Sturgeons as the precious commercial fishes have co-evolved a number of adaptations to their habitat and lifestyle. The relationship between brain morphology and behavioral ecology has been confirmed in many chondrichthyes and teleost fish species. However, very little is known on the central nervous systems of sturgeon species. In this research, the relative brain size (encephalization) and the relative development of four brain areas in two sturgeons are investigated. Two integration areas (the telencephalon and the metencephalon or corpus cerebellum) and two sensory brain areas (mesencephalon and myelencephalon which receive primary projections from eye and octavolateralis senses, respectively) are examined. The analysis of brain size reveals that the integration area is developed more that the sensory area. The volume of cerebellum is significantly large in theses species, comprising up to two third of the total volume of brain. This is different from brain development of most teleost and chondrichthyes species, which have large mesencephalon and telencephalon, respectively. This study suggests that sturgeons have evolved different sensory strategies to cope with the demands of life in the depth of the sea.   

Regarding to the importance of sturgeons specially persian sturgeon (Acipenser persicus), this study was carried out on the microscopic structures of intestines often adult sturgeons. Routine histological processes were used and stained by hematoxylin and eosin method. Internal sur face of intestines was netted but only distal intestine was distinguished by spiral valves. Epithelium of intestines and the valves were ciliated pseudo stratified columar associated with goblet cells increasing to the end of intestines. Some large saccular glands in the sub mucosa of intestines except rectum were present. At the end of rectum the epithelium gradually changes from columnar to completely stratified scuamous prior to the vent.

This study was carried out with the aim of measuring steroid hormones levels residue including 17b- estradiol (E2), 17a- hydroxy progesterone (17a-OHP), testosterone (T) and gonadotropine hormones (GTH I and GTH II) in farmed Persian (Acipenser persicus) and Siberian (Acipenser baerii) sturgeon in International Sturgeon Research Institute (Areo). 10 gram of eggs weighed and centrifuged at 3000 rpm per 10 minutes after homogenizing for extract. Results showed that maximum level of testosterone was 13.2±0.97 ng/ml in Acipenser persicus and showed significant difference compared to Acipenser baerii. Maximum level of progesterone and E2 were 2.9±0.1 and 1.4±0.6 ng/ml in Acipenser persicusand showed significant difference compared to Acipenser baerii (P<0.05). Based on results, sex steroid hormone residue observed in sturgeon eggs so that steroid hormones levels residue was more than gonadotropin I and II level and was different depended on hormone type and species.

The purpose of this study was to determine the presence or absence of a specific satellite DNA on the genus Acipenser (Hind III SatDNA) in Persian sturgeon, Acipenser persicus. Genomic DNA was extracted from caudal fin tissue of A. persicus specimen using the phenol-chloroform method to extract Hind III SatDNA. Hind III SatDNA amplified using the PCR technique and PCR product was evaluated by agarose gel electrophoresis after staining the gel with ethidium bromide. Obtained Hind III SatDNA fragment after extraction from agarose gel and purification, ligated to the plasmid PTZ/57R (Fermentas) and cloned in competent E. coli DH5α cells (Fermentas). Finally three clones containing the Hind III SatDNA fragment were sequenced. Sequencing of extracted Hind III SatDNA from genome of Acipenser persicus showed that it contained 163bp which is registered in NCBI as FJ429174. Comparison Hind III SatDNA extracted from A. persicus in the present study with those extracted from Acipenser gueldenstaedtii, A. ruthenus, A. naccarii, A. brevirostrum, A. baeri, A. fulvescens, A. stellatus and A. sinensis showed 88% and with that from A. transmontanus showed 90% similarity. Presence Hind III SatDNA in A. persicusand high similarity between it and those from the mentioned sturgeons verify this fish belongs to Acipenser genus.

Persian sturgeon (Acipenser persicus) is a benthic species occurring primarily on sandy bottoms in the mid and southern Caspian Sea, especially along the shores of Iran (Berg, 1948; Holcik, 1989). The Persian sturgeon in the Caspian Sea is anadromous, with at least eighteen groups that segregate spatially and temporally for spawning. These populations are supported by some spawners, each of which considered to be of two seasonal races and divided into two or four biological groups (Perevaryukha, 2001).

Sexual cells in male fishes are microscopic and smaller than eggs in females. Due to the late maturation age in sturgeons, the biopsy of gonads and histological studies are one of the most important and reliable ways to detect and separate males and females from each other at early ages. The aim of the present study was to determine and divide the sexes in farmed Acipenser persicus reared under artificial conditions. In order to detect and determine sexual maturation stages, gonads of 81 farmed A. persicus were sampled by biopsy. Samples were fixed and studied by light microscope. Results showed that males and females were 30 (37%) and 51 (63%) individuals, respectively. The determination of sexual maturation stages in A. persicus showed that 16% were at stage I, 23.5% at stage I-II, 59.3% at stage II and 1.2% at stage III. The number of females was higher than that of males, but sexually mature females were at lower maturation stages than males in the same age and rearing conditions.

Primary cell lines were established from the culture of explants of caudal fin of Persian sturgeon, Acipenser persicus. The margin of the caudal fin from a two year old specimen (23 cm in length, and 133 g in weight) was aseptically cut (2 cm), washed three times with PBS containing antibiotics and then minced into 1mm explants and cultured in L-15 medium complemented with antibiotics and FBS (20%) at 22° C. After confluent monolayer formation on the bottom of the flask, the cells were washed with PBS containing antibiotics and dislodged by trypsin-EDTA solution (0. 25%) and shaking the flask. After washing the cells with PBS containing the antibiotics, they were cultured in 5 ml of L-15 medium, FBS (20%), antibiotics at 22 ° C (first subculture). After a confluent monolayer formation, a similar procedure was followed for the second subculture. The emerging cells from explants exhibited fibroblast-like and epitheliallike cells in primary culture but the fibroblast-like cells were seen to predominate after the first subculture. In the present study the establishment of cell lines from the original culture at two passages was investigated.

Sturgeon is one of the most important species of the Caspian Sea aquatics. Unfortunately, this species faces the threat of extinction today. This makes specific studies on any type of sturgeons more important than before. Studies like histological studies, radiology, and sonography, all require a complete understanding of the anatomy of this fish. Since pilot studies showed some misconceptions in description of the sturgeon digestive system, this study was conducted to evaluate more precise anatomical structure of the digestive system of Acipenser persicus as the most important sturgeon species of Iran.A total of 40 adult Acipenser persicus were used in this experiment. They were autopsied primary to the study. All parts of the digestive system from buccal cavity toward rectum and anal orifice were evaluated. The anatomical structure and relations of the different parts of the digestive system including oral cavity, pharynx, esophagus, glandular stomach, muscular stomach, pyloric process, small intestine, spiral intestine, rectum, liver and pancreas were described.The digestive tube is relatively short. The stomach has two parts. The first part, or the proventricle, is U-shaped. The second part or gizzard has thick muscles and is almost surrounded with liver lobes. Pyloric caecum is located on the left side bottom of the gizzard as a sponge like structure. The intestines are made of 3 parts: the small intestine, the spiral colon, and the rectum. The small intestine has two flexures that separate it to three parts named the descending, ascending, and the end part, respectively. The spiral colon is the longest part of the digestive tube. This part has mucosal spiral septum on the inner surface. The rectum is short and located in the middle of the abdominal cavity. However, in the present study the opening was shown to be located in the muscular stomach and the intestine junction, just close to the gall bladder duct opening.

Sex and maturity determination of live fishes without external sexual dimorphism or when there is no developed external characters is very important from different aspects. In this regard, the ultrasonography methods was used to determine sex and maturity of Persian sturgeon (Acipenser persicus). 142 collected samples of live fishes of this species (with an age range of 13-20 years) from Caspian Sea were preserved in water tanks and scanned under 5.0 and 7.5 MHZ linear pie medical transducer. Frontal view of right or left lateral side of each fish between pectoral and anal fins were obtained echogenicity and morphologic ultrasonographic findings were studied for evaluting the difference between testis and ovary and their maturity status. The results obtained from ultrasonography were confirmed by further necropsy examinations. The ultrasonographic accuracy for sex and maturity determination were 100% and 98.6%, respectively. It can be recommended that this method can be used with an accurate method to determine sex and maturity of Persian sturgeon.

We studied genetic difference and resemblance between Acipenser persicus and Acipenser guldenstaedtii using Random Amplified Polymorphic DNA (RAPD) technique. The DNA of tail fin tissue of three A. persicus and A. gueldenstaedtii were extracted using phenol-chloroform method. After electrophoresis of the samples by agarose gel, their concentrations were regulated and Polymerase Chain Reaction (PCR) was conducted by 53 primers. PCR products were electrophoresed on polyacrylamide gel and silver staining was done to reveal the DNA bands of the samples.Among 53 primers, 17 had no site on genomic DNA of A. persicus and A. gueldenstaedtii and did not produce any bands while the remaining 36 primers showed band pattern. Analyzing the PCR products data using RAPD PLOT program showed that the maximum and minimum genetic distance between species were 73% and 65% respettively. Also, the mean-difference between the species was 70% and the maximum and minimum genetic resemblance between the two species were 35% and 27% respectively. Based on the results, we conclude that A. persicus is an independent species from A. gueldenstaedtii.