Phyllidia ovata, Wägele & Raubold & Papu & Undap & Yonow, 2025

Wägele, Heike, Raubold, Lina Marie, Papu, Adelfia, Undap, Nani & Yonow, Nathalie, 2025, On two new Phyllidia species (Gastropoda, Nudibranchia, Doridina) and some histology from the Coral Triangle, ZooKeys 1245, pp. 1-18 : 1-18

Phyllidia ovata sp. nov.

Fig. 2 A, B

Phyllidia sp. 9: Gosliner et al. 2015: 282 ( Philippines); Papu et al. 2022: fig. 5.4 a (Bunaken Is., Indonesia, same specimen).

Phyllidia sp. : Stoffels et al. 2016: figs 4, 7 G ( Ternate, Indonesia).

Phyllidia sp. 10: Gosliner et al. 2018: 217 (same individual in Gosliner et al. 2015 as Phyllidia sp. 9).

Note.

Kato 2002 (http://www.seaslugforum.net/find/6414), size 50 mm, 30 m depth ( Japan).

Type material.

Holotype: • Phsp 15 Bu- 1 ( MZB. Gst. 25761 ), Cela Cela , Bunaken Island, North Sulawesi, Indonesia [1°36'42.4"N, 124°46'4.7"E], collected 13 August 2015 at a depth of 16 m, 35 mm in length alive . Available CO 1 ( MZ 964198 ) and 16 S ( MZ 955502 ) sequences are published in Papu et al. (2022 as Phyllidia sp. 9 ).

Diagnosis.

The mantle is elongate oval, white (rarely with a tinge of blue) with a clean-margined oval black area covering the central notum. Anteriorly, this black pigment forms a rounded U-shape around the first midline tubercle placed in front of the rhinophores (Fig. 2 A, B ). Large white conical tubercles have yellow apices in the middle three rows and are only present in the black area. The broad white mantle skirt has smaller white tubercles decreasing in size towards the margin. Yellow rhinophores arise from translucent white rhinophoral sheaths that are distinctly raised; a rhinophoral tubercle with a yellow cap is present. The hyponotum is grey to white, and the foot sole has a black line in the mid-line; the top of the foot is white with no markings. The anus opening is placed ventrally, beautifully illustrated by Kato (2002), who also recorded the maximum size of 50 mm.

Distribution.

Western Pacific Ocean: Indonesia: Ternate ( Stoffels et al. 2016 as Phyllidia sp. ; provided georeference: -0.03108, 127.23383); Bunaken Island, North Sulawesi ( Papu et al. 2022 as Phyllidia sp. 9 ; provided georeference: 1.61178, 124.76798; https://nudipixel.net/photo/00020926); Sulawesi (https://www.ryanphotographic.com/phyllidiidae.htm#picta); Wakatobi (size 49 mm: http://www.seaslugforum.net/find/4130, https://nudipixel.net/photo/00016149); Japan ( Kato 2002: size 50 mm, 30 m depth: http://www.seaslugforum.net/find/6414; provided georeference: 33.093833, 139.768195): Taiwan, East China Sea (https://www.inaturalist.org/photos/430366532; provided georeference: 25.117593, 121.925725, https://www.inaturalist.org/observations/134824066; provided georeference: 25.14486, 121.80532); Philippines: ( Gosliner et al. 2015: 282 as Phyllidia sp. 9 , 80 m depth; Dauin https://nudipixel.net/photo/00023935); Australia: Western Australia (https://www.inaturalist.org/observations/110074843; provided georeference: -21.86156, 114.16379), Queensland (https://www.inaturalist.org/observations/189262927; provided georeference: -17.20932, 146.07441).

Remarks.

This species is so distinctive that the internet photographs listed above can be confidently assigned to P. ovata , first recorded more than 20 years ago. Interestingly, several images were located in files of P. picta Pruvot-Fol, 1957 and P. coelestis in both iNaturalist and NudiPixel. To further confuse matters, Yonow (2011) depicted an animal from Western Australia (Kimberley) as Phyllidia coelestis (dark form) that resembles our new species in external colouration. However, the anus of this Australian specimen opens dorsally and not ventrally, and there is no black line present on the foot. Additionally, this specimen has black blotches within the white area, another feature not observed in the specimens and images of P. ovata sp. nov.

Etymology.

This species name is the diminutive form of the Latin adjective ovatus, - a, - um (egg-shaped) and refers to both the species’ body form as well as the coloured pattern.

Figures

Figure 2. Phyllidia ovata sp. nov. holotype (Phsp 15 Bu- 1, Cela Cela, Bunaken Island), living specimen 35 mm. A. Dorsal view; B. In situ on a reef wall overgrown with coralline algae, filamentous green algae, sponges, small hydroids, and serpulids.