Vadicola
Vadicola Baker, 1982 (ref. ID; 7824)
Family Tubificidae: Subfamily Rhyacodrilinae (ref. ID; 5857, 5882, 7824)
ref. ID; 7824
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. (ref. ID; 7824)
Male genitalia (all structures paired): vas deferens ciliated, composed of large cells with granular contents, entering atrium subapically or apically. Atrium nonciliated, upright with bulbous head and narrow ejaculatory duct leading to protrusible pseudopenis; atriai lumen leads through a small internal projection in the ejaculatory duct. Diffuse prostate cells on atria absent. Spermathecae with broad bases and large ampullae. Sperm in random masses in ampullae, not attached to walls of ampullae. Coelomocytes large and abundant. (ref. ID; 7824)
Notes
Vadicola gen. nov. is placed in the subfamily Rhyacodrilinae because of the presence of large and abundant coelomocytes, randomly arranged masses of sperm in the spermathecae, rhyacodrline penial setae, and upright atria with the vas deferentia entering apically or just subapically (see Baker and Brinkhurst 1981 for a definition of the Rhyacodrilinae). Vadicola is easily separable from most genera of the Rhyacodrilinae. Monopylephorus, Bothrioneurum, Rhizodrilus, Branchiura and Peristodrilus (see Baker and Brinkhurst 1981, Fig.13), as well as Protruberodrilus Giani and Martinez-Ansemil, 1979 and Paranadrilus Gavrilov, 1955, all have diffuse prostate cells on the atria. This character alone effectively separates Vadicola (without diffuse prostate cells) from the above genera. Epirodrilus Hrabe, 1930 and Jolydrilus Marcus, 1965 both lack prostate cells but the male ducts are quite different from those of Vadicola (compare Fig.2 in this paper with Fig.13 in Baker and Brinkhurst 1981). This leaves only Rhyacodrilus to be separated from Vadicola. All species of Rhyacodrilus possess diffuse prostate cells except for two species from New Zealand. These two species (R. simplex (Benham, 1903), R. fultoni Brinkhurst, 1982) also lack hair and pectinate setae in the dorsl setal bundles (as does V. aprostatus). However, they lack an internal projection of the ejaculatory duct as found in V. aprostatus. In V. aprostatus the cells of the vasa deferentia are modified to act as secretory cells of some type (shown by the very granular inclusions and large size). The lack of diffuse prostatic cells on the atria is taken as evidence that the vasa deferentia are performing part of the supposed functions of the prostate cells (Jamieson 1981). In R. simplex the vasa deferentia are said to be comparatively thick (Benham 1903, p.211) but are figured as being 13-15 µm thick (Benham 1903, Plate XXIV, Fig.8) or as being oval shaped in two cross sections (Benham 1903, plate XXIV, Fig.9; 26x8 µm, 38x10 µm). The cells do not appear to have granular inclusions. In R. fultoni the vasa deferentia are about 25 µm thick and the cells do not appear to have granular inclusions (personal observation). The vasa deferentia in V. aprostatus range from 45 to 75 µm in thickness. It is interesting to note that in both R. simplex (Benham 1903, Plate XXIV, Fig.9) and R. fultoni (personal observation) the atrial lining cells are very large and granular while in V. aprostatus the atrial lining layer is very thin and not especially granular. It is possible that the atrial cells in R. simplex and R. fultoni have the same secretory function as diffuse prostate cells would with the vasa deferentia acting merely as a sperm transport system. In V. aprostatus, with a thin atrial cell layer, the vasa deferentia appear to act as a secretory organ and as a sperm transport system. In the other members of Rhyacodrilus the prostate cells are secretory and therefore the remaining atrial lining cells in these species are most likely not secretory. These differences between Rhyacodrilus sensu strictu and R. simplex and R. fultoni, lead Brinkhurst (1982) to suggest that these species might be separable from Rhyacodrilus once the genus was revised. Rhyacodrilus simplex and R. fultoni, although sharing some of the characteristics of V. aprostatus, are distinct from, and are not considered to be closely related to, V. aprostatus. The internal projection in the ejaculatory duct of V. aprostatus is unique within the Rhyacodrilinae. This projection is obvious in both whole-mounted and sectioned specimens. In Rhyacodrilus the ejaculatory duct has never been reported as being modified (i.e. see Sokolskaya 1976; Semernoi 1971; Brinkhurst 1971, 1982). Jolydrilus possesses a penial sac into which the terminal end of the atria protrudes as a true penis (Marcus 1965); this is not analogous to the projection of the ejaculatory duct in Vadicola. The internal projection of the ejaculatory duct of Vadicola is not believed to be an intromittant organ. Although Vadicola is similar to Rhyacodrilus in some respects, I do not consider it appropriate to widen the definition of Rhyacodrilus to include a species with modified ejaculatory ducts and a marine habitat, especially as Rhyacodrilus is sorely in need of revision (R.O. Brinkhurst, personal communication). (ref. ID; 7824)
Note added in proof
Ainudrilus oceanicus gen et sp. nov. has recently been described by Finogenova (1982) and placed in the Rhyacodrilinae. Although the genital system is superficially similar to that of V. aprostatus, A. oceanicus possesses short vasa deferentia with long tubular atria leading to the copulatory chambers. The atria also possess prostatic cells which are imbedded in the atrial cells walls instead of having the main cell body lie in the coelum. Vadicola aprostatus, with no recognizable prostatic cells on the atria or vasa deferentia, is easily separable from A. oceanicus. (ref. ID; 7824)
Etymology
From the Latin vadum, shallow place; and the Latin colere, to abide, dwell, inhabit; dwelling in the shallows. (ref. ID; 7824)
Distribution
Known only from British Columbia. (ref. ID; 7824)
Type species
Vadicola aprostatus Baker, 1982 (by monotypy) (ref. ID; 7824)
- Vadicola aprostatus Baker, 1982 (ref. ID; 7824 original paper) reported author and year? (ref. ID; 5882)
Vadicola aprostatus Baker, 1982 (ref. ID; 7824 original paper) reported author and year? (ref. ID; 5882)
Descriptions
Marine species. (ref. ID; 5882)
Length 15-23 mm, 75-95 segments; diameter at XI (in fixed, sexually mature, whole mounted, slightly compressed specimens) to 1200 µm, diameter at XI in sectioned material 435-550 µm. Prostomium longer than broad at peristomium, bluntly conical. Coelomocytes abundant anteriorly. Clitellum from 9/10 dorsally, from behind spermathecal pores ventrally; to 1/3 XIII. Anterior setae 3-5 per bundle, posteriorly 2-3 per bundle; all somatic setae with upper tooth thinner and shorter than lower. Ventral setae of XI modified as penial setae with (4-5)6-7 setae per bundle, penial setae (ps) enlarged, straight, with bifid tips; 180-200 µm long, maximally 9.0 µm wide. Penial setae arranged in fan shape with setal heads very closely applied, setal bases well separated; setae enclosed in muscular sac. Muscular sac with large retractor muscles attached to dorsal wall of XI. Male pores paired posteriorly in XI in ventral setal line; spermathecal pores paired in X near 9/10, slightly dorsal to ventral setal line. (ref. ID; 7824)
Male system (all structures paired): sperm funnel (sf) large with asymmetrical lips; lower lip up to 530 µm long, 2-3 times as long as upper lip. Vas deferens (vd) 45-55 µm wide behind sperm funnel, 47-75 µm wide through rest of length; lumen ciliated, 19-23 µm wide. Vas deferens approximately 580-630 µm long, enters atrium apically or just subapically through abrupt narrowing. Cells of vas deferens with very granular contents. Muscle fibers plus some peritoneal cells run among coils of vas deferens. Atrium (a) upright, nonciliated, with bulbous head and narrow ejaculatory duct leading to pore; atrium 230-380 µm high, bulbous head 120-130 µm wide, ejaculatory duct 24-30 µm wide. Atrium with small projection (pj) contained in ejaculatory duct; lumen of ejaculatory duct runs through projecton, ejaculatory duct 31-47 µm wide at projection. Atrium enclosed in layer of loose muscle fibers (mf) and peritoneal cells, muscle fibers 6-14 µm thick over atrial head thickening basally. Atrial head lacking prostate cells. Atrium terminates in a slightly protrusible pseudopenis. Spermatheca (sp) paired, each with broad base (56-70 µm wide) and narrow duct (47-52 µm wide, 105-130 µm long) leading to large spermathecal ampulla; walls of ampulla thick basally, thinning to approximately 3 µm apically. Spermathecal ampulla may extend into IX; sperm in ampulla as loose masses, not attached to walls of ampulla. Spermathecal pores transverse slits. (ref. ID; 7824)
Remarks
Vadicola aprostatus gen. nov., sp. nov., is separable from other members of the Rhyacodrilinae, especially species of Rhyacodrilus, by the absence of diffuse prostate cells on the atria, the projection within the atrial duct, and the marine or brackish-water habitat in which it is found. The layer of muscle fibers and peritoneal cells in V. aprostatus covers the atria entirely; peritoneal cells are visible on the atrial heads but no distinct prostate cells can be observed. This layer of muscle fibers is not compact but is rather loose so that the thickness varies considerably. The penial setae are usually oriented so that they appear simple pointed; manipulation of the setae reveals their bifids tips. (ref. ID; 7824)
Etymology
From the Greek a, without; and the Greek prostates, a gland of the male duct; without prostates. (ref. ID; 7824)
Habitat
Intertidal sediments usually without freshwater influence, sediments often coarse. Mature specimens found August 23, September 7 and October 4, 1979, at Spheringham Point, and August 23, 1981 near the north tip of Hunter Island. (ref. ID; 7824)
Distribution
The whole coast of British Columbia including the Queen Charlotte Islands. (ref. ID; 7824)
Type materials
Holotype: NMCIC1982-1481, a whole-mounted specimen. Type locality: A small beach just below the Sheringham Point Lighthouse, southwest 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 by H.R. Baker, October 4, 1979. (ref. ID; 7824)
Paratypes: NMCIC1982-1482 - NMCIC1982-1485, three whole-mounted specimens and one sectioned specimen from the type locality. USNM074356-074359, three whole-mounted specimens and one sectioned specimen from the type locality. (ref. ID; 7824)
Other material examined: Baker collection. Thirty specimens from the type locality, collected August 23, September 7, and October 4, 1979. One specimen from north side of Hazel Point, Smith Island, Skeena River estuary, 54 degrees 7.1'N, 130 degrees 14.6'W; silty sand under large boulders, midintertidal in Fucus zone, collected by H.R. Baker July 29, 1979. Six specimens from north side of Cape Knox, Graham Island, Queen Charlotte Islands, 54 degrees 10.7'N, 133 degrees 1.0'W; silty, coarse sand under large boulders, in Egregia menziesii zone (a brown algae), lower intertidal, collected by H.R. Baker and K.A. Coates May 18, 1980. Fifteen specimens from six locations near Calvert Island and Hunter Island, sampling sites from 52 degrees 3.0'N, 128 degrees 19.0'W to 51 degrees 29.0'N, 127 degrees 45.0'W, sediment shell sand or coarse sand, usually not silty, lower intertidal in Fucus zone, only one location with obvious freshwater flow over sampling site; collected by H.R. Baker and K.A. Coates, August 20-23, 1981. (ref. ID; 7824)