Apogon binotatus (Poey)

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 : 3-8

Apogon binotatus (Poey)

Identification. Eleven adult specimens of A. binotatus provided the basis for genetic identification of larvae and juveniles (Appendix 1, one adult is shown in Fig. 2 ). Adult A. binotatus can be distinguished from other Apogon by the combination of eight segmented anal-fin rays, body and lateral-line scales of similar size, and body with two distinct dark markings posteriorly — a bar below the second dorsal fin and another on the posterior part of the caudal peduncle, both bars narrow, much deeper than wide ( Böhlke & Chaplin 1993, Gon 2002).

Table 1. Average Kimura 2-parameter distance summary for Apogon species. Intraspecific averages in bold font. na = not applicable (one specimen).

aurolineatus 0.01

= 12)

maculatus 0.20 0.01

N = 18)

phenax 0.19 0.13 0.00

= 32)

binotatus 0.21 0.14 0.10 0.00 = 28)

townsendi 0.24 0.15 0.10 0.13 0.00 = 27)

pseudomaculatus 0.22 0.12 0.10 0.14 0.14 0.00 = 3)

pillionatus 0.23 0.14 0.10 0.12 0.15 0.16 0.01 = 5)

lachneri 0.23 0.16 0.10 0.12 0.13 0.14 0.14 0.00 = 11)

planifrons 0.22 0.18 0.10 0.10 0.17 0.17 0.11 0.15 0.00 = 6)

mosavi 0.23 0.20 0.20 0.22 0.21 0.21 0.24 0.20 0.244 0.00 = 36)

robbyi 0.23 0.20 0.20 0.23 0.20 0.19 0.22 0.21 0.22 0.05 0.00 = 3)

quadrisquamatus 0.25 0.22 0.20 0.24 0.22 0.18 0.23 0.20 0.24 0.09 0.10 0.00

Lineage A

= 1)

Apogon sp 0.23 0.14 0.10 0.12 0.14 0.11 0.11 0.14 0.08 0.23 0.20 0.23 na = 1)

affinis 0.24 0.14 0.10 0.17 0.15 0.14 0.16 0.16 0.18 0.18 0.20 0.21 0.16 0.00 = 2)

robinsi 0.21 0.17 0.20 0.17 0.18 0.18 0.17 0.14 0.18 0.19 0.20 0.20 0.17 0.20 na = 1)

Apogon sp. 2 0.24 0.21 0.20 0.24 0.21 0.18 0.23 0.22 0.22 0.07 0.10 0.09 0.23 0.20 0.21 0.00 = 5)

quadrisquamatus 0.23 0.17 0.20 0.20 0.19 0.17 0.20 0.22 0.21 0.12 0.10 0.14 0.20 0.20 0.18 0.09 0.00

Lineage B

= 5)

Juveniles (Fig. 3). Juveniles identified genetically range from 13.5 to 18.0 mm SL. The body is pale. The upper part of the head and the gut are pink. The fins are mostly clear, but there are melanophores on the tips of the anterior rays of the second dorsal and anal fins and on the outer rays of the caudal fin. There are numerous melanophores on top of the head and over the gut. There is a slender bar beneath the end of second dorsal-fin base and a wider bar on the caudal peduncle. There are 12–13 gill rakers on the lower limb of the first gill arch, counts consistent with values for adults ( Table 2 ).

Comparisons Among Juveniles. Although adult A. binotatus are easily distinguished from other Apogon species by having both body bars slender (much deeper than wide), the posterior bar in juvenile A. binotatus is broader than the anterior bar. It is still narrow relative to the broad posterior bar in A. townsendi , A. phenax , and A. pillionatus . Juvenile A. binotatus is most similar to juvenile A. phenax , but it can be separated from that species by having the anterior bar slender (vs. at least slightly wedge-shaped in A. phenax ) and positioned entirely beneath the second dorsal fin (vs. half or more of the bar behind the fin in A. phenax ). The configuration of the two bars in juveniles of A. binotatus is sufficient to separate them from known juveniles of other Apogon .

Apogon 14.0 mm SL, DNA # BLZ J. Mounts C.

Larvae ( Fig. 4 ). Apogon binotatus larvae analyzed genetically range from 8.5 to 11.0 mm SL. The body is orange to pale orange, and there may be clear (or paler orange) areas on the snout just anterior to the eye, on the caudal peduncle, and near the middle of the trunk. In one 9.0–mm SL specimen there is a wide pale area posterior to the second dorsal fin and anterior to the caudal-fin base. The fins are clear except for a few orange spots along the posterior base of the anal fin and a few spots in the center of the caudal-fin base. There is a line of bright orange pigment on ventral side of the body from the anal fin to the caudal peduncle. There are melanophores on top of the head, in the temporal region, and over the swimbladder. Some specimens have a few melanophores on the lateral surface of the gut. The caudal-peduncle length ranges from 33–37% SL.

Comparisons Among Larvae. Fresh specimens of A. binotatus larvae are extremely similar to A. phenax larvae, but they can often be separated by snout pigment (no or pale orange spot anteriorly in A. binotatus vs. usually a prominent orange spot on snout in A. phenax ). From A. planifrons , larval A. binotatus differs in lacking yellow pigment on the anterior portion of the body; from A. maculatus in lacking prominent orange pigment on the first dorsal fin; from A. aurolineatus larvae in lacking orange/yellow dorsal, anal, and pelvic fins; and from A. mosavi larvae in lacking a distinctive pattern of chromatophores on the median fins. We were not able to reliably separate Apogon binotatus larvae from those of A. townsendi and Apogon sp. 1, although our A. binotatus larvae have more orange color on the body than A. townsendi larvae. However, the extent of orange coloration on the body of some Apogon larvae, and whether or not it is disrupted by pale areas, may change ontogenetically (see “ Apogon phenax ,” below).

Preserved larval specimens of A. binotatus have more melanophores on top of the head than larval A. aurolineatus and a longer caudal peduncle (caudal-peduncle length 33–37% SL in A. binotatus vs. 27–29% SL in A. aurolineatus ). Caudal-peduncle length also is sometimes useful in separating preserved A. binotatus from preserved A. planifrons (caudal-peduncle length 33–37% SL in A. binotatus , 35–40% SL in A. planifrons ), and it may be useful in separating larval A. binotatus from A. maculatus (caudal-peduncle length 30% SL in the single larval specimen of A. maculatus in our study material). We have identified no other features to separate preserved A. binotatus larvae from other known Apogon larvae.

Figures

FIGURE 2. Apogon binotatus, adult, 46.0 mm SL, DNA # BLZ 6325, photograph by J. Mounts and C. Baldwin.

FIGURE 4. Apogon binotatus, larva, 9.0 mm SL, DNA # BLZ 6331, photograph by J. Mounts and C. Baldwin.

Tables

TABLE 2. Typical values and upper and lower extremes of numbers of gill rakers on the lower limb of the first arch in western Atlantic Apogon species. Data are from Böhlke and Chaplin 1968, Böhlke and Randall 1968, Dale 1977, Smith- Vaniz 1977, Randall and Böhlke 1981, Gilbert and Tyler 1997, and Gon, 2002.

Species A. affinis	Typical Number of Gill Rakers on Lower Limb of First Arch 14	Upper and Lower Extremes of Gill Rakers on Lower Limb of First Arch 13–15
A. aurolineatus	10–11	9–12
A. binotatus	13	12–14
A. evermanni	16	15–17
A. gouldi	11–12	11–12
A. lachneri	16–17	16–17
A. leptocaulus	15–16	15–16
A. maculatus	14	13–16
A. mosavi	14–15	13–16
A. phenax	13–14	13–14
A. pillionatus	12	11–13
A. planifrons	15	14–16
A. pseudomaculatus	12	13–14
A. quadrisquamatus	13	12–14
A. robbyi	12–13	12–14
A. robinsi A. townsendi	17 17	16–18 16–18