Phyllidiopsis krempfi Pruvot-Fol, 1957

Papu, Adelfia, Bogdanov, AleXander, Bara, Robert, Kehraus, Stefan, König, Gabriele M., YonoW, Nathalie & Wägele, Heike, 2022, Phyllidiidae (Nudibranchia, Heterobranchia, Gastropoda): an integrative taxonomic approach including chemical analyses, Organisms Diversity & Evolution (New York, N. Y.) 22 (3), pp. 585-629 : 601-603

Phyllidiopsis krempfi Pruvot-Fol, 1957

Our 16 specimens of P. krempfi (Fig. 7.1a–j) have a pink notum with irregular black lines that meander between the tubercles. Two main longitudinal black lines merge in front ◂ Fig. 7 Phyllidiopsis species and specimens with identifiers. Scale bars: 10 mm. 1a–j Phyllidiopsis krempfi : a Phskr18Ba1; b Phfi16Sa2; c Phspi18Ba1; d Phpu16Sa72; e Phsh15Bu1; f Phfi16Sa1; g 18TMphni7; h Phpu15Bu37; i Phpu16Sa58; j Phpu16Sa66. 2a–d Phyllidiopsis burni : a Phssp.a18Ba1; b Phpu16Sa19; c Phpu16Sa47; d Phpu16Sa55. 3a–d Phyllidiopsis sp. a: a Phskr18Ba2; b Phpu16Sa42; c Phpu16Sa45 d Phpu16Sa59

of the rhinophores and run backwards where they can merge behind the anal opening or may stay separate. The rhinophores are black on the tip and posterior part, but pink on the anterior side. The hyponotum and foot sole are grey; the oral tentacles are rectangular in shape, with grey to black along the lateral grooves. Phyllidiopsis krempfi is very similar in its external appearance to P. pipeki Brunckhorst, 1993 , which was described as having two longitudinal black lines and large complex pink tubercles forming a crest on the midline. The foot sole, oral tentacles, and hyponotum are pale pink to grey. In general, it is very difficult to distinguish between these two species, and several of our specimens (Phskr18Ba1, Fig. 7.1a; Phspi18Ba1, Fig. 7.1c; Phsh15Bu1, Fig. 7.1e; Phfi16Sa1, Fig. 7.1f) match the original and subsequent descriptions of P. pipeki (see Brunckhorst, 1993; Yonow, 2011). However, these specimens clearly group with typical P. krempfi colour morphs in our molecular analyses ( Fig. S1 ). Furthermore, some specimens of P. krempfi depicted by Stoffels et al. (2016) have oral tentacles without the black-grey colouration along the sides; these specimens of P. krempfi (RMNH.Moll.336453, 336512, and 336469) show a colouration that matches the original description of P. pipeki , but the tuberculate notum matches the description of P. krempfi . We also have four specimens with characters of P. pipeki on the ventral side, but characters of P. krempfi on the dorsal side, further supporting this synonymy. In our molecular investigations, all P. pipeki colour morphs grouped together with P. krempfi from Sulawesi (this study), Ternate, and Papua New Guinea ( Stoffels et al., 2016), and Terengganu, Malaysia ( Alqudah et al., 2015). Based on these results, P. pipeki is here considered a synonym of P. krempfi . Phyllidiopsis krempfi as a monophyletic group is supported by a bootstrap value of 100 and shows an intraspecific genetic variability of 2.43% (Table S5).

Three P. krempfi specimens were selected for chemical analysis. Specimens Phpu16Sa58 and Phpu16Sa66 (Fig. 7.1i, j) from Sangihe Island had identical chemical profiles with one major metabolite (see Fig. S8a ). Fractionation and HPLC separation of the crude extract of Phpu16Sa66 led to the isolation of 7-isocyano-7,8-dihydrobisabolene (Fig. S4a) as the major metabolite. This natural product was first reported from a Ciocalypta sponge ( Gulavita et al., 1986). The structure was unambiguously established by comparison of its 1 H and 13 C NMR spectra with published data. Intriguingly, the MS data of the main compound in the crude extract of Phpu16Sa66 show a series of m/z values, i.e., 205.191, 232.202, and 259.215 [M + H] +. The m/z 259.215 can be reasonably explained with an undescribed corresponding sesquiterpene core bearing two isonitrile functions (Fig. S4c), and thus, the isolated compound could be regarded as an artefact.

Interestingly, the metabolomic profile of the third P. krempfi specimen (Phpu15Bu37, Fig. 7.1h) collected in Bunaken Island was significantly different from the other two analysed specimens Phpu16Sa58 (Fig. 7.1i) and Phpu16Sa66 (Fig. 7.1j) from Sangihe Island, which is approximately 200 km north of Bunaken Island. In addition to 7-isocyano-7,8-dihydrobisabolene, its extract contained several other major constituents that could be identified as sesquiterpene isonitriles based on diagnostic ions.

Figures

Fig. 1 Sampling locations in Sulawesi, Indonesia

Fig.8 Phyllidiopsis species and specimens with identifiers. Scale bars: 1–3 1 mm; 4 10 mm. 1a–d Phyllidiopsis xishaensis: a Phst16Bu1; b Phst16Bu2; c Phsxi18Ba1; d Phsxi18Bu1. 2a–c Phyllidiopsis annae: