Brinkhurstia donaldi

Clitellum annular, 1 / 3 XII – 1 / 2 XV, male pores in the middle of XIII aligned with setae a; in a few cases the terminal chambers and the penial setae protrude through them. Female pores in furrow 13 / 14, slightly ventral to setal line a. Spermathecal pore a mid – dorsal cleft in furrow 7 / 8. Setae sigmoid, slender, unsculptured; the longest ones in XI and measure respectively: a 328 µm, b 284 µm, c 164 µm, d 280 µm; their lengths decreasing anteriorly and posteriorly; in XX, aa: ab: bc: cd: dd = 6.1: 1.0: 9.0: 1.0: 8.2. Cuticle about 2 µm thick. Septum 3 / 4 incomplete, septa 4 / 5 – 12 / 13 fairly thick. Septal glands in V through VIII. Perienteric blood sinus commencing in IX. Nephridia avesiculate beginning in XI. Dorsal and ventral vessels with large diameters; commissural vessels in V – XI tortuous with thin walls, diameter ca 17 µm; their dorsal loops in V – VIII embedded in the septal glands; commissures in X and XI compressed and hidden by large gregarine gamonts; numerous capillaries beneath and among the epidermal cells, especially in the clitellar region, and among the glandular cells covering the prostates; diameter ca 3.5 µm. Muscular fibres of the body wall ribbon – shaped, 3 µm thick, 21 µm high. Testes and seminal funnels in X; male ducts thin in XI and XII; in XIII becoming sinuous and filled with sperm, forming a highly convoluted epididymis, and finally connecting with the prostate at an intermediate point. Prostates long, convoluted, confined to XIII; with an inner layer of epithelial (glandular?) cells surrounded by a thick layer of muscle cells and covered by large, club – shaped gland cells which diminishes and then disappears near the outlet into the globular terminal chamber, which opens through as a small penial papilla. In each terminal chamber emerges a ribbon – like penial seta, whose proximal end lies in the anterior dorsal part of IX: the two penial setae, each ensheathed in a muscular sac, run parallel near the mid – dorsal line in IX, X and XI; then in XII they diverge sidewards and ventralwards, arcing around the terminal chamber in XIII and exiting through it. Ovaries in XIII; two egg sacs arise near the female funnels and extending backwards to XVI; the histology of the egg sac resembling that of Kathrynella guyanae. Ovaries and egg sacs disappear in fully mature specimens leaving two or three free large ellipsoid eggs (420 by 420 by 300 µm) in the coelom of XV and XVI. Spermatheca with a thick, spindle – shaped muscular duct that runs forward to the middle of VIII abutting on a very large, free, globular ampulla that almost fills the cavity of this segment. Near the insertion of the duct is attached a pedunculated diverticulum. Sperm contained in the diverticulum and in the ental part of the duct.

Remarks. B. donaldi differs from B. americanus, the only described congener, in the form, size and peculiar insertion of the penial setae. Its spermatheca has a diverticulum and a much longer duct (correlated with the length of the penial setae) and opens one segment more anteriorly (Omodeo & Coates 2001).

Distribution. Guyana, Kurupukari creek, flowing into Essequibo River.