Righiella jamiesoni Omodeo & Coates, 2001

Jamieson, Barrie G. M. & Fragoso, Carlos, 2024, A monograph of the Oligochaete family Alluroididae, Zootaxa 5529 (3), pp. 401-435 : 428-429

Righiella jamiesoni Omodeo & Coates, 2001 (see Fig 15 )

Righiella jamiesoni Omodeo & Coates, 2001 , 45–46, Figs 5B – 7 .

Length 35 mm, width 0.8 mm. Body slender, cylindrical, tapering posteriorly. Lateral lines evident in IV–XIV. Segments 105, multiannulated. Anus terminal. Clitellum annular XII–2/3XV. Male pores in XIII in the place of absent setae ab. Female pores in furrow 13/ 14 in setal line a. Spermathecal pore mid–dorsal in furrow 7/8. Setae sigmoid, slender, unsculptured, the longest in X, ca 180 µm, their length decreasing anteriad and posteriad, measuring 134 µ m in V and 156 µ m in XVI. At XX, aa: ab: bc: cd: dd =approximately 3.0:1.0:4.5:1.0:3.8. No penial setae. Cuticle 1.8 µ m thick.

Septa 4/5–11/12 fairly thick. Septal glands in V– VIII moderately developed. Nephridia without bladders, beginning in XVII. Intestine moniliform beginning in XIV; maximum diameter in XVII. Perienteric sinus beginning in XIV; commissural vessels sinuous, moderately large (diameter 18 µm) in V–XI. Muscular fibres of the body wall ribbon–shaped, ca 3 µ m thick and 25 µm high. Sperm funnels in the posterior part of XI; testes regressed; sperm sacs in XIV–XVIII. Male ducts convoluted in XIII, inserting into the prostates at their ental tips. Prostates confined to XIII; formed by an inner epithelial layer surrounded by a thin layer of muscle fibres and covered by long digitiform glands formed by cells with small nuclei; this covering disappears in the convoluted ectal portion which terminates with a penis enclosed in the terminal globular chamber. Ovaries and female funnels regressed in the posterior part of XIII, egg sac regressed, in XIV–XXIII? Two eggs in XXII and XXIII, measuring 300 by 400 µm. The spermatheca with a large globular ampulla in XII and a long duct opening in 7/8; the ectal portion of the duct filled with sperm, the ental portion narrow. Ampulla contained mucous matter containing mineral particles, fragments of sponge spicules and young gregarine trophozoites .

Distribution. Collected in a pool, between buried roots, twigs, mud and silt, next to Kurupukari creek flowing into Essequibo River, Guyana.

Remarks. Righiella jamiesoni lacks penial setae, an absence otherwise peculiar to the African Alluroidinae , but it is metandric whereas all African species are proandric; it also has more complex spermathecae. Righiella also resembles the South American Kathrynella , but that metandric genus has the male pores in XIV, has penial setae and has two simple spermathecae and thick muscular euprostates ( Omodeo and Coates, 2001).

Intestinal contents were organic matter and a few sand granules together with fragments of spiculae of freshwater sponges. The gut lumen of XVI through XL harboured many astomatous ciliates attributable to Anoplophrya , a common commensal of oligochaetes.

Figures

FIGURE 5. Alluroides brinkhursti brinkhursti Jamieson (1968). A. Transverse section (TS) of clitellum, showing single cell layer; the cells with conspicuous secretory granules and each with a basal nucleus. B. TS through the wall of the atrium, showing a group of atrial gland cells with ductule penetrating the muscular sheath of the atrium. C. Longitudinal section through the male pore, showing the ectal end of the atrium, which forms a penis with muscular sheath, ciliated epithelium and rope of spermatozoa in the lumen, forming in the ectal chamber a sperm mass. D. Alluroides pordagei. Oblique section through the atrial bulb, containing a large sperm mass, and the associated atrium. From Jamieson (2006).

FIGURE 7. Alluroides lauzannei Ljungström, 1971. Detail of an atrium. Note the vas deferens entering the apex of the atrium via canaliculi. Relabelled from Lauzanne (1968).

FIGURE 15. Righiella jamiesoni Omodeo and Coates 2001. A. Scheme showing arrangement of genital organs and vascular commissures. B. Cross section through spermathecal duct; C. Cross section through prostate. Abbreviations: a, spermathecal ampulla, at, male atrium, cv, commissural vessels, d, spermathecal duct, md, male duct, os, egg sac, pr, prostate, sps, sperm sac. From Omodeo and Coates (2001), reproduced with permission.