Ali Fakhri

Despite the abundant native species of sea cucumber in Iranian waters in the south of the Iran, not much research has been done to investigate the biological characteristics of this animal. Therefore, the present study was conducted to investigate the tissue structure of the gonads of different species of sea cucumbers on the coast of Bushehr in the northwest of the Persian Gulf. In this study, about 56 cucumbers of different species found on the coast of Bushehr were collected manually during May and June 2023. First, to identify different species, the ossicles were extracted and studied using a light microscope. The gonad samples were fixed in 10% formalin solution. Then, 6micrometer gonadal tissue sections were prepared using routine histological methods and studied with a light microscope. In the present study, five species were identified, including Holothuria atra, H. leucospilota, H. arenicola, H. parva, and H. hilla, all were from the order of the Holothuriida and the family Holothuriidae. All these species were gonochoric (separate sexes). In both males and females, there was only one gonad consisted of a bundle of long, branched tubes (with an average length between 2 and 7.4 cm and an average diameter of 0.8 to 3.5 mm) on the left side of the coelom next to the intestine. The gonads in these species were of the asynchronous type and perivitellogenic eggs were also visible on the margins of the female gonad tubes. In general, according to the present study, the basic tissue structure of the gonads and also the time of sexual maturation of different species of Persian Gulf sea cucumbers are the same.