Malthopsis tiarella Jordan , 1902

Ho, Hsuan-Ching & Koeda, Keita, 2019, A new Malthopsis batfish from Taiwan, with comments on Malthopsis tiarella Jordan, 1902 (Lophiiformes: Ogcocephalidae), Zootaxa 4702 (1), pp. 73-86 : 79-83

Malthopsis tiarella Jordan, 1902

English name: Spearnose seabat

Figures 5–7 ; Table 1 .

Malthopsis tiarella Jordan, 1902:378 , fig. 7 (type locality: Suruga Bay near Numazu, Japan, depth 70–100 fathoms). Ho & Shao, 2008:308 (in part). Ho et al., 2009:394. Ho & Shao, 2010a:9. Ho, 2013:289.

Materials examined. NMMB-P03366 (1, 33.3, stained), off Kaohsiung, southwestern Taiwan, 6 Nov. 2002 . NMMB-P28508 (1, 50.9), off Dong-gang fishing port, Pingtung, southwestern Taiwan, 8 Feb. 2018 .

Diagnosis. A species of Malthopsis belonging to the species group with small prickle-like bucklers on body surface; it can be further distinguished from its congeners in having 6 or 7 dorsal-fin rays; 13 or 14 pectoral-fin rays; indistinct reticulate pattern on dorsal surface (faded in preservation); rostral spine directed upward and forward; interorbital space narrow and naked; skin above the eye with one row of a few bucklers, naked elsewhere; throat and outer regions of ventral surface largely naked; appressed anal fin extending well over caudal-fin base posteriorly; black band on posterior portion of pectoral and caudal fins.

Description. Morphometric and meristic data are provided in Table 1 .

Body depressed, disk markedly triangular in dorsal view, cranium elevated above general surface of other parts of disk; caudal peduncle cylindrical, tapering posteriorly; rostrum small, its base moderately wide for genus, terminal spine conical, directed forward and upward ( Fig. 7B ), distinctly overhanging illicial cavity and beyond mouth; rostral length about half of eye diameter (eye diameter/rostral length 1.9–2.1); eye relatively large (13.4% SL in 50.9 mm specimen, 15.7% SL in 33.3 mm specimen), directed dorsolaterally; no pupillary operculum; interorbital space narrow (6.5–6.7% SL), shallowly concave ( Fig. 7A ); illicial cavity a small triangular cave, relatively broad in outline, wider than high; esca a single oval bulb, bearing 2 small cirri on dorsal margin; mouth small, terminal; small villiform teeth on jaws forming narrow bands, those on fifth ceratobranchial forming 2 large and elongated patches close together, and teeth on vomer and palatines in quadrangular patch.

Scales on body surface in the form of bucklers, relatively sharp and pointed ( Figs. 5–7 ), mostly associated with lateral line, skeleton and body edge; scattered tiny prickle-like bucklers on body surface; dorsal surface loosely covered with small bucklers between principal bucklers, except for eyes and fins. Four bucklers on each side of frontal ridge, first two situated at anterolateral corner of orbit; second pair direct outward, and with rostral spine forming a trident; a gape between second and third; third and fourth bucklers relatively large in size. A pair of bucklers on dorsal surface of base of rostrum. Skin above eye bears a series of 3–6 small bucklers, naked elsewhere.

Dorsal surface of skull with 2 (right side of large specimen with 3) pointed bucklers on each side; followed by a median widely-spaced row of smaller bucklers at postcephalic region; largely naked on both sides of dorsal surface of disk. Small scattered bucklers and tiny prickle-like bucklers, usually 3–5 facets, with few apical spines at center of each buckler ( Fig. 6B ), on abdomen and chest, largely naked on remaining part of ventral surface of gill cavity and thoracic regions; buckler of subopercular dull, bearing few spinelets, none especially enlarged, one directed forward and one directly backward in 33.3 mm specimen and many spinelets in 50.9 mm specimen ( Fig.7C ); one flat, triangular buckler with a pointed spine on post-subopercular margin; caudal peduncle covered by large bucklers, those on dorsal surface forming 5 irregular, scattered rows, 1 median row behind dorsal fin, 2 rows on each sideof dorsal fin, 2 rows on each lateral side associated with lateral line, bucklers of lower row slightly larger than those of upper row; bucklers on ventral surface of caudal peduncle forming 2 regular rows between anus and anal fin, relatively flattened; anus surrounded by 2 or 3 bucklers on each side of posterior portions, these not larger than neighboring ones ( Fig. 7D ).

All fins naked, without bucklers, except for some small ones running out along the base of caudal fin rays; inter-radials of pectoral fins thin, transparent; dermal cirri flap-like, present on disk margin and lateral sides of tail associated with lateral line scales.

Coloration. When fresh, body background light brownish; dorsal surface with light yellowish reticulate pattern and some short dark marks; irregular black patches on dorsal surface of head; indistinct broad band across dorsal fin base and space between dorsal and anal fin; thin black band with darker dots on fin rays on posterior third of pectoral fin, and base and posterior third of anal fin. When preserved, body background grayish, irregular darker patches on dorsal surface of head and central disk; short dark marks on dorsal surface; indistinct broad bands across dorsal-fin base and space between dorsal and caudal fins; dorsal fin blackish; thin black bands on posterior third of pectoral fin and base and posterior third of caudal fin; ventral surface uniformly pale. Peritoneal membrane white with many black dots.

Size. Apparently a small species with adult size slightly over 50 mm SL.

Distribution. Known from Japan (type locality) and Taiwan. Rarely seen in collections; specimens from other localities may represent different species.

Remarks. At first sight of the larger specimen (50.9 mm SL), we thought it to be an undescribed species because of the special reticulate pattern. However, after a detailed examination of that specimen and one additional specimen (33.3 mm SL), we recognized both as M. tiarella . A searched for the holotype in the USNM collection by HCH was not successful. Thus, data of the holotype are currently unavailable.

In the original description, Jordan (1902) reported 7 dorsal-fin rays and 10 (but with a question mark) pectoralfin rays. However, the drawing of the same specimen showed clearly 7 dorsal-fin rays and 14 pectoral-fin rays. It is rare to see such a combination of fin-ray numbers in Malthopsis because most members have 5 or 6 (mostly 5) and 12–13, respectively. Our specimens process 6 or 7 dorsal-fin rays and 13 or 14 pectoral-fin rays which are similar to those of M. tiarella . Although we were not able to examine the holotype, our specimen matches the original description well, especially the number of fin rays and coloration, which are clearly different from M. kobayashii and M. formosa . Accordingly, additional diagnostic characters are provided for present species above.

From the only x-radiograph film of the holotype taken long time ago, there are one forward-directed and one backward-directed spinules on the subopercular buckler. In some cases, the small specimens (<40 mm SL) of M. kobayashii have some forward-directed and one backward-directed spinules on the subopercular buckler. However, all specimens larger than 40 mm SL have these spinules reduced. The 33.3 mm specimen also has the spinules, whereas the 50.9 mm does not.

Ochiai & Mitani (1956) reported two specimens of M. tiarella . A search for these two specimens in the FAKU (Kyoto University, Department of Bioresource Science, Faculty of Agriculture: presently housed at Maizuru Fishery Station) collection was unsuccessful. The authors provided a count of 12 pectoral-fin rays and a drawing of their specimens, which are likely to be M. kobayashii . HCH examined many specimens in FAKU and found that all specimens appeared to be the same species (viz., Malthopsis kobayashii ) with variation in their squamation.

Ho & Shao (2008) provided a photo of M. tiarella , which we reidentified as M. formosa described above.

Figures

FIGURE 5. Malthopsis tiarella Jordan, 1902, NMMB-P28508, 50.9 mm SL. A. dorsal view. B. lateral view. C. ventral view.

FIGURE 6. Malthopsis tiarella Jordan, 1902, stained with red color, NMMB-P03366, 33.3 mm SL. A. dorsal view. B. lateral view. C. ventral view.

FIGURE 7. Malthopsis tiarella Jordan, 1902, from NMMB-P28508. A. lateral view of head. B. dorsal view of head. C. dorsal view of left subopercular region. D. ventral view of caudal region.