The Prolifera prolifica is the smallest of the 19 species of the extremely interesting genus Poeciliopsis, due to its size (males 10 to 18 mm and females 15 to 30 mm). Moreover, only a few litres of water are really sufficient for breeding. However, it is not its body size that determines whether or not a species is suitable for a small aquarium, but above all its personality traits. Xiphophorus pygmaeus, for example, is also a very small species, yet it needs an aquarium of at least 80 litres for successful breeding.
After experience with other species of the genus, I find this viviparous to be the most sympatric. Unfortunately, its colourful splendour is lost at small sizes. If it were a few centimetres larger, it would surely be an equal competitor to many large, low-colour but lovingly kept species.
Enlargement
It is widespread on the Pacific side of Mexico in the states of Sonora, Sinaloa and Nayarit.
Distribution
Sonora: in the lower Rio Yaqui; Sinaloa: in Arroyo Sonolona, which is the type locality of the species; Nayarit: in the Rio Presidio and others up to the vicinity of Tepic. It is also found locally in brackish water.
History
Scientifically, the species was described (along with three others) from northwestern Mexico by R.R. Miller in 1960 [1].
The aquaristic history of the species is essentially very short. From the first description, it took 24 years before (1984) the first specimens caught in the Rio Grande de Santiago around Tepic (Nayarit) were brought to Austria, from where they then spread further.
Colouration
The photographic material at the time the photographs were taken (ORWOCHROM) could not more faithfully capture the colours and, above all, the magnificent brilliance, nevertheless the attached images sufficiently document the colour and pattern of the fish. Let us just add that there were also two males with a black line in the caudal fin. They were immediately isolated and added to the virgin female. As this pattern did not appear again in the offspring, we can assume that it was not a hereditary pattern, but only a colour defect.
Breeding
In practice, it has been shown to be optimal only in monoculture. Attempts to breed the fish with other viviparous species have resulted in an imbalanced condition. In a community of vigorous species (Alfaro cultratus, Poecilia orri, Limia perugiae), P. prolifica was eradicated. However, against slightly larger juveniles of Poecilia chica, Limia nigrofasciata and Phallichthys fairweatheri, it was able to assert itself. When encountering the named species, both sexes of P. prolifica attacked them until they were killed.
Experience has shown that it is an ideal species for small to very small aquariums. Over the years, my fish migrated from the original 100 litre aquarium to an ever smaller one, until finally I kept a “maintenance herd” for three years in a breadbox lid of about 4 litres. Despite the fact that, apart from a carrion fish (Riccia) on the surface, the jar was not covered, the fish never once jumped out. Their numbers were maintained by self-regulation at a ratio of 3-8 adults to 10-45 juveniles.
The size of the aquarium and its equipment do not matter for breeding and rearing. The fish do not need airing or filtering. They are happy with an ambient temperature of between 18 and 25 °C. Temperatures above 25 °C have had a negative effect. Increased mortality occurred exclusively during the short period of high summer, when the temperature did not fall below 27 °C even at night. The water should be at least moderately hard with a neutral to alkaline pH.
It takes both live and dry food. In practice, the main food is always available artemia, seasonally small plankton and various types of finely sown flake preparations.
Reproduction
A peculiarity of some species of the genus Poeciliopsis is that they reproduce by a kind of sexual parasitism (similar to the well-known Poecilia latipinna mexicana). Unisexual females, i.e. without a male partner of their own species, are fertilised by an available male of a related bisexual species. The spermatozoa only contribute their genetic material to activate the process of germ cell (zygote) gating. This form of reproduction is technically called gynogenesis or pseudogamy.
Males of species involved in gynogenetic populations (e.g. Poeciliopsis lucida, monacha or viriosa) have a dark to black colouration when courting (mating). Although P. prolifica is in the same systematic complex with these species, the males do not darken during courtship and the species reproduces in the usual bisexual manner – and, like all species of the genus, by superfetation. This is the second part of the scientific name – prolifica, describing the frequently recurring litters of females. In superfetation, the young are not all born at once, but gradually “on a treadmill” as they develop in the mother’s body.
The young are strikingly slender and, at around 5.5 mm long, relatively small for viviparous animals. The above-mentioned negative effect of the high temperature is reflected, among other things, in undesirably rapid growth and maturation. It is admirable that a 5 mm ‘cap’ was able to grow into a mother in 78 days and that an F1 male from the same litter developed a gonopodium in 30 days. However, the price was a reduction in body size, a reduction in the number of pups born and a shortened life span.
The number of young is not solely influenced by temperature, but is primarily tied to the age of the female. It tends to increase from the first litters with a peak around the 6th to 7th month of age and slightly decreases thereafter. The claim [2] that in superfetators increasing body size of the female is associated with increasing offspring size and longer parturition intervals has not been confirmed (but is unrelated to litter size). Nor can I unreservedly endorse the statement [3] that “Large females become inaccessible and, unless they are fertilized as young, are not at all capable of frequent repeat litters. Thus the reproduction of this species depends largely on stored sperm.” Schultz [3] reports that in a laboratory-bred population originating from a tributary of the Rio Culiaca (Sinaloa St.), individuals with shortened, stocky bodies were found among the young of normal parents. Crosses clarified that the character of the shortened form is recessive (st/st; st = stubby, stocky, short) and is inherited in a true-like manner due to mutation of a single locus (locus = localization, location of a gene on a chromosome). The original parents were heterozygous (st/St). The genetic assembly causes deformation of the vertebrae and gonopodium structures. Most males were therefore unable to copulate.
[1] Miller, R. R. (1960): Four New Species of Viviparous Fishes, Genus Poeciliopsis, from Northwestern Mexico. Occ.Pap.Mus.Zool Univ.Michigan, (619): 1-11.
[2] Thibault, R.E. et Schultz, R.J (1978): Reproductive adaptations among viviparous fishes (Cyprinodontiformes: Poeciliidae). Evolution 32: 320-333.
[3] Schultz, R.J. (1963): Stubby, a hereditary vertebral deformity in the viviparous fish Poeciliopsis prolifica. Copeia 1963 (2): 325-330.