Limnoterrestrial ‘ Typhloplanidae’ (Rhabdocoela, Platyhelminthes), with the description of four new species and a new genus Author Houben, Albrecht M. 47A2BBE9-0820-4E83-B8BD-B41A66C214ED Biodiversity & Toxicology, Agoralaan Gebouw D, B- 3590 Diepenbeek, Belgium. albrecht.houben@gmail.com Author Monnens, Marlies 782F71E0-EF84-48DA-BE72-8E205CB78EAC Biodiversity & Toxicology, Agoralaan Gebouw D, B- 3590 Diepenbeek, Belgium. marlies.monnens@uhasselt.be Author Proesmans, Willem 41B81434-06EE-4BD0-8DCE-4DE73F2A6B30 Agroécologie, INRAE, 17 Rue Sully, F- 21065 Dijon, France. willem.proesmans@gmail.com Author Artois, Tom J. 2EDDE35C-A2F0-4CA2-84AA-2A7893C40AC4 Biodiversity & Toxicology, Agoralaan Gebouw D, B- 3590 Diepenbeek, Belgium. tom.artois@uhasselt.be text European Journal of Taxonomy 2022 2022-03-01 798 70 102 http://dx.doi.org/10.5852/ejt.2022.798.1671 journal article 20416 10.5852/ejt.2022.798.1671 dc185c1a-2bc2-48f1-bbdd-e0ae42f852f1 2118-9773 6323040 F136E044-62C8-4FB3-8160-7DAE663D9600 Hoplopera isis Houben, Proesmans & Artois sp. nov. urn:lsid:zoobank.org:act: 4DA3359A-D279-4286-B7B0-822382D258F7 Fig. 7A–C Diagnosis Dark species of Hoplopera , about 0.8 mm long with inconspicuous tail glands. Dermal rhabdites small, adenal rhabdites in two tracks. Atrial glands present. Spindle-shaped testes. Copulatory organ 20 µm long, without sclerotised structures. Bipartite bursa with sclerotised structure containing two groups of parallel, vertical rods, separated from each other by vertical bars, as a whole resembling a fish pot. Female duct forming a seminal receptacle. Etymology The species epithet is dedicated to Isis Houben , first daughter of the first author (A.M. Houben). Material examined Holotype AUSTRIA • 1 spec. , studied alive and horizontally sectioned; south of Graz, between Glashütten and Trahütten ; 46°49′46″ N , 15°06′09″ E ; 23 Aug. 2011 ; A.M. Houben and W. Proesmans leg.; moss growing in a small stream in a pine forest ; KV.688 ; FMNH . Paratypes AUSTRIA • 5 specs , studied alive, one of which whole mounted; same collection data as for holotype; paratype no. 822 ; HU . Description Specimens are about 0.7–0.9 mm long. The body is rounded anteriorly and possesses a small tail provided with small, inconspicuous tail glands ( Fig. 7C : tg). Rostrally, sharply pointed adenal rhabdites ( Fig. 7B : ar) are arranged in two groups. Very small dermal rhabdites occur all over the body. The paired protonephridiopores ( Fig. 7A : pp) lie posterior and lateral to the mouth. The rosulate pharynx is located just behind the middle of the body ( Fig. 7A : ph). The gonopore ( Fig. 7B–C : gp) is situated at ±80% of the body and connected to a genital atrium ( Fig. 7A–C : ga) that is lined with a high epithelium and surrounded by muscles of uncertain orientation. At its posterior side, the genital atrium receives a large group of eosinophilic glands ( Fig. 7A–C : ag). Two small, spindle-shaped testes ( Fig. 7A : t) lie in front of the pharynx ( Fig. 7A : ph) and ventral to the paired vitellaria ( Fig. 7A, C : vi). In some specimens, one testis seems bigger than the other one. The paired vasa deferentia ( Fig. 7B–C : vde) enter the egg-shaped copulatory organ laterally. Two layers of spiral muscles surround the 24µm long copulatory organ ( Fig. 7A : co), which bears an intracapsular seminal vesicle ( Fig. 7B–C : vs) and an ejaculatory duct ( Fig. 7B–C : de). Coarse-grained intra- ( Fig. 7B– C : gg1) and extracapsular ( Fig. 7C : gg2) eosinophilic glands are associated with the copulatory organ. The relatively long male duct ( Fig. 7C : md) receives the bursa ( Fig. 7A–C : bu) before entering the genital atrium ( Fig. 7A–C : ga). This bipartite bursa consists of an 18 µm long, thin-walled proximal part containing sperm and a 22 µm long distal part, which could be considered the bursal stalk ( Fig. 7B–C : bs). This stalk is surrounded by circular muscles and contains a sclerotised structure ( Fig. 7B : ss) that resembles the structure of a fish pot. It consists of vertical rods that are divided into two groups by a horizontal bar. The proximal and distal part are also delimited by a horizontal bar. As a whole, this bursal stalk is wrapped in a loose matrix surrounded by circular muscles. Fig. 7. Two species of Hoplopera Reisinger, 1924 . A–C . Hoplopera isis Houben, Proesmans & Artois sp. nov. A . Internal organisation of a live specimen. B . Organisation of the genital system of a live specimen. C . Reconstruction of reproductive organs based on horizontal sections. D–F . Hoplopera opaca Reisinger, 1924 . D . Internal organisation of a live specimen. E . Organisation of the genital system of a live specimen. F . Reconstruction of reproductive organs based on sagittal sections. The vitellaria ( Fig. 7A, C : vi) extend from the anterior third of the body to the posterior end where they meet. The oviduct broadens and becomes a seminal receptacle ( Fig. 7A–C : rs), which further becomes a long female duct ( Fig. 7C : fd), lined with a high, nucleated epithelium and surrounded by muscles. The vitelloduct was not observed with certainty, although it is probably an unpaired one that meets the oviduct. Discussion See the general discussion on the genus Hoplopera . Remarks The hard parts and copulatory structures are not visible on the whole-mounted specimen. Therefore, we designate a serially sectioned specimen as holotype .