A molecular phylogeny of the freshwater-fish genus Rasbora (Teleostei: Cyprinidae) in Sri Lanka reveals a remarkable diversification—And a cryptic species

The diversity of the freshwater-fish genus Rasbora (Cyprinidae) on Sri Lanka (five species) is high compared with the four species reported from the peninsula of India, from which the island's cyprinid fauna is derived. The paucity of characters by which species of Rasbora can be phenotypically distinguished renders field identification difficult, adversely affecting the estimation of populations and distributions, with consequences for conservation and management, increasing also the risk of taxonomic inflation. From a sampling of 90 sites across Sri Lanka and based on phylogenetic and haplotype analyses of sequences of cox1 and cytb mitochondrial, and rag1 and irbp nuclear markers, we review the species diversity and phylogeography of Rasbora on the island. Molecular analyses recover, in addition to the five species previously reported, a new (cryptic) species: Rasbora adisi sp. nov. Uncorrected pairwise cox1 genetic distances between species range from 2.0 to 12.3 percent. The Sri Lankan diversification derives from a common ancestor which arrived from India during a sea-level low-stand in the mid-Miocene (15.1 Ma [95% HPD: 11.5–19.8 Ma]), when the present-day island was subaerially connected to the Indian subcontinent by a broad isthmus. This gave rise to a clade comprising five species—R. adisi sp. nov.,Rasbora armitagei, Rasbora microcephalus, Rasbora naggsi and Rasbora wilpita—with a crown age of 9.9 Ma (95% HPD: 7.1–13.3 Ma) and to a clade comprising Indian and Sri Lankan populations of Rasbora dandia, which themselves are reciprocally monophyletic. Morphological analysis of 334 specimens discriminates between most species which, however, are most reliably diagnosed by chromatic characters. The four endemic species exhibit a pattern of inter-basin dispersal via headwater capture, followed by vicariance, explaining the high diversity of the genus on the island.     

Swamp-riverine tropical fish population: a comparative study of two spatially isolated freshwater ecosystems in Peninsular Malaysia

Twenty-four fish species were collected during a study from October 1996 of the swamp-riverine fish populations of two spatially isolated Malaysian freshwater swamp ecosystems. Twenty one species were collected from the Beriah Kanan River, which is located in northern Peninsular Malaysia, compared to only 10 species obtained from the Ulu Sedili River in the south. At both sites, the species Rasbora einthovenii and Hemirhamphodon pogognathu appeared to be the most dominant species, whereas Rasbora pauciperforata and Nemacheilus selangoricus were very rarely caught and Beriah Kanan and Ulu Sedili River, respectively. An analysis of the physico-chemical data showed that although pH, conductivity and ammonium levels were fairly similar at both sites, orthophosphate, hardness and total suspended solids were relatively higher for Ulu Sedili River.     

Swamp-riverine tropical fish population: a comparative study of two spatially isolated freshwater ecosystems in Peninsular Malaysia

Twenty-four fish species were collected during a study from October 1996 of the swamp-riverine fish populations of two spatially isolated Malaysian freshwater swamp ecosystems. Twenty one species were collected from the Beriah Kanan River, which is located in northern Peninsular Malaysia, compared to only 10 species obtained from the Ulu Sedili River in the south. At both sites, the species Rasbora einthovenii and Hemirhamphodon pogognathu appeared to be the most dominant species, whereas Rasbora pauciperforata and Nemacheilus selangoricus were very rarely caught and Beriah Kanan and Ulu Sedili River, respectively. An analysis of the physico-chemical data showed that although pH, conductivity and ammonium levels were fairly similar at both sites, orthophosphate, hardness and total suspended solids were relatively higher for Ulu Sedili River.     

Genetic variation and taxonomy of Rasbora group (Cyprinidae) from Lake Laut Tawar, Indonesia

There were three presumed form of Rasbora found in Lake Laut Tawar, i.e. Depik, Eas and Relo. However, their phylogenetic status was remaining unclear. For this purposes the genetic data were utilized to resolve the taxonomic ambiguity of Rasbora group in Lake Laut Tawar. Approximately 655-bp were amplified from the 5?? region of the mitochondrial cytochrome oxidase subunit I (cox1) gene using the primer pairs (Fish F1 and Fish R1). A total of 14 haplotype sequences were produced from the ingroup where haplotypes 1 to 8 were shared by Eas and Depik, and haplotypes 9 to 14 were belonging to Relo. The genetic divergence varied from 0.2 to 9.6% i.e. between Eas and Relo, 9.6% and between Depik and Relo, 9.5%. The genetic data strongly indicated that Eas and Depik should be regarded as the same species of Rasbora tawarensis.     

Morphological characteristics in relation to diet in five coexisting Thai fish species

Morphological characteristics and intestinal content were analysed for five species of coexisting freshwater fishes in Thailand: Rasbora caudimaculata , Schistura desmotes , Dermogenys pusillus , Xenentodon cancila and Monopterus albus (all found in riffle habitats in Thai streams). Rasbora caudimaculata , S. desmotes and D. pusillus fed predominantly on ephemeropterans, hymenopterans and dipterans, X. cancila fed predominantly on fishes, and larger aquatic invertebrates such as Odonata, and M. albus fed on detritus as well as invertebrate prey such as crustaceans and Odonata. Intestine length, mouth height, mouth width, eye position and mouth orientation varied among all five species. Canonical analysis of discriminance of mouth height, width and intestine length showed a clear dispersion of species, which was supported by intestine content. Evolutionary processes leading to the present differences in morphological characters resulted in each of the five species consuming a different portion of the available resource base, thereby facilitating coexistence.     

Chloramine-T for the control of Ichthyophthirim multifiliis (Fouquet)

Tests were conducted to determine the toxicity of chloramine-T to the free-living stages of the protozoan parasite Ichthyophthirius multifiliis (Fouquet) and the fish Rasbora heteromorpha (Duncker) and Rutilus rutilus (L.) with the view to using the reagent to control ichthyophthiriasis. The toxicity was dependent on the p H value of the water and, to a lesser extent, its hardness. A method of treating the disease is proposed and discussed.     

Functional morphology of the interrenal and chromaffin cells in the teleosts, Rasbora daniconius (Hamilton), Barbus stigma (Cuv. et Val.) and Channa gachua (Hamilton).

The interrenal cells in Rasbora daniconius, Barbus stigma and Channa gachua are mainly found around the postcardinal vein and its major branches in the haemopoietic head-kidney. The chromaffin cells which are identified by the positive chromaffin reaction are found in the walls of the postcardinal vein or dispersed among the interrenal cells. delta5-3beta-HSDH and G-6-PDH activity was observed in the interrenal cells of all three teleosts. The present work indicates that the interrenal cells are capable of steroid biosynthesis and the chromaffin cells contain biologically active catecholamines.     

Diel feeding patterns and daily ration of cyprinid species in the wild determined using an iterative method, MAXIMS

Diel feeding patterns and daily food rations of five cyprinids Amblypharyngodon melettinus, Barbus chola, B. dorsalis, B. filamentosus and Rasbora daniconius in two Sri Lankan reservoirs were studied based on diel surveys using an iterative method, MAXIMS. A. melettinus and B. chola had single peaks of feeding whereas diel feeding patterns with two peaks occurred in the other three species. Daily food rations varied seasonally and with size of fish. The iterative technique used is reliably applicable for quantifying daily rations, and provides a means of linking trophic levels in natural populations of fish.     

Ecological structure of tropical fish assemblages in wet-zone streams of Sri Lanka

The introduction of four fish species into a depauperate stream system in central Sri Lanka provided a 'natural experiment' that enabled us to determine the ecological structure of wet-zone stream fish assemblages. All the species indigenous to this 'introduction' stream system also co-occur naturally with the introduced species in nearby streams. Analyses of habitat use and dietary requirements revealed that most species in the assemblages were segregated on the basis of macrohabitat, microhabitat and food, regardless of origin of the fishes. Macrohabitat and microhabitat utilizations by species were similar in each stream of the 'introduction' system despite differences in stream conditions. Thus species distributions, relative to each other in ecological space, were consistent among streams, and with the combined data. High overlaps along the resource axes of velocity, depth, substratum and food were few. A major proportion of the high overlaps was due to associations with introduced species; especially Barbus nigrofasciatus and Barbus cumingii. The other two introduced species, Barbus titteya and Rasbora vaterifloris , were more specialized, and interacted relatively less with indigenous species. The indigenous species, however, exhibited pronounced complementarity along three resource axes representing depth, velocity and food. Rasbora vaterifloris and B. nigrofasciatus grew to larger sizes in one stream which had fewer indigenous species, suggesting competitive release. In this stream, the most common indigenous species was a dietary specialist that fed on diatoms, and B. nigrofasciatus , which fed heavily on diatoms in other streams, switched to feeding more on macrophytes. Overall, the data suggest that these assemblages are predictable, co-evolved systems with competition serving as an important structuring force that reinforces species segregation.     

Free amino acids in various tissues of a fresh-water teleost, Rasbora daniconius (Ham). I. Qualitative analysis

Seven different tissues of the fish, Rasbora daniconius are analysed chromatographically for their free amino acid contents. Alanine and Cystine followed by Glycine and Glutamic acid are the most common amino acids found in the tissues. On the basis of sex, no apparent difference in amino acid pattern in various tissues is found. Up to 70% of the amino acids of the pools fall in the range of pH from 4.5-6.5. Thus it appears that the pools have some bearing on the maintenance of the tissue pH.     

Spawning seasons of Rasbora tawarensis (Pisces: Cyprinidae) in Lake Laut Tawar,Aceh Province,Indonesia

Background  

Rasbora tawarensis is an endemic freshwater fish in Lake Laut Tawar, Aceh Province, Indonesia. Unfortunately, its status is regarded as critical endangered with populations decreasing in recent years. To date no information on the spawning activities of the fish are available. Therefore, this study provides a contribution to the knowledge on reproductive biology of R. tawarensis especially on spawning seasons as well as basic information for conservation of the species.     

Two new species of Cyprinoid fishes from the fauna of Phu Quoc Island, Gulf of Thailand, Vietnam

Two new Cyprinoid species are described from Phu Quoc Island, Gulf of Thailand. The first new species, Barbucca elongata sp. nova (Balitoridae), differs from the species B. diabolica, which is described previously, in more elongated body covered by small scales (50–67 perforated lateral line scales), conical snout, and coloration. The second new species, Rasbora vietnamensis sp. nova (Cyprinidae), belongs to the species group “R. trifasciata”; it differs from other species of the group in substantially reduced lateral line system with four-seven perforated scales and absence of red pigmentation on the fins and body.     

The chemical control of salvinia molesta (Mitchell) and some related toxicological studies

Laboratory trials were performed to screen the potentials of four herbicides — PARAQUAT, DIQUAT, TOK E-25 and DALAPON — for the chemical control of Salvinia molesta. The herbicides were applied as aerial sprays, and their phytotoxic effects were assessed by visual estimation. Paraquat and Diquat have been found to be the more promising.The toxicities of the four herbicides were tested on three aquatic organisms associated with the plant in the aquatic environment —larva of Nymphula responsalis, Rasbora trilineata and Poecilia reticulata. An attempt was made to correlate the toxicological results with the application rates of the herbicides in terms of safety factors. TOK E-25 has been found to be most toxic, the others being relatively safe.     

Morphological and behavioral variation of <Emphasis Type="Italic">Rasbora paviei</Emphasis> (Cyprinidae,Cypriniformes) from lotic and limnic habitats (Central Vietnam)

Morphological and behavioral traits of Rasbora paviei from river and lake environments are studied. For investigations, the fish were caught from the middle reaches of the Cai River and from the inshore zone of the Kam Lam Reservoir (Khanh Hoa Province, Central Vietnam). Phenotypic differences are found in river and lake fish groups. Experimentally, differences in tactics and efficiency of defensive behavior are found in specimens from different habitats in the presence of a predator—Lepisosteus sp. (Lepisosteidae). In river specimens of Rasbora, the defensive reaction is more efficient in comparison with specimens from the reservoir. The river specimens of Rasbora used predominantly the tactics of group defense from the predator and stayed in a school longer than the lake specimens.     

Length–weight relationships of eight Asian freshwater fish species in Nam Theun 2 Reservoir (Laos PDR)

Length–weight relationships (LWRs) were determined for eight Asian freshwater fish species that were not yet recorded in any peer‐reviewed journal indexed in the Web of Science or the FishBase database. Fish specimens from Nam Theun 2 reservoir in Lao PDR, were collected from April 2012 to August 2016 using several methods to cover a large size‐spectrum for each species. For LWRs using the general equation from Beckman (1948), the parameter b (slope value on the growth pattern) ranges from 2.908 (Puntius brevis) to 3.429 (Rasbora paviana). This study provides an update in maximum lengths for two species and first LWRs for eight common freshwater species found mainly in reservoirs, and thus represents a means for further population dynamic evolution analyses and local fisheries management.     

Feeding Ecology of the Allochthonous Feeder Rasbora daniconius (HAMILTON) (Cyprinidae – Teleostei)

Seasonal fluctuations in the dietary components of Rasbora daniconius inhabiting a perennial eutrophic pond have been studied on the basis of analyses of the gut contents over a period of one year from 1980 to 1981. Modified Points method was adopted for the quantitative estimation of the dietary items. Gut analysis revealed that the fish is predominantly an allochthonous feeder subsisting mainly on terrestrial Hymenoptera and Coleoptera. Flowers and seeds also formed part of the dietary composition of the fish. Allochthonous fauna were preferred at all the stages of the growth of the fish. Females have a greater preference for terrestrial Coleoptera and the males for Formicidae. The feeding intensities of three different length groups and both sexes were also ascertained. This revealed that June, July, October and November are the most intensive feeding periods of R. daniconius. Older and mature fishes were found to be more active feeders than juveniles.     

Experimental studies on toxicity of zinc to a freshwater teleost,rasbora daniconius (Hamilton)

Rasbora daniconius (Ham.) were exposed to zinc sulphate upto 15 days under static bioassay test conditions with renewal of the test solutions every 24 hours. Simultaneously control fish were also kept in water without zinc. The 96 and 240 hr LC₅₀ values were 38.1 and 33.3 PPm of zinc respectively. A reduced mortality rate was observed after 96 hr and LC₅₀ approached a constant value at 240 hr of exposure to the toxicant. Fish showed abnormal behaviour, deposition of mucus and appearance of haemorrhage on the body in case of higher concentrations of zinc, before death. The reported LC₅₀ values in the present study were comparatively higher than those reported by earlier investigators.See offprint requests to: Dr. V. K. Rajbanshi, Department of Limnology and Fisheries, University of Udaipur, Udaipur-313001, India.     

S7核糖体蛋白基因序列变异与(鱼丹)亚科鱼类的单系性研究

使用分子生物学的方法对Dan亚科鱼类的单系性进行了探讨。通过PCR方法,获得了13种鲤科鱼类S7核糖体蛋白基因第1内含子序列,其中包括6种Dan亚科鱼类。使用MEGA软件中的Neighbor-Joining法和Most-Parsimony法分别构建分支系统图。研究结果显示目前所确认的Dan亚科鱼类实际上没有形成单系类群。其中Dan属、波鱼属和低线Lie属位于系统树基部,显示出原始性,而由细鲫属、马口鱼属和Lie属构成的类群相对于Dan亚科中的原始种类起源较晚,可能和较晚起源的东亚鲤科类群之间有更为密切的关系。     

Habitat and relative abundance of fishes in small rivers in eastern Thailand

Total relative abundance of fish and species richness at 95 sites in small rivers varied significantly with physicochemical factors. Species richness was negatively and positively related with pH and dissolved oxygen, respectively. Relative abundance varied inversely with discharge and ambient ammonia and, directly with depth, substratum, ambient oxygen and alkalinity. Fish were represented by 62 species, the most common being Rasbora paviei, Puntius binotatus and Channa gachua. Canonical correspondence analysis related species and their relative abundances with eight environmental variables into four groups. The most species-rich group was associated with approximately average values for the significant variables. The group with the fewest species was associated with high oxygen and low ammonia and alkalinity. The other two groups had similar numbers of species, one being associated with high ammonia and alkalinity and low oxygen. Species in the other group were found at locations where rivers were relatively wide with comparatively high oxygen and low ammonia concentrations.