Spermatozoid life-span of two brown seaweeds, Saccharina japonica and Undaria pinnatifida, as measured by fertilization efficiency

During sexual reproduction of seaweeds, spermatozoid (sperm) discharge is triggered by chemical messengers (pheromones) released by the female gametes. The chemotactic ability of the sperm ensures fertilization success. Using unialgal male and female gametophyte material under designated standard gametogenesis testing (SGT) conditions, the potential life-span of the sperm of two seaweeds, Saccharina japonica and Undaria pinnatifida, was assessed by their ability to fertilize eggs. Results show that within 20-30 min after being discharged, sperm of both species could complete fertilization without an apparent decline in fertilization rate. Although fertilization rate 60–120 min after sperm discharge dropped significantly in both species, some sperm were viable enough to fertilize the eggs. In S. japonica, at 12°C, some sperm were able to fertilize eggs up to 12 h after discharge. In both species, egg discharge rates (EDR) in the male and female mixed positive controls were significantly higher than those of all the sperm-testing groups. Doubling the seeded male gametophytes of S. japonica in the SGT tests significantly increased the EDR, further confirming the effect of the presence of the male on the female in terms of facilitating egg discharge from oogonia.     

Reproductive Biology of Yeilowfin Tuna T. albacares in the West-Central Indian Ocean

Survey of yellowfin tuna in the west-central Indian Ocean was conducted on board of Chinese Iongliners during 2003, 2004 and 2005, which is a part of Chinese Tuna Fishery Scientific Observer Program (CTFSOP). The reproductive biology has been investigated. A total of 1023 samples are collected including 417 ovaries and 606 testes. Spawning activities of yellowfin tuna have been studied for both male and female from January to June. The data showed that the average monthly sex ratio is 0.59, and the minimum length at sexual maturity is 101 cm for female and 110 cm for male respectively. Length at 50% sexual maturity is esti- mated at 113.77 cm for female and 120.20 cm for male, whereas maturation rate is 0.066 cm-1 for female and 0.091 cm-1 for male. Sex ratio by length class indicates that the proportion of male is higher than female's along with size increasing; for instance, in the group of the body length longer than 145 cm, some females have their body length from 145 to 160 cm and males have their body length at 160 cm and even longer. Statistically, yellowfin tuna has a significant seasonal reproduction.     

鲫鲤杂交一代（F_1）自交的受精细胞学观察

采用人工催产、波恩氏液固定、石蜡切片和Ｈ·Ｅ染色等方法，研究了杂交一代（Ｆ１）自交的受精细胞学过程。结果表明，鲫鲤杂交一代自交时有正常的受精细胞学过程。受精后，卵子完成第二次成熟分裂，排出第二极体；１５ｍｉｎ，雌雄性原核形成，２０ｍｉｎ，两性原核完全融合，形成二倍体的合子，４０ｍｉｎ，开始进行卵裂；１ｈ，两个分裂球出现，本实验为Ｆ２代是二倍体提供了证据。     

Impact of external factors on sperm motility of Sepiella maindroni

Sperm motility is important in reproductive biology. To understand the physiological ecology characteristics of sperm of Sepiella maindroni, we studied the activation rate, active time, and lifespan of sperm to evaluate the influence of external factors, including temperature, salinity, pH, glucose, NaCl, KCl, MgCl2, CaCl2, EDTA-2Na and artificial seawater on sperm motility. The results show that the appropriate activation and motility condition for sperm were: temperature 20?30°C (optimum 25°C), salinity 10.6?30.6 (optimum 15.9) and pH 8.0?8.6 (optimum 8.0-8.4). Sperm activity varied in different concentrations of glucose, NaCl, KCl, MgCl2 and CaCl2. None of the selected concentrations of EDTA-2Na solution could activate the sperm. The activation rate in artificial seawater devoid of Ca2+, Mg2+ or HCO3ˉ was low. The results should help further studies on the preservation and activation of squid sperm.     

Sperm Nuclear Expansion and Meiotic Maturation in Normal and Gynogenetic Eggs of the Scallop, Chlamys farreri

Sperm nuclear expansion, meiosis and the association of the male and female pronuclei leading to the four-cell stage in normal Chlamysfarreri eggs were observed under a fluorescence microscope. The effects of ultraviolet （UV） irradiation on the fertilizing sperm were also examined. Both normal and UV-irradiated sperm nuclei enlarged at three distinct phases （phase A, metaphase I; phase B, polar body formation; and phase C, female pronuclear development and expansion） that were temporally correlated with meiotic process of the maternal chromosomes. Sperm nuclei underwent a rapid, initial enlargement during phase A, but condensed slightly during phase B, then re-enlarged during phase C. The effects of UV irradiation were not apparent during transformation of the sperm nucleus into a male pronucleus, and there was not any apparent effect on meiotic maturation and development of the female pronucleus. However, the rate of expansion of the UV-irradiated sperm nuclei and the size of male pronuclei were reduced apparently. Unlike the female pronucleus, the male pronucleus derived from sperm genome inactivated by UV irradiation did not form chromosomes, but became a dense chromatin body （DCB）. At mitotic anaphase, DCB did not participate in the karyokinesis of the first cleavage as evidenced by chromosomal nondisjunction, demonstrating the effectiveness of using UV irradiation to induce gynogenetic scallop embryos.     

Effect of bis(tributyltin)oxide on reproduction and population growth rate of calanoid copepod Schmackeria poplesia

A full life-cycle toxicity test,combined with histology,on calanoid copepod Schmackeria poplesia was used to study the effect of bis(tributyltin)oxide(TBTO).The results indicate no sex-specific differences in TBTO toxicity.Long-term mortalities of the copepods exposed to concentrations higher than 20 ng TBTO L-1were significantly elevated compared with that of control,and larval development was inhibited when they were exposed to 40 and 60 ng TBTO L-1.The percentages of ovigerous females were reduced compared with the control(P0.01)after 24 days exposure to concentrations higher than 10 ng TBTO L-1.Histological examinations suggest that exposure to TBTO might block the posterior end of the diverticula and inhibits the production of egg sacs.A modified Euler-Lotka equation was used to calculate a population-level endpoint,the intrinsic rate of natural increase(rm),from individual life-table endpoints,i.e.mortality rate,time of release of first brood,sex ratio,the fraction of ovigerous females among all females as well as the number of nauplii per ovigerous female.Apart from the highest TBTO concentration(60 ng L-1),where all females aborted their egg sacs,20 ng TBTO L-1was the only concentration that significantly decreased rm compared with that of control(an effect associated with decreased sex ratio).The results show that the S.poplesia is affected by prolonged exposure to low concentrations of TBTO.The full life-cycle toxicity test combined with histology experiments provides more integral understanding of the toxicity of endocrine disrupters.     

Studies on the breeding habits of the minke whale (Balaenoptera acutorostrata) in the Yellow Sea

Minke whales caught in the Yellow Sea range from 4.16 m to 8.60 m in length with an average length of 6.93 m for the female and 6.14 m for the male. Sex ratio of the female is 74.3%. The pregnancy ratio of all sexually matured females is 65.8%. The minimum size of the pregnant whale observed is 6.60 m in length. Females having a body length of more than 7 m long are all sexually matured. According to the studies on the embryos obtained from the females caught in the northern Yellow Sea, there is only one breeding season each year. Mating mostly occurs from July through September, and the length of pregnancy is ten to eleven months with the peak of calving from May through July. Most females breed one calf each time, only two cases with twins. Sex ratio of female fetus is 56.6%, and the newly born calf measures 250–270 cm in body length. This paper was published in Chinese inOceanologia et Limnologia Sinica 13 (4): 338–345.     

贝类精子质量检测与评价方法的研究Ⅲ:FDA-PI双荧光复染法检测马氏珠母贝精子的存活率

将马氏珠母贝新鲜精液和精子水浴致死精液配制含有不同精子死亡率(0%、20%、40%、60%、80%)的5浓度梯度检测样品,并作为理论精子死亡率,采用二乙酰荧光素(Fluorescein diacetate,FDA)-碘化丙啶(Propidium iodide,PI)双荧光复染法检测精子存活率和质膜完整性。结果表明,FDA和PI能有效区分活精子和死精子,活精子发出绿色荧光,死精子发出红色荧光。各样品实测精子死亡率和理论死亡率之间呈极显著正相关,相关系数r=0.99(p<0.01)。FDA-PI双荧光复染法检测马氏珠母贝精子存活率,灵敏度高,重复性好,准确有效。     

Acute toxicity effects of perfluorooctane sulfonate on sperm vitality,kinematics and fertilization success in zebrafish

Perfluorooctane sulfonate(PFOS) has emerged as one of the most concerning contaminants in recent years.This study aimed to investigate the acute toxicity effect of PFOS on sperm viability,kinematics and fertilization success in zebrafish(Danio rerio).Sperm were activated in aqueous media containing a range of PFOS concentrations(0,0.09,0.9 and 9 mg/L).Viabilities and kinematics of the sperm exposed to different PFOS treatments were assessed via computer-assisted sperm analysis(CASA) at 20,40,60,and 80 s after activation.PFOS exposure decreased the percentage of motile sperm,the curvilinear velocity(VCL),and the mean angular displacement(MAD) of spermatozoa,but showed no influence on the straightline velocity(VSL) or the angular path velocity(VAP).Furthermore,a significant decrease in fertiUzation success was observed in spermatozoa that were exposed to 0.9 mg/L PFOS or more.These findings indicate that PFOS pollution in natural aquatic environment may be a potential threaten to successful reproduction offish.     

Histological observation of germ cell development and discovery of spermatophores in ovoviviparous black rockfish (Sebastes schlegeli Hilgendorf) in reproductive season

Black rockfish(Sebastes schlegeli) is an important species for culture; however, its reproductive characteristics have not been fully documented. In this study, we investigated the morphology and developmental process of germ cells in this ovoviviparous rockfish in reproductive season(October 2011–November 2012) with histological methods. We found that the gonad of mature fish showed notable seasonal changes in developmental characteristics and morphological structure. The sperm cells matured during a period lasting from October to December, significantly earlier than the oocytes did. A large number of spermatozoa and other cells occurred in testis at different developmental stages. Vitellogenesis in oocytes began in October, and gestation appeared in April next year. Spermatophores were discovered for the first time in Sebastes, which assembled in testis, main sperm duct, oviduct and genital tract, as well as ovarian cavity in October and April. These organs may serve either as production or hiding places for spermatophores and spermatozoa which were stored and transported in form of spermatophores. Testicular degeneration started from the distal part of testis in April, with spermatophores assembled in degenerating testis and waiting for transportation. The copulation probably lasted for a long period, during which the spermatozoa were discharged in batches as spermatophores. These spermatophores were coated with sticky materials secreted from the interstitial areas of testis and the main sperm duct, then transported into ovary.