Apogon planifrons Longley and Hildebrand

Baldwin, Carole C., Brito, Balam J., Smith, David G., Weigt, Lee A. & Escobar-Briones, Elva, 2011, Identification of early life-history stages of Caribbean Apogon (Perciformes: Apogonidae) through DNA Barcoding, Zootaxa 3133, pp. 1-36 : 11

Apogon planifrons Longley and Hildebrand

Identification. One adult specimen of A. planifrons ( Fig. 8 ) provided the basis for genetic identification of five larva (Appendix 1). No juveniles are present in our material. Adult A. planifrons has eight segmented anal-fin rays, the body and lateral-line scales of similar size, the anterior dark bar positioned entirely below the posterior end of the second dorsal fin and distinctly narrower than the dark bar on the caudal peduncle, 15 or 16 circum-caudalpeduncle scales, and usually 15 (14–16) gill rakers on the lower limb of the first arch ( Böhlke & Chaplin 1993, Böhlke & Randall 1968, Gon 2002). Apogon planifrons most closely resembles A. townsendi and A. gouldi in having the anterior bar entirely beneath the second dorsal-fin base. It can be separated from those species by lowerlimb rakers ( Table 2 ) and circum-caudal-peduncle scales (15–16 in A. planifrons vs. 12 in A. townsendi and A. gouldi ). Apogon planifrons can be further distinguished from A. townsendi in lacking black lateral margins on the caudal-peduncular bar ( Böhlke & Chaplin 1993, Smith-Vaniz 1977, Gon 2002).

Larvae ( Fig. 9 ). Apogon planifrons larvae genetically analyzed in this study range from 9.0 to 10.0 mm SL. The snout is mostly transparent, and there is pale orange coloration on the jaws. The central and posterior portions of the head and the belly have prominent yellow pigmentation. The posterior region of the body is mostly pale orange to orange in 9.0 and 9.5mm SL specimens, with some pale areas on the caudal peduncle. In 10–mm SL specimens, much of the posterior portion of the body is pale, usually with an orange bar beneath the posterior end of the second dorsal fin and an orange blotch on the posterior end of the caudal peduncle. The dorsal fins are clear. There are orange chromatophores at the bases of the pelvic and anal fins, as well as on the proximal portion of the ventral lobe of the caudal fin. There is a line of orange chromatophores along the anal-fin base that extends onto the ventral midline of the caudal peduncle. There are melanophores on top of the head, behind eye in the temporal region, over the swimbladder, and on the lateral surface of the gut. The caudal peduncle is long, 35–40% SL.

Comparisons Among Larvae. Apogon planifrons larvae are easily distinguished from other known Apogon larvae by the bright yellow chromatophores on most of the head and abdominal region and usually by a long caudal peduncle (35–40% SL in A. planifrons vs. 27–37% SL in other Apogon species). Caudal-peduncle length alone is useful for separating preserved larval specimens of A. planifrons from larvae of some Apogon species, but A. phenax , A. binotatus , and A. townsendi also have a long caudal peduncle (32–37% SL). We know of no features that distinguish preserved larvae of A. planifrons from those species.

Figures

FIGURE 8. Apogon planifrons, adult, 37.0 mm SL, DNA # BLZ 5270, photograph by J. Mounts.

FIGURE 9. Apogon planifrons, larva, 9.5 mm SL, DNA # BLZ 7126, photograph by J. Mounts.