Bathyphylax omen Tyler, 1966

Rangareddy, M S, Wahed, Md Abdul, Kumar, B Shravan, Karteek, Basa Srinivas, Reddy, Chavva Lakshmi Charan & Agrawal, Jagrati, 2021, First Record of Bathyphylax omen Tyler, 1966 from the Western Pacific (Actinopterygii, Tetraodontiformes, Triacanthodidae), Bulletin of the National Museum of Nature and Science. Series A, Zoology 47 (1), pp. 37-42 : 37-41

Bathyphylax omen Tyler, 1966

(New Japanese standard name: Yami-kawamuki)

( Figs. 1–3)

Specimen examined. BSKU 127482, 51.4 mm

SL, Pacific coast of Kii Peninsula , southeast of Daiozaki Point, central Honshu, Japan, 360 m depth, bottom trawl, 13 December 2019 .

Description. Dorsal-fin rays VI +14; anal-fin rays 12; pectoral-fin rays 13 (both sides) pelvic-fin rays I+1 (ray very short on right side, absent on left side); upper jaw teeth 16; lower jaw teeth 19; gill rakers 6+1+14=21 (right side); pseudobranch lamellae 8 (right side); olfactory lamellae 12 (right side); vertebrae 8+12=20. Head length 38.1% SL, snout length 15.2% SL, snout depth 12.1% SL, eye diameter 15.0% SL, postorbital length 8.4% SL, interorbital width 9.5% SL, mouth width 6.8% SL, gill opening length 4.9% SL, snout to spiny dorsal-fin origin 44.6% SL, body depth 40.3% SL, body width 19.5% SL, first dorsal-fin spine 30.9% SL, second dorsal-fin spine 28.0% SL, third dorsal-fin spine 21.5% SL, fourth dorsal-fin spine 5.8% SL, fifth dorsal-fin spine 1.8% SL, sixth dorsal-fin spine 2.0% SL, soft dorsal-fin base 14.0% SL, longest dorsal-fin ray 18.3% SL, anal-fin base 12.1% SL, longest anal-fin ray14.2% SL, caudal fin length 24.7% SL, caudal peduncle depth 9.9% SL, caudal peduncle length 16.1% SL, pelvic-fin spine 31.3% SL, pelvic-fin ray 2.5% SL, pelvic length 36.4% SL, pelvic width 16.1% SL; pelvic width in pelvic length 2.3 times.

Anterior three dorsal-fin spines long and well developed, the fourth spine much shorter than the third but protruding through the dorsal surface of body and easily seen, the fifth and sixth spines shorter than the fourth and not easily discernible; pelvis thin and basin-like, its ventral surface externally flat; snout shorter than rest of head, dorsal profile of snout slightly concave; mouth slightly supraterminal; teeth conical, arranged in a single series in each jaw; gill opening moder- ate, reaching ventrally to level of three-fourths down pectoral-fin base; pseudobranch short, reaching ventrally to level slightly above dorsal origin of pectoral-fin base; number of spinules per upper mid-body scale plate 4–8, arranged in a vertical row with an accessory spinule some- times in front of or behind the major row.

Color when fresh: dorsal half of body pinkish, with three longitudinal distinct red stripes, the first originating around nape coursing along base of spiny dorsal fin to origin of soft dorsal fin, the second originating just behind postero-dorsal edge of orbit and running on side of body to end of soft dorsal-fin base, the third starting just behind posterior edge of orbit, running on mid body, curving very slightly down below third dorsal-fin spine, and ending just above posterior part of anal-fin base with a short disconnection below anterior part of soft dorsal fin; dorsal side of caudal peduncle reddish pink; dorsal half of snout reddish pink; ventral half of head and body anterior to anus white; ventral surface of pelvis white covered with many dark brown spots ( Fig. 2); distal half of pelvic-fin spine white and proxi- mal half light pink; dorsal-fin spines pink; rays of soft dorsal and caudal fins light pink; pectoral and anal-fin rays transparent.

Remarks. The spikefish genus Bathyphylax Myers, 1934 is differentiated from other spike- fishes by the following combination of charac- ters: the anterior three dorsal-fin spines well developed, much longer than the posterior three spines; mouth slightly supraterminal; pelvis thin and basin-like, its ventral surface externally flat and its width 1.3–2.7 times in its length; snout shorter than rest of head; teeth conical, arranged in a single series in each jaw; pseudobranch short, 12–16 lamellae, reaching ventrally to between levels of dorsal origin and very slightly below dorsal origin of pectoral-fin base ( Tyler, 1968, 1983; Santini, 2006). Bathyphylax is currently known from three species, B. bombifrons Myers, 1934 (Indo-West Pacific), B. omen Tyler, 1966 (western Indian Ocean) and B. purvosti Santini, 2006 (Marquesas Islands).

Santini (2006) showed that Bathyphylax purvosti is easily distinguished from the other two species by its long snout (17–28% SL vs 14.9– 15.8% SL in B. bombifrons and 13.8–15.5% SL in B. omen ). Bathyphylax bombifrons is similar to B. omen but the dorsal profile of the snout is concave in B. bombifrons and slightly concave or relatively straight in B. omen Tyler (1968 , 1983). Tyler (1983) tried to quantify the degree of concavity of the snout by measuring the depth of the snout midway between the anterior tip of the dor- sal lip and the anterior edge of the orbit. He mea- sured the snout depth of five specimens of B. bombifrons and three specimens of B. omen . His measurements resulted in small differences between the two species: the snout depth is 10.8– 13.4% (average 12.0%) SL in B. bombifrons and 12.5–15.5% (average 13.9%) SL in B. omen ( Tyler, 1983) . Matsuura and Tyler (1997) reported additional three specimens of B. bombifrons from New Caledonia in which the snout depth is 11.7–11.9% SL.

The newly collected specimen is identified as Bathyphylax omen by the fresh coloration clearly showing that the third red stripe originates just behind the posterior edge of orbit, running on the mid body, curving slightly down below the third dorsal-fin spine, and ends just above the posterior part of the anal-fin base with a short disconnec- tion below the anterior part of the soft dorsal fin ( Fig. 1A). When it was fixed and transferred to 70% ethanol, the third stripe changed its color from red to dark brown and ends at a level in front of the anal-fin origin ( Fig. 1B): there is no dark marking, neither line nor spot, above the anal-fin base where the very short red line (looks like a red spot) is found in the fresh specimen.

Although previous authors did not have opportunities to see the fresh color of either B. bombifrons or B. omen, Tyler (1968 , 1983) and Matsuura and Tyler (1997) reported the difference in the course of the running pattern of the third longitudinal stripe in preserved specimens of these two species. In B. bombifrons , the third line starts just behind the eye and courses over the pectoral-fin base, and curves distinctly downward toward the anus, whereas that of B. omen does not curve distinctly downward but, rather, continues along the body toward the end of the anal-fin base. In addition to the color, the dorsal profile of the snout of the specimen from Japan is slightly concave, which is another character of B. omen .

However, the depth of the snout in the speci- men from Japan is 12.1% SL, which figure is included in the range of B. bombifrons but very close to the low end of the range of B. omen . In spite of Tyler`s (1983) efforts to differentiate the two species by the snout depth, it is difficult to clearly separate them by the relationship of the proportional measurements of the snout depth and standard length ( Fig. 4). Although we cannot deny the possibility that B. omen is a junior synonym of B. bombifrons , we identify the specimen from Japan as B. omen by the color pattern and the dorsal profile of the snout.

The third dorsal-fin spine of the specimen from Japan is 21.5% SL, longer than that of the previously reported specimens of B. bombifrons (13.4–13.8% SL) and B. omen (14.3–14.6% SL) ( Tyler, 1983). The number of spinules per dorsal mid-body scale plate in the Japanese specimen is 4–8, being arranged in a vertical row, whereas there are 3–8 spinules in the previous specimens of B. omen ( Tyler, 1983) .

Hoese et al. (2006) included Bathyphylax bombifrons in the lZoological Catalogue of Australia. Volume 35. Fishesz; however, they gave only distributions of this species in New South Wales and Queensland, without catalogue num- bers of voucher specimens. When considering the similarity of B. bombifrons and B. omen , it is impossible to know which species or both they included in their record. This has led us to exclude Australian records of B. bombifrons until Australian specimens are examined.

The new Japanese standard names, lYami-kawamuki zokuz and lYami-kawamukiz, are proposed for Bathyphylax and B. omen , respectively. lYamiz means ldarkz, implying ldark deep seaz, the habitat of this species, lkawamukiz refers to spikefish, and lzokuz means genus.