Lagenopolycystis mutabilis Artois & Schockaert 2025, sp. nov.

Lagenopolycystis mutabilis Artois & Schockaert sp. nov. urn:lsid:zoobank.org:act: 086FF139-FB29-46EF-BEED-5014C6D90FD4 (Fig. 7) Diagnosis. Species of Lagenopolycystis with a prostate stylet of 100–134 µm (x̄ = 123 µm, n = 8), curved over its whole length with a strong curl proximally and distally and a rounded end. The accessory stylet is 28–35 µm (x̄ = 33 µm, n = 8) and attached at the very proximal end of the main stylet, apparently with a slightly variable shape. The tube of the ‘seminal receptacle’ is unknown. Distribution. KENYA • South of Mombasa, Tiwi, Tiwi Beach, S4°1’1” E39°3’5”, coarse sand and shell gravel from a tide pool near the reef front (TYPE LOCALITY) (6 October 1991). Mombasa, McKenzie Point on walking distance south of the Kenya Marine and Fisheries Research Institute, very fine sand and algae from a shallow tide pool just past the second obelisk (1 October 1991); same locality, S4°0’4” E39°4’2”, on seagrass and in relatively fine sediment from shallow tide pools (30 September 1991) and in coarse shell-gravel on a rock in the mid- and low littoral (27 September 1991). Material examined. Eight whole mounts, one of which designated the holotype (FMNH id.luomus. fi/KV. 547), the rest deposited as reference material in the collections of Hasselt University (HU XXIII. 4.29– HU XXIII.4.35). One whole mount (HU XXIII. 4.31) could not be measured. One serially sectioned specimen (HU XXIII. 4.36). Etymology. The species name refers to the variable position of the accessory stylet. Mutabilis (Lat.): changeable. Additional remarks. The ratio length of accessory stylet/ prostate stylet is extremely small in this species, which makes it very easy to distinguish from all other species within the genus. In most specimens, the accessory stylet is somewhat comma-shaped, whereas in one specimen from McKenzie Point (UH XXIII.4.32; Fig. 7B, F) it is more straight. Moreover, the position of the accessory stylet seems to vary slightly from specimen to specimen, especially when only looking at the distal part of this stylet. However, it is always attached just distally from the curl, which is apparent when carefully observing the very position of attachment. Published as part of Monnens, Marlies, Schockaert, Ernest R., Diez, Yander L., Revis, Nathalie, Janssen, Toon, Jouk, Philippe E. H., Tessens, Bart, Van Steenkiste, Niels W. L. & Artois, Tom J., 2025, On the genus Lagenopolycystis Artois and Schockaert, 2000 (Platyhelminthes, Kalyptorhynchia, Polycystididae), pp. 357-376 in Zootaxa 5659 (3) on pages 369-370, DOI: 10.11646/zootaxa.5659.3.3, zenodo.org