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BULLETIN OF MARINE SCIENCE, 60(3): 872-893, 1997 BEHAVIOR PATTERNS AND SEXUAL DIMORPHISM IN THE SPOTTED DRAGONET, DIPLOGRAMMUS PAUClRADIATUS (PISCES: CALLIONYMIDAE) Michael E. Harrington ABSTRACT Dragonets (Pisces: Callionymidae) have long been recognized as exhibiting high degrees of sexual dimorphism. In the century following Darwin's (1896) suggestion that sexual di- morphism in Callionymus lyra has evolved through sexual selection, there has been no pub- lished research on sexual selection in any species of dragonet. The present study provides II detailed description of sexual dimorphism in the spotted dragonet, Diplogrammus paucira- diarus, as well as a description of the behavior patterns involved in courtship, spawning, and agonistic interactions. Observations in the field and laboratory revealed the conIext in which sexually dimorphic traits were expressed, thus providing a basis for future research on sexual selection. Like most dragonets, the males of D. pauciradiarus are larger than the females, and the former develop longer dorsal and caudal fins. Males can also develop black pigmen- tation on the lower jaw (mouth bar), a black bar across the eye (eye bar) and orange pig- mentation on the head. and all three pigment patterns are accentuated (if present) during courtship and agonistic encounters. Males are highly aggressive toward each other and form dominance hierarchies. During both courtship and agonistic encounters, males perfornl lateral displays that involve raising the first dorsal fin. Spawning occurs during the last 2 hours of light (dusk) and involves ascending into the water column to release pelagic eggs. Because the sexually dimorphic traits of the males are involved in both courtship and agonistic be- havior patterns. they may have evolved in response to either female mate choice, male-male competition, or a combination of both selective forces. Comparisons are made with other dragonets, though the behavior of most species remains unstudied. For at least 100 years, dragonets (Pisces: Callionymidae) have been noted for exhibiting high degrees of sexual dimorphism (Darwin, 1896), and it is often suggested that the differences between males and females of a species have evolved due to sexual selection. For example, Holt (1898) hypothesized that the sexually dimorphic characters in males of Callionymus lyra evolved through sex- ual selection via female choice. But in the century that followed, studies of sexual selection have been published for species in all the other groups mentioned by Darwin (except the Callionymidae), including cichlids, cottids, goldfish, pipefish, salmon, sharks, sticklebacks, swordtails, and wrasses. To study the possible selective pressures responsible for the evolution of sexual dimorphism in a species, one must first document the dimorphic characters and the behavior patterns in which the characters are expressed. Sexual dimorphism in the spotted dragonet, Diplogrammus pauciradiatus. and other species within the family Callionymidae, has been documented to some degree (Chang, 1951; Davis, 1966; Takita et al., 1983), but a more detailed description is needed to choose traits that likely influence the reproductive success of both males and females. In addition, little is known about the behavior of any dragonet species. Thus, it is essential to document behavior patterns (particularly those involved in aggression, courtship, and spawning) before attempting to study how sexually dimorphic traits and behavior patterns influence reproductive success in these animals. Thus, the formation of an ethogram for D. pauciradiatus is a necessary prerequisite to experiments on sexual selection. 872 HARRINGTON: D. PAUC1RAD1ATUS BEHAVIOR PATTERNS AND DIMORPHISM 873 The behavior patterns described in the ethogram are organized according to the scheme used by Myrberg (1972) with the following exception: color patterns are described in a separate section on sexual dimorphism. More recently published ethograms have additional designations of social vs. non-social behavior patterns (Clayton and Vaughan, 1988; Almada et al., 1990; Santos and Barreiros, 1993). This is a potentially misleading categorization, particularly for motor patterns that are used in both courtship and agonistic encounters (social by definition). Because males of D. pauciradiatus are not territorial and do not build nests, patterns such as staring are not included, though they may take on additional meaning when performed from a nest (Santos and Barreiros, 1993). Although quantitative analyses, such as sequential contiguity analysis (Myr- berg, 1972), were not carried out to confirm the groupings of motor patterns, many behaviors of importance to research on sexual selection (e.g., courtship) are highly ritualized and their occurrences are predictable. Aggressive encounters are more variable, but dominance relationships can be determined using simple be- haviors like chase, flee, and lateral display. Thus, the following ethogram will provide a sufficient basis for subsequent experiments on female mate choice and male-male competition in D. pauciradiatus (Harrington, 1996). MATERIALS AND METHODS Sexual Dimmphism.-Individuals were collected from sites in Biscayne Bay, Florida (Fig. I), during most months in 1993 and all months in 1994 (I.5-m-wide pushnet with 3-mm mesh). All fish were measured using either a ruler or dial calipers. Color patterns were observed in both the field and laboratory, and many individuals were observed in the laboratory while they were anesthetized with tricaine methane sulfonate (MS-222). The addition of MS-222 also enhanced the coloration of males with respect to mouth bar and orange head pigmentation (see Results), as both pigment types can fade when the fish are handled (i.e., stressed). A Wild dissecting microscope was used to observed the genital openings and other small structures (e.g., preopercular spines). Separate pushnet samples were obtained at site A (Fig. 1) during November, 1994, and September, 1995, and all dragonets collected were preserved in 70% Ethanol. The following data were obtained using dial calipers (nearest 0.1 mm): standard length as defined by Davis (1966), left pelvic fin-length (length of longest ray), first dorsal fin-length (length of longest spine), and caudal fin-length (length of longest ray). Pigmentation patterns were also recorded. Fin-length comparisons were made between males and females and between males with and without mouth bars and orange pigmentation. In each case, fin length was plotted against standard length, and a regression line was generated using Cricket Graph 1.2 on a Macintosh IIsi computer. Each pair of regression lines was first tested for differences in slope (0. = 0.05) using a two-tailed t test. If the slopes were not significantly different, the elevations were compared (0. = 0.05) in a second t test (Zar, 1984). Behavior Pattems.-Field observations were made using snorkel and SCUBA at site A (Fig. I), the time of day varying from early afternoon to dusk. Laboratory observations (over 200 h) were carried out on single- and mixed-sex colonies. The number of individuals in mixed-sex colonies ranged from 30 (15 males and 15 females) to 8 (2 males and 6 females). Fishes were housed in 400-800 liter aquaria (92-184 X 47 X 62 cm) with sandy substrate (3 cm deep) and plastic seagrass. Salinities were maintained at 34%0, temperatures ranged from 24° C to 27° C, and the tanks received fluorescent white light from 07:00 to 19:00. Colonies were observed during all hours of light. All colonies were fed frozen brine shrimp chopped into small pieces (single-edged razor blade) to facilitate feeding, es- pecially among the smaller females. Laboratory observations were supplemented with video tape recordings and 35-mm photography. These records allowed for more detailed analyses of behavior patterns in which rapid movements occurred (i.e.. lateral displays). Laboratory observations of spawning were confirmed by the collection of fertilized eggs in the aquaria. This was accomplished by passing a 30-cm2 net (500-f..Lmmesh) through the upper 30 cm of the water column 8-12 times. The contents were then transferred to a 1000-ml container of water from the same aquarium. Eggs were observed immediately, and larvae were observed on the following day. 874 BULLETIN OF MARINE SCIENCE. VOL. 60. NO.3. 1997 3 KILOMETERS _ /"lVIRGINIA 1 ~ KBY N 4KBY BISCAYNE ~ ; SAFETY VALVE .. " f .. I n J 0 m BAY rf V '<:] 11 t} CD BLLIOT!' KEY !j . J f ~:~ Figure I. Collection sites for D. pauciradiatus in Biscayne Bay, Florida. Marked areas were sampled with a 1.5-m-wide pushnet (3-mm mesh). The highest densities of fish were collected at sites A and B. RESULTS Sexual Dimorphism.-More than 900 dragonets were collected over the course of the study, and the length-frequency distributions for males and females are shown in Figure 2. The maximum standard lengths were 43.0 mm (males) and 29.0 mm (females). The maximum lengths of the first dorsal fin were 74.1% (males) and 33.3% (females) of the standard length. The maximum lengths of the caudal fins were 56.0% (males) and 33.5% (females) of the standard length. Males (~ 9 mm SL) possess external genital papillae that are recognizable under a dissecting microscope. No such structure is present in females at any size. These results are summarized in Table 1. The overall mottled, sandy color of this species is not sexually dimorphic, but individuals altered their overall "darkness" on differently colored substrates HARRINGTON: D. PAUCIRADIATUS BEHAVIOR PATTERNS AND DIMORPHISM 875 70 60 I:J Males (n=596) • Females (n=316) 50 I-< QJ 1 40 Q '.5 30 o Eo-< 20 10 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 Standardlength(mnl) Figure 2. Length-frequency distributions for all males and females of D. pauciradiatus collected during the present study for laboratory observations or experimentation. Fishes were collected using a push net at the sites marked in Figure 1. All size classes from early juvenile (9-12 mm SL) to large adult (females: 24-29 mm SL; males: 37-43 mm SL) are represented.

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