Paraustrorhynchus smeetsae Artois, Reygel, Tessens & Van Steenkiste, 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 : 366-367

Paraustrorhynchus smeetsae Artois, Reygel, Tessens & Van Steenkiste n. sp.

Paraustrorhynchus n. sp. in Tessens et al. 2014

( Fig. 6 )

Locality. Goa ( India), AIT Beach (15°34’2.8”N, 73°44’28.5”E), protected bay with coarse sand with shell gravel, specimens collected by B. Tessens and N. Van Steenkiste, 3 rd and 12 th December 2008.

Material examined. Several animals studied alive, five whole mounts (three suitable for observation of hard structures), one whole mount designated holotype (FMNH http://id.luomus.fi/KV.607), the others paratype (HU 591–594) two additional serially-sectioned (sagitally) specimens (HU 595–596).

Etymology. Named after Prof. Karen Smeets (UHasselt), in appreciation of her dedication towards the UHasselt research group.

Diagnosis. Species of Paraustrorhynchus with a dorsal dark-blue pigment pattern consisting of a transversal band dorsally from the pharynx, separated from a mid-dorsal band in the second body half. Prostate stylet type II double walled, ± 47 µm long, funnel-shaped, curved, with two fin-like structures just proximal from the curve. Outer stylet with proximal longitudinal slit; inner stylet lacking in the proximal 1/3 of the stylet. Prostate stylet type III ± 26 µm, consisting of a common proximal plate ± 38 µm broad, from which two arms depart. Both arms with broad serrated distal ends, ± 24 µm and 16 µm wide respectively, are largely overlapping.

Description. The animals are opaque, with scattered light-brown pigment and a prominent blue pigment pattern ( Fig. 6 A, B ) consisting of a transversal band dorsally from the pharynx separated from a longitudinal band in the caudal body half. The pigmentation consists of small granules under the body wall. Its relation to specific cells is not clear, but the pattern is similar in the observed animals. Depending on the degree of contraction and squeezing, internal structures such as the copulatory bulb may disrupt the pigment pattern. The animals have two eyes and are 300–700 µm long ( = 530 µm; n = 5; measured on whole mounts).

The internal organisation, including that of the male and female atrial system, corresponds completely to that of P. isoldeae (see above). The stylet type II ( Fig. 6 D, E ) is 45–49 µm long (x‾= 47 µm; n = 3). It is a doublewalled, curved tube. Near the distal, pointed end the stylet is twisted over a short distance. The inner stylet can be followed over the whole length of the outer stylet except in the distal twist and in the proximal 1/3 of the stylet. At one side, the proximal 1/3 of the outer stylet shows a longitudinal slit, which broadens at the level of the proximal end of the inner stylet, leaving the inner stylet apparently uncovered at this side. At about its midpoint, the outer stylet is provided with two small, fin-like structures. In one whole mount, one of the fin-like structures is missing; probably it is not visible due to compression and orientation of the stylet. The prostate stylet type III ( Fig. 6 G, F ) consists of two arms proximally connected to a single folded broad plate (36–41 µm wide; x‾ = 38 µm; n = 3). The ventral arm widens to a broad plate (20–29 µm wide; x‾= 24 µm; n = 3), and has ± 3/4 of the its distal rim serrated. The dorsal arm ends in a less broad plate (15–17 µm wide; x‾= 16 µm; n = 3), which has a completely serrated distal rim. Both arms are almost equal in length and determine the length of the stylet type III (24–30 µm; x‾= 26 µm; n = 3). Measurements of the length and especially the width in the middle of the stylet depends on the inclination of the proximal plate and the position of both arms due to the compression of the preserved specimens.

Figures

FIGURE 6. Paraustrorhynchus smeetsae n. sp.: (A) Bright-field micrograph of a living animal, anterior region. (B) Brightfield micrograph of a living animal, posterior region. (C) Prostate stylet type III (holotype). (D) Prostate stylet type II (holotype). (E) Interference contrast micrograph of the prostate stylet type II (holotype). (F) Same technique, same specimen, prostate stylet type III. Scalebar: A and B 100 µm, C–F 10 µm.