Exyrias akihito, Allen & Randall, 2005

Allen, Gerald R. & Randall, John E., 2005, Exyrias Akihito, A New Species Of Coral-Reef Goby (Gobiidae) From The Western Pacific, Raffles Bulletin of Zoology 53 (2), pp. 231-235 : 232-235

Exyrias akihito , new species

( Figs. 1-6 ; Table 1)

Exyrias belissimus (in part) – Murdy, 1985: 4, Pl. 1B, Fig. B (Java).

Exyrias sp. 1 – Kuiter & Tonozuka, 2001: 669, Figs. A-D (Java, Bali, and Sulawesi).

Exyrias sp. – Allen & Adrim, 2003: 58 (Bali and Manado, Sulawesi).

Exyrias sp. – Allen et al, 2003: 321, middle left fig. ( Indonesia and

Philippines). Exyrias sp. – Hayashi & Shiratori, 2003: 94 ( Japan). Exyrias species – Kimura & Matsuura, 2003: 183, upper fig. (Bitung,

Sulawesi). Exyrias sp. – Senou, Suzuki, Shibukawa & Yano, 2004: 240, upper

and lower figs. (Ishigaki, Iriomote Islands, Japan).

Material examined. – Holotype - NSMT-P 71648 , 67.1 mm SL, Amitori Bay , Iriomote Island, Yaeyama Islands, Okinawa Prefecture, Japan, 28 m depth, Y. Ikeda, K. Sugiyama & K. Hagiwara coll., 30 Jun.2001.

Paratypes – AMS I.20956-028, 100.3 mm SL, Tijou Reef (approximately 13°04'S 143°57'E), Great Barrier Reef , Queensland, 3-12 m, rotenone , AMS party coll., 23 Feb.1979 ; AMS I.22581- 011, 2 ex., 38.4-111.2 mm SL, Escape Reef (approximately 15°49'S 145°50'E), Great Barrier Reef , Queensland, 10-14 m , AMS party coll., 29 Oct.1981 ; BLIH 19830335 , 29.7 mm SL, El Nido, Palawan Island , Philippine Islands, H. Masuda & A. Ono coll., 6-25 Mar.1983 ; BLIH 19960130 , 38.4 mm SL, Amitori Bay , Iriomote Island, Yaeyama Islands, Okinawa Prefecture, Japan, Y. Ikeda & A. Iwata coll., 9 Jul.1996 ; BLIH 20010003 , 34.9 mm SL, same locality as BLIH 1996130, 35 m, K. Yano coll., 18 Jun.2000 ; BLIH 20010004 , 25.2 mm SL, same locality as BLIH 19960130, 26 m, Y. Ikeda, K. Sugiyama & K. Hagiwara coll., 1 Jul.2001 ; BLIH 20010005 , 38.2 mm SL, same locality and as BLIH 19960130 , 27 m, Y. Ikeda, K. Sugiyama & K. Hagiwara coll., 1 Jul.2001 ; BLIH 20010006 , 39.0 mm SL, same locality as BLIH 19960130, 27 m, Y. Ikeda, K. Sugiyama & K. Hagiwara coll., 28 Jun.2001 ; BLIH 20010010 , 23.5 mm SL, Funauki Bay , Iriomote Island, Yaeyama Islands, Okinawa Prefecture, Japan, 43 m, K. Yano coll., 27 May.2001 ; BPBM 28781 , 37.2 mm SL, Pulau Pari , off Pulau Tikus, Seribu Islands, Java, Indonesia, outer reef in 23 m depth, quinaldine, J. E. Randall coll., 5 Nov.1982 ; WAM P.31214-001, 66.6 mm SL, Padoz Reef (approximately 5°10'S, 145°49'E) Madang Lagoon , Papua New Guinea, 15-18 m, rotenone, G . R. Allen coll., 16 Oct.1996 ; WAM P.32255-003, 2 ex. specimens, 27.2-33.9 mm SL, Kawe Island (approximately 0°02'S, 130°08'E), Raja Ampat Islands, Papua Province, Indonesia: large bay on east side of island, 8-14 m, quinaldine, G . R. Allen coll., 18 Nov.2002 ; WAM P.32615-001, 81.3 mm SL, male, Lawadi Village (10°15.81'S, 150°43.14'E), Milne Bay Province, Papua New Guinea, outer reef in 15 m, quinaldine and hand net, G . R. Allen coll., 20 Nov.2003 .

Comparative material. – Exyrias bellismus: BPBM 29677, 4: 43-55 mm, Pulau Pari, Seribu Islands, Java, Indonesia; BPBM 15767 , 87 mm, Madang, Papua New Guinea ; BPBM 32567 , 3 : 36-77 mm, Nagada Harbour , Papua New Guinea ; BPBM 1283, 116 mm, Shortland Island , Solomon Islands ; BPBM 15696 , 2 : 50-51 mm, Yacht Harbor , Guadalcanal, Solomon Islands ; BPBM 21855 , 2 : 57- 73 mm, Salu Islet , Singapore , 2: 57-73 mm; BPBM 29386 , 85 mm, Low Isles off Port Douglas, Queensland ; BPBM 9740 , 2 : 62.5-69 mm, Uru Island , Palau ; BPBM 9754 , 3 : 19-58 mm, Uru Island , Palau ; BPBM 31405 , 2 : 66.5-74.5 mm, Auluptagel , Palau ; BPBM 9956 , 3 : 54-82 mm, Phonpei , Caroline Islands ; BPBM 29384 , 25 mm, Phonpei , Caroline Islands , W side of Phonpei Passage ; WAM P29928-019 , 7 : 36-77 mm, Cocos-Keeling Islands ; WAM P31650- 001 , 94 mm, Cassini Island , Kimberleys, Western Australia ; WAM P30309-010 , 69 mm, Cassini Island ; WAM P27662-030 , 74 mm, Clerke Reef , Rowley Shoals, Western Australia ; WAM P29054- 003 , 77 mm, West Island , Ashmore Reef, Timor Sea ; WAM P30412- 007 , 2 : 44-49 mm, Bohaydulong Island , Bodgaya Islands, Sabah ; WAM P31546-004 , 30 mm, Gam Island , Raja Ampat Islands, Irian Jaya .

Diagnosis. – Pectoral rays 17; segmented caudal-fin rays 17; branched caudal-fin rays typically 13, rarely 12, 14, or 15; longitudinal scale series 28 (28-30); dorsal-fin spines elongate and filamentous, the second longest, 1.59-2.07 in SL; generally light bluish grey in life with small yellow to brownish orange spots on head and body, those on body mostly conjoined to form longitudinal stripes along scale rows; four pairs of dark brown spots on lower side of body, followed by a single spot at caudal-fin base; a few smaller dark brown spots on body, mostly in a row dorsally and one ventrally; dorsal and caudal fins covered with numerous, relatively large, orangish to yellowish brown spots.

Description. – Dorsal-fin rays VI-I,10; anal-fin rays I,9; pectoral-finl rays 17; pelvic-fin rays I, 5; segmented caudalfin rays 17; branched caudal-fin rays 14 (12-15); longitudinal scale series 28 (28-30); transverse-scale count from origin of second dorsal fin ventroposteriorly to anal-fin base 9; transverse-scale count from anal-fin origin dorsoanteriorly to first dorsal-fin base 9; predorsal-scale count 8 (7-8); vertebrae 10 + 16.

Mouth terminal; jaws extending to a vertical at anterior edge of pupil; jaw teeth small and conical, densely packed in several rows, those in outermost row the largest; tongue broad with straight anterior margin, broadly attached anteriorly to floor of mouth. Anterior extent of gill opening reaching to below middle of opercle. Arrangement of cutaneous papilla system and cephalic sensory pores as shown in Fig. 2 .

Body moderately elongate and laterally compressed, more strongly compressed posteriorly; body depth at pelvic-fin base 4.05 (3.67-4.15) in SL; body depth at anal-fin origin 4.17 (3.68-4.82) in SL. Head laterally compressed, its width slightly less than its depth at level of preopercular margin. Head length 3.37 (3.24-3.44) in SL. Snout length 2.47 (2.17- 3.31), eye diameter 3.75 (3.38-4.23), and interorbital width 20.74 (15.69-30.94), all in head length. Distance between snout and origin of first dorsal fin 3.20 (2.92-3.23), between snout and origin of second dorsal fin 1.86 (1.80-1.91), between snout and origin of anal fin 1.78 (1.69-1.87), and between snout and origin of pelvic fins 3.09 (3.10-3.22), all in SL.

Membranes of first dorsal fin deeply incised (especially between first and second spines), the dorsal spines elongate and filamentous, second spine longest, 1.59 (1.77-2.07) in SL; longest (penultimate) ray of second dorsal fin 3.46 (3.01- 4.39), longest ray (penultimate) of anal fin 3.34 (3.24-4.19), pectoral-fin length 2.87 (2.96-3.23), pelvic-fin length 3.50 (3.55-4.01), caudal-fin length 2.16 (2.13-2.29), all in SL.

Color of holotype in alcohol after three and a half years of preservation: generally yellowish tan with four pairs of dark brown spots on scale row at level of upper edge of pectoralfin base; a single dark brown spot at caudal–fin base in line with double dark spots; fins translucent tan. Most of the paratypes are similar in colour except for the most recently collected specimens (WAM P.32615-001), which differ as follows: overall pale brown, the scale edges a little darker with characteristic row of paired dark brown spots (each pair within a brown blotch) and single dark brown spot at caudalfin base; the latter spot closely followed by two more dark spots; a series of blackish blotches dorsally on body below base of dorsal fins; an irregular row of smaller dark brown spots on lower side of body; a row of still smaller spots on upper side of body; a broad dark brown bar below eye, and a prominent dark brown spot on opercle; dorsal and caudal fins greyish brown with traces of numerous spots; anal and paired fins grey-brown.

Color in life (from underwater photographs of Figs. 2-4 ): orange-yellow to brownish yellow with pale bluish grey to pale blue spots, most conjoined to form longitudinal series along scale rows; edges of scales narrowly dark brown, especially dorsally on body; four pairs of small dark brown to black spots on scale row at level of upper edge of pectoralfin base, these spots surrounded by a zone of orange-yellow or brownish yellow; a single dark brown to black spot on caudal-fin base in line with double dark spots, followed by one or two lesser dark spots on base of fin; a row of small dark brown spots along back at base of dorsal fins, another on lower side, and a few still smaller dark brown spots along upper side, all surrounded by yellow or brownish orange; head with yellow to brownish orange spots, mostly forming irregular rows, some projecting obliquely downward and forward from eye; dorsal and caudal fins translucent bluish grey with round to oval yellowish to orangish brown spots, mostly with slightly darker edges, many as large or larger than pupil; anal fin pale translucent greenish or yellowish with similar but fewer and more elongate spots, mainly in basal half of fin; second dorsal and anal fins sometimes with a narrow pale blue margin; paired fins pale greenish or yellowish to nearly white. Senou et al. (2004: 240, upper fig.) illustrated a large adult in color. The pale blue spots are relatively larger, the edges of the scales more conspicuously dark brown, the double dark spots much less distinct, and the dusky-edged orange-yellow spots in the median fins more numerous and relatively smaller, most smaller than pupil. A photograph in Hayashi & Shiratori (2003: 94, lower fig.) shows a broad dusky bar below the eye (still containing orange-yellow spots).

Etymology. – The new species is named akihito in honour of the Emperor of Japan, in recognition of his significant contribution to our knowledge of gobiid systematics. Many of the type specimens of E. akihito were supplied by the Biological Laboratory of the Imperial Household in Tokyo. The name akihito is treated as a noun in apposition.

Comparisons. – Exyrias akihito is easily differentiated from the other members of the genus by its extremely elongate dorsal-fin spines. It is also distinguished on the basis of its paler coloration, particularly the numerous yellow or brownish orange spots on the head and body.

This new goby is most similar to E. belissimus ( Figs. 7 -8), with which it has been confused in the past. For example, Murdy (1985, Pl. l fig. B) illustrated a juvenile of the new species as E. belissimus . The latter species has the same double-row of dark brown spots on the side (though vertically elongate and often obscured by dark brown bars, especially in adults), and the dorsal spines are filamentous. However, they are not as long as those of E. akihito . The third or fourth dorsal spine is longest in E. belissimus . It measures 20.2- 36.9% SL in eleven Bishop Museum specimens from 44.7- 87.0 mm. The second dorsal spine is longest in E. akihito , 49.7-62.8% SL in the six type specimens of Table 1.

There is also a clear modal difference in the number of pectoral-fin rays. All type specimens of E. akihito possess 17 rays, compared to the usual count of 18 for E. belissimus . Murdy (1985) reported an average count of 17.8 for E. belissimus , however he included at least three specimens of the new species (AMS I.20956-028 and AMS I.22135-001) in the Material Examined for E. belissimus . Therefore, it is possible that Murdy’s mean count for pectoral-fin rays may have included one or more specimens of E. akihito . We have counted 25 specimens of E. belissimus ; 22 have 18 rays, and one each has 16, 17, and 19 rays. There is also an average difference in the number of branched caudal-fin rays. Murdy (1985) gave the mean as 14.2 for E. belissimus (n = 12), 14.5 for E. ferrarisi (n = 2), and 13.7 for E. puntang (n = 10). The average count of branched caudal-fin rays for 16 specimens of E. akihito is 13.1.

Distribution and habitat. – Exyrias akihito is currently known from the northern Great Barrier Reef, Papua New Guinea, Indonesia (Bali, Java, north Sulawesi, and Raja Ampat Islands), Philippines (Palawan), and the Yaeyama Islands of southern Japan. It is typically found in clear water in the vicinity of coral reefs, usually on sand or rubble bottoms, at depths between 10- 43 m. By contrast, the three other species of Exyrias are generally found in shallow water with soft silt or mud bottoms in estuaries or on turbid coastal reefs. An exception in depth is a specimen speared by the second author in the lagoon off Madang, Papua New Guinea at a depth of 50 m.

Figures

Fig. 1. Holotype of Exyrias akihito, male, NSMT-P 71648, 67.1 mm SL, 28 m, Amitori Bay, Iriomote Island, Yaeyama Islands, Okinawa Prefecture, Japan (Y. Ikeda).

Fig. 2. Head of paratype of Exyrias akihito, 81.3 mm SL, showing cutaneous papilla system (solid dots) and pores (pale dots and arrows).

Fig. 3. Underwater photograph of Exyrias akihito, about 50 mm total length, 15 m, off Lawadi Village, Milne Bay Province, Papua New Guinea (G. Allen).

Fig. 4. Underwater photograph of Exyrias akihito, about 60 mm total length, Seribu Islands, Java (J. Randall).

Fig. 5. Underwater photograph of Exyrias akihito, about 70 mm total length, Palau, 15 m (J. Randall).

Fig.6. Underwater photograph of Exyrias belissimus, about 80 mm total length, 10 m, Milne Bay Province, Papua New Guinea (G. Allen).

Fig. 7. Exyrias belissimus, 77 mm SL, Pohnpei, Caroline Islands (J. Randall).