Phyllidia haegeli ( Fahrner & Beck, 2000 )

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 : 599

Phyllidia haegeli ( Fahrner & Beck, 2000)

Phyllidia haegeli (Fig. 5.3a–e) is represented in our collections by seven specimens. The species possesses an anal opening on the ventral side, but the colouration and tubercular pattern resemble that of P. varicosa . The species is characterised by four black lines running along three longitudinal tubercular ridges, which meet behind the rhino-tubercle and usually meet behind the second median tubercle. Shorter horizontal black lines may originate from the longitudinal stripes and extend to the margin resembling the trapezoidal markings of P. picta or P. elegans . Single rounded tubercles on the ridges are capped by yellow, often with confluent bases, whereas the small tubercles on the blue marginal band may lack this yellow cap. One distinct yellow tubercle lies anteriorly between rhinophores. The marginal band resembles that of P. coelestis in being blue, somewhat granular, with tiny tubercles and flecks of black. The foot sole is grey to blue with a somewhat darker stripe or band down the middle. We assume that there was no such band remaining on the type specimen when it was examined: Fahrner and Beck (2000) clearly state that the specimen was not photographed alive (as they thought it was a P. varicosa , presumably with a ventral black line?) and that the black pigment disappeared after some time. Figure 5.3d depicts one of our P. haegeli specimens (Phva16Sa51) in the field showing the high degree of similarity to P. varicosa and the probable misidentifications that will have occurred when only photographs are examined (e.g., on internet sites such as Sea Slug Forum and iNaturalist) when not specifically searching for the position of the anal opening. In future, each specimen of P. varicosa will have to be carefully examined. Phylogenetic analyses support the monophyletic clade with a bootstrap value of 100 and a rather low intraspecific variability of 0.7% (Table S4).

One P. haegeli specimen (Phco15Bu1, Fig. 5.3a) was analysed chemically using LC-HRMS (Fig. S7a). Its metabolomic profile is dominated by sesquiterpenes functionalised with isonitrile and formamide moieties, whereas amphilectene-type diterpenoids found in P. coelestis and P. elegans are absent.