Rhizodriloides
Rhizodriloides Juget, 1987 (ref. ID; 6585 original paper)
- Rhizodriloides phreaticola Juget, 1987 (ref. ID; 6585 original paper)
Descriptions
Length 3-4 mm, up to 50 segments, width at segment V up to 0.24 mm, width at clitellum up to 0.40 mm. Prostomium conical with rounded tip, about as long as broad at peristomium, 65-100 µm long. Clitellum well developed, from X to XII; body wall at clitellum in XI up to 40 µm.
Setal formula:
- 1-2-3-4-5 3-4-5 2-3-4-5
- 1-2-3-4-5-(6) 4 to 11 2-3-4-5
Somatic setae exclusively bifid with upper tooth shorter and thinner than lower, 44-57 µm long, with distal nodulus. Number of somatic setae 1 to 5 (exceptionaly 6) in preclitellar segments, 2 to 5 in postclitellar segments; all dorsal and ventral setae similar in shape. Penial setae in XI inserted as an arc, 4-11 per bundle, 50-60 µm long, 1-2 µm wide, with subterminal nodulus and hooked tip. The penial setae are sometimes lacking in clitellate specimens. Large globular coelomocytes do not occur in the body cavity. Male duct with large sperm funnel at X, vas deferens joins atrium apically. Atrium oval, up to 80 µm long and 30 µm wide. The prostate gland consists of a cellular layer covering the atrium. Long eversible pseudopenis large penis sac, 40 µm wide; length of everted penis up to 200 µm. The opening of male pores are ventral and the distance from one another is about 60 µm. Spermathecae in X or X-XI, with elongate ampulla divided into a proximal and distal portion the total length of which may reach 200 µm, 3 to 6 times longer than the mean width. Ampullae filled with thread-like spermatozoa. Spermatozeugmata or spermbundles absent. Short ducts with muscular wall opening in ventral setal line. Sperm sacs extend into segment VIII anteriorly and segment XIII posteriorly, ovisacs extend into segment XIV. (ref. ID; 6585)
Discussion
The large eversible pseudopenes eliminate this species as a Rhyacodrilus in Rhyacodrilinae. The absence of coelomocytes, the location of the spermathecae in X, the sructure of the male ducts with vas deferens longer than the atrium and entering it apically, the eversible pseudopenes in muscular penial sacs, the modified penial setae constitute a combination of features unique within the subfamily. According to Dr. Brinkhurst (pers. com.), R. phreaticola looks like the "missing link" between Rhizodrilus and Monopylephorus. The etymology of the newly erected genus Rhizodriloides takes into account its affinities with those two taxa. The somatic characters of R. phreaticola resemble those of Rhyacodrilus balmensis Juget, 1959, described from a lake cave (Jura) and living with R. phreaticola and R. amphigenus in subterranean waters of the alluvial plain of the Rhone. R. phreaticola and R. balmensis are distinguished chiefly by details of the male genitalia. R. phreaticola has eversible pseudopenes and penial sacs. Non eversible pseudopenes of R. balmensis are contained and open in the anterior part of large prominent glandular porophores. Recent examination of some living specimens of R. balmensis from the cave of La Balme (Jura) enabled us to supplement the original description of this species. (ref. ID; 6585)
Ecological notes
Rhizodriloides phreaticola is a stygobiont limivorous species found in subterranean intestitial waters of the alluvial plain of the French upper Rhone, with preferences for hyporheic waters. (ref. ID; 6585)
Remarks
This species was recorded as Rhyacodrilus sp. in two recent publications (Juget 1984; Juget & Dumnicka 1986). (ref. ID; 6585)
Material examined
30 whole mounted specimens on 10 slides from the alluvial plain of the river Rhone, deposed in the author's collection. (ref. ID; 6585)