Parvidrilus jugeti, 2012

Martínez-Ansemil, Enrique, Châtelliers, Michel Creuzé Des, Martin, Patrick & Sambugar, Beatrice, 2012, The Parvidrilidae - a diversified groundwater family: description of six new species from southern Europe, and clues for its phylogenetic position within Clitellata (Annelida), Zoological Journal of the Linnean Society 166 (3), pp. 530-558 : 537-538

PARVIDRILUS JUGETI DES CHÂTELLIERS & MARTIN SP. NOV. ( FIG. 3 )

Holotype: MHNL 44003361 , 07.07.1998, mature specimen, stained in paracarmine and whole-mounted in Canada balsam. Corveissiat Cave (46°14′34′′N, 05°29′01′′E, 378 m asl), Ain (01), France, 7.vii.1998.

Paratypes: MHNL 44003364 , one mature specimen ; MHNL 44003365 , one mature specimen; all specimens stained in paracarmine and whole-mounted in Canada balsam. Corveissiat Cave , France, 20.xii.2007 .

Other material examined: Six other specimens, wholemounted in Canada balsam, in the collection of one of the authors (MCdC): Corveissiat cave (one immature specimen, 7.vii.1998; three mature specimens, 20.xii. 2007; two mature specimens, 10.iii.2008) .

Etymology: Named after Jacques Juget (1928–2006), mentor to one of us (MCdC), and friend and colleague to all of us, as a tribute to his lifelong contribution to the knowledge of the Clitellata, and particularly subterranean oligochaetes (see Creuzé des Châtelliers, Lafont & Giani, 2007).

Description: Length 1.96 mm, 28 segments (one complete mature specimen). Width 68 Mm at V, 85 Mm at XII. Prostomium bluntly conical, 25 Mm long, 40 Mm wide at base; prostomium epidermis with numerous stained cell nuclei, indicating a possible sensory or glandular function. Body wall not papillate, cuticle smooth. Clitellum not seen.

Dorsal (dorsolateral) and ventral (ventrolateral) setae present from III, posteriorly situated in each segment. Dorsal bundles with two (three) simplepointed needles (10–20 Mm long), alternating with one (two) thin and flexible hair setae (length 80 Mm at V, 110 Mm at VIII, 200 Mm at XI) ( Fig. 3 , ds). Hair setae apparently smooth when observed on permanent mount using an oil immersion lens. Ventral bundles with two (three) sigmoid, bifid crotchets with upper tooth slightly thinner and smaller than lower tooth, and accompanied by one hair seta in preclitellar segments (90 Mm long); from XII, ventral hair setae absent, two crotchets per bundle ( Fig. 3 , vs). Crotchets without nodulus, 20–25 Mm long, and shaft out of the body wall, with distal half enlarged on the convex side. Within ventral bundles in preclitellar segments, the uppermost seta bifid, followed by one hair seta; these two setae separated from the other two bifid setae by a distance greater than that between them. No modified genital setae.

No eyes. Brain short, limited to III. Ventral nerve cord in contact with epidermis, beneath muscles of the body wall. Digestive tract complete; eversible pharynx with dorsal pad, sinuous, ciliated oesophagus, with pharyngeal glands present in III- IV, followed by a simple intestine, dilating in from X and ending in a terminal anus. Layer of chloragogen cells surrounding digestive tract possibly present; details not observable. Coelomocytes absent. Middorsal glandular pouches not observed.

Testes in XI, as an unpaired, dorsal lump of cells with small nuclei in posterior end of coelomic cavity ( Fig. 3 , t); numerous spermatozoa below this cellular mass, with well-defined tails, detached in the coelom ( Fig. 3 , sp). Sperm funnels and vasa deferentia not seen. Atria elongate, tubular (265 Mm long, 11 Mm wide), one atrium entering and restricted to XIII, with distal end folded up anteriad, the other one extending straight into XIV ( Fig. 3 , a). Atria proximally merging below the nerve cord into a common ejaculatory duct, and opening ventrally in anterior part of XII, in front of setal line, through a penis-like structure, surrounded by a thick muscular ring ( Fig. 3 , mp). Atrial ampullae longitudinally striated, with large lumen filled in with undefined material (cellular? secretory?), different from mature spermatozoa visible in XI; atrial walls very thick, highly refringent under DIC. One mature oocyte ( Fig. 3 , ov), full of vitellus, ventrally, in anterior part of XII, near 11/12, suggesting the location of an unpaired ovary; a few small ovarian morulae freely developing into the coelomic cavity. Female funnels and spermathecae not observed.

COI sequence: EMBL accession number: HE800203 ( Corveissiat cave , France) .

Remarks: The long, narrowly tubular atria of P. jugeti sp. nov., which extends to XIV, are quite distinctive amongst the Parvidrilidae known to date. The high refringence of the atrial walls is unique. The outer atrial surface is striated all along the ampullae. Parvidrilus jugeti (and possibly P. meyssonnieri ) is (are) the only parvidrilid(s) known thus far that lack spermathecae.

The exact location of ovaries (paired or unpaired?) in P. jugeti remains obscure. A mature oocyte was observed ventrally in XII, on the right side of the specimen, close to 11/12, which suggests the existence of an unpaired, ventral ovary. In this specimen, it is likely that this female gonad has disappeared after having produced the few morulae observable in the coelomic cavity of XII, as documented previously in naidids ( Chekanovskaya, 1962).

Distribution and habitat: Parvidrilus jugeti is known only from the type locality in the Corveissiat cave, Ain (01), France. Sedimentary rock formation (karstic area); in a little pond, very finely clayey sediment, with little organic matter.

Figures

Figure 3. Parvidrilus jugeti sp. nov. Right lateral view of genitalia in segments XI-XIII (holotype). Abbreviations: a, atrium; ds, dorsal seta; mp, male pore; nc, nerve cord; omo, ovarian morula; ov, oocyte; sp, spermatozoa; t, testis; vs, ventral seta. Scale bar = 50 Mm.