Lethrinus xanthochilus Klunzinger

Wilson, G. G., 1998, A description of the early juvenile colour patterns of eleven Lethrinus species (Pisces: Lethrinidae) from the Great Barrier Reef, Australia, Records of the Australian Museum 50 (1), pp. 55-83 : 79-81

Lethrinus xanthochilus Klunzinger

PI. 3E, Fig. 3B

Material examined. (10 specimens: 19-92 mm). AUSTRALIA Great Barrier Reef region , AMS I.34912-007 (1: 19 mm), AMS I.34912-008 (1: 22 mm), AMS I.34922- 001 (1: 73 mm), AMS 1.34923 - 001 (1: 26 mm), USNM 336684 (1: 25 mm), lost (1: 48 mm) ; PAPUA NEW GUINEA Trobriand Islands , AMS I.17102-081 (1: 44 mm), AMS 1.17099 - 005 (3: 66-92 mm) .

Diagnosis. Body moderately deep, depth 2.6-3.2 in SL; 4.5 dorsal scale rows, 15-16 ventral scale rows; maxillary serrations 7 at 18-19 mm, 1-4 (usually 2-3) at 20-28 mm, absent at greater than 28 mm; cheek scales retained until 44 mm; dorsal spine 5 the longest at 18-19 mm, 3 or 4 the longest at greater than 20 mm.

001 (2 specimens), Green Island . Details of scalation, myomeres and internal pigmentation are not shown .

Diagnostic colour notes. At 18-75 mm, dorsum cream to pale bronze, body abruptly silvery off-white ventrally, silvery off-white interspace along mid-body (22-45 mm) with 2-3 short brown stripes below; black suborbital blotch at 20-45 mm; shoulder blotch inconspicuous; pectoral base scarlet at greater than 50 mm, spinous fins with dense melanophores at greater than 19 mm, appearing black when folded at rest.

Colour notes. A species with distinctive early-juvenile colour patterns which differ markedly from the adult colouration, capable of rapid colour pattern changes. At 18-20 mm, recently-settled: snout, nape and dorsum cream to pale tan, ventral half of head and body abruptly silvery off-white, lateral-line cryptic, prominent silvery off-white interspace along mid-body between cheek and base of caudal rays (PI. 3E), diffuse grey to brown banding and blotches along body, 4-6 irregular bands forming along dorsum, 2-3 similar bands (or single broad band) on caudal peduncle, usually bisected by mid-lateral interspace; series of 3-4 exceedingly faint grey blotches between lateralline and mid-lateral interspace, 2 short primary stripes in approximately pectoral and ventral configurations (PI. 3E, Fig. 3B,4), may fuse below dorsal spines 8-10 and extend onto caudal peduncle as single stripe; diffuse darkmarkings forming onhead as small blotch below orbit, blotches along rear margin of preoperculum and operculum, and band passing through lips; fins mostly hyaline, anterior half of spinous fins with black patches over off-white to yellow, appearing black when folded at rest.

At 20-73 mm (PI. 3E): background of body gradually darkening with growth to pale bronze dorsum and off-white belly; dark markings on head and body more intense, particularly in field, dark brown to black (PI. 3E), shoulder blotch more distinct although only at capture or after death, ventral network of indistinct bands joining blotches along lateral-line with belly at greater than 50 mm, 2-3 diffuse bands across snout and nape (PI. 3E); silvery off-white interspace becoming clearer (20-45 mm) then indistinct (50-73 mm); dark mid-lateral stripe occasionally displayed in field, width approximately 4.0 in body depth, moderately-intense; pigmentation on fins more intense, pectoral fin pale pink at greater than 50 mm, scarlet patch at pectoral base from 50 mm.

Colour in alcohol. At 18-20 mm, body off-white, dark markings on head, body and fins distinct although faded; 21-92 mm (PI. 3E), dorsum off-white to pale tan, silvery off-white ventrally, dark patterns along body, head and fins distinctly retained, silvery white mid-lateral interspace usually prominent (21-50 mm), red pectoral base (50-92 mm) indistinguishable.

Ecology. Uncommon at Green Island, settlement and nursery habitat preferences uncertain, at 20-73 mm only found over shoreline seagrass cover (0.2-2.0 m; Cymodocea , Halodule , Thalassia ), specimens 44-92 mm from the Trobriand Islands ( Papua New Guinea) collected over sand near patch reefs, 0-1 m; a solitary 35 mm individual at Green Island was noted sheltering amongst epiphytic algae at the base of the seagrass canopy, two 40 mm individuals were noted foraging with congeners ( L. obsoletus and L. variegatus ), Halichoeres miniatus , Lutjanus fulviflamma and Siganus fuscescens of a similar size, fleeing over the seagrass canopy when closely approached; not appearing site attached, other field behaviours unknown.

Field identification. A distinctive species, easily recognised in the field by its prominent silvery white midlateral interspace (20-50 mm) and black suborbital

markings. The red patch at the pectoral-fin base may be a reliable character for the field identification of individuals greater than 55 mm, along with the presence of intense black fin pigmentation (but see "Identification note" below).

Identification note. The intense black pigmentation on spinous fins of preserved specimens may lead to confusion with L. miniatus . No confirmed juvenile records exist for the latter species on the GBR, although two specimens are known from Sydney Harbour (Australian Museum, I.19103-01O and 1.24474-002). Morphological differences distinguishing L. miniatus and L. xanthochilus at less than 110 mm include a concave interorbital area in L. xanthochilus (at greater than 40 mm) (flat or convex in L. miniatus ), a slight to moderately-humped interorbital margin in L. xanthochilus (straight in L. miniatus ) and deeper body profile of L. miniatus .

Remarks. Carpenter & Allen (1989) queried the occurrence of L. xanthochilus in Australian waters, although Williams & Russ (1994) noted several records from the central and northern regions of the GBR. The individuals described here represent the first confirmed juveniles to be collected from Australian waters.