SummaryHere we report natural autotetraploid and chromosomal characteristics in the subfamily Botiinae from Northeast Thailand. Kidney cell samples were taken from tiger botia (Syncrossus helodes), red-finned loach (Yasuhikotakai modesta), silver botia (Y. lecontei) and skunk botia (Y. morleti). The mitotic chromosome preparation was prepared directly from kidney cells. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results showed that the tetraploid chromosome numbers of S. helodes, Y. modesta, Y. lecontei and Y. morleti were 4n (natural autotetraploid)=100 for all species, and the fundamental numbers (NF) were 122 for all species. The presences of metacentric, submetacentric, and telocentric chromosomes were 12-10-78 for all species. No cytologically distinguishable sex chromosome was observed. The nucleolar organizer regions (NORs) were observed at the region adjacent to the short arms of a pair of submetacentric chromosome for all species. These results show the evolutionary relationship between species of loach fish from Thailand. The karyotype formula was deduced as:S
Summary This is the first heteromorphic nucleolar organizer regions (NORs) and chromosome analysis of Rolland s demoiselle (Chrysiptera rollandi). Kidney cell samples were taken from five male and five female fish. Mitotic chromosome preparations were prepared directly from kidney cells. Conventional and Ag-NOR staining techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of C. rollandi was 2n=46, and the fundamental number (NF) was 50 in both males and females. The types of chromosomes were 2 large submetacentric, 2 large telocentric, 2 medium acrocentric, 32 medium telocentric, and 8 small telocentric chromosomes. In addition, the short arm of acrocentric chromosome pair 2a and the long arm of telocentric chromosome pair 6a (non-homologous chromosome) showed clearly observable NORs heteromorphic (2a6a) in both sexes and chromosome size was not related to sex. The karyotype formula for C. rollandi was:2n (
The Australian red-claw crayfish (RCC) Cherax quadricarinatus (von Martens 1868) (Crustacea: Decapoda: Parastacidae) has been introduced and promoted for freshwater aquaculture in many countries including Thailand. This study i) evaluates the growth performance of RCC in near-natural conditions relative to captive conditions and ii) investigates how successfully RCC can compete with a trophically and functionally analogous native species. Growth of RCC was compared among two aquaculture systems (concrete tank and earthen pond) and a treatment with simulated natural conditions. After 12 months of rearing, total length and weight were greatest in the earthen pond and poorest in the near-natural treatment, with significant differences in total length between the near-natural treatment and the two culture systems. Length-weight relationships showed that the RCC had positive allometry in the culture systems but negative allometry in the near-natural treatment. Competition was evaluated by means of a biotic resistance test and an additive–substitutive experiment between RCC and the native freshwater crab Esanthelphusa dugasti (Rathbun, 1902) (Crustacea: Decapoda: Gecarcinucidae). Specific growth rates after 90 days of the experiments suggest that the crab inhibited growth of RCC. This implies that the invasion of RCC in Thai waters could be limited by competition from resident freshwater crabs.
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