Oxylapia polli in the aquarium. Fish and Photo by Patrick De Rham.
Oxylapia polli was described as a new genus and new species by Kiener and Mauge in 1966. The type locality of the species, first collected in 1963, is the Nosivolo River at Marolambo, situated approximately 170 km to the south-east of the capital city of Tananarive. The Nosivolo is a right bank tributary of the Mangoro, the largest river of Madagascar's eastern slope.
In February 1989, two ichthyologists working in the USA, Peter Reinthal and Melanie Stiassny, managed to reach Marolambo by land. They were able to collect 12 native species of fish, including a fair number of O. polli specimens. However, the most remarkable result of their trip was the discovery of a new cichlid species belonging to the previously monotypic genus Ptychochromoides (described now as Ptychochromoides katria). This was also the first cichlid species to be added in recent times to the list of 9 recorded by Kiener and Mauge in their 1966 work. The reason this easy-to-collect cichlid has not been discovered before, at least at the same time as Oxylapia, remains a mystery.
In October 1994, following an abortive overland attempt a year earlier, Jean-Claude Nourissat and I finally made it from Tana to Marolambo in a small mission plane, an airstrip having been recently completed close to this isolated little town (Nourissat, 1995). Before landing the plane circled above Marolambo and we were briefly able to admire the beautiful and interesting landscape. The dark Nosivolo River, strewn with rocks, was shining in the sun. Stretches of calm water alternated with numerous rapids. We could see another river which tumbled down huge falls before joining the Nosivolo. The surrounding mountainous landscape was green, an indication of the prevailing wet climate, but even from the air we could see that low scrub had totally replaced the original forest.
|Aereal view of the Nosivolo river near Marolambo. Fish and Photo by Patrick De Rham.|
We were very well received by the local authorities and with their help were able to muster a small team of fishermen. While they were getting ready, we went down to the river below the old colonial Residence in which we had been lodged, where we found some people fishing with cast nets. After only a few minutes we were presented with our first "Katria", the local name for the new Ptychochromoides katria species discovered by Reinthal and Stiassny. We were slightly disappointed at the lack of colour in these fishes, but after this early success we felt confident that the other Nosivolo cichlid, the curious Oxylapia polli, now our main target, would shortly be collected. Soon afterwards our fishing team arrived and we were taken by pickup to a beautiful place some 4 km downstream, where the river runs through a succession of falls and rock-fringed pools.
|The Nosivolo river in east Madagascar. Drawing by Cichlid Press.|
Our fishermen eagerly began to cast their nets and were soon back with dozens of Katria. Leaving aside the unavoidable exotic tilapias (Oreochromis sp.), they caught also several "Filelabato" (literally: stonelickers, two goby species, Chonophorus cf. macrorynchus and Sicyopterus sp.) and one "Sindrano", Agonostomus telfairi, a very interesting specialised freshwater mullet, endemic to the fast-flowing waters of Madagascar's east coast and Reunion Island. But no Oxylapia. What puzzled us was that in spite of our repeated efforts to describe and even sketch an Oxylapia, the fishermen could not understand what other more or less katria-like fish we were so eager to obtain. Unfortunately we didn't know the native name of the fish and had no photo with us. The afternoon came to an end and we had to return to Marolambo.