Diversity in the family Isodiametridae (Acoela): New species bring back old problems Author Atherton, Sarah 0000-0003-3024-472X Department of Zoology, Naturhistoriska riksmuseet, Stockholm, Sweden & sarah. atherton @ nrm. se; https: // orcid. org / 0000 - 0003 - 3024 - 472 X sarah.atherton@nrm.se Author Jondelius, Ulf Department of Zoology, Naturhistoriska riksmuseet, Stockholm, Sweden & Department of Zoology, Systematics and Evolution, Stockholm Universitet, Stockholm Sweden & ulf. jondelius @ nrm. se; https: // orcid. ord / 0000 - 0003 - 2847 - 2192 ulf.jondelius@nrm.se text Zootaxa 2022 2022-08-02 5169 5 401 424 journal article 111181 10.11646/zootaxa.5169.5.1 d8cabaec-c613-4882-8a1c-e08d69a084e7 1175-5326 6952712 EB5A2C38-2D31-4F02-BEC1-2AA31761EFEA Baltalimania salinsula sp. nov. Figure 4 Zoobank registration. urn:lsid:zoobank.org:act: 7464785C-58B6-499C-BDCA-BEF48B373812 Materials examined. Digital video and photographs of original living specimen, Holotype ( SMNH Type-9425) FIGURE 4. Baltalimania salinsula sp. nov. A. micropictograph of the posterior focusing on the reproductive structures B. drawing of the whole body C. micropictograph of the whole body D. micropictograph of the male copulatory organ; dp digestive parenchyma, eg egg, f frontal organ, l lipid globule, mco male copulatory organ, mp male gonopore, p penis, r rhabdoid glands, st statocyst, t testes, v vacuole. Type locality. Saltö Badstrand , Strömstad , Sweden ; 58°52’41 N , 11°06’56 E Habitat. 2 m depth, marine, medium sand Diagnosis. Body length 0.85 mm . Body pigmentation absent. Frontal organ small. Rhabdoid glands distributed in longitudinal rows. Vacuoles absent. Paired testes and ovaries. Seminal bursa absent. Male copulatory organ with penis partially invaginated into the seminal bursa. Penis 27 µm long, curved. Male gonopore subterminal. Etymology. This species is named for its type locality, Saltö (Latin: sal salt; insula island) Description. Living specimen 0.85 mm long and to 0.18 mm maximum width. Free-swimming specimens elongate with rounded anterior end and pointed posterior. Body colorless, except for parenchyma, which is dark yellow or brown from food. Numerous lipid droplets of varying sizes present in digestive parenchyma and throughout the body, clear to yellow in color. Digestive parenchyma extends from just posterior of statocyst to posterior eggs. Mouth not observed. Frontal organ small, not extending to level of statocyst. Statocyst present 115 µm from anterior end, 15 µm in diameter with 11 µm statolith. Vacuoles absent. Epidermis completely ciliated. Cilia 6–7 µm long. Rhabdoid glands distributed in longitudinal rows. Posterior rhabdoid glands partially subepidermal, colorless, 8–10 µm in length. Ovaries and testes paired. Ovaries anterior to male copulatory organ, present in the posterior ~¼ of the animal. Seminal bursa absent. Vagina and female gonopore not observed. Male copulatory organ close to posterior end, globular with a width of 56 µm and a length of 52 µm. Penis partially invaginated into seminal vesicle. Penis small, 27 µm long, and curved. Male gonopore located at ventral midline.