Apogon maculatus Poey

Apogon maculatus (Poey)

Identification. Fifteen adult specimens of A. maculatus provided the basis for genetic identification of one larva and three juveniles (Appendix 1, one adult is shown in Fig. 21). The combination of characters that distinguishes A. maculatus adults from other Apogon species is eight segmented anal-fin rays, lateral-line and body scales of similar size, a dark pupil-size spot present below the posterior end of the second dorsal fin, 17–20 circum-caudal-peduncle scales, and a large, dark caudal blotch that extends ventrally well below the lateral midline (Böhlke & Chaplin 1993; Gon 2002). One adult specimen from Belize, BLZ 5023, is more divergent in COl from other specimens of A maculatus than is typical within the genus (Fig. 1), but the specimen does not appear remarkably different morphologically. In the combined data set (see summary data in Table 1), average intraspecific variation in A. maculatus is 1%, whereas in most other Apogon species it is 0%. Apogon pillionatus and A. aurolineatus also are characterized by 1% average intraspecific variation.

Juveniles (Fig. 22). The three juveniles are 16.0–22.0 mm SL. All have the adult pattern of pigmentation except that the caudal-peduncle blotch is not fully developed in all specimens. The juveniles have 13–14 gill rakers on the lower limb of first gill arch.

Comparisons Among Juveniles. Juvenile A. maculatus can be separated from A. pseudomaculatus and juveniles of other Apogon by characters listed above (see “Comparisons” under Apogon pseudomaculatus).

Larva (Fig. 23). The single larval specimen, 12.0 mm SL, is largely orange. The fins are mostly clear, but there are orange chromatophores on several rays of the first dorsal fin. There are numerous melanophores on top of the head and behind the eye on the cheek. The dark spot below the posterior portion of the second dorsal-fin base characteristic of juveniles and adults is beginning to develop, and several large, dark melanophores of the incipient caudal-peduncle blotch are present just anterior to the caudal-fin base.

Comparisons Among Larvae. The larval specimen of A. maculatus most closely resembles larval A. aurolineatus and small A. phenax larvae in having a bright orange body color, but it differs from those species and all Apogon larvae studied herein in having orange pigment on the first dorsal fin (vs. yellow in A. aurolineatus, none in the other species). Additionally, larvae of A. maculatus have more melanophores on top of the head than A. aurolineatus. Larval A. maculatus lacks the conspicuous orange spot above the upper lip of A. phenax, the bright yellow pigment on the head of larval A. planifrons, and the distinctive pattern of chromatophores on the fins of larval A. mosavi. Caudal-peduncle length may be useful in separating preserved larval A. maculatus from some other Apogon larvae: peduncle length 30% SL in A. maculatus vs. 32–40% SL in larval A.binotatus, A. phenax, A. planifrons, A. townsendi, and Apogon sp. 1. Additionally, the presence of the incipient dark trunk blotches typical of juvenile and adults may indicate precocious development that, in combination with the bright orange body color, could be useful in distinguishing A. maculatus larvae from other known Apogon species. Among our other Apogon larvae, only an 11.0-mm SL specimen of A. phenax (Fig. 12 c) has the incipient dark bars of juveniles and adults, but the body is considerably paler than in larval A. maculatus, especially posteriorly. More larval material is needed.