Cyp19 expression and sex change timing in captive-bred false clownfish.

The false clown anemonefish (Amphiprion ocellaris) is a protandrous hermaphrodite with a distinctive reproductive behavior. This study elucidates the genetic mechanisms and timing of sex changes in captive-bred A. ocellaris by examining the expression of key genes involved in this process, specifically cyp19a1a and cyp19a1b.

Gene expression of acetylcholinesterase in hybrid catfish (Clarias gariepinus X Clarias macrocephalus) exposed to chlorpyrifos and carbaryl.

After serving as an eurotransmitter, acetylcholine is hydrolyzed by acetylcholinesterase (AChE). Inhibition of AChE is considered to be a specific biomarker for exposure to organophosphate and carbamate insecticides. In this study the AChE gene was isolated from hybrid catfish brain by RT-PCR methods using degenerate primers.

Isolation and physical mapping of sex-linked AFLP markers in nile tilapia (Oreochromis niloticus L.).

Gynogenetically produced XX and YY Nile tilapia (Oreochromis niloticus) and diploid control groups were screened for amplified fragment length polymorphisms (AFLPs) to search for sex-linked or sex-specific markers. Family-level bulked segregant analysis (XX and YY gynogenetic family pools) and individual screening (XX and YY gynogenetics and XX and XY control individuals) identified 3 Y-linked (OniY425, OniY382, OniY227) and one X-linked (OniX420) AFLP markers. OniX420 and OniY425 were shown to be allelic.

Analysis of repetitive DNA sequences in the sex chromosomes of Oreochromis niloticus.

In the Nile tilapia, Oreochromis niloticus, sex determination is primarily genetic, with XX females and XY males. While the X and Y chromosomes (the largest pair) cannot be distinguished in mitotic chromosome spreads, analysis of comparative hybridization of X and Y chromosome derived probes (produced, by microdissection and DOP-PCR, from XX and YY genotypes, respectively) to different genotypes (XX, XY and YY) has demonstrated that sequence differences exist between the sex chromosomes. Here we report the characterization of these probes, showing that a significant proportion of the amplified sequences represent various transposable elements.