Sphaerobathytropa ribauti, VERHOEFF, 1908

Schmidt, Christian, 2007, Revision of the Neotropical Scleropactidae (Crustacea: Oniscidea), Zoological Journal of the Linnean Society 151, pp. 1-339 : 78-80

SPHAEROBATHYTROPA RIBAUTI VERHOEFF, 1908

Sphaerobathytropa ribauti Verhoeff, 1908 – Verhoeff (1938 *); Vandel (1940, 1941, 1946 *); Legrand (1944, 1954); Vandel (1962a,b, 1968); Schmölzer (1965 *, 1971); Cifuentes (1983); Vivar, de la Vega & Cifuentes (1984); Schmalfuss (1980, 2003 *).

Sphaerobathytropa antarctica Vandel, 1962b – nomen nudum.

Sphaerobathytropa antarctica Vandel, 1963 – Vandel (1968); Leistikow & Wägele (1999 *); Schmalfuss (2003 *) – syn. nov.

Material examined

Type specimens: Two ♀, and four microscopic slides: (1) pleon and pereion segment 7; (2) pereion segments 2–5 with legs; (3) pleon and some fragments; (4) two juveniles, one entire, the other broken into three pieces (syntypes, France, St Béat, leg. Ribaut, ZSM). Slides 1–3 are poorly preserved .

Other samples: [ For the South American localities, see Remarks on next page.] One ♂ holotype of Sphaerobathytropa antarctica , dissected second antenna, maxilliped, second maxilla, mandible, tergites 1–3, pereiopod 7, pleopods 1 and 2 and pleon with uropod on slides CV 4955-1 to 4955-9 ( Argentina, Réserve du Nahuel Huapi , 40°50′ S, 71°30′ W, altitude 1200 m, Los Cantaros, près de Puerto Blest, forêt valdivienne très humide, leg. Delamare Deboutteville, 8 March 1959) ; fragments of one specimen (1.5 mm wide) – segment 1 with maxilliped, segments 4–6 with 4 pereiopods, pleon without pleotelson and with two pleopod exopodites only, and two separate pereiopods (with labels ‘ Ecuador, Archidona , iv.1965 ’ and ‘ Sphaeroniscus gerstaeckeri Vandel’ , IRSNB 24421 ); two ♂, three ♀ ( France, St Béat, leg. Ribaut, April 1939, CV); one ♂, one ♀ ( France, Ste. Engrace, 13 March 1956, CV); one ♀ (Pyrénées, K. W. Verhoeff collection, USMN 56114 ); one ♀ m, two ♀ (Pyrénées mountains, with contradictory labels, leg. Verhoeff 1917 or leg. Ribaut, ZMG 467 ) .

Description ( Figs 247–256 )

Male maximum 2 mm long, female maximum 4 mm long. Dorsally with light brown pigment and pale muscle insertion spots. Second antennae pigmented. Endoantennal conglobating ability ( Fig. 1 ). Cephalothorax approximately as long as high. In lateral view, the lateral end of the linea marginalis is below the middle. Eyes composed of five (male) or six (female) ommatidia (in the examined specimens). Frontal shield hardly exceeding vertex, its upper margin in frontal view evenly rounded. Behind frontal shield a simple transverse furrow. No delimited ‘frontal triangle’ as described by Verhoeff. Linea supraantennalis absent. First coxal plate without any trace of a sulcus arcuatus, but with schisma along whole lateral margin, lower lobe on both corners somewhat shorter than upper lobe. Second coxal plate with a large transverse lobe on inner face, third coxal plate with a very small transverse lobe on the inner face. Fourth coxal plate laterally narrowed, fifth broadly rounded, and sixth and seventh laterally truncate. Tergites covered with approximately circular scales with narrow distance between them (not overlapping) and broad, shell-shaped tricorn setae similar to those found, for example, in Trichorhina , Calycuoniscus or the Spelaeoniscidae . These tricorn setae irregularly arranged on the tergites, except for a row along posterior margins. Noduli laterales distinctly larger than tricorn setae (resembling simple setae at lower magnification); their sheath has lateral lobes at the base, and is as long as the free distal portion of the seta. Noduli located at distance from posterior margin; on the first tergite, the nodulus is more approximate to the anterior margin than to the posterior margin.

First antenna three-jointed, second article shortest, and distal article bearing a number (six?) of aesthetascs, with no gap or difference between apical and subapical aesthetascs. Second antenna ( Fig. 4 ) short and stout, if bent backwards hardly reaching posterior margin of first tergite. Two-jointed flagellum bearing apical cone of about half the length of the apical article; lateral setae approximately 0.25 times as long as apical cone, and inserted at its basal 0.2. Articles of second antenna with narrow setae and overlapping cuticular scales.

Mouthparts: right mandible: pars incisiva with three teeth, lacinia mobilis with slender base and several small ‘teeth’, hairy lobe with scales of different size and one penicil, one more penicil proximal to the lobe. Left mandible with pars incisiva of four teeth, lacinia mobilis strong, with three teeth, hairy lobe with some scales and two penicils, one more penicil proximal of the obe. Pars molaris of both mandibles represented by tuft of hairy setae (exact number could not be counted) on a common socket. Outer faces of both mandibles with some overlapping scales and a few simple tricorn setae.

First maxilla mesal endite with two slender penicils, its laterodistal corner rounded (?probably distorted). Lateral endite with lateral group of four teeth (or tooth setae) and mesal group of five (simple?) teeth. On caudal (ventral) face, small triangular lobe beside lateral group and small, simple seta at some distance from mesal group. Distal 0.25 of lateral margin fringed with ‘hairs’ (= pectinate scales?). Second maxilla apically indistinctly bilobate, mesal lobe much narrower and bearing a group of sensory pegs. Between the lobes with two small setae, lateral lobe only with a few small ‘hairs’.

Maxilliped base bears overlapping scales and slen- der setae, like the second antenna. Maxilliped endite rectangular, with two produced, acute-angled lobes on apical margin and a large seta on caudal face. Palp three-jointed, basal article with two large setae, second article bearing one proximal tuft of one enormously large and one or two minute setae and one distal tuft of one large and several smaller setae on mesal margin and two unequal setae on lateral margin. Apical article with apical tuft of setae and one (or two?) smaller setae on lateral margin.

All pereiopods with large, overlapping epicuticular scales and few, but large tricorn-like setae. Ventral faces of merus, carpus and propodus with two to four large setae. Dactyli with simple dactylar setae with a few aesthetasc-shaped setae beside it, one seta each on frontal and caudal faces, and a simple, curved ungual seta. Inner ‘claw’ shorter than outer claw. Pereiopod 1 with antenna-cleaning brush composed of comparatively few, large scales on carpus and a row of ventral, spine-shaped structures (setae or scales?) on the propodus. One of the ventral setae of the carpus has several tips. Pereiopod 7 has overlapping scales and different setae. Scale-rows belonging to waterconducting system absent. Genital papilla ventral shield exceeded by a truncate lobe; orifices near apical corners.

Pleopods: male pleopod 1 endopodite straight, with distalmost tip strongly curved outwards. Spermatic furrow with basal row of scales and distal row of 10–15 small spine-shaped setae along the medial margin. Pleopod 1 exopodite transverse, as wide as endopodite, without marginal setae. Male pleopod 2 endopodite slender, slightly longer than exopodite. Pleopod 2 exopodite triangular, with elongate distal part, one or two lateral marginal setae and a field of hair-like pectinate scales beside the medial margin (not drawn). Pleopod exopodites 3–5 each have one or two marginal setae and a few ‘hairs’. Pleopod 5 exopodite on the caudal (dorsal) face with a transverse stripe of few large pectinate scales.

Pleotelson with medial lobe slightly projecting beyond the uropod protopodites and with convex sides. The median portion is strongly convex. Uropod protopodites dorsoventrally flattened, exopodites short and stout, inserting near the inner corner, endopodites inserting basally on the protopodite, laterally flattened.

Remark

Re-examination of the type specimen of Sphaerobathytropa antarctica and of specimens of S. ribauti clearly demonstrated that no substantial differences exist. The differences mentioned by Vandel (1963) are erroneous. The obvious identity of both nominal species raised the question of how the species was transferred from South America to the Pyrénées or vice versa. Vandel (1963) mentioned only one male specimen. Re-examination of samples of terrestrial isopods from the IRSNB revealed a second specimen, which was labelled ‘ Sphaeroniscus gerstaeckeri ’. As that species is so different from Sphaerobathytropa that confusion can be excluded, doubt arises concerning how the labels and the specimen were placed in this tube. Probably, Vandel had examined specimens of Sphaerobathytropa ribauti from his personal collection (now in MNHN), probably for comparison with the South American Scleropactidae that he was working on at that time, and then added the two specimens to the wrong tubes. If he had used a pipette for handling these minute animals, it can be easily imagined that the specimen and the fragments of another specimen (even smaller than an entire specimen) adhered inside the pipette and then were released unnoticedly.

Some minor differences seen between the drawings presented here probably represent intraspecific variation, and others certainly depend on the preservation of the specimens. For example, the second antenna looks stouter in the holotype of Sphaerobathytropa antarctica than in the other specimen, because it is more compressed between slide and cover glass. The size of the lobe on the inner face of the second coxal plates differs even between left and right side of the same specimen ( Fig. 248 ).

The occurrence of Sphaerobathytropa in the Pyrénées is well established by a large number of localities and specimens. In contrast, only one specimen is recorded from Argentina. Taking into consideration the small size of the specimens, these data led to the conclusion that the two specimens were accidentally added to the tubes with other samples from South America, and that specimens of Sphaerobathytropa were actually never found in South America. Vandel’s first thought, a labelling error ( Vandel, 1962b, 1963), was correct.

Geographical distribution and ecology (Map Fig. 257 ) According Vandel (1962a), Sphaerobathytropa ribauti is very common on the north slope of the Pyrénées. It is frequently found at altitudes up to 1000–1200 m, but rarely up to 1600 m. Several scattered records are known from the Aquitaine basin and the south of the Massif Central.

The habitat is described as gorges with forest and high humidity.There, the animals are found in decaying wood, in leaf litter, under stones, and in soil crevices.

Figures

Figure 1. Cephalothorax: Colomboscia cordillierae, Scleropactes ecuadoriensis, Scleropactoides curvatus, Chileoniscus marmoratus (from left).

Figure 4. Second antenna, flagellum: Globopactes hispidus (above), Circoniscus incisus (middle), Sphaerobathytropa ribauti (below).

Figure 247. Sphaerobathytropa ribauti Verhoeff, 1908: ♀, 2.4 × 1.0 mm, habitus lateral, pleon caudal/dorsal; ♀, 2.8 × 1.25 mm, cephalothorax frontal and lateral; ♂, 2.1 × 0.75 mm, cephalothorax dorsal (France, St Béat, leg. Ribaut, April 1939, MNHN) (the pleon is drawn in such a position that the pleotelson is seen in strictly dorsal view).

Figure 248. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, 2.1 × 0.75 mm, tergites (France, St Béat, leg. Ribaut, April 1939, MNHN).

Figure 249. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, 2.1 × 0.75 mm, first antenna and mouthparts (France, St Béat, leg. Ribaut, April 1939, MNHN).

Figure 250. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, 2.1 × 0.75 mm, second antenna (France, St Béat, leg. Ribaut, April 1939, MNHN).

Figure 251. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, 2.1 × 0.75 mm, pereiopods 1–4, frontal view (France, St Béat, leg. Ribaut, April 1939, MNHN).

Figure 252. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, 2.1 × 0.75 mm, pereiopods 5–7 frontal, uropod ventral (France, St Béat, leg. Ribaut, April 1939, MNHN).

Figure 253. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, 2.1 × 0.75 mm, pleopods 1, 4 and 5 caudal, pleopods 3 and 4 frontal (France, St Béat, leg. Ribaut, April 1939, MNHN).

Figure 254. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, holotype of Sphaerobathytropa antarctica Vandel, 1963, distal part of right mandible, maxilliped and second maxilla.

Figure 255. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, holotype of Sphaerobathytropa antarctica Vandel, 1963, coxal plates 1–3, pleotelson and uropods, pereiopod 7.

Figure 256. Sphaerobathytropa ribauti Verhoeff, 1908: ♂, holotype of Sphaerobathytropa antarctica Vandel, 1963, pleopods 1 and 2, second antenna.

Figure 257. Geographical distribution of Sphaerobathytropa ribauti, according to the literature [based on the map given by Vandel (1962a)]; specimens from only three or four locations had been examined.