Tvaerminnea karlingi, LUTHER, 1943

Van Steenkiste, Niels W. L. & Leander, Brian S., 2018, Molecular phylogeny of trigonostomine turbellarians (Platyhelminthes: Rhabdocoela: Trigonostomidae), including four new species from the Northeast Pacific Ocean, Zoological Journal of the Linnean Society 182, pp. 237-257 : 252-253

TVAERMINNEA KARLINGI LUTHER, 1943

( FIG. 6G)

Tvaerminnea karlingi Luther, 1943: 80–84 , figs 91–104; Ax, 1951: 369, table 11; Ax, 1956: 112– 114, 172, 179, fig. 27, tables 5, 8; Ax, 1959: 47, 99; Luther, 1962: 44–46, fig. 18; Straarup, 1970: 191, 198, table 1; Karling, 1974: 29, 60, table 1, figs 68–70; Hellwig, 1987: 175, 198, table 6; Ax, 2008: 307–309, fig. 135.

Tvaerminnea karlingi pacifica Karling, 1986: 208–209 , figs 33–38; Ax, 2008: 308, fig. 135D.

Tvaerminnea karlingi karlingi Karling, 1986: 208 .

New localities: Mud Bay Park , Surrey, British Columbia, Canada (49°05 ′ 09 ″ N, 122°51 ′ 39 ″ W), mud and algae in intertidal mudflat (29/07/2015). Departure Bay, Nanaimo, British Columbia, Canada (49°11 ′ 43 ″ N, 123°57 ′ 32 ″ W), coarse sand and shell hash in the low intertidal (12/04/2015) .

Known distribution: Northeast Atlantic Ocean: Baltic Sea (Luther, 1943, 1962; Ax, 1951; Straarup, 1970), Irish Sea ( Boaden, 1963), North Sea ( Hellwig, 1987). Mediterranean: Gulf of Lion ( Ax, 1956). Bosporus ( Ax, 1959). Northeast Pacific Ocean: California ( Karling, 1986).

Material: Observations on two live animals. Three whole mounts ( BBM MI4055 – MI4057 ). 18S rRNA (G e n B a n k a c c e s s i o n # M F3 2 1 7 5 5), 2 8S r R N A (GenBank accession # MF321764 ) .

Remarks: Animals as described by Luther (1943, 1962) and Karling (1986). The stylet measures 22–27 μ m (x = 25 μ m; n = 3) and consists of a tube, transversal folds and a crescent-shaped plate ( Fig. 6G). The bursa is only visible in the live animals and appears to have one or two tooth-like sclerotized folds. Based on the morphology of this ‘bursa comb’, Karling (1986) distinguishes two morphotypes: T. karlingi karlingi from the Northeastern Atlantic and Mediterranean, and T. karlingi pacifica from California. Unfortunately, we cannot attribute our specimens to one of these morphotypes, because the bursa comb is not visible in the whole-mounted specimens from British Columbia. Given the disjunct distributions of the Atlantic and Pacific population and the recognition of different morphotypes, it is not unlikely T. karlingi consists of two or more cryptic species (see also discussion on C. axi ).

MOLECULAR PHYLOGENETIC RELATIONSHIPS

The final 18S and 28S rRNA sequence data sets comprised 42 taxa and 1723 bp and 36 taxa and 1727 bp, respectively. This results in a concatenated data set (18S + 28S) of 42 taxa and 3450 bp for our phylogenetic analyses. Bayesian and ML topologies were congruent.

Results of the phylogenetic analyses are summarized in Figure 7A. The ingroup consists of two clades: (1) a clade with Litucivis serpens Ax & Heller, 1970 ( Adenorhynchinae Ax & Heller, 1970 ), and a polytomy of some representatives of Brinkmanniellinae , including T. karlingi , Cilionema hawaiiensis Karling et al., 1972 , and two species of Coronhelmis Luther, 1948 ; and (2) a clade with several genera of Trigonostominae , including Parapharyngiella Willems et al., 2005b , Trigonostomum , Beklemischeviella , Proxenetes , Ceratopera and Ptychopera . The outgroup consists of Microvahine corallicola Karling et al., 1972 ( Paramesostominae Luther, 1948 ); Promesostoma marmoratum (Schultze, 1851) von Graff, 1882 ( Promesostominae Luther, 1948 ); Byrsophlebs delamarei ( Ax, 1956) Karling, 1985 ( Byrsophlebidae von Graff, 1905 ); and Thalassoplanella collaris Luther, 1946 ( Typhloplanidae von Graff, 1905 ).

WithinTrigonostominae, all genera are monophyletic with high support values (bs = 100; pp = 1). Ceratopera sensu Den Hartog is paraphyletic because of the position of C. pacifica comb. nov. (formerly M. pacifica ) and C. complicata sp. nov., which are deeply embedded within Ceratopera . Parapharyngiella is the sister taxon of all other genera of Trigonostominae . Phylogenetic relationships among the remainder genera remain partly unresolved except for a sister group relationship between Beklemischeviella and Proxenetes .