Paraustrorhynchus isoldeae Artois, Reygel & Schockaert, 2019

Lin, Yitao, Reygel, Patrick, Feng, Weitao, Chen, Jiajia, Tessens, Bart, Van Steenkiste, Niels W. L., Schockaert, Ernest R., Artois, Tom J. & Wang, Antai, 2019, Four new species of the genus Paraustrorhynchus (Rhabdocoela: Kalyptorhynchia: Polycystididae), Zootaxa 4550 (3), pp. 357-373 : 362-364

Paraustrorhynchus isoldeae Artois, Reygel & Schockaert n. sp.

( Fig. 5 )

Locality. Nouméa ( New Caledonia): Baie des Citrons (22°17'43"S, 166°26'8"E), on algae and on seagrass in the lagoon, 8 th August 2003 (Type locality); Nouville ( New Caledonia), on algae ( Pavonia sp.) collected on the beach west of the Centre Hospitalier Spécialisé (CHS) Albert-Bousquet (22°15’ 59"S, 166°23’41"E), 10th August 2003. All collections by E. Schockaert.

Material examined. Several animals studied alive, one of which with an egg. Two whole mounts, one designated holotype (FMNH, http://id.luomus.fi/KV.606), the other paratype (HU 590).

Etymology. Named after Isolde Artois, daughter of TA.

Diagnosis. Species of Paraustrorhynchus with mid-dorsal dark-blue Y-shaped pigment pattern. The pigmentation consists of small granules under the body wall, its relation to specific cells is not clear but the pattern is similar in all observed animals. Prostate stylet type II ± 80 µm long, L-shaped, with both halves more or less of equal length, ending in a sharp point. Proximal half funnel-shaped, showing a longitudinal slit. Inner stylet lacking in the most proximal half of the stylet. Prostate stylet type III consisting of a proximal, folded plate from which two arms depart. One arm rather straigth, broadening towards a 35-µm-broad distal rim, provided with teeth. The other arm more curved, ending in a blunt point that is asymetrically serrated. Prostate stylet type III in total ±41 µm long, ±45 µm wide proximally, ±10 µm wide in the middle and ±35 µm distally.

Description. The animals are 1.3 to 1.6 mm long (measured on whole mounts). The length based on a micrograph of a live specimen is 1.2 mm. The animals are opaque, with scattered light-brown pigment and a prominent dark blue Y-shaped dorsal pigment pattern ( Fig. 5A ). Anteriorly, the dark blue pigmentation, organised in irregular patches, runs from side to side behind the eyes as a narrow band. Mid-dorsally, the dark blue pigmentation runs from behind the eyes to the posterior end of the animal. The pigmentation consists of small granules just beneath the body wall. Depending on the degree of contraction of the animal and squeezing, internal structures such as an egg or the copulatory bulb may disrupt the pigment pattern. The pigmentation disappears in fixed specimens.

The proboscis measures about 1/8 of the body length in live animals. The pharynx is situated in the first body half. The gonads are paired. The testes lie almost behind the pharynx. Vitellaria are situated dorsally and extend at both sides from the pharynx to the caudal body end. Well-defined, yellowish-brownish ovaries lie at the caudal body end. The internal organisation, including that of the male and female atrial system, corresponds to that of P. pacificus (see Karling & Schockaert 1977 for details). The prostate stylet type II ( Fig. 5C,E ) is 74–85 µm long. It is L-shaped, with a funnel-shaped proximal part and a sinusoid distal part, which tapers towards a pointed end. Both parts are more or less of equal length. The inner stylet is clearly visible over most of the length of the stylet, but is lacking in the proximal half of the funnel-shaped part. This part shows a broad longitudinal slit. The prostate stylet type III ( Fig. 5B,D ) consists of a proximal folded plate, from which two arms depart. One arm departs from one proximal corner of the common plate and runs more or less straight, widening to a 35-µm-broad and serrated distal rim (only one specimen measured, the other has a partialy-folded stylet, not suitable for exact measurement). The second arm departs from the opposite proximal corner of the common plate and is somewhat curved, with a blunt end that is asymetrically serrated. In total the prostate stylet type III is 39–43 µm long and 44–45 µm wide proximally, 9–11 µm wide at its midpoint.

Figures

FIGURE 5. Paraustrorhynchus isoldeae n. sp.: (A) Bright-field micrograph of a living animal with an egg/embryo (dorsal view). (B) Prostate stylet type III (holotype). (C) Prostate stylet type II (holotype). (D) Interference contrast micrograph of the prostate stylet type III (holotype). (E) Same technique, same specimen, prostate stylet type II. Scalebar: A 200 µm, B–E 10 µm.