Karlingocelis karlingi, Schockaert & Curini-Galletti, 2025

Karlingocelis karlingi sp. nov.

ZooBank: urn:lsid:zoobank.org:act:

( Fig. 1 View FIGURE 1 )

Diagnosis. Species of Karlingocelis with ovaries at about 1/3rd between pharynx and brain and about 15 testes in a row between the vitellaria. Stylet 110–120 µm long with one pair of hooks about 60 µm long. Karyotype: n=5; FN=8.

Occurrence. Heron Island , Queensland, Australia, in front of the Research Station ; in slightly silty medium-coarse sand in tidal channels among coral outcrops (Lat. –23.443430, Long. 151.913221) ( October 1993) ( type locality). Heron Island, Shark Bay, lower intertidal, silty medium-coarse sand (Lat. –23.443516, Long. 151.918393) ( October 1993) .

Material studied. Several animals studied alive. Nine whole mounts from the type locality, one of which designated as holotype ( QM G238524 ) ; the remaining as paratypes ( CZM 840–848 ) ; four sectioned animals from the type locality ( CZM 849–852 ) . Three individuals from Shark Bay studied alive .

Etymology. Genus and species names dedicated to the late Prof. Tor G. Karling (1909–1998), Finland-born Swedish zoologist, who primarily contributed to the knowledge of free-living Platyhelminthes in 65 years of active research, and who described the first species of the new genus (see species below).

Description. The animals are colourless, with clusters of cnidocytes, arranged into a more or less regular dorsal line. In sections, the cnidocytes appear clearly enclosed into cnidosacs. The dorsal epidermis is low, with short cilia and insunk nuclei. The pharynx, slightly behind the body’s middle, is very long and has a long, glandular oesophagus. Behind the pharynx, a diaphragm can be seen.

With a row of about 15 testes running from just in front of the ovaries to the base of the pharynx. The globular seminal vesicles enter the more or less elongated prostate vesicle separately, at its postero-ventral side. The straight to faintly curved stylet is 95–115 µm long, 14 µm wide and with an oblique terminal opening. With two strongly sclerified hooks, about 60 µm long and 5–7 µm thick, in the male atrium. They have sharp, recurve distal tips and a conspicuous apophysis at their middle ( Fig. 1 D–F View FIGURE 1 ). Each hook is attached to a thick muscle, while a set of thinner muscles, not supporting hooks, alternate with them. In one individual, these thinner muscles bear a distinctly sclerified distal tip ( Fig. 1 G View FIGURE 1 ). All these fibers are connected basally to the muscle sheet surrounding the prostate vesicle. Further muscles depart distally from the prostate vesicle and insert on the body wall next to the genital pore.

The ovaries are at about 1/3rd between pharynx and brain, in front of the vitelline follicles that reach up posteriorly to the male copulatory organ. The ovo-vitelloducts join each other just in front of the copulatory organ and form the common female duct with a high epithelium, ciliated in its terminal part. A short dorsal genito-intestinal duct connects the female duct to the gut, just before it reaches the female pore. The cement glands around the female pore are strongly developed.

Karyotype. With five pairs of evenly-sized chromosomes; three pairs are meta- to submetacentric, and two pairs consist of distinctly acrocentric chromosomes ( Fig. 1 H View FIGURE 1 ).