金乌贼繁殖行为与交配策略

2014年6月于室内大型水槽使用摄像系统对金乌贼繁殖过程进行连续观察与记录,通过定性和定量比较分析,解析其繁殖过程中游泳、捕食、求偶、争斗、交配及产卵等行为特征。结果显示:金乌贼游泳主要依靠漏斗喷水的反作用力,持续游泳能力较弱;繁殖期的金乌贼继续摄食,能发现周围20—38 cm范围内的凡纳滨对虾,攻击距离为7—24 cm,能在2.1—6.1 s内完成对对虾的捕获且成功率极高,外源营养为卵(精)巢不同步发育、分批产卵和复杂的繁殖行为继续提供能量支持;金乌贼具明显的求偶行为,规格差异是影响求偶的重要因素,其中雄性亲本更倾向选择与自身规格相当或略小的雌性,而雌性亲本则更倾向于选择大规格(较大规格争斗易获胜)的雄性;金乌贼一次交配持续125—398 s,雄性有明显的精子移除行为和领域性,交配后雄性伴游在雌性周围3—24 cm范围内,不允许其他乌贼靠近,平均伴游61 min后会再次交配。精子移除、伴游以及多次交配是雄性金乌贼有效提高父权贡献率的关键行为基础;研究结果表明,金乌贼采取"多夫多妻"的混交婚配策略,两性亲本均存在多次交配现象,这能有效提高雌雄的生殖成功率和受精卵的遗传多样性。

Reproductive behavior and mating strategy of Sepia esculenta

Sepia esculenta Hoyle is widely distributed in Chinese coastal waters, and the taste and the highly value of nutrients make it one of the most important economical species in China. This organism can grow up to 200 mm in mantle length during its short lifespan of 1 year or less. Mature S. esculenta individuals migrate to inshore areas to mate and spawn during the breeding period, which is from June to July in Xuejiadao, Qingdao in China. The reproductive behavior and mating strategy, which include mate selection and sperm competition, determine the quality (e.g. dorsal mantle length or body weight of newly hatched larvae) and quantity of offspring, and play an important role in generating genetic diversity. Here, sexually mature S. esculenta were captured using a basket trap off the coast of Xuejiadao, Qingdao, China, between May and June of 2014. The reproductive behaviors of S. esculenta, including swimming, predation, courtship, battle, mating, and egg-laying were analyzed using both qualitative and quantitative comparisons after observation in an indoor pool with an image pickup system. The results revealed that the swimming power of S. esculenta was mainly linked to the funnel and could not be sustained for long periods of time. S. esculenta continued to feed on Litopenaeus vannamei ((10.4±0.6) cm in total length) within a distance ranging from 20 to 38 cm and could rapidly catch prey (in 2.1-6.1 s), illustrating that it utilized the energy from feeding for the non-synchronous ovarian (testicular) development, batch spawning, and complex reproductive behaviors. Before mating, S. esculenta demonstrated obvious courtship behavior. The males tended to choose females of similar or slightly smaller sizes, whereas the females tended to choose larger males. The males competed for females and the winner had an opportunity to mate with female. The male would begin by lightly touching the cheek of the female, and also maintained a head-to-head position during the mating. Before ejaculation, the males moved arm III to remove the sperm masses attached to the residual buccal membranes from previous matings. After sperm removal, the male held spermatophores ejected through its funnel with the base of hectocotylized left arm IV and then pressed the coiled arm on the ventral portion of the female''s buccal membrane. A successful mating lasted a relatively long time (125-398 s), but the mating process could easily be interrupted by interference from other individuals nearby, especially other males. The male continued to guard the spawning female (staying 3-24 cm from the female), and repeated matings occurred at an average interval of 61 min during the mate guarding process. Fertilized female S. esculenta individuals began to lay eggs approximately 4.5 min after mating. The eggs were relatively large (long axis diameter: 16.4-20.0 mm; short axis diameter: 10.5-12.6 mm). Although males involved in guarding females delayed their search for other mates, they may have reduced the probability that the female would remate with other males. Sperm removal, guarding, and repeated mating could effectively improve the male success rate. The mating strategy of S. esculenta was promiscuity, and repeated instance of mating, in both males and females, could effectively improve the reproductive success rate and level of genetic diversity.