A new species of long-finned Corydoras species has been described from the Parana River drainage in northern Argentina.
The new species, named Corydoras longipinnis in a paper by Joachim Knaack published in the most recent issue of the journal Vertebrate Zoology, superficially resembles the well-known C. paleatus.
Corydoras longipinnis can be distinguished from other members of the genus in having a combination of a short snout, 20"21 dorsal lateral scutes, 18"20 ventral lateral scutes and elongation of the dorsal and pectoral fins in mature males (the specific name comes from the Latin longis, meaning long and pinna, meaning fin).
Besides the elongate dorsal and pectoral fins in males, C. longipinnis also differs from the very similar C. paleatus in the colour pattern of the developing fry.
Although long-finned mutants of C. paleatus can be potentially confused with C. longipinnis, the egg (1.94 mm diameter in C. paleatus vs. 1.27 mm C. longipinnis) and clutch sizes (44"68 in C. paleatus vs. 130"170 in C. longipinnis) differ considerably.
An albino mutant of the new species is also reported. Corydoras longipinnis is a rheophilic species collected from fast-flowing streams amongst submerged branches.
The presence of numerous odontodes in the abdominal region in this species is hypothesized to help the fish to maintain a better grip on the substrate.
The paper also discusses the phylogenetic relationships of the new species (it is hypothesized to be closely related to Scleromystax) and the existence of a second undescribed species of long-finned Corydoras resembling C. paleatus.
Ian Fuller, the UK corydoradine catfish expert, told Practical Fishkeeping: "They have been around for quite a few years, and in fact my stock of this species came from Joachim Knaack three years ago when Hans-Georg Evers took me to meet him. Coming from Argentina, they do not like to be kept too warm - 17-22 degrees C.
"For a long time they were just being called long-finned C. paleatus, which was a dangerous link when you consider that we have long straggly finned man made varieties coming from the Czech Republic.
"To try and separate them from these mutant species I allocated the number CW003, which I am pleased to say seemed to do the trick.
"There are a few people that have been successfully breeding C. longipinnis for a few years now. I know two currently in the UK."
For more information, see the paper: Knaack, J (2007) Beitrge zur Kenntnis der Callichthyidae (Teleostei: Siluriformes). III. Corydoras longipinnis sp. n. " ein neuer Panzerwels aus dem ro Dulce in Argentinien (Teleostei: Siluriformes: Callichthyidae). . Vertebrate Zoology 57, 35"55. (In German)