Survey of Penaeus monodon Post Larvae in Semi Saline Zone of Kholpatua River of Satkhira Near Sundarbans Reserved Forest Bangladesh

This study monitored the present status ofPenaeus monodon post larvae （PL.） of Kholpatua river in Satkhira. The survey was conducted in Kholpatua river from January 2014 to December 2014 and was compared with the ten years old secondary data. The results showed that there was a 41.57% decrease in number of catches ofP. monodon PL. over the course of time from ten years ago to the year of 2014. Although the number of active fishermen＇s boats have increased from 250 to 360 in ten years. The study also showed that the severe shrimp seed collection activities reduced the availability ofP. monodon PL. at Satkhira district, which has a severe negative impact on the availability of total catches. To control such decrease of P. monodon PL. in Bangladesh, more intensive study should be done.

A cadmium metallothionein gene of ridgetail white prawn Exopalaemon carinicauda(Holthuis,1950) and its expression

Metallothioneins （MTs） are a group of low molecular weight cysteine-rich proteins capable of binding heavy metal ions. A cadmium metallothionein （EcMT-Cd） cDNA with a 189 bp open reading frame （ORF） that encoded a 62 amino acid protein was obtained from Exopalaemon carinicauda. Seventeen cysteines were in the deduced amino acid sequence, and the cysteine （Cys）-rich characteristic was revealed in different metallothioneins in other species. In addition, the deduced amino acid sequence did not contain any aromatic amino acid residues, such as tyrosine （Tyr）, tryptophan （Trp）, and phenylalanine （Phe）. EcMT- Cd mRNA was expressed in all tested tissues （the ovary, muscle, stomach, and hepatopancreas）, and its expression profiles in the hepatopancreas were very different when shrimps were exposed to seawater containing either 50 pmol/L CuSO4 or 2.5 gmol/L CdC12. The expression of EcMT-Cd was significantly up-regulated in shrimp exposed to CuSO4 for 12 h and down-regulated in shrimps exposed to CdC12 for 12 h. After 24 h exposure to both metals, its expression was down-regulated. By contrast, at 48 h the EcMT-Cd was up-regulated in test shrimps exposed to CdC12. The transcript of EcMT-Cd was very low or even absent before the zoea stage, and the expression of EcMT-Cd was detected from mysis larvae-I, then its expression began to rise. In conclusion, a cadmium MT exists in E. carinicauda that is expressed in different tissues and during different developmental stages, and responds to the challenge with heavy metal ions, which provides a clue to understanding the function of cadmium MT