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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Discordiprostatus

Discordiprostatus Baker, 1982 (ref. ID; 6552 original paper)

Family Tubificidae: Subfamily Phallodrilinae (ref. ID; 5857, 5882)

Synonym Monopylephorus Levinsen, 1884 sensu Brinkhurst, 1971 (in part); sensu Brinkhurst & Baker, 1979 (in part) (ref. ID; 6552)

ref. ID; 6552

Definition

Marine or brackish water tubificid oligochaetes. Hair setae absent. Ventral setae of XI (penial setae) modified. Ventral setae of X unmodified. Spermathecal and male pores paired in X and XI, respectively. Functional alimentary canal present. Vasa deferentia present. Atria paired, each highly modified with four distinct parts; ental part of atrium partially covered with layer of diffuse prostate cells. Ectal three parts of atrium tubular, with external muscle layer, lumen may be ciliated. Stalked prostate gland attached to ectal end of atrium, terminal part of atrium as a protrusible pseudopenis. Spermathecae slender with bulbous bases and small distal ampullae. Sperm as random masses in ampullae, sperm heads attached to or embedded in walls of ampullae. Coelomocytes small and sparse or absent. (ref. ID; 6552)

Remarks

The atria of Discordiprostatus gen. nov. are unique within the Tubificidae. No other genus possesses an anterior diffuse prostate and a posterior stalked prostate. Although Discordiprostatus resembles Nootkadrilus in some respects, the presence of vasa deferentia, atria with diffuse prostate glands, and penial setae of two distinct forms (hairlike and bifid) in Discordiprostatus clearly distinguishes this genus from Nootkadrilus. (ref. ID; 6552)

Etymology

After the two types of prostate gland (Latin discordis, different, unlike) found on atria. (ref. ID; 6552)

Type species

Discordiprostatus longisetosus (Brinkhurst & Baker, 1979) comb. nov. (ref. ID; 6552)
  1. Discordiprostatus longisetosus (Brinkhurst & Baker, 1979) comb. nov. (ref. ID; 6552 redescribed paper) reported author and year? (ref. ID; 5882)
    Syn; Monopylephorus longisetosus Brinkhurst & Baker, 1979 (ref. ID; 6552), Baker & Brinkhurst, 1981 (ref. ID; 6552)

Discordiprostatus longisetosus (Brinkhurst & Baker 1979) comb. nov. (ref. ID; 6552 redescribed paper) reported author and year? (ref. ID; 5882)

Synonym

Monopylephorus longisetosus Brinkhurst & Baker, 1979 (ref. ID; 6552), Baker & Brinkhurst, 1981 (ref. ID; 6552)

Descriptions

Marine species. (ref. ID; 5882)

Revised description

Length to 6.6 mm, 29-42 segments, width at X 240-360 µm (in fixed, slightly compressed precopulatory and sexually mature specimens), width at X in sectioned material 145-175 µm. Prostomium as long as or slightly longer than broad at peristomium, rounded cone shape. Clitellum over 1/2X-12/13 dorsally, ventrally from 9/10 to 12/13. Somatic setae bifid, anteriorly (2,3) 4-6 per bundle, upper tooth shorter and thinner than lower; posteriorly 3-4 per bundle, upper tooth much reduced or setae simple-pointed. Ventral setae of XI modified as penial setae with (5,6) 8-10 (11,12) enlarged bifid setae (setae of differing sizes within bundle) 54-103 µm long, 2.1-4.3 µm wide basally, and one very elongate, hairlike seta (220-530 µm long, maximally 2.8 µm thick) per bundle, hairlike seta in muscular sac which usually penetrates 10/11 into X, sac is attached to dorsal body wall. Male pores open posteriorly in XI on papillae, pores slightly ventral to ventral setal line; spermathecal pores open at 9/10 slightly dorsal to ventral setal line. (ref. ID; 6552)
  • Male system (all structures paired): sperm funnel relatively large, vas deferens present but short and narrow (30-38 µm long, maximally 14 µm wide); vas deferens in X, usually enclosed (covered) by a sheath of prostatic cells. Atrium tubular, composed of four parts, an ental part with reduced or absent muscle layer posterior to the vas deferens and three ectal parts with distinct external muscle layer. Ental part of atrium ciliated, partially protruded into X, composed of an anterior part with diffuse prostate cells and a posterior dilated part with no covering of diffuse prostate cells. Anterior ectal part of atrium a short ciliated duct (120-135 µm long, 17-25 µm wide) with thin muscle layer; median ectal part of atrium bulbous (120-125 µm long, 35-73 µm wide; ciliated?) with thick (7-11 µm) muscle layer; joining ectal part of atrium through abrupt narrowing. Posterior ectal part of atrium long, widening basally (240-350 µm long to tip of pseudopenis), at narrowest 27 µm wide, at widest 36 µm wide, with thin muscle layer (2.0-3.6 µm thick); stalked prostate gland entering atrium at junction of posterior median and ectal parts of atrium. Atrium terminating as protrusible pseudopenis; penial sac short. Spermathecae paired, each long and slender (225-475 µm long, 25-45 µm wide medially) with slightly bulbous base (35-70 µm wide), lumen of bulbous base not strongly cuticularized. Ampulla of spermatheca small with sperm heads embedded in distal wall. Spermatheca with thin (1-2 µm thick) external muscle layer. (ref. ID; 6552)

    Remarks

    The atrium of this species is unusual in that it bears both diffuse prostate cells and a stalked prostate gland. This feature necessitates an amendment to the present definition of the subfamily Phallodrilinae. The spermathecae in this species appear to develop after the male ducts are fully developed as many specimens were found with complete male ducts, spermatids and eggs, but missing or rudimentary spermathecae. (ref. ID; 6552)

    Type locality

    Ocean Falls, British Columbia. (ref. ID; 6552)

    Material examined

    NMCIC1979-20a, b, c (serial sections), NMCIC1979-21a, b (two whole mounts), NMCIC1979c (several specimens in fluid of which one was sectioned for this study) (all of above paratype material); Baker collection. Many other specimens from the coastline of British Columbia. (ref. ID; 6552)