| As a kind of important commercial marine animal, cephalopods play an indispensable roal in fishery resource of the globe. Most of cephalopods have a shot lifecycle. In general, the lifecycle is only one year, and reproductive period takes up the main time. But reproductive behaviors have been known in only a few species, such as the mating patterns. In the studies, we aim at the reproductive biology of Sepia esculenta based on SEM and TEM, microsatellite DNA markers, in order to offert more information to do some favors to its breeding, conservation and so on. The results of the study are showed as follows:1. Observation of reproductive behaviors:Parents of S. esculenta were capured at the waters of Qingdao (35°N,119°E) from 2008-05 to 2009-6, and cultured in the indoor pond with the water temperature of 20-24℃and the salinity of 28-33. Reproductive behaviors were observated and digital collected, including sprerm competition, courtship, sperm displacement, mating, fertilization, egg deposition and so on. The mating manner was head to head. Male individuals always lost their vitality after mating, and then died soon. There was not egg care was to parents. After 25-35d hatching, offsprings broke from the egg membranes, which were similar to mature individuals. 2. The study on ultrastructure of spermatozoa:Electron microscopy was used to reveal the morphology and ultrastructure of the spermatozoon of golden cuttlefish Sepia esculenta, and the influence to the sperm after ultralow temperature treatment. The results showed that the sperm of S. esculenta was consisted of head, mid-piece and tails, covered by smooth membrane. The head made up of acrosome and nucleus, with bubble-shaped arcrosome in front of nucleus whose shape was ellipse. The space between arcrosome and nucleus was called subacrosomeal space, which looked like a bow. The mid-piece contained plenty of mitochondrias and vertical central granules. The tail was long and thin, with the typical structure of the "9+2". Under the ultralow temperature treatment, arcrosome were fractured. There were lots of holes on the membrane of the head. Karyotheca was separated from the nucleolus. Mitochondrias dropped off and the inside membrane became deformed. Tails of the sperms intertwined together, and a few of flagella occurred off.3. Genetic diversity of 3 generations of S. esculenta:the genetic diversity in three generation populations of S. esculenta collected in the waters of Qingdao (QD2008, QD2009, QD2010) was detected based on 8 microsatellite DNA markers (secu6, secu43, secu75, secu101, secu105, secu113, secu117, secu146).133 individuals were examined in this study, which were catched from May,2008 to Aug.2009. The results revealed that the level of diversity had high level and not fluctuate largely in the past three years. The average number of alleles of 8 loci were 12 (2008),15 (2009),12.75 (2010). The average expected and observed heterozygosity of HE=0.664-0.926, Ho=0.667 (0.429-0.905) in 2008; HE=0.868 (0.569-0.958), Ho=0.671(0.135-0.922) in 2009; and HE=0.816(0.464-0.935),0.722(0.050-0.950)in 2010. The heterozygous deficiency existed in the 3 generation populations due to most of Fis values>0.4. Multiple paternity of S.esculenta:22 parent individules were caught at the waters of Qingdao during May to July in 2009. According to morphologic characteristics,2 females (F8, F18) and 18 males took part in the mating.87 offsprings were examined randomly by 8 microsatellite DNA loci. The results showed that 42 offsprings were from F8, which fathers may be M4 and M5; and 45 offsprings from F18, which fathers may be M12 and M13. Each female parent maybe mates with as least two male parents, and then impregnate with them. Meanwhile, the sperms located in the seminal receptacle of one female patent were detected by microstallite DNA markers. It showed that at least 2 males mated with the same female. In a word, the mating pattern of S. esculenta existed polygamous.
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