Pseudosphromenus cupanus dayi, Sri Lanka's Brown Spike-tailed Paradisefish
Pseudosphromenus cupanus dayi (Brown Spike-tailed Paradisefish). This is a local sub-species of Pseudosphromenus cupanus, with native haunts in Sri Lanka. (Some writers want to see it as a species on its own: Pseudosphromenus dayi.) Aquarium breeding activities have inadvertently spilled populations of this sub-species into the waters of the Mekong delta, far away in Vietnam. By the way, the curious mis-spelling of a genus name that was meant to be "like Osphronemus" appeared in the original description (a printer's error?) and is now cast in eternal bronze by the rules of scientific nomenclature! The "Day" being honored in its specific name is Francis Day (1829-1889), an ichthyologist who, as Inspector of Fishes in British India, wrote The Fishes of India.
If you're intrigued by anabantoids, but you are uninspired by flashy and commonplace overbred bettas and degenerate gouramis, this is an unusual labyrinth fish to keep, if you can find it. If you do run into these fishes at your LFS, you probably won't be impressed with their pallid brown-and-tan coloring, but once you get them comfortable in a typical anabantoid weed-swamp with a gentle current they will color up within hours. This fish has a warm pinkish tan body with two horizontal broken black stripes that meet at the base of the tailfin. The scales on the upper body are lightly tipped black. The throat has a red blush; the unpaired fins are a brick orange, darkening almost to black, and tipped pale blue. The central rays of the caudal fin are extended, with black tips. And the ventral fins are brilliant scarlet, tipped pale blue. Pretty stylish. The fishes are shy, mild-mannered and graceful. They move with an eelish, Betta-like stealth through dense plant cover, using unobtrusive rowing movements of their transparent pectorals, though they are perfectly capable of a quick dash for cover when alarmed. They lurk under floating vegetation, their upturned mouths adapted for feeding on water-surface insects. Fruit flies make a welcome addition to their diet; they're a little less fond of picking food out of the gravel.
They tolerate a wide range of temperatures, from as low as 60o to 90oF. Males will ordinarily ignore each other. But they have a low-key subtle repertory of aggressive threat signals. Ordinarily the pennant-shaped ventral fins are carried folded back hydrodynamically against the body and are not used for active swimming or balance. But when a male comes to a stop, he back-waters with his transparent pectorals and extends his ventral fins for a brake, unfolding their bright red flags. This everyday swimming technique has become stereotyped into a defiant stance you could call "alert display." In a slightly more aggressive move, the more aggressive male smoothly follows the other at a distance of 3 or 4cm. This may be kept up for half a minute at a time, but I never saw this "dogging" escalate into a chase. Slightly more aggressive again is "tail display," in which a male faces his rival and swings his tail to the side, holding his body in a curve. "Tail display" brings the extended fin rays into prominent view, so that the rival sees that he is faced with a sexually-mature male. In the type, P. cupanus, of which I was keeping the dayi subspecies, coloration is variable, but it's interesting to note that all the variant populations have these behaviorally essential bright orange to reddish ventral fins and all have the caudal fin produced to a point.
We may selectively breed fishes for arbitrarily-selected features that we find appealing, but if left to themselves female Spike-Tailed Paradisefishes apparently select for masculine features that have a function in aggressive display: red-flag ventral fins and impressively extended black tail fin-rays. They're important in the Spike-Tailed Paradisefish message system.
A pair spawned for me under a coconut shell. (Often you read of P. cupanus spawning in a bubble nest contained under a broad leaf, in mid-water.) The female performed a waggling head-down dance that induced the male to circle her and nip at her flanks. For her part, she was as aggressive as he was. The dim shadows at the top of the coconut shell seemed to attract them. There was no trace of bubble-nest building. The episodes of pre-spawning behavior were interrupted by intervals of feeding and the usual solitary cruising. Within a couple of hours of her first enticing dance, spawning commenced. The male circled round the dancing female with increasing excitement, as they rose up into the darkness under the shell. He embraced her in his tense curved flanks (this reads like a romance paperback with an embossed metallic cover) and they rolled together, paused a moment, and she expelled 7 to 10 eggs, each slightly less than 1mm in diameter. The eggs sank slowly, and when the spawning pair recovered, which seemed to take slightly longer after each embrace, they would both catch up the eggs and carry them up to the roof of their coconut-shell cave. A few bubbles were caught up there, too rudimentary really to term a "bubble nest." Then an episode would follow of checking the lower side of the coconut shell for any overlooked eggs, and a little search in the nearby gravel. Then the female would initiate the next embrace sequence, with a renewed head-down waggling dance.
A "sneaker" male? The extraordinary thing about this spawning sequence is that a second male in the 10-gallon tank found a cramped hideout under a nearby shard of coconut. There he lurked like a bandit behind a rock in a western, about ten centimeters away, waiting his chance, and at the right moment, he joined in the embrace. The spawning pair seemed too preoccupied to chase him away. Did he contribute his milt? He certainly took some eggs in his mouth and rose up in the darkness to the roof of the shell. Where he deposited them? Where he ate eggs? I can't tell you. If this was a so-called "sneaker" male, it's a well-documented tactic among some Lake Malawi cichlids.
The surprises for me weren't over with the spawning. Afterwards it was the female who took over guard duties and chased off both males. But even her spawning behavior waned after forty-eight hours, and there were no fry that I found.
Links. The best description of Pseudosphromenus cupanus dayi posted on the Web, with photos that include some breeding shots, is Russell Carroll's. Grant Gussie's good brief newsletter article, "Pseudosphromenus dayi," is archived at the Calgary Aquarium Society website.
Pseudosphromenus dayi at FishBase. Pseudosphromenus dayi at AquaWorld.
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