Lethrinus obsoletus
Creators: name: Wilson, G. G.
Publisher: name: Zenodo
Year: 1998
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Perciformes
Lethrinidae
Lethrinus
Lethrinus obsoletus
Lethrinus olivaceus
Lethrinus ornatus

description: <i>Lethrinus obsoletus</i> (Forsskal) PI. 2E-H, Fig. 5B,C,E Material examined. (72 specimens: 17-81 mm). AUSTRALIA Great Barrier Reef region, AMS 1.20772 - 027 (1: 81 mm), AMS 1.34911 - 008 (4: 18-27 mm), AMS 1.34911 - 009 (3: 36-39 mm), AMS 1.34911 - 010 (1: 33 mm), AMS 1.34912 - 009 (1: 33 mm), AMS 1.34913 - 003 (1: 25 mm), AMS 1.34913 - 004 (1: 25 mm), AMS 1.34913 - 005 (1: 27 mm), AMS 1.34913 - 006 (1: 43 mm), AMS 1.34919 - 002 (2: 31-35 mm), AMS 1.34919 - 003 (1: 31 mm), AMS 1.34926 - 001 (1: 18 mm), AMS 1.34927 - 001 (1: 58 mm), USNM 336685 (1: 20 mm), USNM 336686 (3: 26--34 mm), USNM 336687 (4: 37-40 mm), not retained (45: 17-63 mm). Diagnosis. Body moderately deep, depth 2.5-3.0 in SL; 5.5 dorsal scale rows, 15-16 ventral scale rows; maxillary serrations 5-7 at 16-18 mm, 1-4 at 25-29 mm, 0-2 at 30- 39, absent thereafter; cheek scales present at 16-30 mm, variable at 31-39 mm, absent at less than 39 mm; dorsal spine 4 or 5 the longest at less than 35 mm. Diagnostic colour notes. Body and head cream to pale grey-tan; banding intense, shoulder blotch cuboidal or vertically-rectangular, seldom with pale halo, not crossing lateral-line; dorsal margin of lateral-line silvery cream; 2-4 orange-tan primary stripes, pectoral stripe of greatest width and intensity; dark mid-lateral stripe frequently displayed (20-80 mm), intense, width approximately 5.0 in body depth; fins mostly hyaline. Colour notes. Minimal change in colour patterns throughout juvenile ontogeny, frequently displays dark intermittent patterns, able to switch colour patterns in 1-3 seconds. At 17-19 mm, recently-settled: body cream, abdomen silver, lateral-line cryptic; 4-7 indistinct grey bands along dorsum, may join faint ventral bands at lateralline; shoulder-blotch dark grey, often inconspicuous, cuboidal (Fig. 5B), never crossing lateral-line, without pale halo, rapidly switched on or off within 2-3 seconds; 2-3 indistinct primary stripes, pale orange-tan, dorsal and ventral stripes often indistinguishable, pectoral stripe marginally widerthan orbital stripe; nape and snout yellowtan, cheek silver without dark markings; fins hyaline. At 20-80 mm (PI. 2E-G): body pale grey-tan, belly off-white, lateral-line usually distinct, dorsal margin offwhite; banding and shoulder blotch distinct and intense when alive (PI. 2E,F), fading after death (PI. 2G), medial dorsal bands usually joining 2-3 cuboidal blotches below lateral-line (PI. 2E,F), ventral bands extending diagonally between blotches and belly, shoulder blotch distinct, mostly vertically-rectangular (Fig. 5C,E, PI. 2F,G), occasionally cuboidal (Fig. 5B, PI. 2E), seldom bordering lateral-line, rarely with pale halo; dark mid-lateral stripe frequently seen in field, dark brown to black, width approximately 5.0 in body depth; primary stripes orange-pink to orangetan, dorsal stripe seldom conspicuous, pectoral stripe slightly wider than others (as in PI. 2G); head similar to body, nape and snout uniform or mottled tan, black nearvertical band often bisecting orbit in field, grey blotch below orbit from 22 mm (inverted v-shaped band from 45 mm) and dark grey to brown blotches along rear margin of preoperculum and operculum in captivity; fins mostly hyaline, pale pink distally in field, anterior half of spinous fins off-white with scattered brown patches. Colour in alcohol. At 17-20 mm, body off-white, dark banding and shoulder blotch dulled, primary stripes lost, fins hyaline; at greater than 25 mm, body and head olive to grey-tan, belly off-white, banding and dark head markings distinct though dulled, primary stripes lost; fins hyaline. After preservation, <i>L. obsoletus</i> juveniles (18-80 mm) are often indistinguishable from <i>L. lentjan</i> and <i>L. nebulosus,</i> preventing identification beyond <i>L. obsoletusl lentjanlnebulosus.</i> Ecology. Common, mostly solitary, occasionally joins small (approximately 10-15 individuals) multi-species schools with similarly-sized congeners <i>(L. atkinsoni, L. genivittatus, L. harak, L. variegatus), Stethojulis strigiventor, Parupeneus barberinus</i> and <i>P. indicus,</i> and particularly <i>Siganus fuscescens;</i> settles at 16-18 mm into shallow seagrass cover (0.2-4 m; <i>Halodule, Thalassia, Cymodocea)</i> on fringing and lagoonal reefs, an ontogenetic shift apparent to adjacent reef-flat habitats at 70-90 mm, individuals 90-140 mm only occasionally encountered within shallow areas; forages diurnally off seagrass leaves (18-30 mm) or on benthic items (at greater than 30 mm), no aggressive interactions noted, individuals 18-25 mm rapidly seek shelter within the seagrass canopy when disturbed. Field identification. Generally an easy species to identify in the field, although can be confused with <i>L. genivittatus, L. lentjan</i> and <i>L. nebulosus</i> (Table 1). Small specimens (18-25 mm) can be distinguished from <i>L. nebulosus</i> and <i>L. lentjan</i> by their intense shoulder blotch (Fig. 5) and orange to orange-tan primary stripes. At this size, <i>L. obsoletus</i> and <i>L. genivittatus</i> can be reliably separated by their primary stripes, dorsal bands, and shoulder blotch. At greater than 25 mm, <i>L. obsoletus</i> can be distinguished from other species by the prominent orange-pink to orangetan pectoral stripe. During display of the dark mid-lateral stripe, the off-white dorsal border of the lateral-line, in combination with a moderately-deep body profile (cf. pale dorsal border with slender body in <i>L. variegatus),</i> is diagnostic. At all sizes, individuals may need to be observed for several minutes before the full range of colour patterns can be ascertained. At less than 40 mm, the collection of specimens for examination of freshly-killed colours may also be necessary. Further notes on separating these species in the field are given in the "Field Identification" sections of <i>L. genivittatus</i> and <i>L. lentjan.</i> <i>Lethrinus obsoletus</i> appears unique among GBR lethrinids in continuing to display a dark mid-lateral stripe pattern throughout the adult stage (PI. 2H). Previous descriptions. Wheeler (1961) included a colour sketch of a captive 88 mm TL specimen (as <i>Lethrinus ramak)</i> along with brief descriptions of the stress, resting and freshly-killed colouration displayed by "very young" specimens (sizes not given). Masuda &amp; Kobayashi (1994) provided a colour plate of a specimen 35 mm total length. Identification notes. Carpenter &amp; AlIen (1989) note the presence of a "knob" on the outer surface of the maxilla in <i>L. obsoletus</i> to be useful for separating this species from other lethrinids. This character is indistinguishable at less than 80 mm. Alternative meristic and morphological measurements (particularly the number of dorsal scale rows, presence of cheek scales and number of maxillary serrations), along with the shoulder blotch and primary stripes, represent the easiest means of distinguishing smaller <i>L. obsoletus</i> from other close species. <i>Lethrinus olivaceus</i> Valenciennes PI. 3A,B, Fig. 3C,D Material examined. (15 specimens: 32-124 mm). AUSTRALIA Great Barrier Reef region, AMS I.34919-004 (1: 36 mm), AMS I.34928-001 (1: 38 mm), AMS I.34929- 001 (1: 39 mm), AMS I.34930-001 (1: 32 mm), AMS I.34931-001 (1: 40 mm), AMS I.34931-002 (1: 63 mm), USNM 336688 (1: 34 mm), USNM 336689 (1: 53 mm), USNM 336690 (1: 32 mm), not retained (5: 44-124 mm); INDONESIA EasternArchipelago, NMV 46333 (1: 111 mm). Diagnosis. Body moderately elongate, body depth 2.9- 3.2 in SL; 5.5 dorsal scale rows, 16-17 ventral scale rows; maxillary serrations absent at greater than 32 mm; cheek scales retained until 40 mm; dorsal spine 3 or 4 the longest. Diagnostic colour notes. Dorsum pale olive-grey, shading to silvery off-white ventrally; dark markings intense, shoulder blotch horizontally-rectangular, ventral bands diagonal (Fig. 3D, PI. 3B), width of dark mid-lateral stripe approximately 6.0 in body depth; single dark blotch below orbit at 40-63 mm, 2 blotches below orbit and 2 bands between mouth and orbit at 124 mm; spinous fins with dense melanophores, appearing dark grey when folded at rest. Colour notes. At 32-63 mm: dorsum off-white tan to olivaceus tan, body silvery off-white ventrally, lateral-line mostly cryptic, occasionally faded yellow-tan stripe along ventral margin; dark markings prominent, particularly in field (as in PI. 3B), rapidly switched on in 1-3 seconds when approached or otherwise disturbed, 5-7 indistinct dark bands along dorsum between head and caudal peduncle, 2-3 similar bands along caudal peduncle, 2-3 dark blotches below lateral-line, first blotch of greatest intensity forming a horizontally-rectangular shoulder blotch below dorsal spines 5-7 (Fig. 3D, visible though faded inPI. 3A,B), network of diagonal dark bands between blotches and belly (Fig. 3D); intense dark mid-lateral stripe common in field, banding switched olT, narrower than that of other Jethrinids, width 6.0 in body depth, switched on or off rapidly; lips, snout and nape mouled grey, preoperculum and venlral half of operculum silvery white with indistinct dark blotches along posterior margins. funher dark blotch forming below orbit; fins mostly hyaline, anterior half of spinous fins with off-white and yellow patches interspersed by dark grey blotches, pale orange-pink distally at greater than 40 mm, appearing dark grey when folded at rest. At 124 mm, as in smaller specimens, dark markings on head and body more intense, 5-6 dark blotches on operculum. 2 dark blotches below orbit and 2 bands between mouth and orbit: fins with oblique maroon bands, interspaces off-white yellow. pale scarlet dislally. Colour in alcohol. Dorsum pale off-white tan. shading to off-w hite belly: distinctive markings on body and head slightly faded; dense melanophores retained on tins. Ecology. Uncommon al Green Island. restricted to shoreline seagrass areas (0.2-1.5 m: <i>Cymodocea, fIafodllfe. Thaiassia),</i> occurring over shallow (2-4 m) open sand/coral rubble at greater than 100 mm; not appearing site-attached, a single 35 mm individual was observed swimming in a loose multi-species school with similar-sized <i>Siganus juscescens, Halichoeres</i> species (Labridae) and congeners <i>(</i> <i>L. atkinsoni,</i> <i>L. harak,</i> <i>L. obsoletus),</i> periodically picking food items off seagrass blades and adjacent substratum; no aggressive interactions noted, other field behaviours unknown. Field identification. Rarely encountered in the field as early juveniles, a combination of the slender body and snoutprofiles, horizontal shoulderblotch,narrow mid-lateral stripe, ventral diagonal banding and absence of coloured primary stripes may distinguish this species. The intense fin pigmentation characteristic of dead specimens was not noted in field observations, althoughis faintly visible in the colour plate of a 150 mm juvenile given in Myers (1989). During display of the dark mid-lateral stripe pattern, <i>L. olivaceus</i> may be confused with numerous species, particularly <i>L. genivittatus.</i> Individuals may need to be followed for several minutes before other patterns are displayed. Previous descriptions. Kuiter &amp; Debelius (1994) included a colour plate of <i>L. olivaceus</i> (as <i>L. microdon)</i> showing the characteristic horizontal shoulder blotch and ventral banding. A 150 mm juvenile (as <i>L. semicinctus)</i> is shown in Myers (1989, PI. 56E), displaying the intense shoulder blotch and narrow mid-lateral stripe characteristic of field observations. Lieske &amp; Myers (1994, PI. 53) also figured the <i>L. olivaceus</i> dark mid-lateral stripe pattern. Remarks. Freshly collected <i>L. olivaceus</i> juveniles are unlikely to be confused with other <i>Lethrinus</i> species of a similar size. Specimens retained frozen or in alcohol for extended periods were noted to display near-identical banding to <i>L. genivittatus,</i> particularly if the orange primary stripes in the latter species had faded. Such material may be reliably separated using the number of dorsal scale rows, shape of the shoulder blotch, and intensity of pelvic-fin pigmentation. <i>Lethrinus ornatus</i> Valenciennes PI. 3C Material examined. (11 specimens: 20-91 mm). AUSTRALIA Great Barrier Reef region, AMS 1.34917 - 001 (1: 32 mm), AMS 1.34932 - 001 (1: 36 mm), not retained (6:20-69); INDONESIA Maumere Bay (Flores), not retained (2: 20 mm); SOLOMON ISLANDS New Georgia Island, AMS 1.22128 - 154 (1: 91 mm). Diagnosis. Body relatively deep, its depth 2.5-2.8 in SL; 5.5 dorsal scale rows, 15 ventral scale rows; maxillary serrations 2-4 at 20 mm, absent at greater than 28 mm; dorsal spine 5 the longest at 20-60 mm (rarely 4 at greater than 50 mm). Diagnostic colour notes. Primary stripes 4, bright orange, of similarwidth and intensity, interspaces silvery off-white; fins hyaline, pink to pale scarlet distally; pale scarlet band along rear margin of operculum at greater than 28 mm; dark markings seldom displayed. Colour notes. A striking species with few differences in colouration between adults and juveniles, difficult to confuse with other <i>Lethrinus</i> species. At 20-80 mm (PI. 3A): dorsum and nape pale grey-tan, flank silvery offwhite, belly off-white; 4 prominent bright orange primary stripes, of similar width and intensity, fine grey borders, interspaces grey-tan or silvery off-white, dorsal stripe extending to below medial dorsal rays, remaining stripes terminating at base of caudal peduncle; black banding and cuboidal shoulder blotch seldom displayed infield although common at capture (PI. 3C) and after death, rapidly switched on or off, 6-7 bands along dorsum, most connecting with further banding between lateral-line and belly, 2-3 similar bands along caudal peduncle; dark midlateral stripe occasionally displayed in field, dark grey, width approximately 4.0 in body depth, obscuring dorsal and orbital stripes, pectoral and ventral stripes usually remaining visible though dulled; head similar to body, snout yellow-brown, cheek silvery off-white, may have diffuse tan blotch, eye often bisected by near-vertical black band in field, pale scarlet band developing along rear margin of operculum from 28 mm (faded in PI. 3C); fins mostly hyaline, caudal and pectoral fins pale pinkish yellow, anterior half of spinous fins off-white with dark grey patches basally, deep pink to scarlet distally in field, diffuse pink at capture (as in PI. 3C) and when freshly-killed. At greater than 80 mm, body, head and fins as in smaller specimens, dark mid-lateral stripe and banding absent. Colour in alcohol. Dorsum pale grey-tan with 5-6 dark bands; ventral half of body and primary stripes faded to off-white, dark banding below lateral-line dissected by primary stripes into 3-6 series of square blotches; banding retained along caudal peduncle; fins hyaline. Ecology. Uncommon at Green Island, settles at 19-21 mm into shallow reef seagrass habitats, remaining there until 70-80 mm; solitary, not appearing site attached, seldom in close association with other fishes, occasionally joining small loose schools with juvenile <i>Stethojulis strigiventor, Siganusjuscescens, Parupeneus indicus</i> and congeners of a similar size, particularly in the presence of piscivorous carangids or lutjanids; at 40-70 mm periodically resting briefly at the base of the seagrass canopy in tall-dense <i>Cymodocea</i> and <i>Halodule,</i> fleeing over the canopy when disturbed. Field identification. Juvenile <i>L. ornatus</i> are best distinguished in the field by their deep body profile, intense orange primary stripes and rarity of conspicuous dark banding or mid-lateral stripe patterns (cf. frequent displays in other species with bright primary stripes). Recentlysettled specimens display near-identical colouration to later stages, although less conspicuously. <i>Lethrinus olivaceus</i> Valenciennes PI. 3A,B, Fig. 3C,D Material examined. (15 specimens: 32-124 mm). AUSTRALIA Great Barrier Reef region, AMS I.34919-004 (1: 36 mm), AMS I.34928-001 (1: 38 mm), AMS I.34929- 001 (1: 39 mm), AMS I.34930-001 (1: 32 mm), AMS I.34931-001 (1: 40 mm), AMS I.34931-002 (1: 63 mm), USNM 336688 (1: 34 mm), USNM 336689 (1: 53 mm), USNM 336690 (1: 32 mm), not retained (5: 44-124 mm); INDONESIA EasternArchipelago, NMV 46333 (1: 111 mm). Diagnosis. Body moderately elongate, body depth 2.9- 3.2 in SL; 5.5 dorsal scale rows, 16-17 ventral scale rows; maxillary serrations absent at greater than 32 mm; cheek scales retained until 40 mm; dorsal spine 3 or 4 the longest. Diagnostic colour notes. Dorsum pale olive-grey, shading to silvery off-white ventrally; dark markings intense, shoulder blotch horizontally-rectangular, ventral bands diagonal (Fig. 3D, PI. 3B), width of dark mid-lateral stripe approximately 6.0 in body depth; single dark blotch below orbit at 40-63 mm, 2 blotches below orbit and 2 bands between mouth and orbit at 124 mm; spinous fins with dense melanophores, appearing dark grey when folded at rest. Colour notes. At 32-63 mm: dorsum off-white tan to olivaceus tan, body silvery off-white ventrally, lateral-line mostly cryptic, occasionally faded yellow-tan stripe along ventral margin; dark markings prominent, particularly in field (as in PI. 3B), rapidly switched on in 1-3 seconds when approached or otherwise disturbed, 5-7 indistinct dark bands along dorsum between head and caudal peduncle, 2-3 similar bands along caudal peduncle, 2-3 dark blotches below lateral-line, first blotch of greatest intensity forming a horizontally-rectangular shoulder blotch below dorsal spines 5-7 (Fig. 3D, visible though faded inPI. 3A,B), network of diagonal dark bands between blotches and belly (Fig. 3D); intense dark mid-lateral stripe common in field, banding switched olT, narrower than that of other Jethrinids, width 6.0 in body depth, switched on or off rapidly; lips, snout and nape mouled grey, preoperculum and venlral half of operculum silvery white with indistinct dark blotches along posterior margins. funher dark blotch forming below orbit; fins mostly hyaline, anterior half of spinous fins with off-white and yellow patches interspersed by dark grey blotches, pale orange-pink distally at greater than 40 mm, appearing dark grey when folded at rest. At 124 mm, as in smaller specimens, dark markings on head and body more intense, 5-6 dark blotches on operculum. 2 dark blotches below orbit and 2 bands between mouth and orbit: fins with oblique maroon bands, interspaces off-white yellow. pale scarlet dislally. Colour in alcohol. Dorsum pale off-white tan. shading to off-w hite belly: distinctive markings on body and head slightly faded; dense melanophores retained on tins. Ecology. Uncommon al Green Island. restricted to shoreline seagrass areas (0.2-1.5 m: <i>Cymodocea, fIafodllfe. Thaiassia),</i> occurring over shallow (2-4 m) open sand/coral rubble at greater than 100 mm; not appearing site-attached, a single 35 mm individual was observed swimming in a loose multi-species school with similar-sized <i>Siganus juscescens, Halichoeres</i> species (Labridae) and congeners <i>(</i> <i>L. atkinsoni,</i> <i>L. harak,</i> <i>L. obsoletus),</i> periodically picking food items off seagrass blades and adjacent substratum; no aggressive interactions noted, other field behaviours unknown. Field identification. Rarely encountered in the field as early juveniles, a combination of the slender body and snoutprofiles, horizontal shoulderblotch,narrow mid-lateral stripe, ventral diagonal banding and absence of coloured
description: Published as part of <i>Wilson, G. G., 1998, A description of the early juvenile colour patterns of eleven Lethrinus species (Pisces: Lethrinidae) from the Great Barrier Reef, Australia, pp. 55-83 in Records of the Australian Museum 50 (1)</i> on pages 75-78, DOI: 10.3853/j.0067-1975.50.1998.1274, http://zenodo.org/record/4652850
description: {"references": ["Wheeler, J. F. G., 1961. The genus Lethrinus in the Western Indian Ocean. Colonial Office Fishery Publications No. 15: 1 - 51.", "Masuda, H., &amp; Y. Kobayashi, 1994. Grand Atlas of Fish Life Modes. Tokai University Press, Tokyo, pp. 465.", "Carpenter, KE., &amp; G. R. AlIen, 1989. FAO species catalogue: Vol. 9. Emperor fishes and large-eye breams of the world (family Lethrinidae). An annotated and illustrated catalogue of lethrinid species known to date. FAO Fisheries Synopsis No. 125, Volume 9. FAO, Rome, pp. v + 118.", "Myers, R. F., 1989. Micronesian reef fishes. 1 st edn. Coral Graphics, Guam, pp. vi + 298.", "Kuiter, R. H., &amp; H. Debelius, 1994. Southeast Asia tropical fish guide. IKAN-Unterwasserarchiv, Frankfurt, Germany, pp. 321.", "Lieske, E., &amp; R. F. Myers, 1994. Collins Pocket Guide: Coral Reef Fishes. Indo-Pacific &amp; Caribbean. Harper Collins Publishers, London, pp. 400."]}