M.N. Siti Azizah

Paleo-Drainage Basin Connectivity Predicts Evolutionary Relationships across Three Southeast Asian Biodiversity Hotspots

Understanding factors driving diversity across biodiversity hotspots is critical for formulating conservation priorities in the face of ongoing and escalating environmental deterioration. While biodiversity hotspots encompass a small fraction of Earths land surface, more than half the worlds plants and two-thirds of terrestrial vertebrate species are endemic to these hotspots. Tropical Southeast (SE) Asia displays extraordinary species richness, encompassing four biodiversity hotspots, though disentangling multiple potential drivers of species richness is confounded by the regions dynamic geological and climatic history. Here, we use multilocus molecular genetic data from dense multispecies sampling of freshwater fishes across three biodiversity hotspots, to test the effect of Quaternary climate change and resulting drainage rearrangements on aquatic faunal diversification. While Cenozoic geological processes have clearly shaped evolutionary history in SE Asian halfbeak fishes, we show that paleo-drainage re-arrangements resulting from Quaternary climate change played a significant role in the spatiotemporal evolution of lowland aquatic taxa, and provide priorities for conservation efforts.

Influence of cryoprotectants on abnormality and motility of baung (Mystus nemurus) spermatozoa after long-term cryopreservation☆

Study on the effect of cryoprotectants on abnormality and motility of baung, Mystus nemurus spermatozoa were evaluated using transmission and scanning electron microscopy. Four cryoprotectants, dmso, ethanol, methanol and glycerol at concentration of 10% were tested in triplicates. Three ml of fresh sperm which was diluted with 60 ml of ringer solution was added to each of twelve 5-ml vials containing of 0.50-ml of the cryoprotectants. The vials were placed in an icebox containing dry ice 5 min and then storage into container containing liquid nitrogen for 13 months. The effect of cryoprotectants on the spermatozoa abnormality and motility were significant (P<0.05). The spermatozoa abnormality was significantly lower in methanol (62.65%) compared with the other cryoprotectants. The spermatozoa motility was higher in methanol, but not significantly different with ethanol (P>0.05). It is a negative correlation between sperm motility and abnormality. Generally, higher abnormalities of spermatozoa resulted low motility.

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

BackgroundRasbora 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.MethodsMonthly sampling was conducted from April 2008 to March 2009 by using selective gillnets. The gonadosomatic index, size composition and sex ratio were assessed. The gonadal development was evaluated based on macroscopic and microscopic examinations of the gonads.ResultsThe gonadosomatic index (GSI) varied between 6.65 to 18.16 in female and 4.94 to 8.56 for male. GSI of the female R. tawarensis was higher in March, September and December indicating the onset of reproductive seasons, the GSI and oocyte size being directly correlated with gonadal development stages. Although, a greater proportion of mature male than female was detected during the study, the sex ratio showed that the overall number of female was higher than male. The ovaries had multiple oocyte size classes at every stage of gonadal development, thus R. tawarensis can be classified as a group synchronous spawner or a fractional multiple spawner.ConclusionThe spawning seasons of R. tawarensis were three times a year and September being the peak of the reproductive season and the female was the predominant sex. This species is classified as a group synchronous spawner.

Isolation of microsatellites in the bighead catfish, Clarias macrocephalus and cross-amplification in selected Clarias species

The present study documents the isolation of eight polymorphic microsatellite markers from the bighead catfish, Clarias macrocephalus and cross-amplification in two other catfish species. The number of alleles per locus in C. macrocephalus ranged from 2 to 21. The most polymorphic locus was NCm-G12 with 21 alleles while the least polymorphic locus was NCm-H2 with only two alleles. Locus NCm-F8 significantly deviated from Hardy–Weinberg equilibrium (P value <0.05) after Bonferroni correction. Linkage disequilibrium was non-significant in all loci comparisons. The observed and expected heterozygosities varied from 0.033 to 0.967 and from 0.033 to 0.942, respectively. Mean polymorphic information content for the eight loci was 0.765. Cross-amplification was successfully performed with two other catfish species, C. batrachus and C. meladerma for all eight loci. Locus NCm-D8 was monomorphic in both species while NCm-F8 was monomorphic only in C. batrachus. These newly developed markers would be useful for better management and conservation of the economically important C. macrocephalus species.

Genotyping of microsatellite markers to study genetic structure of the wild striped snakehead Channa striata in Malaysia

Genetic variability and differences in wild striped snakehead Channa striata from Malaysia were analysed by genotyping nine novel nuclear microsatellite loci. Analysis revealed moderate-to-high genetic diversity in most of the populations, indicative of large effective population sizes. The highly diversified populations are admixed populations and, therefore, can be recommended as potential candidates for selective breeding and conservation since they each contain most of the alleles found in their particular region. Three homogenous groups of the wild populations were identified, apparently separated by effective barriers, in accordance with contemporary drainage patterns. The highest population pairwise FST found between members of the same group reflects the ancient population connectivity; yet prolonged geographical isolation resulted in adaptation of alleles to local contemporary environmental change. A significant relationship between genetic distance and geographical isolation was observed (r = 0·644, P < 0·01). Anthropogenic perturbations indicated apparent genetic proximity between distant populations.

Preliminary studies on cryopreservation of snakehead (Channa striata) embryos

This paper reports the findings of the ongoing studies on cryopreservation of the snakehead, Channa striata embryos. The specific objective of this study was to collect data on the sensitivity of C. striata embryo hatching rate to low temperatures at two different developmental stages in the presence of four different cryoprotectants. Embryos at morula and heartbeat stages were selected and incubated in 1M dimethyl sulfoxide (Me2SO), 1M ethylene glycol (EG), 1M methanol (MeOH) and 0.1M sucrose solutions at different temperatures for a period of time. Embryos were kept at 24 °C (control), 15 °C, 4 °C and -2 °C for 5 min, 1h and 3h. Following these treatments, the embryos were then transferred into a 24 °C water bath until hatch to evaluate the hatching rate. The results showed that there was a significant decrease of hatching rate in both developmental stages following exposure to 4 °C and -2 °C at 1h and 3h exposure in each treatment. Heartbeat stage was more tolerant against chilling at -2 °C for 3h exposure in Me2SO followed by MeOH, sucrose and EG. Further studies will be conducted to find the best method to preserve embryos for long term storage.