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.

A checklist of the marine and estuarine fishes of Madang District is presented, combining both previous and new records. After the recent PAPUA NIUGINI 2012 expedition, a total of 1337 species in 129 families have been recorded from the region. One species and one family is not native (Cichlidae: Oreochromis mossambicus), but has been introduced. The native fish fauna of Madang therefore consists of 1336 species in 128 families. The largest families are the Gobiidae, Labridae, Pomacentridae, Apogonidae, Serranidae, Blenniidae, Chaetodontidae, Syngnathidae and Muraenidae, Scorpaenidae and Lutjanidae, Myctophidae, Acanthuridae, Scaridae, Holocentridae, Carangidae, Pomacanthidae and Tetraodontidae, and Caesionidae. A total of 820 fish species (61.4 % of the total marine and estuarine fish fauna) are recorded from Madang for the first time. The fish fauna of Madang includes a total of 187 species of transitional waters and 1326 species in marine habitats. A total of 156 species of the marine or estuarine species also occurs in freshwater. Zoogeographically, 1271 species have a wide distribution range, most frequently a broad Indo-West Pacific distribution. Among the remaining species, only 8 are endemic to Madang District. Anthropogenic threats to the fish fauna and habitats of Madang District include extensive fishing in Madang Lagoon, sometimes with destructive fishing practices; the discharge of untreated sewage of human settlements, mining and industrial developments into the lagoon and nearby oceanic habitats; and destruction of mangrove habitats by extensive construction work on the shores. These anthropogenic threats may call for conservation and monitoring measures in the near future.

Background Paedocypris is a newly established genus of fish in Southeast Asia. Paedocypris is characterized by several unique features, including a tiny adult size (thus named miniature fish or minifish), fragmentary habitats of acidic peat blackwater swamps, an unusual reproduction mode and truncated development. These peculiarities lend themselves excellent for studying chromosome evolution and rapid speciation in vertebrates but also make them highly controversial for the phylogenetic position.Methodology and Principal FindingsWe have established an organ procedure to prepare chromosome spreads from tiny organs of minifish and performed a cytogenetic study on two species of the genus Paedocypris, namely P. carbunculus (Pc) and P. sp. “Singkep” (Ps). We found 30 and 34 chromosomes in diploid cells of Pc and Ps, respectively, which are unusual in teleost fishes. The diploid metaphase has 5 pairs of metacentrics and 7 pairs of subtelocentrics in Pc compared to 3 pairs of metacentrics and 11 pairs of subtelocentrics in Ps, whereas the haploid metaphase contains 5 metacentrics and 7 subtelocentrics in Pc compared to 3 metacentrics and 11 subtelocentrics Ps. Chromosome behavior in first meiosis revealed the presence of a chromosomal ring consisting of 2 metacentrics in Pc, suggesting that centric fusion rather than fission was responsible for the karyotypic evolution from Ps to Pc. Flow cytometry revealed that Pc had a 45% nuclear staining intensity relative to medaka whose genome is 700 Mb in size and contains 0.81 pg DNA. The Pc genome should have 315 Mb in length and 0.36 pg of DNA, which represent one of the smallest values in vertebrates, suggesting genome miniaturization in this organism.ConclusionsOur data demonstrate that gross chromosome rearrangements and genome miniaturization have accompanied the evolution of Paedocypris fishes. Our data also place Paedocypris outside currently described taxa of the Cypriniformes.

Food webs summarise trophic interactions of the biotic components within an ecosystem, which can influence nutrient dynamics and energy flows, ultimately affecting ecosystem functions and services. Food webs represent the hypothesised trophic links between predators and prey and can be presented as empirical food webs, in which the relative strength/importance of the respective links are quantified. Some common methods used in food web research include gut content analysis (GCA) and stable isotope analysis (SIA). We combine both methods to construct empirical food web models as a basis for monitoring and studying ecosystem-level outcomes of natural (e.g. species turnover in fish assemblage) and intentional environmental change (e.g. biomanipulation). We present 12 food webs from tropical reservoir communities in Singapore and summarise the topology of each with widely-used network indices (e.g. connectance, link density). Each reservoir was surveyed over 4–6 sampling occasions, during which, representative animal groups (i.e. fish species and taxonomic/functional groups of zooplankton and benthic macroinvertebrates) and all likely sources of primary production (i.e. macrophytes, periphyton, phytoplankton and riparian terrestrial plants) were collected. We analysed gut content in fishes and bulk isotope (d13C and d15N) profiles of all animals (i.e. fishes and invertebrates) and plants collected. Both sets of information were used to estimate the relative strength of trophic relationships using Bayesian mixing models. We document our protocol here, alongside a script in the R programming language for executing data management/analyses/visualisation procedures used in our study. These data can be used to glean insights into trends in inter- and intra-specific or guild interactions in analogous freshwater lake habitats.

The freshwater fish diversity of Brunei Darussalam is reviewed. At present, a total of 104 species of freshwater fishes from 59 genera, 24 families and 10 orders is recorded. Eight species including one introduced species and two from brackish waters present new records for Brunei. The family Cyprinidae has the highest diversity with 40 species. Forty-six species are believed to be endemic to Borneo including six species known only from Brunei Darussalam namely Barbodes xouthos, Rasbora tubbi, Gastromyzon cranbrookii, Gastromyzon venustus, Neogastromyzon brunei and Ompok platyrhynchus and three are exotics.