 per column. Ventral locomotor ciliature forms a single field that lies from the TbA back between the TbL/V series back to the tip of the tail, with bare spots surrounding the ventral openings.
Digestive tract: Mouth terminal, narrow (9 µm diameter), surrounded by sharp tooth-like projections; shallow buccal cavity expands from oral opening to its base and is lightly cuticularized; pharynx has sub-basal pharyngeal pores at U26; intestine is broadest in front, narrowing quickly at the mid- to hind-gut and bending around the caudal organ; anus is ventral at U83.
Reproductive tract: Hermaphroditic; testes beginning just before the PhJIn, containing pulses of sperm, and extending as vasa deferentia back to the rear of the frontal organ, though their termini were not seen; ova develop from rear to front, the largest (52 × 36 µm in size) lying above the rear fore-gut; frontal organ elongate ovoid, its nozzle in close contact with the ovum, with a beak-like cavity lying on the left that has a ventral pore, and an accessory chamber to the rear; sperm not seen internally; short, thick caudal organ has spiral muscles throughout, except for the rearmost glandular sac, the fore half appearing glandular, the rear half bearing an internal canal; caudal organ barely overlapping the accessory chamber of the frontal organ.
Ecology:
Occasional in frequency of occurrence (10–30% of samples), scarce to prevalent in abundance (3 to greater than 30% of a sample; often a sub- [sdom], co- [cdom], or dominant [dom]); littoral in fine, well sorted to coarse-very coarse, poorly to very poorly sorted, coralline sand with small amounts of detritus, at low water neap to extreme low water, 0–15 cm depth; sublittoral in fine to coarse, medium well to very poorly sorted coralline sand and coral debris at 1–14 m water depth, sometimes between coral platforms or between patches of fringing reef.
Geographical distribution:
RED SEA: EGYPT:{Marsa Bareika N [sdom], Daghashland [video], Far Garden [dom] [video], Giftun Island SE [cdom] [3-videos]/SS, ^Giftun Village Spit Outside (27°10'N, 33°49'E) [video], Middle Garden, Moon Beach, Sharm el-Naga [cdom], Sharm el-Sheikh, Tip Ras Mohamed NP [video]}.
Remarks:
There are seven video sequences of Macrodasys macrurus sp. n., all from the upper Red Sea in Egypt. Five of these are available as MPEG 2 (and MPEG 1) from Hummon (2009)[1]: #1172 a mature adult of Lt=620 µm (LPh=203 µm) from Far Garden, S. Sinai, Egypt; #1167 a mature Lectotype adult of Lt=590 µm (LPh=207 µm), collected in June 1994 from Giftun Village Spit O, Egypt; #1173 a mature adult of Lt=477 µm (LPh=195 µm) from Daghashland, Egypt; #1170 a subadult of Lt=276 µm (LPh=122 µm) from Giftun Island SE, Egypt; and #1168 a juvenile of Lt=140 µm (LPh=73 µm) also from Giftun Island SE, Egypt.
Etymology:
Macrurus (Greek: macros + oura = meaning long tail) refers to the appearance of a distinctly long tail, enhanced by the relative few TbP that it bears.
Taxonomic affinities:
Macrodasys macrurus sp. n. is the only species in the genus with an ovoid head, a long tail, PhJIn at U33–U41, which also has 11 TbA per side in arcs; a TbL formula of 5=2,0/2,1 (2 along the fore and 0 along the rear pharynx/2 along the rear intestine and 1 behind the anus); a TbD formula of 4=0,0/4,0; a TbV formula of 17=0,3/14,0; and TbP 7 per side. There is no other species in the genus has a beaked frontal organ and a non-overlapping caudal organ, combined with columns of TbV and TbD, and a paucity of TbL.
Original Description
- Hummon, W; 2011: Marine Gastrotricha of the Near East: 1. Fourteen new species of Macrodasyida and a redescription of Dactylopodola agadasys Hochberg, 2003 ZooKeys, 94: 1-59. doi
Other References
- ↑ 1.0 1.1 Hummon W (2009) Tetranchyroderma parapapii sp. n. (Gastrotricha, Thaumastodermatidae), a North American analog to the European T. papii, with a redescription of the latter. Meiofauna Marina 17:121-132.
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