Because of limits in applicable karyological techniques and also the presence of a large number of
small chromosomes in Penaiedae family, the study on the number, structure, and the formula of the
chromosomes in these shrimps is difficult. The present cytogenetic study was conducted on Penaeus
(Fenneropenaeus) merguiensis native to Persian Gulf and Oman Sea by preparing spreads from
various early stages of this species including embryos, nauplii, protozoa, myses, postlarvae as well as
adult tissues such as gill, hepatopancreas, testis and ovary. For this purpose, two methods of splashing
of cell suspension and squashing of tissues on warm and cold slides were used. Different doses of
colchicine and incubation periods on obtaining and the quality of chromosomes were examined as
well. It was only possible to obtain acceptable quality metaphase chromosomes using adult testis. The
testicular tissue contained both mitotic and meiotic cells, so diploid and haploid chromosome numbers
could be counted, respectively. The modal diploid number of this species was found to be 2n=88 which
was confirmed by the modal haploid chromosome number of n=44 in the adult testes. Tentative
karyotype of Penaeus (Fenneropenaeus) merguiensis contained 21 pairs of meta- and submetacentric
chromosomes and 23 pairs of acro- and telocentric chromosomes. The chromosome arm number was
calculated NF= 130.