Macolor niger (Forsskål)

Leis, J. M., 2007, Larval Development in the Lutjanid Subfamily Lutjaninae (Pisces): the Genus Macolor, Records of the Australian Museum 59, pp. 1-8 : 4-6

Macolor niger (Forsskål)

Table 2, Figs 1, 2

Two pelagic larvae, 4.8 & 10.0 mm: NSMT-PL 149 (West Pacific: 7°56'S 161°04'E), NSMT-PL-188 (West Pacific: 3°15.2'S 151°05'E). 4 settlement-stage larvae, 16.1–19.3 mm: AMS I.43883-001, -002, -003 (Great Barrier Reef), AMS I.43869-001 (Nusa Nane Isl, Solomon Isls). 2 recent recruits, 26 & 32 mm: AMS I.34722–001 (Upolu Isl, Samoa), IORD 83–275 (Iriomote Isl, Ryukyu Isls) .

Body compressed and deep, but decreasing in depth from 50% at 4.8 mm to c. 37% at settlement. Body deeper at P 1 base than at anus, but this differential decreases with growth (Table 2). Gut coiled and compact, with virtually no gap between anus and anal fin. Prominent gas bladder immediately dorsal to gut. Caudal peduncle of moderate depth and length. Myomeres 24 (10–11+13–14). Gill rakers c. 55 at settlement, c. 70 at 26 mm and c. 75 at 32 mm.

Head bluntly triangular, compressed and large, decreasing in relative size from c. 45% at 4.8 mm to 35–38% at settlement. Snout less than eye diameter and bluntly triangular, becoming rounder following settlement. Mouth large and moderately oblique; tip of maxilla reaching to a pectoral fin (heavily pigmented) is folded upward. Photo by M. Lockett.

;;

length

spine P 1 + i 10 18 17 18 17 18 18 17 17 17 18 is

head sp;

, HL fins 11,, 11,10 11,, 11 11, 11,, 11,10 10,,10

length

;

pectoral A 15, III III III III III III III III III III III)

predosal-fin and anal, sp D IX (I X,14 X 14, 14, X 14, X, X 14 X,14,14 X, 13 X X, 13 X 13,

, dorsal PreDL to Preop Ang length

;

refer P 1 1 0.8 1.1 1.4 1.3 1.2 1.2 1.0 0.5 0.8 0.9 0.8 preanal D A and, ray P 2 1.5 3.1 4.8 4.5 4.8 5.5 7.8 10.4 10.8 10.3 13.5,

;

sp

PreAL length P 3 2 1.2 3.1 3.9 3.9 3.8 4.0 4.9 5.5 5.1 5.7 6.5: are

peduncle 2

Dsp 1.0 2.7 4.2 3.5 4.1 4.0 d d d 5.2 4.7

Abbreviations

, caudal Dsp 1 Dsp 0.5 1.7 1.0 3.3 4.8 1.8 1.2 3.3 4.1 1.2 3.7 1.3 4.5 d d 1.8 6.6 d 1.4

individuals

.

PedL; anus at) PedL 1.2 1.7 3.7 3.8 3.3 3.9

d

5.3 7.1

d

3.5

d

4.2 4.6 recently-settled body) depth,) P BD anus (( 1 1.7 3.8 5.2 5.5 d 6.3 8.6 10.1 11.1 6.1 5.6 7.4 and (anus BD 2.4 4.7 6.2 6.3 6.6 7.2 9.4 7.2 6.4 8.7 larvae; BD base rays. SnL 0.6 1.1 1.6 1.5 1.9 2.2 2.7 2.2 1.5 1.6 1.9

Macolor P at

1

incipient for depth, ED HL 0.8 2.2 4.3 1.5 2.1 5.7 6 2.4 2.1 5.9 7.4 2.7 10.7 3.4 11.5 4.5 2.3 6.6 2.5 7.1 3.1 8.2 values meristic body

(P

,

) 1 damaged i; PreDL

2.0 3.8 5.8 6.6 6.4 7.0 9.7

11.2

5.9 6.5 7.5

;

BD,. d PreAL 3.0 6.0 8.9 9.9 10.2 11.2 16.9 18.2 9.8 9.5 12.4

and

)

length spine in

mm

Morphometric

(

snout SnL diameter,; preopercle angle, sp SL pelagic niger 4.8 149 PL 188 10.0 PL- s ettlement-stage niger 16.1 – 43883 002. 17.4. 001 – 43869 001 43883 17.6. –. – 003 43883 19.3 settled niger – 26.0. 34722 001 32.3 – 83 275 settled macularis – 16.8 82 299 B 17.3 85 316 - A – 82 299 20.3

I I I I I. Table

2

, ED eye

PreopAng Macolor NSMT NSMT Macolor AMS AMS AMS AMS Macolor AMS IORD Macolor IORD IORD IORD level between anterior edge of eye and pupil. Canine teeth present in all specimens. Nasal pit unroofed at 4.8 mm, but two nostrils present by 10 mm. Scales start forming over most of the body at about 17 mm, and by 19 mm a full set of scales is present.

Spination on head well developed, and spines smooth. The longest head spine, a strong spine at angle of preopercle, decreases in relative length from 16% at 4.8 mm to c. 6% at settlement, and rapidly after settlement to c. 2% at 32 mm. On outer border of preopercle, two moderate size spines are located immediately adjacent to angle spine, one above and one anterior. Other spines on preopercle outer border are small. On outer, upper limb, there is no small spine at 4.8 mm, but one appears by 10 mm, and settlement-stage larvae have 10–13 small serrations that decrease to c. 8 in the 26 mm recruit. On the lower outer limb, there are 2 small spines at 4.8 mm, increasing to 4 by 10 mm, and 5–6 by settlement: in recruits, the lower, outer limb extensively and finely serrated. Spination on the inner preopercular border smaller and more limited. Lower, inner border with 3 small spines at 4.8 mm, 5 by 10 mm, and 6 by 16 mm, but these become eroded and ultimately lost by 19 mm. Inner, upper border with a single, small spine by 10 mm that is lost by 19 mm. Opercle has a single spine. Subopercle lacks spines until 18 mm, when a single, small spine is present, increasing to 3 small spines at 19 mm: these do not increase in number or size following settlement. Interopercle with a single spine just dorsal to the preopercular angle spine until settlement, when the ventral edge also becomes serrate. The supraorbital ridge smooth at 4.8 mm, with 5–6 weak spines posteriorly by 10 mm. These reduced to 3 eroded spines by 17 mm and absent in the settled individuals.

A small spine present on dorsal postcleithrum in 10 mm and larger individuals (absent in 4.8 mm larva). Two large supracleithral spines present at 4.8 mm, three in 10–17.6 mm larvae, two in the 19.3 mm settlement-stage larva, and only a single, tiny spine in settled individuals. A single dorsal posttemporal spine present in 4.8 and 10 mm larvae, one or two dorsal spines in 16–17 mm settlement-stage larvae, three at 19 mm, and 6–9 in the settled individuals. A single ventral posttemporal spine is present from 10–19 mm, but the settled individuals have 2–4 spines. A pterotic ridge is present by 10 mm, and a frontal ridge by 16 mm.

In 4.8 mm flexion-stage larva, a full compliment of 9+8 primary caudal rays present. Based on other lutjanids, flexion probably complete before 6 mm. All elements of D, A and P 2 fins present in the 4.8 mm larva, with last spine of D fin transforming from a soft ray to a spine. P 1 fin of 4.8 mm larva has 11 rays plus incipient rays, but the 10 mm and larger individuals have a full compliment of P 1 rays. Fin spines robust and chevron-shaped in cross-section, except P 2 spine which has two leading-edge ridges, and is concavely trapezoidal in cross-section in all specimens. Weak serrations present on the trailing edges of many fin spines. In 4.8 mm larva this includes D spines 1–6, A spines 1–2, and P 2 spine. At 10 mm, trailing edge serrations are present only on D spines 2–4, A spines 1–2 and P 2 spine. A portion of leading edges of fin spines have very weak serrations at 4.8 mm (Dsp 2, P 2) and 10 mm (Dsp 2–3, P 2, Asp 1–2). Fin spines smooth or nearly so in settlement-stage larvae: 16 mm larva has a few inconspicuous, eroded serrations on the trailing edges of Dsp 1 and Asp 1, and barely visible eroded serrations on the leading edge ridges of P 2 sp. At 4.8 and 10 mm, there is no obvious internal structure in fin spines, but settlementstage and settled individuals have fine reticulate internal structure in larger fin spines. Dsp 2 is longest fin spine in the two pelagic larvae (32–35% SL), but by settlement, Dsp 2, Dsp3, and P 2 sp are of similar length (c. 20–24%SL). A spines become more robust than D spines from about 10 mm. First ray of P 2 fin longer than spine, a disparity that increases with development especially following settlement.

Pigment: Larvae are lightly pigmented, but pigment intensifies as settlement approaches. The 4.8 mm larva has a single, small ventral melanophore on the caudal peduncle. The 10 mm larva has no ventral pigment, but the peduncle melanophore may have moved to an internal position just ventral to the urostyle. Both 4.8 and 10 mm larvae have a single, intense, internal melanophore in a saddle-like position on urostyle. Both melanophores near the urostyle persist in settlement-stage larvae, although they become increasingly difficult to see as external, lateral pigment intensifies (see below). No ventral pigment forms on the abdomen or head until settlement approaches. Similarly, no dorsal pigment forms on tail or trunk until settlement. At 4.8 mm, there is a single dorsal melanophore on the midbrain, but by 10 mm, both mid- and forebrain are largely covered dorsally and laterally by dense, evenly-spaced melanophores: these are retained. The 10 mm larva has internal melanophores on hindbrain both dorsally and ventrally.At the base of opercular spine, the 4.8 mm larva has a prominent melanophore, and the 10 mm larva has a cluster of large, prominent melanophores, which are retained in settlement-stage larvae. The gas bladder and dorsal surface of the gut are covered by a saddle of melanophores. The fins of the 4.8 mm larva lack pigment except for a single, distal melanophore in the trailing-edge chevron groove of Dsp2, and two melanophores, one each at base of two caudal rays. By 10 mm, the spinous dorsal fin is extensively pigmented, with the distal portions of fin membrane and spine chevron groove covered with fine melanophores. The area covered decreases from about two thirds anteriorly to only a few distal melanophores posteriorly ( Fig. 1B). In addition, a few melanophores are present basally on membranes near soft rays 3–5. By 10 mm, P 2 fin has a few melanophores on soft rays 1 & 2 and membranes near the spine tip.

As settlement approaches, pigment intensifies and spreads, taking on aspects of the juvenile pigment pattern. The anterior half of the spiny dorsal fin becomes intensely pigmented, and this pigment spreads ventrally onto the lateral surface of the body, eventually forming a large black blotch extending nearly to the lateral line. Similarly, the middle portions of the soft dorsal fin become intensely pigmented, and this pigment spreads ventrally to form a second, large blotch extending to the lateral line. Following settlement, these two blotches merge along the back, leaving unpigmented the middle portion of the dorsal fin. The pigment extends along the dorsal surface of the caudal peduncle to join the caudal pigment. The posterior third of the caudal peduncle becomes heavily pigmented, as does the caudal-fin with the exception of the distal portions of the dorsal-most and ventral-most rays. Pigment also extends along the ventral surface of the caudal peduncle, joining a large blotch extending dorsally from the heavily pigmented soft rays of the anal fin. The pelvic fin becomes heavily pigmented, and this pigment then extends dorsally to the base of the pectoral fin before settlement. The pectoral fin also becomes heavily pigmented. The heavy brain and opercular pigment present at 10 mm spreads and coalesces and then spreads across the cheek below the eye to form a large blotch extending as far forward as the anterior edge of the eye by settlement. Finally, a separate small cluster of pigment forms at the tip of the snout. In life, the portions of the body that are not black are coloured white, resulting in a striking, and distinctive pattern (in contrast, non-black portions of the fins remain unpigmented). The distinctive post-settlement colour pattern is illustrated by Kishimoto et al. (1987) and Randall (2005).

Remarks. Larvae of M. niger smaller than 4.8 mm are likely to have more extensive fine serrations on the fin spines, and also more pigment ventrally on the tail, if patterns of development are similar to those of other lutjanine species ( Kojima, 1988; Watson & Brogan, 1996; Leis & Rennis, 2004; Lindeman et al., 2005; JM Leis, unpublished). The very limited pigment on the head and fins of the 4.8 mm larva is unusual for a lutjanine species. The distinctive saddle-like melanophore on the urostyle may be present in smaller larvae. The fine serrations of the fin spines if present in smaller larvae, combined with the pigment characters above may assist in the identification of smaller larvae, as will the distinctive fin-ray counts.

Larvae of M. niger have all diagnostic characters of lutjanids, thus confirming the placement of Macolor as a lutjanid genus. Without access to larvae of M. macularis , no larva-based test of Macolor monophyly can be made, but there is nothing particularly distinctive about the development of M. niger that would support Macolor monophyly, considering the range of larval morphology and development evident in other lutjanine genera. In contrast, the fact that both Macolor species share similar and otherwise unique ontogenetic changes in colour and body shape following settlement seems to indicate that the two species do form a monophyletic group.

The general morphology of M. niger larvae is similar to other lutjanines, but the monophyly of the Lutjaninae remains to be established. Larvae of basal lutjanids (i.e., species in the subfamilies Etelinae and Apsilinae, sensu Johnson, 1980 ) lack two apparently derived characters present in the other three lutjanid subfamilies (i.e., Paradicichthyinae , Lutjaninae , and also Caesioninae, sensu Johnson [1980] , which is clearly a lutjanid subfamily; see also Reader & Leis [1996]). These characters are a second ridge on the leading edge of the P 2 spine and delayed formation of the second and subsequent spines on the outer, upper edge of the preopercle ( Leis, 2005). Lutjanines and caesionines have serrations on the supraorbital ridge that is lacking in the other subfamilies, although one of the two paradicichthyine species also has serrations on the supraorbital ridge (Leis & Bray, 1995). These three characters are present in Macolor niger larvae, and the second P 2 ridge is present in newly settled juveniles of M. macularis (supraorbital serrations are absent, as would be expected following settlement, and it is not possible to determine the sequence of formation of the preopercular spines from settled juveniles alone). This corroborates the placement of Macolor with the lutjanines and caesionines, but, as yet no characters of larvae support monophyly of the Lutjaninae .