Dragonet

The following genera are classified within the Callionymidae: • Anaora J. E. Gray, 1835 • Bathycallionymus Nakabo, 1982 • Callionymus Linnaeus, 1758 (including Calliurichthys) • Diplogrammus Gill, 1865 (including Chalinops) • Draculo Snyder, 1911 • Eleutherochir Bleeker, 1879 • Eocallionymus Nakabo, 1982 • Foetorepus Whitley, 1931 • Neosynchiropus Nalbant, 1979 • Paracallionymus Barnard, 1927 • Protogrammus Fricke, 1985 • Pseudocalliurichthys Nakabo, 1982 • Repomucenus Whitley, 1931 • Spinicapitichthys Fricke, 1980 • Synchiropus Gill, 1859 • Tonlesapia Motomura & Mukai, 2006 ==Description==

These "little dragons" are generally very colorful and possess cryptic patterns. Their bodies are elongated and scaleless. A large preopercular spine is characteristic of this fish, and has been reported to be venomous in some species. All fins are large, showy and elongated; the first high dorsal fin usually has four spines; in males, the first of these spines may be further adorned with filamentous extensions. Dragonets have flattened, triangular heads with large mouths and eyes; their tail fins are fan-shaped and tapered. The largest species, the longtail dragonet (Callionymus gardineri) reaches a length of . At the other end of the spectrum, the Saint Helena dragonet (Callionymus sanctaehelenae) reaches a length of just . Many species exhibit marked sexual dimorphism: males and females are coloured and patterned differently from each other, and (in addition to the spine filament) males have a much higher dorsal fin. This difference is extreme in the high-finned dragonet (Synchiropus rameus). ==Reproduction==

Dragonet spawning occurs during late afternoons, right before the sun sets. The fish's spawning behavior is divided into four distinctive stages: courtship display, pairing, ascending, and the release of eggs and milt. Both sexes display by spreading their pectoral and caudal fins, and moving around or by the side of the other sex. Males will sometimes also spread their dorsal fins, repeatedly open and close their mouths, and position themselves on top of the females and rub their abdomens with their bodies. If a female accepts a male for spawning, they form a pair. Occasionally, another male might intrude upon the pair as they are mating and attempt to sneak fertilizations with the female. Such an act would result in aggression by the original male. Prior to spawning, a male and female dragonet pair will ascend approximately 0.7-1.2 meters up a water column from the sand at the bottom of the ocean. The male assumes a parallel position to the female, touching the female's side with the part of its body near its ventral fin. This sexual dimorphism may have evolved in males in response to female mate choice, male-male competition, or both. ==Competition/aggression==

Male dragonets form dominance hierarchies and act extremely aggressively towards each other. They are often observed chasing and biting, which occurs primarily when two males are close to a female during courtship and pairing. As a result of this behavior, male dragonets suffer higher mortality rates than females do after attaining maturation. The highest mortality rates in adult males occur during breeding. Males have evolved larger bodies, as well as longer spines and rays, in order to achieve dominance in reproduction. They have also developed bright colors so as to more effectively compete for female attention. These secondary sex characteristics further reduce the survival potential of male dragonets, as they increase the risk of predation, require greater energy costs, and escalate the risk of suffering injuries. ==Feeding==

Feeding by the dragonet occurs throughout the day, including the intervals between courtships and spawning. The fish feeds entirely on benthic sources, primarily copepods, amphipods, and other small invertebrates living on blades of sea grass. Species of dragonets from different locations show variations in specific food preference, attributable to the different availabilities and abundances of food organisms in those places. All of them feed by extending their highly protractible jaws toward their food and drawing it into the mouths, frequently followed by the expulsion of sand. No evidence suggests that dragonets are territorial. Individuals do not defend specific areas of substrate, as well as any resources that might be present on them, from intrusion by conspecifics or other fish species. ==Locomotion==

Four types of swimming are observed in the dragonet. The first is burst swimming, the most common of the four, and utilized during foraging. The dragonet uses its pelvic fins to propel its body off of a substrate, and then its pectoral fins to guide itself forward. The second is continuous swimming, often utilized by males when approaching a potential mate or retreating during an aggressive encounter with another male. The dragonet uses its pectoral fins to propel its body forward, and its pelvic fins to lift and guide itself. The third type of swimming is rapid swimming, which is observed when the dragonet is attacking or fleeing. The fish primarily uses its caudal fins to achieve a quick speed. Finally, the fourth type is vertical swimming, utilized by the dragonet during spawning when it ascends. The pectoral fins are used to propel the fish's body up the water column. ==Defense==

In defense against its predators, the dragonet rapidly buries itself under the sand at the bottom of the ocean so that only its eyes remain visible. Many species of the fish also are capable of producing and secreting foul-tasting and -smelling substances that may ward off any potential predators. ==Timeline==

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