FAU Institutional Repository http://purl.fcla.edu/fau/fauir This paper was submitted by the faculty of FAU’s Harbor Branch Oceanographic Institute. Notice: ©1998 Rosenstiel School of Marine and Atmospheric Science, University of Miami. This manuscript is available at http://www.rsmas.miami.edu/bms and may be cited as: Alshuth, S, R., Tucker, J. W., Jr., & Hateley, J. (1998). Egg and larval development of laboratory-reared sergeant major, Abudefduf saxatilis (Pisces, Pomacentridae). Bulletin of Marine Science, 62(1), 121-133. BULLETIN OF MARINE SCIENCE, 62(1): 121-133, 1998 EGG AND LARVAL DEVELOPMENT OF LABORATORY-REARED SERGEANT MAJOR, ABUDEFDUF SAXATILIS (PISCES, POMACENTRIDAE) Sabine R. Alshuth, John W. Tucker, Jr. and Jonathan Hateley ABSTRACT Development of sergeant major, Abudefduf saxatilis, from late egg to early juvenile is described from captive-spawned and wild eggs and 71 laboratory-reared specimens. General morphological features include lateral compression, deep head, deep abdomen, and increasing preanal length through transformation. Notochord flexion had started in a lO-d old, 5.3 mm TL larva. Flexion was complete by 9.2 mm TL (17 d) and transformation at about 18.7 mm TL (28 d). Pelvic spines and rays developed during early preflexion (4.2 mm TL). The caudal fin began development at 4.4 mm TL. During preflexion (5.0 mm TL), dorsal rays and spines were present, and the anal fin began forming. Anal rays and spines were completed during flexion (9.2 mm TL). Newly hatched larvae had two distinct branched melanophores, one at the anterior part of the forehead, another behind the auditory vesicle. Preflexion larvae (up to 3.5 mm TL) also had melanophores along the ventral body midline between the anus and the notochord tip. Fairly heavy internal pigmentation occurred above the gut. The heavily pigmented pelvic fin was evident in 4.3 mm TL preflexion larvae. During late preflexion (3.5-5.5 mm TL) body proportions and pigmentation changed dramatically. Ventral pigment decreased, and the preanal body became deeper and heavily pigmented with scattered stellate melanophores. Flexion larvae had more pigmentation and were less transparent. The spinous dorsal fin became heavily pigmented during flexion. Throughout postflexion, postanal pig­ mentation increased, and during transformation, it spread toward the caudal fin. At 32 d, juveniles essentially had full adult coloration. Data from this study and for two species previously described facilitates larval identification for three of the 16 species in the western Atlantic. Pigmentation, pelvic fin size, and pectoral fin rays (17-18) probably are the most useful characters for identification of sergeant major larvae. They have larger, more heavily pigmented pelvic fins and a more heavily pigmented spinous dorsal fin than yellowtail dam­ selfish (Microspathodon chrysurusv and beaugregory Stegastes leucostictus. Pectoral fins of the latter two species are larger and more pigmented. One of the most common of all marine tropical fishes is the sergeant major, Abudefduf saxatilis, which belongs to the large perciform family Pomacentridae. The damselfish family contains about 235 species worldwide (Allen, 1975; Nel­ son, 1984), with most occurring on Indo-Pacific reefs. Sixteen are abundant in parts of the western Atlantic (Robins et aI., 1986). The sergeant major is distrib­ uted from Rhode Island and the northern Gulf of Mexico to Uruguay and is very common on western Atlantic coral reefs. It also occurs in the eastern Atlantic and Red Sea (Fishelson, 1970). Like many damselfish, sergeant majors deposit demersal adhesive eggs on hard substrates, usually in sheltered areas (Shaw, 1955). The eggs are elliptical and attached by adhesive filaments. Five to seven days after fertilization, hatching of the planktonic larvae takes place right after sunset (Thresher, 1984; Foster, 1987; McAlary and McFarland, 1993), when potential diurnal predators have retired to the reef structure. The known range of hatching times for damselfish is 2-7 d. Although early life history of many damselfish is known, embryological and larval descriptions have been published for relatively few Atlantic species. Thresher (1984) provided a table of typical egg lengths for 11 genera. For the eastern Atlantic, Fishelson (1964) described eggs and hatchlings of Dascyllus aruanus; Re (1980) described eggs and hatchlings of Abudefduf luridus; and Re 121 122 BULLETIN OF MARINE SCIENCE, VOL. 62, NO. I, 1998 and Gomes (1982) described eggs and hatchlings of the Azorian chromis (Chrom­ is chromis). For the western Atlantic, Brinley (1939) described eggs and hatch­ lings of beaugregory (Stegastes leucostictus); Myrberg et al. (1967) described eggs of brown chromis (c. multilineata), and Potthoff et al. (1987) described larvae and juveniles of yellowtail damselfish (Microspathodon chrysurus). There are a limited number of papers dealing with A. saxatilis. Shaw (1955) described embryology from fertilization through hatching. Cummings (1968) re­ ported reproductive habits in the Bahama Islands and briefly described 36-h old larvae. Fishelson (1970) studied behavior and ecology in the Red Sea. Prappas et al. (1990) observed reproductive behavior in a large closed system aquarium. McAlary and McFarland (1993) studied the effect of light and darkness on hatch­ ing. This report describes development of sergeant major from late egg to early juvenile, 32 d after hatching (dah). Because eggs have been described previously (Shaw, 1955) they will be treated only briefly here for clarification and complete­ ness. MATERIALS AND METHODS SPECIMENS, Twenty-five specimens at ages 0,2 and 17 dah were taken from larvae reared in a 3.5­ m ' fiberglass tank at HBOI; eggs had been collected from one nest of captive sergeant majors in a 21,200-m' aquarium 8 m deep. Forty-six specimens aged 1.2,4, II, 20, 24, 28, and 32 dah were taken from larvae and juveniles reared in two 1.6-m' fiberglass tanks at the Bermuda Division of Fisheries; eggs had been collected from three nests of wild fish at 10-15 m depths off south central Bermuda. Larvae were sequentially fed oyster trochophores (Bermudian specimens only), rotifers, and copepods, supplemented with Artemia after 10 d. During the 32-d rearing period, water temperature range was 23.9-27.9°C at HBOI (25.0-27.9°C to 17 dah, for described specimens) and 27.0-28.8°C at BDE Specimens were fixed and preserved in 5% buffered freshwater formalin. MEASUREMENTS. Measurements were made with an ocular micrometer in a stereomicroscope, except for standard and total length of postflexion larvae longer than 8 mm SL, which were determined with a millimeter scale. Body length (BL), notochord length (NL), standard length (SL), total length (TL), head length (HL), and head depth (HD), were measured as in Tucker (1982). Snout length, eye diameter (ED), predorsal length (Snout to DSpl), and preanus length (snout to anus) were measured as in Potthoff et al. (1987), Snout to ORal was the horizontal distance along lateral midline from tip of snout to first dorsal ray. Snout to PvSpl was the horizontal distance along lateral midline from tip of snout to first pelvic spine. Body depth was the vertical depth of body measured at transverse level of pectoral-fin origin (maximum depth). MERISTlCS, Most specimens were fairly transparent, and internal structures such as myomeres were visible during preflexion without clearing and staining. Vertebrae were not counted. The following counts were taken from larvae and juveniles with a stereomicroscope: caudal rays, dorsal spines and rays, anal spines and rays, pectoral rays, and pelvic spine and rays. DEVELOPMENTAL TERMINOLOGY. Length is a useful basis for linking characters of unidentified spec­ imens with those in larval descriptions. However, length might not be the most appropriate basis for comparing larvae of different species, which undergo notochord flexion and transformation at different sizes, usually within a narrow range for a single species but over a wide range for the family or even within a genus, In the present study, both TL and stage of development are given in the text. TL and BL can be compared in Tables I and 2, Yolksac larvae were from hatching until complete exhaustion of yolk and oil. Preflexion, flexion, and postflexion larvae were as defined in Moser ct al. (1977). Juveniles had all fin rays developed and were fully scaled. RESULTS PIGMENTATION AND MORPHOLOGY (Figs. 1,2) Eggs.-Adhesive, elliptical eggs (Fig. lA) attached in single layer to substrate, Short and long diameters of 20 eggs ranged from 650 to 670 mm and 1100 to 1250 mm. In late stage eggs (1-5 h before hatching), embryos had stellate me­ lanophores along ventral midline (Fig. lA). Eyes fully pigmented, and mouth ALSHUTH ET AL.: SERGEANT MAJOR DEVELOPMENT 123 Table I. Summarized morphometric data for 63 laboratory-reared Abudefdufsaxatilis. First line: mean ± standard deviation; second line: range. Body length: NL was used through flexion and SL after flexion. Days after Number of Body length Total length Snout length Eye diameter Head length hatching specimens (mm) (mm) (mm) (mm) (mm) 0.2 20 2.9 ± 0.2 3.1 ± 0.2 0.10 ± 0.08 D.31 ± 0.08 0.55 :!: D.05 2.6-3.2 2.9-3.5 D.08-D.27 D.19-0.36 0.45--0.56 1.2 8 2.9 ± 0.2 3.2 ± 0.2 D.18 ± 0.D7 0.30 ± 0.07 0.56 ± 0.06 2.7-3.2 2.9-3.4 0.11-0.28 0.I8-D.35 0.46-0.63 4.0 5 3.3 ± 0.1 3.6 ± 0.2 0.31 ± D.16 0.47 ± D.15 o.rz ± 0.08 3.2-3.4 3.4-3.9 0.20-D.59 0.40-0.73 0.59--0.79 II 5 4.8 ± 0.3 5.7 ± 0.5 D.62 ± D.IO 0.75 ± 0.D8 1.8 ± 0.\ 4.5-5.2 5.0-6.5 0.53-0.73