Faunulus nielsi Houben, Proesmans & Artois, 2022

Houben, Albrecht M., Monnens, Marlies, Proesmans, Willem & Artois, Tom J., 2022, Limnoterrestrial ‘ Typhloplanidae’ (Rhabdocoela, Platyhelminthes), with the description of four new species and a new genus, European Journal of Taxonomy 798, pp. 70-102 : 75-77

Faunulus nielsi Houben, Proesmans & Artois gen. et sp. nov.

urn:lsid:zoobank.org:act:E8B0D042-259A-427D-8F29-5DB6ED8C8411

Fig. 2

Diagnosis

Provisionally the same diagnosis as the genus.

Etymology

The species epithet is dedicated to Niels Houben, son of the first author (A.M. Houben).

Material examined

Holotype AUSTRIA • 1 spec., live observations and sagittal sections; Kreuzberg near Weyer; 47°51′36″ N, 14°39′09″ E; 29 Aug. 2011; A.M. Houben and W. Proesmans leg.; forest soil of Pinus, Sambucus, Corylus, and Cornus; KV.686 ; FMNH.

Paratypes AUSTRIA • 2 specs, live observations, one of which whole mounted; same collection data as for holotype; paratype no. 821 ; HU.

Description

Specimens about 1 mm long. The body shape is pointed anteriorly and blunt to rounded posteriorly (see Fig. 2A ). On free-swimming specimens, a small tail can be observed. Both anterior and posterior ends possess very typical, strongly eosinophilic glands that appear rod-shaped, like big rhabdites, and are situated more or less parallel to each other. Rostrally, rhabdite glands ( Fig. 2A : ar) are present and arranged in two groups. The distal part of the epidermis is completely filled with coarse, strongly eosinophilic secretions, which probably are dermal rhabdites ( Fig. 2B : dr?). The protonephridiopores were not observed with certainty. The slightly forward slanted rosulate pharynx ( Fig. 2A : ph) is located centrally.

The gonopore ( Fig. 2A–B : gp) is situated at ±65% of the body and connected to a genital atrium ( Fig. 2A– B : ga) that is surrounded by muscles, although their orientation could not be observed with certainty.

The paired, differently sized testes ( Fig. 2A : t) lie in front of the pharynx and ventral to the paired vitellaria ( Fig. 2A–B : vi). One testis is relatively large, while the other is barely visible. The paired vasa deferentia ( Fig. 2B : vde) enter the copulatory organ laterally ( Fig. 2A : co). Two layers of spiral muscles surround the 50 µm long copulatory organ, which bears an intracapsular seminal vesicle ( Fig. 2B–C : vs) and a cirrus ( Fig. 2B–C : cir). Large, coarse-grained, extracapsular eosinophilic glands ( Fig. 2B : gg) are associated with the copulatory organ, although the point of entry remains uncertain. The 30 µm long cirrus is more or less straight and covered with spines in its distal part (see Fig. 2B–F : cir). The most distal part of the cirrus bears the larger spines and is enveloped in a conical, sclerotised pouch ( Fig. 2C : sp).

The female duct ( Fig. 2B : fd) is relatively long and lined with a high, nuclear epithelium. Proximally it widens into a seminal receptacle ( Fig. 2B : rs) that receives the oviduct and the vitelloduct.

Discussion

Faunulus nielsi Houben, Proesmans & Artois gen. et sp. nov. strongly resembles species of Adenocerca Reisinger, 1924 because of the combination of following features: centrally positioned pharynx, presence of tail glands and a spiny cirrus, and absence of a bursa ( Van Steenkiste et al. 2010). However, F. nielsi Houben, Proesmans & Artois gen. et sp. nov. differs from all species of Adenocerca in having testes that lie rostral to the pharynx. In all species of Adenocerca, they are situated posterior to the pharynx and lie next to the copulatory organ. Moreover, there is a difference in size between the two testes of F. nielsi Houben, Proesmans & Artois gen. et sp. nov., which was never reported for Adenocerca. This size difference is consistent for all observed specimens. All species of Adenocerca either have no dermal rhabdites (Adenocerca teshirogii Kolasa, 1981) or dermal rhabdites occurring throughout the whole epidermis. Conversely, what we assume are dermal rhabdites occur solely in the caudal body part of F. nielsi Houben, Proesmans & Artois gen. et sp. nov. Because of the unique combination of features present in the new species described, we find it justified to erect a new genus within ‘Typhloplanidae’.

Remarks

Animals seem to feed on rotifers since trophi were found in the gut.

Figures

Fig. 2. Faunulus nielsi Houben, Proesmans & Artois gen. et sp. nov. A. Internal organisation of a live specimen, B. Reconstruction of reproductive organs based on sagittal sections of the holotype (KV.686). C–F. Male copulatory organ of the paratype (paratype no. 821).