Acinetid Suctoria

Diagnostic characters of Trematosoma and Limnoricus Jankowski, 1981 . The taxonomy of acinetid Suctoria is quite confusing and species with similar characters like a flattened lorica and one to few rows of tentacles have been grouped in different genera, viz Trematosoma and Limnoricus (see Jankowski 1981; Dovgal 2002; Dovgal et al. 2008; Dovgal & Lozowskiy 2008). Species of Trematosoma, Limnoricus ceter Jankowski, 1981, and L. seticolus (Jankowski, 1981) possessed a stalk separated from the lorica, whereas L. ponticus Dovgal & Lozorowskiy, 2008 showed a thecostyle with the lorica gradually diminishing in diameter to the basis (Pritchard 1852; Maupas 1881; Gruber 1884; Collin 1909; Precht 1935; Guilcher 1950; Allgén 1951; Jankowski 1981; Dovgal & Lozorowskiy 2008; this paper). Based on this observation, Dovgal et al. (2008) discussed placing L. ponticus in a different genus but refrained from this. The differences between L. ceter, L. seticolus, and species of Trematosoma appear to be more species-specific than genus-specific, and at some stage L. ceter and L. seticolus may have to be transferred to Trematosoma .

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TABLE 7. (Continued)

Species Character T. amphiasci (Precht, 1935) T. bocqueti (Guilcher, 1950) T. complatana (Gruber, 1884) T. constricta (Collin, 1909) T. falcata (Jankowski, 1981) T. ovata (Pritchard, 1852) T. pusilla (Maupas, 1881) T. rotunda (Allgén 1951) , T. husselae sp. nov. Arrangement of tentaclesone row left and right with ca. 9 tentacles each, small gapone row left and right with 18–20 tentacles each, small gap; [2 short and 2 or 3 long tentacles at each corner of lorica, broad gap]one row left and right with ca. 10 tentacles occurring also laterally, broad gapone row left and right with small gap; [and 11–14 or 8–28 tentacles]one row left and right with 5–6 tentacles each, small gapsingle row, ca. 11single row, 4–5 tentaclesca. 12–19 tentacles in one? rowone row left and right with 8–16 tentacles each, small gapLength of tentaclesshort; [11– 12 µm, thick and 48–50 µm, thin]-; [11–12 µm or 48–50 µm]-; [50 µm]long; [30–69 µm; 17–31 µm]very short-short; [10 µm]4–6 µm; [4 µm]4–6 µmEndogenous buddingnot observed yet+, embryo 25 µm x 10 µmnot observed yet+not observed yetnot observed yet+not observed yet+, embryo 13–15 µm x 8–10 µmOriginal basibiont; [additional basibionts]CopepodaCopepoda; [on debris]-; [Hydrozoa; Bryozoa] Crustacea: Paguridaegreen algaeHydrozoaBryozoa; [algae; Hydrozoa; tubes of Polychaeta; Copepoda]NematodaKinorhynchaOriginal location(s); [additional location]Baltic Sea: Kiel Bight; [Adriatic Sea]English Channel: Roscoff; [Western Australia]Ligurian Sea: GenuaEnglish Channel: Roscoff; Mediterranean Sea: BanyulArctic Ocean, MurmanskNorth Sea: United KingdomAlgeria: Algier; [Adriatic Sea] Falkland Islands; [India, Sundarbans North Sea: Sylt]North Sea: Sylt] Remarks, Fernandez- Batisse 1972; Collin 1912; original description described Curds 1985; Curds 1985: this paper additional Leborans et Post et al. 1983 Curds 1985 brief, illustration without Fernandez- Acineta ovoidea references al. 2012 and more detailed name by Leborans et Allgén, 1951 = description in Collin Alder 1851; al. 2012 synonym of T. 1912; Fernandez- Curds 1985 rotunda, because Leborans & Gabilondo just lateral view; 2006; Fernandez- Ghosh & Mandal Leborans et al. 2013 2019

One more distinctive genus-specific character might be the reproduction via semi-circumvaginative budding in L. ponticus versus internal budding in T. bocqueti, T. constricta, T. pusilla, and T. husselae sp. nov.; however, reproduction in L. ceter and L. seticolus is unknown, semi-circumvaginative budding may represent a character of L. ponticus only (Table 7; Maupas 1881; Collin 1912; Batisse 1972, 1975; Jankowski 1981; Curds 1985; Dovgal et al. 2008; Dovgal & Lozowskiy 2008; this paper). The differing types of budding within Suctoria were used by Batisse (1975) to justify new taxonomic categories. These types of reproduction were mainly based on cultivated species allowing in-depth studies. Unfortunately, such detailed information is lacking for almost all species of Limnoricus and Trematosoma . Although we had quite a large amount of specimens of T. husselae sp. nov. available, we noticed only swarmers inside the zooid and a swarmer, which seemed to have left its parent (comp. Figs 2A, 4D, and 5A, B with Fig. 4E). The image provided for L. ponticus about semi-circumvaginal budding did not allow to see that character clearly, so we relied on the statements of the authors (Dovgal et al. 2008, fig. 2B; Dovgal & Lozowskiy 2008, fig. 2).