Mola tecta, Nyegaard & Sawai & Gemmell & Gillum & Loneragan & Yamanoue & Stewart, 2018

Nyegaard, Marianne, Sawai, Etsuro, Gemmell, Neil, Gillum, Joanne, Loneragan, Neil R., Yamanoue, Yusuke & Stewart, Andrew L., 2018, Hiding in broad daylight: molecular and morphological data reveal a new ocean sunfish species (Tetraodontiformes: Molidae) that has eluded recognition, Zoological Journal of the Linnean Society 182, pp. 631-658 : 644-648

MOLA TECTA SP. NOV

( TABLE 1; FIGS 1–10, 12)

urn:lsid:zoobank.org:act:0AE4167C-A2FE-4E77-BD45-B0D465410988

New English name: Hoodwinker ocean sunfish. New Japanese name: Kakure-manbo

Orthragoriscus mola (not of Linnaeus) – Lidth de Jeude, 1890: 189–190, Pl. 8.

Mola ramsayi (not of Giglioli) – Gauldie, 1992: 263–266 [description of skin structure], figs 4–6 – Bass et al., 2005: 405–413 [as ‘Atlantic group’], figs 2, 3, table 1; accession numbers AY940816 and AY940826 (partial D-loop); AY940834 and AY940838 (cyt-b).

Mola group C Yoshita et al., 2009: 237, NNSW- 1 in table 1 and figs 3, 4; Accession number AB439108 (D-loop).

Mola species C of Yoshita et al., 2009 – Ahuir-Baraja et al., 2017: 1133, table SI, fig. 2 – Sawai et al., 2017: 99–102, figs 1, 2, table 1.

Holotype: NMNZ P. 057679 ( Fig. 4) (fresh measurements: 101.1 cm TL; measurements after fixation: 101.2 cm TL), male, North Taranaki Bight, west coast North Island, New Zealand (38°25.5 ′ S 174°9.0 ′ E), trawl, 78 m, 25 December 2015; coll.: observer Scott Yeoman FV Ivan Golubets, OBS 4552/050. Measurements (fresh and after fixation) provided in Supporting Information, Table S 3.

Paratypes: Eleven specimens (49.9–90.5 TL): AIM MA29864 (51.1 cm TL), female, whole specimen in isopropyl alcohol, Poor Knights Islands , New Zealand (35°29.3'S 173°43.7’E), 8 November 1969 ; NMNZ P.001418 (60.2 cm TL), male, whole specimen in isopropyl alcohol, off Hawke’s Bay, New Zealand (39°25 ′ S 177°6 ′ E), June 1952 ; NMNZ P.002980 (64.6 cm TL), male, whole specimen in isopropyl alcohol, North Rona Bay , Eastbourne, Wellington Harbour, New Zealand (41°16 ′ S 174°55 ′ E), drag net, coll.: Robert Falla, 30 November 1960 ; NMNZ P.005890 (49.9 cm TL), female, whole specimen in isopropyl alcohol, off Great Barrier Island , New Zealand (36°5 ′ S 175°35 ′ E), trawl 36–37 m, coll.: C. Gaelic, 25 June 1973 ; NMNZ P.006126 (64.8 cm TL), female, whole specimen in isopropyl alcohol, Oriental Bay , Wellington Harbour, New Zealand (41°17.40 ′ S 174°47.587 ′ E), beach cast, 29 June 1955 ; NMNZ P.033995 (57.2 cm TL), male, whole specimen in isopropyl alcohol, Bay of Plenty, Opotiki Beach , New Zealand (37°45 ′ S 177°20 ′ E), November 1996 ; NMNZ P.034187 (79.7 cm TL), male, whole specimen in isopropyl alcohol, Bay of Plenty, surf at Opotiki , New Zealand (37°45 ′ S 177°20 ′ E), hand, coll.: Andy Glazier ; NMNZ P.034217 (69.8 cm TL), male, whole specimen in isopropyl alcohol, Bay of Plenty, Opotiki Beach , New Zealand (37°44 ′ S 177°20 ′ E), coll.: Andy Glazier, December 1996 ; NMV A18725 (90.5 cm TL), whole specimen in isopropyl alcohol, Port Phillip Bay, Victoria (37°52 ′ S 144°49 ′ E), coll.: F. Hadathy & S. Praljak, 28 August 1995 ; NMV A26565-001 (78.5 cm TL), whole specimen in isopropyl alcohol, Barwon Heads , Victoria (38°17.4 ′ E 144°27.36 ′ S), coll.: Warren Chapman, 30 April 2009 ; SAMA F7542 (c. 90 cm TL), whole specimen in ethanol, Spencer gulf, South Australia (34°47.4 ′ S 138°28.8 ′ E), coll.: J. Verrier, 27 June 1994 [current specimen label indicates 1989, considered an error by collection authority ( R. Foster , SAMA, personal communication, February 2017)] .

Other material: Sixteen specimens (62–242 cm TL): AIM MA30933 (102 cm TL), cast from fresh specimen, New Zealand ; G06 (62 cm TL), live specimen (not retained), northeast of North Island , New Zealand, (36°30 ′ S 177°45 ′ E), long-line, 8 July 2013 ; NZ01 (212 cm TL), fresh specimen (not retained), Otago Harbour , New Zealand (45°49 ′ S 170°37 ′ E), beach cast, 18 February 2015 ; NZ07 (100 cm TL), fresh specimen (not retained), Banks Peninsula , New Zealand (43°50 ′ S 172°40 ′ E), beach cast, 30 April 2014 ; NZ08 (151 cm TL), fresh specimen (not retained), Banks Peninsula , New Zealand (43°50 ′ S 172°40 ′ E), beach cast, 30 April 2014 ; NZ09 (193 cm TL), fresh specimen (not retained), Banks Peninsula , New Zealand (43°50 ′ S 172°40 ′ E), beach cast, 30 April 2014 ; NZ12 (155 cm TL), female, fresh specimen (clavus, skin sample retained), Birdling’s Flat , Banks Peninsula, New Zealand (43°49 ′ S 172°42 ′ E), beach cast, 10 May 2014 ; NZ14 (170 cm TL), fresh specimen (not retained), near Birdling’s Flat , Banks Peninsula, New Zealand (43°50 ′ S 172°40 ′ E), beach cast, 14 December 2015 ; NZ17 (81 cm TL), male, fresh specimen (clavus, skin sample retained), west of South Island , New Zealand (41°32 ′ S 170°56 ′ E), purse seine, 12 April 2014 ; NZ18 (65 cm TL), female, fresh specimen (clavus retained), east of North Island , New Zealand (38°47 ′ S 178°25 ′ E), long-line, 17 May 2014 ; NZ19 (69 cm TL), male, fresh specimen (clavus retained), east of North Island , New Zealand (35°9 ′ S 176°3 ′ E), long-line, 10 August 2014 ; OMNZ VT3249 (78 cm TL), cast from fresh specimen, Kaka Point , Clutha District, New Zealand, (46°22 ′ S 169°44 ′ E), beach cast, 7 March 1963 ; OMNZ VT3248 (242 cm TL), cast from fresh specimen, Otago Harbour , Dunedin, New Zealand (45°49 ′ S 170°38 ′ E), beach cast, 1961 ; OMNZ X2017.19 (169 cm TL), female, fresh specimen (not retained), North Taranaki Bight, New Zealand (38°26 ′ S 174°9 ′ E), beach cast, 18 January 2017 ; RMNH. PISC.D.2059 (223 cm TL), female, mounted skin, Ameland, Netherlands, beach cast, 13 December 1889 ; TMAG D3912 (150 cm TL), fresh specimen (not retained), Lindisfarne , Tasmania, Australia (42°51 ′ S 147°20 ′ E), beach cast, 12 December 2014 .

Diagnosis: Within the investigated size range (50– 242 cm TL), M. tecta sp. nov. is diagnosed from others in the genus Mola by the following combination of characters: slender body shape without head bump or chin bump; tapered profile when viewed from the front, with the widest point across the eye area; short dorsolateral ridge to posterior end of pectoral fin; rounded profile without protruding snout. Pronounced smooth band consisting of creased, elastic skin with highly reduced density of body scales; distinctive smooth band back-fold diving the clavus into a smaller upper and larger lower portion. Rounded clavus, slightly crenulated, with an indentation associated with the smooth band back–fold. Usually 11–13 pectoral fin rays, 17–19 dorsal fin rays, 16–18 anal fin rays, 15–17 clavus fin rays (13–15 principal rays, 2 minor rays along the edges of the smooth band back-fold); usually 5–7 separate ossicles on the clavus edge in specimens over 65 cm TL; no ossicles or ossification associated with the smooth band back-fold, ossicles on paraxial fin rays separate, of similar size to the neighbouring clavus ossicles. Body scales with conical, non-branching erect central point of differing sizes.

Description: Description of the holotype ( Fig. 4) followed by a range of paratypes and sample specimens in brackets (see Table 1 for the contribution of data from individual paratypes and sample specimens).

A species of Mola with the typical characteristics for the genus, most notably a deep body, highly compressed laterally, truncated, lacking a true caudal fin, near-symmetrical, spineless dorsal and anal fins. Eyes small, round; two small nostrils located in front of eye; mouth small, terminal; teeth fused, beaklike; gill openings small, oval, located in front of the pectoral fins, and covered by a soft gill membrane; gill rakers are concealed under the subcutaneous gelatinous layer; all fins are spineless; caudal fin and pelvic fin absent; pectoral fin small, round, located mid-laterally, fitting into a shallow groove in the side of the body; caudal fin replaced by a clavus, comprised of highly modified elements of the dorsal and anal fins; body covered in thick subcutaneous gelatinous layer except for pectoral, dorsal and anal fins, skin covered in thick mucus, anal opening immediately anterior of anal fin.

No head bump (0), no chin bump (0), no swollen dorsolateral or ventrolateral ridges on body (0); short dorsolateral ridge to posterior end of pectoral fin reflecting the underlying cranio-skeletal structure, front profile tapered (in all investigated specimens) ( Figs 5, 6). Lateral profile rounded, without protruding snout (0) or any indications thereof (0) ( Fig. 5B). Holotype of typical body dimensions ( Fig. 7); M. tecta maintains its body proportions with growth, with similar length and depth measurements as percentages of TL across the investigated size spectrum; total body depth ( TBD) relative to TL appears to decrease with growth, due to shorter dorsal and anal fins relative to TL in larger specimens ( Figs 6, 7A).

Eleven (11–13) pectoral fin rays, 18 (17–18) dorsal and 17 (16–18) anal fin rays, 15 (13–15) regularly spaced principal clavus fin rays, with 7 (5–7) above, and 8 (7–8) below the smooth band back-fold. An additional 2 (2) minor fin rays embedded along the edges of the smooth band back-fold; minor fin rays and back-fold positioned between the two paraxial fin rays ( Fig. 8). Seven (0–7) ossicles: 3 (0–3) above, and 4 (0–4) below the smooth band back-fold ( Figs 4, 5C), positioned on the crest of slight crenulations on the clavus trailing edge ( Fig. 8B,C), adult ossicle number established around 65 cm. Paraxial ossicles separate, situated on either side of the smooth band back-fold (in all investigated specimens) ( Fig. 8).

Shape of scales is similar across much of the body and clavus. For comparison with other Molidae , we refer here to the skin on the body posterior of the pectoral fin ( Fig. 1). Scales with a raised central point, which is smooth and conical without branching tips ( Fig. 9). The scales butt against each other; the boundaries become highly visible in the dried state (not shown). Size of the raised, central point on the body scales vary, with larger scattered between smaller ( Fig. 9A, B). Smooth band nearly free of scales (in all investigated specimens); scales only slightly reduced, and of smaller sizes, on the elastic skin of the smooth band back-fold (density of scales on back-fold varies between individuals). Clavus rounded with an indent at smooth band back-fold ( Figs 4, 5C) (back-fold and indent may be less evident in small, preserved specimens due to stiffening of the back-fold during preservation).

Coloration of holotype after defrosting uniform grey, darker dorsally, lighter ventrally ( Fig. 4). The colour of live specimens appears grey or dark brown with dusky white, mottled spots and patterns ( Fig. 6A; Supporting Information, Fig. S1). Darker dorsally, lighter ventrally. It is not known whether live M. tecta can rapidly change the contrast of its skin patterns, as Mola sp. A and Mola sp. B can (Nyegaard M and Sawai E, personal observation), but we consider it likely. The colour of freshly dead specimens is similar to live specimens, or uniform grey to grey-blue ( Figs 5, 6B–E).

the English name, ‘Hoodwinker’, pertains to the figurative meaning ‘trickster, deceiving by disguise’, c. 1600.

Habitat and distribution: Mola tecta has been confirmed in the southeast of Australia (New South Wales, South Australia, Tasmania and Victoria) ( Yoshita et al., 2009; this study), around New Zealand (this study), and off South Africa ( Bass et al., 2005) ( Fig. 10). Photographs (e.g. Supporting Information, Fig. S1A) indicates that it also occurs in Chilean waters. This suggests that M. tecta is distributed widely in the temperate waters of the Southern Hemisphere, with occasional, but presumably rare, occurrences in the Northern Hemisphere (see below under Broader Molidae literature). Migrations are unknown.

Biology: It attains at least 242 cm TL, probably more. It likely exhibits a similar biology to the other Mola species whereby feeding takes place during deep dives (e.g. Nakamura, Goto & Sato, 2015; Thys et al., 2016). Digestive tract contents of three specimens ( Table 1) consisted of salps ( Thetys vagina and Pyrosoma sp. ), and the remains of a nectonic siphonophore, and in one instance, a 3 × 5 mm Styrofoam ball. All dissected specimens were heavily infested with parasites, particularly in the intestines (cestodes) and in the liver (likely larval Trypanorhynch cestodes). The shape of the gonads differs between the sexes; the ovary is singular and ball-shaped, the testis are paired, elongated and rod-like and do not appear to frill during maturation. Spawning grounds, eggs, larvae and pre-juveniles are not known.

Etymology: The species name tecta is derived from the Latin tectus (disguised, hidden), as this species evaded discovery for nearly three centuries, despite the keen interest among early sunfish taxonomists and the continued attention these curious fish receive. The Japanese name is derived from the species name tecta : ‘hidden’ (Kakure), ‘sunfish’ (manbo), while Remarks: The clavus fin ray structure of NZ 19 ( Table 1) appeared abnormal with a secondary, irregular smooth band back-fold present below the main back-fold. Also, in addition to 14 regularly spaced principal fin rays, we found 5 smaller, less rigid and highly irregular fin ray-like structures; 4 of these were set close to each other, bending towards the main back-fold, while the fifth was Y-shaped and associated with the secondary back-fold. Their irregularity and disordered appearance pointed to malformations, which are not uncommon in the other Mola species ( Sawai et al., 2009). The formation of ossicles (8) also appeared affected.