Marionina mendax Rota, 2013

Martin, Patrick, Schmelz, Rüdiger M. & Dole-Olivier, Marie-José, 2015, Groundwater oligochaetes (Annelida, Clitellata) from the Mercantour National Park (France), with the descriptions of one new genus and two new stygobiont species, Zoosystema 37 (4), pp. 551-569 : 560-562

Marionina mendax Rota, 2013

Marionina mendax Rota, 2013: 125 .

MATERIAL EXAMINED. — Station 1, slide 11.006.01(a): one fully adult specimen.

REMARKS

A recent revision of the common and widespread Marionina argentea ( Michaelsen, 1889) ( Rota 2013) resulted in the description of three new species, Marionina deminuta Rota, 2013 , M. mimula Rota, 2013 , and M. mendax Rota, 2013 , and a more precise morphological diagnosis of M. argentea sensu stricto. Our specimen would previously have been identified as M. argentea . Twelve additional specimens in the present collection, belonging to the Marionina argentea group, belong to a new species, M. sambugarae Schmelz , n. sp., described below. Additional specimens in the collection belong to the Marionina argentea group, but due to poor fixation they could not be assigned to any of the nominal species within the group (i.e. they may or may not belong to either M. mendax or M. sambugarae n. sp.). Marionina argentea sensu stricto as defined by Rota (2013) was not found.

The specimen was identified as M. mendax based on the following observations: body length 2.4 mm, width at clitellum 0.12 mm; 22 segments; length of setae 40 µm on XI, 38µm on XIII, pharyngeal glands in VI without dorsal lobes; preclitellar nephridia at 7/8, 9/10, efferent duct demarcated; coelomocytes oval, 10-16 µm long, with some coarse, refractile vesicles; clitellum closed dorsally, open ventrally, cells in dense transverse rows with hyalocytes distinctly larger than granulocytes, the latter mostly longer than wide, ventrolateral border of clitellum lined by granulocytes only; male pores in XII, male glandular bulb 22 µm long and 18 µm high; spermathecae each with two rounded ectal glands, diameter 12 and 8 µm, respectively.

Here we list only those characters that distinguish M. mendax from at least one of the other species of the M. argentea group (see Rota 2013: table 1), including M. sambugarae Schmelz , n. sp. (see below). The observable characters are in complete agreement with the original description of M. mendax , with the sole exception of a possible disagreement in the number of transverse clitellar gland cell rows: 22 in our specimen, as opposed to 16 countable in fig. 1D of Rota (2013). However, this character is not dealt with in the text of the original description, and the figure may not show the full extension of the clitellum. The presence of only granulocytes at the ventrolateral border is not described in Rota (2013), but it is visible in her figure 1D ( Rota 2013: fig. 1D [ggc]) and may distinguish the species from M. deminuta , which has a conspicuous longitudinal ventrolateral row of hyalocytes just above the male glands (cf. Rota 2013: fig. 3B); it is not clear, however, whether these are the bordering cells. Some characters could not be observed in our specimen, such as the posterior border of the brain.

Marionina sambugarae Schmelz , n. sp. ( Fig. 4 )

Marionina cf. argentea [non Marionina argentea ( Michaelsen, 1889) ] – Giani et al. 2011: 93.

TYPE MATERIAL. — Holotype. MNHN HEL 526 , slide 11.262.01, adult specimen (c), stained whole mount. Legit M.-J. Dole-Olivier. Type locality: Braissette, Uvernet-Fours , Mercantour National Park, France (station BRABA, sample code BRA, Braissette), 44°17’53.67”N, 6°47’13.84”E, 2440 m a.s.l., spring, 11.VIII.2010 . Paratypes. Twelve adult specimens, stained whole mounts. Type locality (station BRABA, sample code BRA, Braissette), 11.VIII.2010 ; MNHN HEL 526 , slide 11.262.01(a,d): 2 specimens, IRScNB, I.G. 32392, slide 11.264.02(c,e): 2 specimens. Tende , Roya River (station H1RO, replicate sample No 1, sample code PT1, Pont Tende), 5.VIII.2009 ; MNHN HEL 527 , slide 11.006.01(c): 1 specimen, MNHN HEL 528 slide 11.006.02(a): 1 specimen. Colmars , Verdon River (station H3VER, sample code H3 V, Haut Verdon 3 aval pont la Chaumie), 6.IX.2010 ; IRScNB, I.G. 32392, slide 11.255.04(a): 1 specimen. Allos (station RAVVER, sample code RAV, Source du ravin du Lac d’Allos), 2.VIII.2010 ; MNHN HEL 529 , slide 10.343.01: 1 specimen. Allos (station MEOVER, sample code MEO, Méouilles), 3.VIII.2010 ; IRScNB, I.G. 32392, slide 11.258.06(b): 1 specimen. Colmars (station INFVER, sample code INF, Infiltrés), 5.VIII.2010 ; IRScNB, I.G. 32392, slide 11.259.07(b,c): 2 specimens. Uvernet-Fours (station CHARBA, sampling code CHAR, Charbonnière Fours St. Laurent), 1.IX.2010 ; IRScNB, I.G. 32392, slide 11.264.07(a): 1 specimen.

OTHER MATERIAL. — Six specimens from Slovenian caves, for further details see “ Marionina cf. argentea ” in Giani et al. (2011).

ETYMOLOGY. — Named in memory of the late Beatrice Sambugar, eminent researcher on subterranean oligochaetes, and a dear colleague.

DISTRIBUTION. — France, Mercantour National Park ( Fig. 4 ); Slovenia, caves in Grosuplje and Logatec ( Giani et al. 2011).

DESCRIPTION

Length c. 1.5 mm, diameter c. 0.1 mm, 21-24 segments.Two setae per bundle, absent on XII and laterally on II. Lateral setae not shifted dorsally. Setae straight and pointed ectally, curved entally. Maximum length 28-38 µm, small in II (21- 24 µm), increasing in size from II to V to c. 30 µm; measured lengths ventrally on XI 28-35 µm, on XIII 28-38 µm. Setae of caudal segments not larger than those of XI or XIII. Epidermal gland cells not seen.

Head pore at 0/I, prostomium short, with two bulges in lateral view, separated into dorsal forefront and a ventral snout (cf. Rota 2013: fig. 1A), the latter with mid-frontal recess in epithelium. Brain posteriorly truncate or slightly incised, c. 70 µm long, about twice as long as wide, widest posteriorly. Pharyngeal pad about as long as wide or high. Postpharyngeal ganglia present. Pharyngeal glands in IV one unpaired dorsal lobe, no ventral lobes, in V one unpaired dorsal lobe and a pair of primary ventral lobes projecting anteriad, in VI a pair of large and elongate ventral lobes, each with a small dorsal projection posteriorly; lobes in VI separate. Chloragocytes inconspicuous, diameter c. 12 µm. Dorsal blood vessel from XII, bifurcating anteriorly in III, behind pharyngeal pad, lateral commissural vessels in IV-V not observed. Midgut pars tumida in XV-XVI, covering one segment length. Preclitellar nephridia 2 pairs, at 7/8 and 9/10, anteseptale with coils of canal, separated from postseptale by slight constriction; postseptale about 1.5-2.0 × as long and high as anteseptale; efferent duct arising terminally, about as long as postseptale; no terminal vesicle. Coelomocytes c. 16 µm long, broadly oval, spindle-shaped in oblique view, filled with irregularly shaped vesicles; strongly refractile crystals present in some cells of some specimens.

Clitellum from XII-1/2 XIII, ending 1-2 cell rows before setae of XIII, not developed (= open) mid-ventrally and middorsally ( Fig. 4C ). Dorsal and ventral borders of clitellum lined by flat granulocytes. Ventral clitellum-free area about as wide as distance between male pores, dorsal border of clitellum undulating. Gland cells laterally about 9 µm high and 9-16 µm wide, flatter dorso- and ventro-laterally. Cells in c. 21-24 dense to indefinite transverse rows (as defined by Schmelz & Collado 2010: 17).

Testes and sperm funnels in XI, ovaries and male pores in XII. Seminal vesicle absent, cysts of developing sperm in XI. Sperm funnels c. 50 µm long, diameter between 12 and 24 µm, depending on angle of observation. Collar c. 8 µm high and wide, merging into glandular body. Vasa deferentia ventrally in XII, diameter 4-5 µm, length not measurable, penetrating the male gland (“penial bulb”) through its centre. Male glands roughly spherical, often slightly longer than wide and slightly wider than high, measured lengths 20-32 µm, measured widths 17-24 µm. Subneural glands absent.

Spermathecae consisting of ectal duct and ampulla; ampullae attached to oesophagous separately and latero-dorsally. Spermathecal ectal pores laterally at 4/5. Ectal glands not distinguished, ectal duct c. 22 µm long and 11 µm wide, with straight canal and undulating outer surface caused by bulges of cell nuclei. Ampulla spherical or oval, depending on level of contraction of animal, diameter c. 18 µm, walls 2-3 µm thick, inner and outer surface distinct, lumen filled with spermatozoa roughly arranged along long-axis; ental duct not seen, apparently short, if present at all.

REMARKS

Marionina sambugarae Schmelz , n. sp. belongs to a complex of species that were previously identified as Marionina argentea ( Michaelsen 1889) , until it was split into four different species, three of them new to science ( Rota 2013): M. mendax Rota, 2013 , M. deminuta Rota 2013 , M. mimula Rota, 2013 and M. argentea ( Michaelsen, 1889) sensu stricto. Marionina sambugarae Schmelz , n. sp. is therefore the fifth member of this species group, and the only one in the group with a dorsally interrupted clitellum. The taxonomic value of this character may be questioned because it is not dealt with in Rota (2013), nor is it mentioned in the descriptions of M. argentea by Michaelsen (1889), Nielsen & Christensen (1959) and Chalupský (1992). However, Schmelz & Collado (2010) state that the clitellum of M. argentea is dorsally developed, based on observations of numerous specimens from soil and surface freshwater habitats across Europe. Furthermore, Rota (2013) gives otherwise very detailed descriptions of the clitella in the four species – their ventral interruption included – hence a dorsally interrupted clitellum, if present, would have been mentioned and described.

Besides, further characters distinguish M. sambugarae Schmelz , n. sp. from each of the four other species (characters of M. sambugarae Schmelz , n. sp. in brackets). Marionina argentea sensu stricto (as conceived in Rota 2013) has: coelomocytes finely granulated, spindle-shaped, up to 25 µm long (vs coarsely granulated, oval, c. 16 µm long); nephridial postseptale merging gradually into efferent duct (vs abrupt rise of efferent duct); and one or two distinct spermathecal ectal glands (vs indistinct or absent). Marionina mimula has: brain deeply incised posteriorly (vs truncate or slightly indented); dorsal blood vessel bifurcating in I (vs bifurcation in III); coelomocytes finely granulated (vs coarsely granulated); male gland diameter 32-48 µm (vs 20-32 µm); and a rosette of 7-8 spermathecal ectal glands (vs indistinct or absent). Marionina deminuta has: 16-21 segments (vs 21-24); setae at XI and XIII 19-24 µm long (vs 28-38 µm); coelomocytes finely granulated, spindle-shaped (vs coarsely granulated, oval); ventral border of clitellum consisting of hyalocytes (vs granulocytes); and two conspicuous spermathecal ectal glands (vs glands inconspicuous or absent). Marionina mendax has: pharyngeal glands in VI without dorsal projections or lobes (vs with dorsal projections). This subtle character, newly introduced by Rota (2013) to distinguish among species of the M. argentea complex, seems indeed to be constant: the only specimen in the collection without dorsal lobes in VI has a dorsally complete clitellum, and was hence identified as M. mendax .

M. sambugarae Schmelz , n. sp. is evidently most similar to M. mendax , these perhaps being sister species. Similarities extend to the coelomocytes, the shape of the prostomium, and the distribution pattern of lateral clitellar gland cells (cf. Rota 2013 Fig. 1A, D ). Among the five species in the group, only M. mendax and M. sambugarae Schmelz , n. sp. have oval and coarsely granulated coelomocytes. In the other three species, coelomocytes are spindle-shaped and very finely granulated.

Granules in the coelomocytes of the types of M. sambugarae Schmelz , n. sp. are smaller than the granules in living specimens of M. mendax , and they are not present in all cells and specimens. Coarse refractile granules of enchytraeid coelomocytes are best seen in living specimens and they usually disappear completely during clearing and dehydration. In exceptional cases they may be preserved, as in some specimens of the types series, the holotype included. Nevertheless, the true aspect of the granules in M. sambugarae Schmelz , n. sp. can only be inferred, because living specimens were not available. Since granules in cells of the single specimen identified as M. mendax are as small as those in the types of M. sambugarae Schmelz , n. sp., we assume that the live aspect of the coelomocytes is similar in the latter to that in M. mendax : cells completely filled with irregularly shaped refractile crystals, leading to a bright white colour of specimens under reflected light. The alternative character state of fine granulation, realized in the other species of the M. argentea group, can be excluded, because fine granulation leads to a fine and regular pattern of coelomocyte vesicles after fixation, different from the irregular patterns seen in M. sambugarae and also illustrated for M. mendax ( Rota 2013: fig. 1A).

A further possible distinguishing character of Marionina sambugarae Schmelz , n. sp. is the absence of spermathecal ectal glands. Rota (2013) illustrates conspicuous ectal glands for all four species described, and ectal glands are also described for Marionina argentea in Nielsen & Christensen (1959), although they are not seen in the corresponding figure ( Nielsen & Christensen 1959: fig. 140). It cannot be excluded that inconspicuous ectal glands are present in M. sambugarae Schmelz , n. sp. and have become invisible due to the fixation method.

A dorsally interrupted clitellum was also recorded in six specimens identified as “ Marionina cf. argentea ” in a previous study on groundwater oligochaetes in Slovenia ( Giani et al. 2011), and it was already supposed there that these specimens might represent a new species because the clitellum is closed dorsally in Marionina argentea ( Schmelz & Collado 2010) . The Slovenian material conforms to the description of M. sambugarae Schmelz , n. sp., but it is not included in the type series. The fact that this species has been found in subterranean habitats of France and Slovenia and not in surface habitats accross Europe, suggests that Marionina sambugarae Schmelz , n. sp. is a true stygobiont species.

Figures

FIG. 4. — Marionina sambugarae Schmelz, n. sp.: A, segments IV-VI, lateral view (facing left) (paratype MNHN HEL 11.262.01d); B, clitellar region, lateral view (holotype MNHN HEL 11.262.01c); C, clitellar region, dorsal view, showing dorsally interrupted clitellum (paratype IRScNB I.G. 32392 slide 11.264.02e).Symbols: Ü, dorsal lobe of pharyngeal gland in VI. Scale bars: 100 µm.

FIG. 1. — Location of the stations where oligochaetes were found in the Mercantour National Park.