Pseudoposthia hanssoni Atherton & Jondelius 2022, sp. nov.

• Main Authors: Atherton, Sarah, Jondelius, Ulf
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2022
• Subjects: Biodiversity; Taxonomy; Animalia; Xenacoelomorpha; Acoela; Isodiametridae; Pseudoposthia; Pseudoposthia hanssoni; North Atlantic
• Online Access: https://doi.org/10.5281/zenodo.6953865; http://treatment.plazi.org/id/CF6B87F3E62B8504FF6FFBE0FE48FE40

Pseudoposthia hanssoni sp. nov. Figure 11 Zoobank registration. urn:lsid:zoobank.org:act: 0E41935C-E677-427A-BA6C-EB5683043453 Materials examined. Digital video and photographs of original living specimens, Holotype (SMNH Type-9481) and Paratype (SMNH Type-9482). Type locality. Väderöarna naturhamn, Skagerrak, Sweden, 58°34’52 N, 11°03’52 E Habitat. 4–6 m depth, coarse sand and rocks with some shell hash Diagnosis. Body length 0.45 mm long and to 0.15 mm wide in squeezed preparation. Frontal organ well-developed. Rhabdoid glands numerous and scattered. Several large vacuoles present in posterior half of the body. Ovaries and testes paired. Bursa absent. Unwalled false seminal vesicle located ventral to the ovaries and anterior to the largest egg, leading directly to the gonopore posterior to the penis. Glandular penis straight, 9–10 µm long. Gonopore large and distinct, surrounded by thick muscular sphincter. Etymology. This species is named in honor of the late Dr. Hans G. Hansson, expert in North Atlantic marine fauna and long-time staff member at Tjärnö marina laboratorium. Description. Animal short and wide, body length 0.45 mm and width to 0.15 mm in squeeze-preparation. Specimens widest at midbody with broadly rounded anterior end and pointed rounded posterior end. Body colorless, transparent, except for parenchyma, which varies from bright green or yellowish-brown based on microalgae food. Digestive parenchyma extends from first ¼ body length to just anterior of posterior vacuoles. Mouth present just anterior to body’s midpoint. Several vacuoles present laterally in posterior half of the body. Frontal organ well-developed. Statocyst present 50 µm from anterior end, 11–12 µm in diameter with 7-8 µm in diameter statolith. Epidermis completely ciliated and ~5 µm wide in longitudinal sections. Cilia ~6–8 µm long. Rhabdoid glands numerous and scattered across the body. Rhabdoids partially subepidermal, 8–10 µm in length in living specimen. Paired ovaries with numerous eggs. Largest egg medial and ...