News / Species Spotlight / Circular Dragonet (Synchiropus circularis) (03/07/18)

Circular Dragonet (Synchiropus circularis)

Species Spotlight - Circular Dragonet (Synchiropus circularis)
Mandarinfishes are among the most colorful and iconic of coral reef organisms. Thanks to their curious appearance, coupled with a unique swimming style, these are consistently among the most popular fishes among reef aquarists.

The name Manadarinfish applies to a pair of dragonets (Family Callionymidae) found in the West Pacific. The true Mandarinfish is Synchiropus splendidus. This is the most abundant member of the group and occurs in both red and green morphs. Slightly less common is the Spotted Mandarinfish (S. picturatus). Together, these two are occasionally treated as belonging to a distinct genus or subgenus, Pterosynchiropus (though the classification of this group is far from resolved at the present time).

There is, however, a third species which belongs in the conversation, the rarely seen Circular Dragonet (Synchiropus circularis). As the name suggests, this fish features a series of circular markings along the sides, not so dissimilar to what occurs in the Spotted Mandarinfish. Unlike that species, though, the males of S. circularis have a notably tall spinous dorsal fin equipped with filamentous extensions and a series of concentric stripes. This latter trait is more in keeping with the familiar Scooter Dragonets, such as S. marmoratus, S. morrisoni and S. moyeri.

In essence, the Circular Dragonet sits as a bridge between the morphology of both groups, giving it the mystique of a missing link among the dragonets. We as of yet know precious little about its life history. Specimens are reported everywhere from Bali to the Philippines and New Guinea, and the species itself was described from Tinian in the Mariana Islands. Its clearly a widespread fish, but sightings are surprisingly sparse. Interestingly, there is good documentation of a mixed-species spawning from the Philippines, between female S. circularis and male S. splendidus, though whether this produces hybrid offspring remains unclear.

Aquarium care is identical to other dragonets. A mature reef aquarium of moderate size is recommended to help supplement their diet of small crustaceans. Eventually, most will learn to accept frozen copepods and other smaller shrimps. Avoiding competition for food is critical to maintaining a healthy specimen, which means limiting the number of bethivorous wrasses, gobies, etc. Multiple females are safe to keep together, as is a single male and multiple females, but woe betide the foolish aquarist who places multiple males together, as they will fight ceaselessly. Remember, male dragonets have larger dorsal fins.