Effect of cryoprotectant and concentration on the sperm quality of walking catfish, Clarias batrachus, post-cryopreservation.

BACKGROUND: Walking catfish, Clarias batrachus is one of the native and most popular freshwater catfish species in Indonesia. However, cultivation faces challenges, particularly due to the scarcity of larvae resulting from underdeveloped breeding technologies. Cryopreservation is a method of storing sperm to maintain viability for a long period and support the breeding technology of the fish. Cryoprotectant, in this context, plays an important role in determining the success of sperm cryopreservation. OBJECTIVE: To determine the best type and concentration of cryoprotectant for cryopreservation of walking catfish sperm. MATERIALS AND METHODS: A total of five different types of cryoprotectants, namely DMSO, glycerol, ethyl glycol, ethanol, and methanol, were tested at four concentration levels namely 0%, 5%, 10%, 15%, and 20%, each with four replications. RESULTS: The type and concentration of cryoprotectant had a significant effect on sperm motility and viability (P < 0.05). The best outcomes were obtained with 5% DMSO and ethyl glycol, 10% glycerol and methanol, as well as 15% ethanol. CONCLUSION: The highest motility and viability values were obtained with 5% DMSO, resulting in its recommendation for cryopreservation of walking catfish sperm. Doi.org/10.54680/fr24510110612.

Motility, viability and fertility of goldfish Carassius auratus (Pisces: Cyprinidae) post short-term cryopreservation.

BACKGRUND: Goldfish Carassius auratus is a popular ornamental fish extensively cultured worldwide. Sperm cryopreservation is a common fish breeding method that ensures sperm availability around the year. Studies on cryopreservation of goldfish sperm, especially on the suitability of cryoprotectant types and pre-freezing time, are scarcely available. OBJECTIVE: To determine the most suitable type of cryoprotectant and pre-freezing for the successful cryopreservation of goldfish sperm. MATERIALS AND METHODS: A completely randomized design with two factors was utilized in this study. The first factor is the type of cryoprotectants, which included methanol, ethanol, ethylene glycol, glycerol, and DMSO. The second is pre-freezing times of 10, 20, 30, and 40 min at each of the pre-freezing temperatures of 4 degree C, -10 degree C, and -79 degree C, meaning that the total times for the ramping down of temperature were 30, 60, 90 and 120 min, respectively. The Ringer solution and 10% egg yolk were used as extender and extracellular cryoprotectant. The sperm was stored at -179 degree C for 7 days. RESULTS: The ANOVA test showed that cryoprotectants and pre-freezing significantly affected the motility, viability, and fertility of goldfish sperm after freezing in liquid nitrogen for 7 days (P<0.05). Furthermore, 10% DMSO combined with 15% egg yolk with an pre-freezing time of 20 min can maintain sperm motility, viability, and fertility higher than other treatments, by 79%, 80%, and 33%, respectively. The agarose gel electrophoresis showed no DNA fragmentation in all samples, including fresh sperm. CONCLUSION: We conclude that 10% DMSO combined with 15% egg yolk and 20 min pre-freezing is the best treatment for goldfish sperm cryopreservation. DOI: 10.54680/fr23310110412.

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.

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 Earth's land surface, more than half the world's 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 region's 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.

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.

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.

Morphological variation between isolates of the nematode Haemonchus contortus from sheep and goat populations in Malaysia and Yemen.

Haemonchus contortus is a highly pathogenic nematode parasite of sheep and goats. This work was conducted to investigate the population and host variations of the parasitic nematode H. contortus of sheep and goats from Malaysia and Yemen. Eight morphological characters were investigated, namely the total body length, cervical papillae, right spicule, left spicule, right barb, left barb, gubernaculum and cuticular ridge (synlophe) pattern. Statistical analysis showed the presence of morphological variation between populations of H. contortus from Malaysia and Yemen, with minor variation in the synlophe pattern of these isolates. Isolates from each country were grouped together in the scatterplots with no host isolation. Body, cervical papillae and spicule lengths were the most important characters that distinguished between populations of the two countries. This variation between Malaysia and Yemen may be attributed to geographical isolation and the possible presence of a different isolate of this worm in each country.

Phylogenetic study and barcoding of the blood cockle, Tegillarca granosa, found on the west coast of peninsular Malaysia using the COI gene.

Blood cockles are among the most economically important brackish water invertebrates found in Malaysia. However, our knowledge of blood cockle phylogeny and systematics is rudimentary, especially for the species Tegillarca granosa. It is unclear, for instance, whether the cockles occurring on the west coast of peninsular Malaysia constitute a single species, or multiple, phylogenetically distinct species. We performed the first DNA molecular phylogenetic analysis of T. granosa to distinguish it from other related species found in other parts of the world and to create a DNA database for the species. An approximately 585-nucleotide fragment of the mitochondrial DNA (cytochrome oxidase I, COI) was sequenced for 150 individual cockles, representing 10 populations: three from the north, four from the central part and three from the southern part of peninsular Malaysia. Phylogenetic analyses of the resulting dataset yielded tree topologies that not only showed the relationship between T. granosa and its closest relatives but its position in the evolutionary tree. Three mitochondrial clades were evident, each containing an individual genus. Using the mutation rate of the COI gene, the divergence time between T. granosa and its closest related species was estimated to be 460 thousand years ago. This study provides a phylogenetic framework for this ecologically prominent and commercially important cockle species.

Remarkably low genetic variation but high population differentiation in the climbing perch, Anabas testudineus (Anabantidae), based on the mtDNA control region.

Anabas testudineus (Anabantidae) is an important food fish in Southeast Asia. We analyzed the mitochondrial DNA control region sequence data to evaluate the genetic variability and population structure of this species. Sixty specimens were collected from four populations in Sumatra and two populations in Peninsular Malaysia. We found a very low level of genetic variability, with five of the six populations exhibiting total absence of genetic variation. Based on analysis of molecular variance, 84.72% of the total variation was among populations and 15.28% within populations. A geographical division based on FST values indicated highly significant genetic differentiation among populations from the four drainage systems: Aceh, Sumatra Utara, Pulau Pinang, and Terengganu (FST ranging from 0.633 to 1.000). No phylogeographic relationships among populations were detected, despite the generation of four distinct clades in a neighbor-joining phylogenetic tree.