Bacescuella
Bacescuella Hrabe, 1973 (ref. ID; 5945, 6913)
Family Tubifidae: Subfamily Phallodrilinae Brinkhurst (ref. ID; 5945)
ref. ID; 6550
The marine tubificid genus Bacescuella was established by Hrabe (1973) for the Black Sea species B. pontica Hrabe, 1973. Subsequently, three more species have been described by Erseus (1978, 1980).
Definition (after Erseus 1980, slightly modified)
A group of meiobenthic marine, littoral tubificids. Hair setae absent. Modified genital setae absent. Male pores paired, located in the line with ventral setae in posterior part of segment XI. Spermathecal pore, if present, unpaired, located middorsally in anteriormost part of segment X. Coelomocytes, if present, small and sparse, not of the Rhyacodriline-type. Nominal alimentary canal present. Male efferent ducts paired. Vasa deferentia absent to moderately long; when present, ciliated; as wide as or slightly narrower than atria. Atria slender, tubelike; each terminating in a copulatory apparatus containing either a protrusible penis or highly modified lips. Penes (where present) without cuticular lining. Two pairs of discrete prostrate glands present, one at each end of atria. Spermatheca absent or present, one at each end of atria. Spermatheca absent or present; where present, unpaired, middorsal, small, may have loose sperm in ampulla. External spermatophores attached to epidermis in or near clitellar region. Spermatophores small, round or ovoid capsules, stalked or broadly attached, containing a random mass of sperm. (ref. ID; 6550)
Type species
Bacescuella pontica Hrabe, 1973 (ref. ID; 6550)
- Bacescuella arctica (ref. ID; 5882)
- Bacescuella labeosa Baker & Erseus, 1982 (ref. ID; 6550 original paper) reported author and year? (ref. ID; 5882)
- Bacescuella mediterranea Erseus, 1980 (ref. ID; 6550)
- Bacescuella parvithecata Erseus, 1978 (ref. ID; 6550) reported author and year? (ref. ID; 5882)
- Bacescuella pontica Hrabe, 1973 (ref. ID; 5912, 6550)
Descriptions
Marine species. (ref. ID; 5882)
Bacescuella labeosa Baker & Erseus, 1982 (ref. ID; 6550 original paper) reported author and year? (ref. ID; 5882)
Descriptions
Marine species. (ref. ID; 5882)
Length 3.1-4.0 mm, 39-46 segments, width at clitellum 0.26-0.41 mm (in fixed, slightly compressed, sexually mature specimens). Prostomium conical, rounded, about as long as broad at peristomium. Clitellum extending over segments X-XII. Pharyngeal glands extending into V (occasionally VI), chloragogen cells from VII. Anterior segments with secondary annulations. Somatic setae bifid, upper tooth shorter and thinner than lower, no modified genital setae present. Setae (3) 4-7 (8,9) per bundle dorsoanteriorly, (2,3) 4-6 (7) per bundle ventroanteriorly; posteriorly (2) 3,4 setae per bundle. No setae present in XI. Male pores paired on small papillae, in ventral setal line in posterior part of XI. Spermathecal pore unpaired, middorsal in X near IX/X. Ovoid external spermatophores in some sexually mature specimens (as many as six spermatophores observed in one specimen), attached to body wall in clitellar region. Spermatophores about 30 µm wide in shorter dimension, 43-51 µm wide in longest dimension, broadly attached to body wall, without stalks. Spermatophores very thin walled; sperm in random masses. (ref. ID; 6550)
Male system (all structures bilateral paired): sperm funnel with large lips, vas deferens ciliated, 10-12.5 µm wide, about 120 µm long; composed of nongranulated cells, joining atrium apically. Atrium tubular; 11-21 µm wide; 0.2-0.3 mm long (exact length difficult to establish) with very thin external muscle layer; atrium ciliated, composed of granular cells; large stalked prostage gland joining atrium near junction of vas deferens and atrium. Atrium joining copulatory apparatus subapically through abrupt constriction; a second large prostate gland entering atrium just ental to constriction. Copulatory apparatus upright, somewhat bilobed, narrowing basally; about 165 µm high, apically 53-57 µm wide, at constriction narrowing to approximately 30 µm wide. Apical bulb of copulatory apparatus hollow, containing two nongranular asymmetrical lips (cuticle not especially thickened). Lips protruding from inner surface of the apical bulb and surrounding entrance point of atrium; lips not attached to outer surface (surface nearest body wall). Basal part of copulatory apparatus with many internal folds, folds with slightly thickened cuticle; copulatory apparatus eversible. Spermatheca small, when fully developed 50-80 µm long, basally 25-30 µm wide with duct gradually widening towards the apical, spherical ampulla. Ampulla containing globular mass of randomly arranged sperm. (ref. ID; 6550)
Remarks
Bacescuella labeosa sp. nov. is separated from the other four members of the genus by the presence of an unpaired dorsal spermatheca (missing in B. pontica, B. arctica, and B. mediterranea), a moderately long vas deferens (short in B. parvithecata) and by the lips of the copulatory apparatus (as compared with protrusible penes in the rest of the genus). The specimens from Seal Cove and St. James Island appear identical to the Sheringham Point specimens. (ref. ID; 6550)
Habitat
Intertidal marine sands with or without freshwater influence. (ref. ID; 6550)
Etymology
The name labeosa is derived from the Latin labeosus (= with large lips). (ref. ID; 6550)
Type locality
A small beach just below the Spheringham Point lighthouse, south-west coast of Vancouver Island, 48 degrees 22.6'N, 123 degrees 55.05'W. Midintertidal silty, coarse sand, under and between large rocks; freshwater seepage present. Collected October 4, 1979. (ref. ID; 6550)
Type materials
Holotype: National Museum of Natural Sciences Invertebrate Collection (NMCIC) 1981-688, a sagittally sectioned specimen. (ref. ID; 6550)
Paratype: NMCIC 1981-689;690;691, three whole mounted specimens, the United States National Museum of Natural History (USNM) 70702-70704, one sectioned and three whole mounted specimens all paratypes (from type locality and date). (ref. ID; 6550)
Other material examined:
- H.R. Baker collection: Four mature (postcopulatory) specimens collected October 4, 1979 and five not quite mature (precopulatory) specimens collected September 7, 1979; all from type locality. One specimen (precopulatory) from the east side of St. James Island, Queen Charlotte Islands, 51 degrees 56.1'N, 130 degrees 0.1'W; lower intertidal shell sand under and between rocks in Egregia menziezii zone, without noticeable freshwater influence; collected May 16, 1980. One mature specimen from Seal Cove near the Prince Rupert Coast Guard Base, Prince Rupert, 54 degrees 19.85'N, 130 degrees 16.65'W; very muddy sand with some freshwater influence. Collected May 15, 1980. (ref. ID; 6550)
- C. Erseus collection: one sectioned, mature specimen collected October 4, 1979, and five specimens (precopulatory) collected September 7, 1979; all from type locality. (ref. ID; 6550)
Bacescuella parvithecata Erseus, 1978 (ref. ID; 6550) reported author and year? (ref. ID; 5882)
Descriptions
Marine species. (ref. ID; 5882)
Descriptions
See the description of Phallodrilus. (ref. ID; 5912)