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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Diachaeta

  1. Diachaeta (D.) mura Righi, 1989 (ref. ID; 6019)
  2. Diachaeta (D.) xpe Righi, 1992 (ref. ID; 6019 original paper)

Diachaeta (D.) xpe Righi, 1992 (ref. ID; 6019 original paper)

Descriptions

Length 25 mm, middle-body 1.2 mm dia. Number of segments 128. Pigment absent. Tentaculiform, short and thick prostomium invaginated with segment I. Setae disposed in 4 pairs of regular longitudinal series from II onwards. The setae are sigmoid, with distal nodulus, unicuspidate apex and without ornamentation. The setae length varies from 87 to 107 µm (M=97 µm) in the middle-body and from 92 to 158 µm (M=124 µm) in the posterior region, the smaller setae are lateral. There are no differentiated genital setae. The setal relations are in the middle-body region (segments XLV-L) aa:ab:bc:cd:dd=5.1:1.0:6.0:0.7:14.3 (ab=90 µm) and in the posterior region (segments CXIX-CXXV) aa:ab:bc:cd:dd=3.7:1.0:4.1:0.7:9.9 (ab=96 µm). The clitellum lies in segments XIII-XXIII (=11), it is annular, most tumid in the dorsum and with well-marked intersegmental furrows. The pair of ridges of puberty are slender and milk-white, and are positioned a little below the line of setae c in 1/2 XVII-1/2 XX. The genital pores are microscopic. The male pores open in the ventral region of XIX, on the ridges of puberty and the female pores are posterior in XIV, line a. The nephridiopores open soon after the intersegmental furrows, in line with c or cd. Dorsal pores are recognized from 4/5 or 5/6 backwards. The septa 6/7-11/12 are funnel-shaped and long, 8/9-11/12 are the thickest, the following are slender and flat. A large, conic and very muscular gizzard lies in the cavity of VI, but it corresponds externally to parietal segments VII-IX. The three pairs of calciferous glands open into the ventral side of the oesophagus in VII-IX. They are small, sac-like and they have tubular structure. The oesophagus become larger from X to XIV, where it is milk-white in colour and its mucosa has high longitudinal and very vacuolarized folds. The transition oesophagus-intestine lies in XVII. The intestinal diameter grows to XIX, continuing uniformly in the rear. There are no intestinal caeca. The typhlosole begins in XIX, it increases up to XXI, going uniformly backwards. In the crosss-section it is an unfolded dorsal thick blade and it is 1/3 of the height of the intestine. Three pairs of thin lateral hearts are in VII-IX and 2 pairs of bulky intestinal hearts are in X and XI. There is one subneural vessel. Each segment has one pair of holonephridia with a large preseptal funnel and 3 postseptal loops. The duct between loops I and II and the bladder (loop III) is not glandular. The nephridiopores have no sphincter. One pair of testes sacs coalesces ventrally in XI ascending at the side of the oesophagus. The pair of slender tubular seminal vesicles is ventral in XIII-XIV, it is wide and dorsal at the rear, ending in XVII. One pair of ovaries and female funnels lie in XIII. There are not spermathecae. (ref. ID; 6019)

Remarks

Diachaeta (D.) xep is very near to D. (D.) mura Righi, 1989, known in Brazil, State of Amazonas, Manaus. The two species are distinguished by colour, setae and dorsal pores. (ref. ID; 6019)

Etymology

The name of the new species comes from the Tupi language where xepe=smooth, referring to the surface of the setae. (ref. ID; 6019)

Type locality

The worms were collected manually from the soil in Peru, Department of Loreto' Yurimaguas (5 degrees 54'S-76 degrees 05'W) in 1987 and preserved in 10% formalin. The study was made by dissections, pieces mounted in glycerine-water (1:1) and serial histological sections (10 µm) stained by Mallory's triple method (Pantin 1964). (ref. ID; 6019)

Examined materials

One clitellate worm (ZU-123). (ref. ID; 6019)

Type deposited

The material is deposited in the Department of Zoology, University of Sao Paulo, Brazil. (ref. ID; 6019)