Phyllophichthus xenodontus Gosline, 1951

Smith, David G., Bogorodsky, Sergey V. & Mal, Ahmad O., 2014, Records of the eels Kaupichthys atronasus (Chlopsidae), Phyllophichthus xenodontus (Ophichthidae), and Gorgasia preclara (Congridae) from the Red Sea, Cybium 38 (4), pp. 301-306 : 303-304

Phyllophichthus xenodontus Gosline, 1951

( Figs 2 , 3 ; Tab. I)

Phyllophichthus xenodontus Gosline, 1951: 316 , fig. 17a,

b (Hawaiian Is.); holotype USNM 162709 (formerly Univ. of Hawaii 318). McCosker, 1979: 64 (Hawaiian Is.). McCosker and Castle, 1986: 185 ( South Africa). Allen and Swainston, 1988: 34 ( Australia). Myers, 1999: 57 ( Micronesia). Randall and Earle, 2000: 8 (Marquesas Is.). Allen and Adrim, 2003: 24 ( Indonesia). Heemstra et al., 2004: 3316 (Rodrigues, Mascarene Is.). Randall, 2007: 69 (Hawaiian Is.). Ho et al., 2010: 30 (Taiwan). Golani and Bogorodsky, 2010: 12 (Red Sea).

Phyllophichthus macrurus McKay, 1970: 4 (Western

Australia); holotype: WAM P.4015-001 .

Material

Red Sea: USNM 314692 (2 spms, 167-193 mm TL), Egypt , Gulf of Aqaba, Bay at El Himeira, 9-12 m, 8 Sep. 1969, Springer et al. coll. Seychelles : USNM 314690 (1 spm, 206 mm TL), Seychelles , Aldabra Atoll, West I., flat in front of beach facing Settlement Camp, 0-0.8 m, 14 Aug. 1967, Fehlman coll. ; USNM 314691 (1 spm, 247 mm TL), same locality, 20 Aug. 1967, Fehlman coll. Taiwan : USNM 314694 (1 spm, 390 mm TL), southern Taiwan , Pingtung County, Cut between large outstanding rock and Ch’uanfan-shih, 0-6 m, 23 Apr. 1968, Springer et al. coll. Solomon Islands : USNM 383451 (1 spm, 202 mm TL), Solomon Islands , Santa Cruz Islands , Duff Islands , Lakao at northwest end at Temomoa Point in a small cove in surge channels in big boulders, 0-10 m, 24 Sep. 1998, Williams et al. coll. Vanuatu : USNM 350167 (2 spm, 354- 284 mm TL), Vanuatu , Erromango , Dillon’s Bay, tide pool on SW side of bay along Williams Point, 0-1 m, 25 May 1996, Williams et al. coll .; USNM 363457 (1 spm, 313 mm TL), Vanuatu , Banks Islands , Mota Lava, Milli Bay, rubble and sand area at base of a reef slope, 23-29 m, 19 May 1997, Williams et al. coll. Marquesas Islands : USNM 408708 (1 spm, 321 mm TL), Marquesas , Motu One, west side, 7-9 m, 1 Nov. 2011, Williams et al. coll. Hawaii : USNM 162709 (holotype, 239 mm TL), Oahu , Hauula Park, 28 Jun. 1949, Gosline et al. coll .

Description

In % TL: preanal 44.3-51.0, predorsal 8.4-10.7, head 7.9- 10.0, depth at anus 1.7-2.4. In % head length: snout 23.8- 27.2, eye 8.2-11.9, interorbital 8.6-11.0, snout-rictus 34.1- 39.4, snout-lower jaw 9.3-12.1, gill opening 6.1-9.9, interbranchial 12.1-15.7, pectoral fin 13.8-27.2. Pores: LL 75-ca 83, POM 6, IO 6, SO 4 + 1, ST 3. Vertebrae: PD 9-11, PA 69-83, Total 156-180.

(From Gosline 1951, with some added data). Head and body subcylindrical, becoming compressed toward tip of tail; anus near midlength. Dorsal and anal fins low, discon- tinuous, caudal fin absent, tip of tail pointed and hardened. Dorsal fin on both Red Sea specimens begins over approximately posterior third of appressed pectoral fin; anal fin begins shortly behind the anus; pectoral fins well-developed. Gill opening round, slightly below mid-side of body, opening onto lower part of pectoral-fin base. Eyes well developed. Snout long and tapering, overhanging tip of lower jaw, somewhat depressed at tip, lower surface flattened, with a median groove extending nearly to tip. Anterior nostril large and conspicuous, on ventral side of snout opposite tip of lower jaw, directed ventrally; three prominent papillae on anterior, right and left sides, and a prominent leaf-like flap on posterior border, those of the two sides touching each other. Posterior nostril opening into mouth under a broad, infolded flap which is delimited on outside of upper lip as a groove below anterior border of eye.

Teeth conical; intermaxillary teeth well developed, arranged as five pairs in parallel longitudinal rows; about four weak teeth in inner edge of maxilla before posterior nostril, four or more even weaker embedded teeth behind; lower jaw with a row of some 18 strong laterally directed teeth on each side, these rows not continued forward around toothless symphysis; vomerine teeth absent.

Preoperculo-mandibular canal with six pores: first on underside of lower jaw, slightly before tip and just before anterior end of longitudinal dermal groove; second below anterior margin of eye; third below mideye; fourth slightly behind posterior margin of eye and directly below posteriormost infraorbital pore; fifth in preopercular canal behind rictus; sixth above and behind, and close to, the fifth pore. Six infraorbital pores: first on edge of upper lip, about midway between anterior nostril and eye; second below mideye; third below posterior margin of eye; fourth slightly before rictus; fifth above and somewhat anterior to the fourth, behind eye and slightly below mideye level; sixth behind eye and slightly above mideye. Four paired supraorbital pores: first small, on underside of snout near tip; second on top of snout above posterior base of anterior nostril; third on top of snout about midway between anterior nostril and eye; fourth on top of head slightly before mideye; a fifth unpaired median pore in the commissure connecting right and left sides, near mideye level. Three supratemporal pores, a median pore and one on each side.

The colour of the two Red Sea specimens in preservative is a nearly uniform light brown in general appearance. The dorsal surface of the head and trunk is covered with small, closely spaced, light brown spots; on the tail, the speckled pattern descends to cover nearly the entire body. The fins are colourless.

Distribution and habitat

From Hawaii and French Polynesia in the east, westward to Japan and Australia in the Pacific, and through the Indian Ocean to the east coast of Africa and the Red Sea. Found in relatively shallow water, most specimens collected with ichthyocide.

Remarks

Significant variation occurs over the range of this species, most noticeably in the number of vertebrae (Tab. I). The two specimens from the Red Sea have fewer total (156) and preanal vertebrae (69-71) than those from elsewhere (164-180 and 74-83 respectively); there is also a slight difference in predorsal vertebrae (11 vs 9-10). At the other end of its range, the specimen from the Marquesas has more total vertebrae (180) than any of the others, and it also has significantly more preanal vertebrae (83). The specimens from the Seychelles seem to have slightly fewer vertebrae (164- 168) than those from the western Pacific (167-170). Specimens from Hawaii have 168-175 total vertebrae ( McCosker, 1979) a number similar to the western Pacific specimens, but the preanal count of 81 in the holotype is much higher and in fact is closer to the Marquesas specimen. There are also a few slight differences in proportions. For example, the Red Sea specimens have a slightly shorter preanal length (44.3-47.7%TL vs 48.1-51.0) than the others. The pectoral fin is shorter in the Red Sea specimens (13.8-17.8% head) than the others (18.9-27.2%). However, the Hawaiian holotype is an outlier here, with length of 27.2% head; the next highest value is 24.4% head in the specimen from Taiwan. It appears, then, that this species consists of several populations that vary to differing degrees in different characters. Our sample size is too small to assess the range of variation within each population, and there is no way to determine the geographic boundaries between populations. For this reason, we refrain from applying names to any of them at this time. The nature and extent of geographic variation has not been determined for the great majority of Indo-Pacific eel species. Much work remains to be done.

Figures

Figure 2. - Phyllophichthus xenodontus, USNM 314692 (193 mm TL). Photo S. Raredon. Scale bar = 10 mm.

Figure 3. - Phyllophichthus xenodontus, head showing pores and nostrils. Modified from Gosline (1951: fig. 17a). Arrows indicate median pores.