Photo by Peter Southwood.
Platanna klipfish. Photo by Guido Zsilavecz
Elongated sand klipfish. Photo by Guido Zsilavecz
Platanna klipfish. From ML Penrith 1969
Peter wants to know if the fish he photographed is the elongated sand klipfish, Cancelloxus longior. It is not. As can be seen from the photos, the elongated sand klipfish is, as the name suggests, much longer and slender than the platanna klipfish. Both are sand-dwelling, however, and often live very much in the same environment. For example, in the sandy patch just beyond the first "constriction" at Sandy Cove, Oudekraal, both species can be found. The elongated sand klipfish are abundant in the middle of the patch, and just swimming closely over the sand will cause them to flee very suddenly and rapidly. The platanna klipfish prefer the edges of the patch where it meets the reef. Finding one will not be as easy. When uncovered it too will flee, it does so less explosively and over a much shorter distance. The digging techniques are quite different, with the elongated sand klipfish putting its body into an "S" shape and by sideways movements "sinking" into the sand, while the platanna klipfish uses its pectoral fishes to throw sand over itself while wrigging its body.
Why "platanna" klipfish? JLB Smith formed the Xenopoclinid family in 1961 when he described two new sand-dwelling klipfish, which, due to their external morphology, are clearly related. Klipfish have their ventral fins reduced to a few rays only, and in most species these are either completely separated from each other, or joined closely up to a point. Within the Xenopoclinids there is a membrane joining the rays, which make them look like a webbed foot, as can be seen in the diagram by ML Penrith. This obviously must have appeared like a frog's foot to JLB Smith, as he named the family after Xenopus, a genus of toads. In Afrikaans these toads are commonly called platanna (short for "plat Anna" - why that name I don't know), and hence the name platanna klipfish.
See "Coastal fishes of the Cape Peninsula and False Bay", available from SURG, for more details.
Coastal fishes of the Cape Peninsula and False Bay, a divers' identification guide, G Zsilavecz, 2005.
Smiths' Sea Fishes, MM Smith and PC Heemstra, 1986.
The systematics of the fishes of the family clinida in South Africa. ML Penrith, Annals of the South African Museum, Volume 55, September 1969, Part 1.
Fishes of the family Xenopoclinidae, JLB Smith. Ichthyological Bulletin No. 20, February 1961, Department of Ichthyology, Rhodes University.