The Midwater Signalfish P. longipinnis. Credit: Gerry Allen
There are a great many fishes found in shallow tropical waters that remain unavailable to aquarists, but few are as beautiful and recommendable as the signalfishes. These small, peaceful bottom-dwellers are ornately patterned, vibrantly colored and exhibit some endearing behavioral quirks, yet, due to their penchant for deep sandy habitats, they have been entirely ignored by aquarium collectors and, even amongst zoologists, the group remains something of a mystery. Much of the obscurity surrounding these fishes has to do with our poor understanding of their place in the grander scheme of fish evolution—just who is it that they are related to? For a while, they were lumped into the heterogenous family, Percophidae, whose members shared general similarities of fin and body shape. Later, it was thought that they possessed certain morphological nuances with the sanddivers (Family Trichonotidae) and were reclassified there, but more recent molecular study has changed things around yet again.
Molecular data says signalfishes are sister to the sandburrowers, Family Creediidae.
Signalfishes have now been elevated to their own family (Hemerocoetidae), sister to another obscure group of tropical psammophiles, the sandburrowers, Family Creediidae. And, as it turns out, neither of these are of close relation to the sanddivers, as that family is in fact the sister group to the vast goby lineage. [For good measure, Percophis brasiliensis was found to be sister to certain Antarctic fishes called notothenoids, illustrating just how little we knew about the true evolutionary history of all these diverse fishes.] The take-home message from all this taxonomy is this: these are not gobies, even though they might sort-of, kind-of look like gobies.
Some oddball hemerocoetids. Credit: B. Hutchins/Western Australian Museum & Port Phillips Marinelife
Classification within the hemerocoetids remains fraught with challenges, as the group has yet to undergo any meaningful revision. Eight genera comprise the family, though only half of these contain more than a single species or two. These four species-poor taxa (Enigmapercis, Dactylopsaron, Matsubaraea, Squamicreedia) are seldom encountered and have restricted ranges, often in subtropical or deepwater habitats, while the five species in Hemerocoetes are found in deep waters around New Zealand and are recognizable for lacking the spinous dorsal fin. The remaining three groups—Pteropsaron, Osopsaron, Acanthaphritis—tend to be more colorful and are generally found closer to shallow-water reef habitats, though always on sandy substrates.… More:
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