Malthopsis velutina, Ho, 2020

Ho, Hsuan-Ching, 2020, Two new deep-water batfish of the genus Malthopsis from the Pacific Ocean (Lophiiformes: Ogcocephalidae), Raffles Bulletin of Zoology 68, pp. 859-869 : 865-869

Malthopsis velutina , new species Polynesian triangular batfish

( Figs. 4 , 5 ; Table 2)

Holotype. MNHN 2008-1227 (1, 56.9), Campagnes Musorstom 9, ALIS, sta. cp1268, 7°55′59″S, 140°43′1″W, Eiao Island, Marquesas Islands, Polynesia , South Pacific Ocean , perch trawl, 420–430 m, 4 September 1997.

Paratypes. Ninety-two specimens, 37.8–55.2 mm SL, all collected by ALIS (Campagnes Musorstom 9), from Marquesas Islands, Polynesia, South Pacific Ocean , using perch trawl. MNHN 2001-0028 (1, 43.4), sta. cp1229 , 9°43′59″S, 138°51′0″W, Hiva Oa Island , 310–320 m, 30 August 1997. MNHN 2003-0996 (6, 45.7–55.2), sta. cp1306 , 8°55′1″S, 140°14′6″W, Nuku Hiva Island , 283–448 m, 10 September 1997. MNHN 2005-1150 (55, 37.8–50.9), collected with holotype . MNHN 2006-1461 (2, 46.9–50.9), sta. cp1269 , 7°55′59″S, 140°43′1″W, Eiao Island , 420–430 m, 4 September 1997. MNHN 2008-1228 (4, 44.2–52.8) and MNHN 2008-1231 (23, 37.8–48.6), collected with holotype .

Non-types. MNHN 2000-5509 (5 juveniles, 16.7–19.6), sta. cp1238, 9°40′59″S, 139°3′0″W, Hiva Oa Island , 280–370 m, 31 August 1997 .

Diagnosis. A species of Malthopsis with body covered with fine bucklers and prickles forming a velvet-like integument, and black patches on body surface, including upper portion of eye. It can be further distinguished from congeners by following combination of characters: rostral spine short (x = 4.0% SL) and blunt, directed upward rather than forward; subopercular buckler small, with several spinules at its tip; a large eye (x = 13.7% SL); narrow interorbital space (x = 5.3% SL); anal fin reaching base of caudal fin when fully laid back; and usually six dorsal-fin rays and 12 or 13 pectoral-fin rays.

Description. Dorsal-fin rays six (usually six, rarely five or seven); pectoral-fin rays 13 (usually 12 or 13, rarely 11); anal-fin rays four. Body depressed, markedly triangular in dorsal view, its width slightly greater than length; posterior portion of skull elevated above rest of disk; tail base narrow; caudal peduncle narrow and slender, semi-cylindrical, flattened ventrally and tapering posteriorly. Orbit large, 13.5% SL (12.9‒15.3, x = 13.7), directed dorsolaterally; no pupillary operculum. Rostrum blunt, stout, with a narrow base, directed upward rather than forward ( Fig. 5A, B ), slightly overhanging illicial cavity and mouth; rostrum very short, 3.2% SL (3.2‒5.5, x = 4.0), much shorter than orbital diameter; OD/RL 4.3 (2.6‒4.4, x = 3.5); interorbital space narrow, 5.2% SL (4.8‒6.1, x = 5.3), forming a deep groove ( Fig. 5A ); OD/IO 2.6 (2.1‒3.0, x = 2.6); frontal ridge slightly convex.

Illicial cavity small, oval to rounded, its opening as high as wide; esca a single oval bulb, bearing two (one or two, mostly two) small cirri on dorsal margin; mouth small, terminal; small villiform teeth on jaws forming narrow bands, those on fifth ceratobranchial forming two large, elongated, adjacent patches; teeth forming a wide quadrangular patch on vomer and a smaller oval patch on each palatine.

Squamation on dorsal surface of disk well developed, consisting mainly of small, low variable-sized bucklers ( Figs. 4 , 5 ), interspaces between bucklers densely covered with tiny prickles, forming velvet-like integument; bucklers on frontal ridge small and blunt, two small preorbital bucklers which overlap anterior border of orbit; five (four or five) small, subequal-sized bucklers on frontal ridge; interorbital space densely covered by small bucklers ( Fig. 5A ); membranes above eye densely covered by small bucklers and prickles. Posterior portion of skull covered with small bucklers, except for two (two or three) slightly larger bucklers on each side ( Fig. 5A ); no naked area on body disk; one irregular median row of slightly larger bucklers predorsally, ending before dorsal-fin origin as two large side-by-side bucklers ( Fig. 5D ).

Disk margin with a cluster of suborbital bucklers anteriorly, forming three poorly-defined rows posteriorly, all bucklers small and low, with a narrow base; lower two rows of bucklers associated with lateral-line channel, apices blunt, not well elevated; those of median row directed laterally, those of lower row directed ventrally; neuromasts along lateral-line channel well-defined. Subopercular buckler small, extending slightly beyond disk margin laterally; terminating on uppermost and middle rows of disk-margin bucklers; with a small, well-defined, forward-directed spine, a backward-directed spine and several smaller spinelets (variable in size and coverage) at its tip ( Fig. 5C ); two small post-subopercular bucklers, each bearing few small spinelets distally. Pectoral-fin base on posterior part of disk, covered completely with small bucklers dorsally except for small naked areas surrounding gill openings.

Dorsal surface of tail weakly armoured, entirely covered with small, low, apically pointed bucklers ( Fig. 5D ); a loose row of four (three to five) large dorsolateral bucklers extending from last pair of predorsal bucklers below dorsal fin on each side; a longer, highly irregular, semi-oblique row of small bucklers along lateral margin of tail to caudal-fin base; an irregular row of flattened bucklers on dorsal midline between dorsal and caudal fins; dorsal tail rows uniting to form a single, slightly elevated buckler at its base. Lateral margin of tail with two rows of small, low bucklers associated with lateral line, similar to those of disk margin.

Ventral surface of disk predominantly covered with small, low, flat bucklers; very stout and small apical spines present on each buckler; belly densely covered with small variablesized bucklers, some slightly larger on breast than on belly and numerous prickles on interspaces ( Fig. 5E ); rear margin of anus surrounded by slightly enlarged, indistinct bucklers; ventral surface of tail with two regular rows of small bucklers ( Fig. 5F ), coalescing to a bulbous buckler at caudal-fin base. Fins generally naked, without bucklers, sometimes with small bucklers on rays near caudal-fin base; inter-radials of pectoral fins thin, transparent; dermal cirri short, thin, flap-like, present on disk margin and lateral sides of tail associated with lateral-line neuromasts.

Anal fin usually short, reaching only to base of caudal fin when fully depressed, except for some larger specimens, including the holotype, with anal fin reaching base of caudal fin.

Colouration. Fresh colour unknown. The preserved holotype ( Fig. 4A, B ) has dorsal surface yellowish-brown with a black supraorbital membrane; large, deep brown smoky patches on dorsal surface of disk and base of tail; two saddle-like blotches on tail, one at dorsal fin base and one between dorsal and caudal fins; dorsal surface of pectoral fin light brown; origin and posterior half of caudal fin deep brown; ventral surface pale uniformly; peritoneum pale with many black dots. Some paratypes have more or less consistent colouration as described for the holotype, but some have black colour surrounding the orbital, and the smoky patches on dorsal surface of disk vary in size, sometimes a paler patch centrally on dorsal surface and each side of base of tail, and some with smaller irregular patches on both sides of body disk.

Distribution. Known from the type series and non-type specimens collected in the Marquesas Islands, French Polynesia, and likely endemic to the region. Bathymetric range 280‒ 448 m.

Size. The largest examined specimen is 56.9 mm SL, which suggests this is a small-sized species.

Etymology. The specific name velutina , meaning velvety, is in reference to its body covered with fine bucklers and prickles forming a velvet-like integument. Used as adjective in apposition.

Comparisons. Malthopsis velutina has a unique squamation that easily distinguishes it from all other congeners. It is similar to a species group that has the body surface of disk densely covered by bucklers and tiny prickles (e.g., Malthopsis austrafrica Ho, 2013 , M. asperata Ho, Roberts & Shao, 2013 , M. formosa Ho & Koeda, 2019 , M. gnoma Bradbury, 1998 , M. kobyashii Tanaka, 1916 , M. provocator Whitley, 1961 , M. tiarella Jordan, 1902 ), but differs from these species in having the dorsal surface densely covered by tiny spinules forming a velvet-like integument. Other congeners with prickles on the ventral surface of the disk all have large, either sharp or blunt bucklers on the dorsal surface of the disk. Moreover, M. velutina has distinct spines directed forward and backward on the tip of the subopercular buckler, whereas all other species with prickles on the body surface have a dull subopercular buckler and lack distinct forward-directed spine(s).

Remarks. The squamation of M. velutina is somewhat similar to that of Ogcocephalus darwini Hubbs, 1958 and Ogcocephalus porrectus Garman, 1899 , which may indicate that these species have adapted to a similar environment, like a fine-sandy bottom. However, O. darwini and O. porrectus are found in relatively shallow waters, 3.5‒73.5 m and ca. 120 m, respectively ( Bradbury, 1980), whereas M. velutina was collected from much deeper water, 280‒ 448 m.

At present, M. velutina and Malthopsis gigas Ho & Shao, 2010 are the only two Malthopsis species known from French Polynesia, the easternmost range of the genus in the Pacific Ocean. Malthopsis gigas has a much larger body size (up to 135 mm SL) and very different squamation. The two species likely use different habitats and have different ecological niches.

Comparative material. Malthopsis annulifera : listed in Ho & Shao (2010a); M. asperata : listed in Ho et al. (2013); M. austrafricana : listed in Ho (2013); M. formosa : listed in Ho & Koeda (2019); M. gigas : listed in Ho & Shao (2010a); M. kobyashii : listed in Ho & Shao (2010b); M. provocator : listed in Ho & Last (in press); and M. tiarella : listed in Ho & Koeda (2019).

Figures

Fig. 4. Malthopsis velutina, new species, holotype, MNHN 2008-1227, 56.9 mm SL. A, dorsal view; B, ventral view.

Fig. 5. Malthopsis velutina, new species, holotype, MNHN 2008-1227, 56.9 mm SL. A, dorsal view of head; B, lateral view of head; C, dorsal view of left subopercle; D, dorsolateral view of anterior tail region; E, ventral surface of disk; F, ventral view of anterior tail region.