Paedocypris , a new genus of Southeast Asian cyprinid fish with a remarkable sexual dimorphism, comprises the world's smallest vertebrate

Abstract

Paedocypris is a new genus of paedomorphic cyprinid fish from highly acidic blackwater peat swamps in Southeast Asia. It includes two new species, one of which (Paedocypris progenetica) appears to be the smallest fish and vertebrate known, with the smallest mature female measuring a mere 7.9 mm. Paedocypris has many 'larval' features typically associated with paedomorphic fish (e.g. narrow frontals that leave the brain unprotected dorsally by bone and a precaudal larval-fin-fold), but, uniquely among fishes, males also possess highly modified pelvic fins with hypertrophied muscles and a keratinized pad in front of the pelvic girdle, which, we hypothesize, function together as a clasping or holding device, thereby suggesting an unusual reproductive mode. Unfortunately, habitat destruction jeopardizes the survival of these fishes and thus opportunities for further research.

Priocharax nanus, a new miniature characid from the rio Negro, Amazon basin (Ostariophysi: Characiformes), with an updated list of miniature Neotropical freshwater fishes

“…More than 50 miniature freshwater species occur in South and Southeast Asia (Kottelat & Vidthayanon, 1993), 24 miniature species were listed by Conway & Moritz (2006) for Africa, and there are only seven miniatures in freshwaters of North America (Bennett & Conway, 2010). Even though those lists are clearly out of date for some areas, with more miniatures having been described for example in Asia (Kottelat et al, 2006;Britz 2009;Conway et al, 2011) the diversity of miniature freshwater fishes in the Neotropical region exceeds by far that of other continents for which similar lists have been compiled. Weitzman & Vari (1988) also considered size at maturity (under 20 mm SL) as a criterion to include the species in their list of miniatures even if the species was known to exceed the 26 mm SL cut-off point, a procedure that was followed later by Kottelat & Vidthayanon (1993).…”

DNA Barcoding Indonesian freshwater fishes: challenges and prospects

“…13, [41][42][43][44][45]. The distribution of the number of species description per decade highlights that taxonomic studies have been fragmented during the pre-modern period but also that despite two centuries and a half of ichthyological inventories; many species are still described regularly throughout Indonesia, not only from the most remote rivers and lakes of Wallacea and Sahul.…”

“…This subfamily harbors many miniature taxa including highly developmentally truncated ones [62], some of which have only been described very recently. For example, the genus Paedocypris that includes the world's smallest fish species (Paedocypris progenetica), was only described in 2006 [42]. Paedocypris currently includes three endemic species of the highly stenotopic peat swamp forest found in Peninsular Malaysia, Sumatra and Borneo.…”

Emerging semantics to link phenotype and environment

“…Miniaturization is essentially the evolution of small body size and the associated set of phenotypes, typically reduction or loss of structures (Hanken & Wake, 1993;Weitzman & Vari, 1988). Authors have related this extreme change in body size to organisms whose habitats include highly acidic waters, typical of peat bog or black water habitats (Kottelat et al, 2006). As a proof-of-concept, we tested the hypothesis that miniaturization is correlated with environmental variables.…”