Nematomenia banyulensis ( Pruvot, 1890 )

Cobo, M. Carmen, Farris, William J. & Kocot, Kevin M., 2024, New data on the biodiversity of Solenogastres (Mollusca, Aplacophora) in the Mediterranean Sea: findings from the program “ Our Planet Reviewed ” Corsica 2019 - 2022, Zoosystema 46 (21), pp. 543-576 : 556

Nematomenia banyulensis ( Pruvot, 1890)

Dondersia banyulensis Purvot, 1890: XXII .

Nematomenia banyulensis – Handl & Salvini-Plawen 2001: 371.

MATERIAL EXAMINED. — Corsica (France) [4 specimens] • 1 specimen (used for sclerite preparation, DNA extraction and histology); CORSICABENTHOS 2 ( Table 2 ); 60-100 m depth; MNHN-IM-2019-1747; GenBank: OR456215; OR458911; (1 microscope slide with sclerites, 1 SEM stub; 12 slides with 5 µm serial sections) • 3 specimens (preserved in ethanol); CORSICABENTHOS 1, 2 ( Table 2 ); 60-100 m depth; MNHN-IM-2019-16177, MNHN-IM-2019-16178, MNHN-IM-2019-16180 .

DESCRIPTION

Elongate-bodied animal (15-30 × 1 mm) of bright red color ( Fig. 3C ). Color fading after fixation and turning orange to yellowish. Without a cuticular keel but with a prominent dorsal line formed by the sclerites that is translucent and shiny. Usually coiled, even while alive. Thin cuticle, with imbricate, rounded leaf-like scales ( Fig. 7A ) with a bifid proximal end (65-78 × 40-45 µm) ( Fig. 7D ), with less abundant oar-shaped scales (60-70 × 20 µm) ( Fig. 7B ) between them. With differentiated knife-shaped scales along the pedal groove (40 × 10-14 µm) ( Fig. 7C ). Without radula. Ventrolateral foregut gland of type A / Acanthomenia type. Without copulatory stylets.With a dorso-terminal sensory organ visible externally in live animals.

REMARKS

As for the previous species, the external aspect was important for species identification. N. banyulensis is, however, similar to N. flavens , a species described from the same locality and in the same work ( Pruvot1890). An important difference between both species is the external aspect when they are alive, as N. banyulensis is bright red and N. flavens is yellow ( Pruvot 1890, 1891: figs1, 2; Odhner1920; Salvini-Plawen 2003; Handl & Salvini-Plawen 2001). Color can be lost after fixation; thus, it has been suggested that some later records of the species may be a misidentification ( Salvini-Plawen 2003). Nevertheless, they can be distinguished based on the sclerites, as the short scales with a bifid proximal end (founded in the Corsica specimens, Figure 7D ) are exclusive to N. banyulensis ( Pruvot 1890; compilation of sclerite drawings in Handl & Salvini-Plawen 2001: figs 7-9). A third species of Nematomenia has also been described from the Mediterranean Sea, N. corallophila ( Kowalevsky, 1881) . While N. corallophila shares coloration with N. banyulensis , it is important to note that the former’s description lacks detailed anatomical information and it just highlights that it is epizootic on Corallium rubrum (Linnaeus, 1758) ( Kowalevsky 1881; Salvini-Plawen 2003). The absence of type material impedes a comprehensive comparison of the two species and as a result, we agree with Salvini-Plawen (2003), and the identification of specimens as N. corallophila can be only considered when observed on this specific coral. For the first time we include here DNA barcodes for N. banyulensis . The quality of the obtained serial sections does not allow to a perfect reconstruction of all the internal organs but was good enough to confirm the absence of radula and copulatory stylets.

N. banyulensis was first described off Banyuls-sur-Mer ( France) at a depth of between 60 and 80 m ( Pruvot 1890, 1891) which corresponds with the depths of the localities from Corsica. Other records of this species include localities in the Adriatic Sea, off Naples and in the North Atlantic Ocean (English Channel, Shetland Islands, Roscoff, Giiteborg and Norwegian fjords) at depths between 45 and 300 m ( Thiele 1894; Pruvot 1899; Seaward 1990; Handl & Salvini-Plawen 2001), and it has been found epizoically on hydrozoans, including Lafoea dumosa (Fleming, 1820) , Lytocarpia myriophyllum (Linnaeus, 1758) and Grammaria abietina (Sars, 1851) in muddy bottoms ( García-Álvarez et al. 2014). With the specimens included in this work, we add new locations in the Mediterranean Sea. Specimens from Corsica were not observed on cnidarians, but this can be explained as they were collected using dredges and found while sorting sieved material.

Figures

FIG. 3. — Habitus of A, Dondersia festiva Hubrecht, 1888 (photo of the living animal – MNHN-IM-2019-18277); A’, Dondersia festiva (photo of the living animal – MNHN-IM-2019-16169); A’’, detail of the dorsoterminal sensory organs (MNHN-IM-2019-16169); B, Anamenia gorgonophila (Kowalevsky, 1880) (photo of the living animal on Paramuricea sp.): B’, Anamenia gorgonophila (photo of the preserved specimen – MNHN-IM-2019-18270); C, Nematomenia banyulensis (Pruvot, 1890) (photo of the preserved specimen – MNHN-IM-2019-16178); D, Dorymenia vagans (Kowalevsky & Marion,1887) (photo of the preserved specimen – MNHN- IM-2019-18274). Scale bars: 1 mm. Symbols: arrows, dorsoterminal sensory organs; stars, anterior end of the animals.

FIG. 7. — SEM images of the sclerites of A-D, Nematomenia banyulensis (Pruvot, 1890) (MNHN-IM-2019-1747); E, Tegulaherpia cf. myodoryata (MNHN- IM-2019-16176); F, Simrothiella margaritacea (Koren & Danielssen,1877) (MNHN-IM-2019-18280); G, H, Dorymenia vagans (Kowalevsky & Marion,1887) (MNHN- IM-2019-18274); I, Anamenia gorgonophila (Kowalevsky, 1880) (MNHN-IM-2019-18270). Scale bars: 20 µm.