Molecular Prey Identification And Artificial Reproduction Of Octopus Minor

Octopus minor (Sasaki 1920) is a common commercially important cephalopod, widely being distributed along the coastal waters of China. Recently because of the sharp overfishing and environmental degradation, the fish catch of O. minor declined seriously. So, there is a realistic significance to study on fundamental biology and artificial reproductive technique of Octopus minor. And the broad farming area makes the culture of O. minor a great potential.This thesis studies the and fundamental biology of Octopus minor, including the molecular prey identification during maturing, multiple paternity, the developed eggs collecting methods and culture of hatchings. What has studied in this article is aim to provide theoretical technical support to the culture, breeding, artificial propagation and releasing, exploitation and restoration of natual resources. Here are the major achievements:1. Molecular prey identification of O. minor during maturing by Barcoding20-25 male and female Octopus minor individuals respectively were captured using traps from swan lake, Rongcheng, Shandong Province in the middle of each month of April-July,2014. Through the anatomical observation and weighing founding that: the male octopuses were mature, whereas the female whose gonad index significantly increased during April-July with 0.106 in July nearly nine times larger than 0.010 in April, and the female were under maturing phase; the mean weight of male was larger than that of the female every month of April-July; the mean weight of the both sex groups had no obvious difference between June and July and the same is true between April and May, however, the average weight in June was larger than that of May(P< 0.05) with 117.29g in female increasing to 192.4g and 128.68g in male to 202.88g; empty stomach rate in male was 73.26% greater than 5O% in female and the mean weight of stomach content getting from female was larger than that in male. indicating the feeding intensity of females stronger than males; the weight of both females and males remarkably increased from May to June with no significant changes of visceral mass weight.The stomach content could yield large PCR DNA fragments of mtCOI using universal primer LCO1490 and HCO2198 and the total success rate was 87.88% with ranging 556-708bp; except itself and a parasite,8 species of pray was detected in O. minor. They consist of Acanthogobius flavimanus account for 31.03%, followed by Acanthogobius hast a (12.07%) and the rest six species (18.97%), Acanthogobius hasta, Pholis crassispina, Tridentiger bifasciatus, Diopatra sp.1, Alpheus brevicristatus, Oratosquilla oratoria, Charybdis japonica.2. Multiple paternity in the Octopus minor by microsatellite DNA analysisFemale Octopus minor were captured using traps from swan lake, Rongcheng, Shandong Province and kept in 5 indoor in June-August,2012 and the female adults spawned after several days. A subset of muscle tissue from 43 adult individuals was also sampled for population genotyping. And ten broods (B1-B10) from this sample, each containing 15 embryos and the corresponding female, were obtained until the embryos had developed to a stage suitable for DNA extraction and genotyping. Multiple paternity in the ten broods was tested using five microsatellite DNA markers. The results proved the hypothesis that multiple paternity presented in the O. minor and showed the minimum number of fathers by GERUD:of the 10 broods typed,4 were sired by a single male,3 were sired by 2 different males and 3 were sired by 3 different fathers. The minimum number of fathers produced by the single-locus method was one less father than the GERUD method in B10. Of the 6 multiply sired broods,4 (66.7%) were significantly skewed from equal paternal contributions, which suggested that sperm competition and/or cryptic female choice might be important for post-copulatory paternity biasing in this species.3. The hatch of fertilized eggs and experimental rearing of newly hatchlings of O. minorThis chapter presents a egg collector and basic growth relations in experimental rearing of newly hatchlings of O. minor.We improve the low-yielding egg collector according to the wild nest, the character of "the wide entrance and narrow exit", and the bellicose behavior of O. minor, with network blocking one end of the collector. The number of mean collected eggs using the developed method and collector is 102.82,1.71 times larger than 37.91 obtained before the improvement, greatly increasing the eggs amount.Basic growth relations and pattern were studied in experimental rearing of newly hatchlings of Octopus minor during 80 days using Potamocorbula laevis and Ruditapes philippinarum as feeding diets. Results showed that the newly hatchlings of O. minor no longer had external yolk, with smooth mantle and the length of the first pair of arm was about 2.9 times of the mantle length, with two lines of suckers counting (66±4.60), (55±3.76), (43±4.59) and (41±3.82) (n=3) per arm from first pair to forth pair; 1-15d hatchlings were fed on shellfish P. laevis (shell length 15.4-20.3mm) during the night and then were fed on R. philippinarum (shell length 33.2-39.3mm); the total survival rate of hatchlings decreased from 80.99% at 30d to 54.65% at 70d; in the hatchlings rearing process, growth rate showed a highly significant linear relation with feed efficiency (P<0.01),y= 1.452x-2.731 (R2= 0.865); ratio of MLd/TL increased more faster than the ratio of the AL/TL along with time showing the mantle grew faster than the arms; the amount of SC of each arm had no significant increase; the Wt of cultured hatchlings showed a highly significant power regression relation with culture days (P<0.01), Wt= 0.301 e0.010t(R2= 0.854). Finally, the growth rate of O. minor hatchlings was 122.05%, with an average growth rate 9.97% per 10 days.