Responses to threat by female bobucks,<Emphasis Type="Italic"> Trichosurus caninus</Emphasis>, during different stages of offspring development

The costs of reproduction are widely recognised as a major selective force in the evolution of various behavioural and life-history characteristics. In particular, the behaviour of reproductively active animals is likely to change when breeding increases risk of predation. We investigated the effect of an experimentally derived threat on the vigilance and escape behaviour of female Trichosurus caninus with and without dependent offspring and at different stages of offspring development. Females with offspring showed a heightened response to the threat in comparison to females without offspring. In addition, females with offspring displayed a stronger response at earlier stages of their offsprings development.Communicated by P. Bednekoff     

Loss of mating opportunities influences refuge use in the Iberian rock lizard,<Emphasis Type="Italic"> Lacerta monticola</Emphasis>

Because time spent in refuge may be costly if prey lose opportunities to forage, fight, or mate, prey allow predators to approach closer before beginning to flee when opportunity costs are high. Because the same opportunity costs may apply to refuge use as to escape, prey should make similar trade-offs between risk of emerging and cost of remaining in refuge. In the Iberian rock lizard, Lacerta monticola, we studied the effects of sex, reproductive season, speed of predator approach, and potential loss of mating opportunities on time spent in refuge following simulated predatory attacks. Lizards of both sexes adjusted refuge use to the level of risk by spending more time in refuge when approached rapidly than slowly. Females remained in refuge for equal times in the mating and postreproductive seasons, but males emerged sooner during the mating season, suggesting adjustment to a cost of lost opportunity to search for mates during the mating season. When a tethered female was nearby, males emerged from refuge earlier than if no female was present, indicating a trade-off between risk and mating opportunity. Approach speed affected emergence time when females were absent, but not when a female was present. Approach speed did not affect the probability that, after emerging, a male would return to court the female. For males that courted females intensely (bit them) before entering refuge, approach speed did not affect latency to emerge, but males that courted less intensely emerged sooner if approached slowly than rapidly. These findings show that males adjust the length of time spent in refuge to both risk of predation and reproductive cost of refuge use.Communicated by A. Mathis     

Reproductive plasticity in bumblebee workers (<Emphasis Type="Italic">Bombus terrestris</Emphasis>)—reversion from fertility to sterility under queen influence

Worker sterility in the bumblebee Bombus terrestris is conditional and is linked to the social development of the colony. Workers refrain from reproducing or overtly challenging the queen until gyne production has initiated, at the so-called competition point (CP). It is not known whether this behavior is hard-wired or workers show reproductive plasticity. It also remains unclear whether worker reproductive decision is under queen and/or worker control. In this study, we tested worker reproductive plasticity in an attempt to assess whether and under which conditions worker sterility/fertility are reversible. We introduced egg-laying workers into colonies with different social structures for 1 week then monitored their reproductive status. We revealed a remarkable reproductive plasticity in the introduced workers that was social-condition-dependent. In the presence of a pre-CP queen, the introduced workers reverted to sterility, whereas in the presence of a post-CP queen, such workers remained egg-layer. Reversion to sterility does not occur when direct contact with the queen is prevented, as the introduced workers remained egg-layer in the queenright colonies with a confined queen. Egg-laying workers that were introduced into queenless colonies mostly maintained their fertility regardless of colony social phase. This shows that worker transition from cooperative to selfish behavior is reversible depending on the social context.     

Vitellogenesis in the deep-sea shark Centroscymnus coelolepis

At present, information on the reproductive physiology of Centroscymnus coelolepis, which is one of most important and widespread deep-sea shark species, is completely lacking. In this study, we investigated vitellogenesis, a key step in the reproduction biology of fishes. Specimens of C. coelolepis were collected at 2850 m depth in the Western Mediterranean Sea. The size of the collected sharks (range: 35.5–65.0 cm TL) was much lower than those typically reported for the Atlantic and Pacific Oceans. The marked distinctiveness of Mediterranean and Atlantic/Pacific populations was reflected by the achievement of sexual maturity at a smaller size in Mediterranean specimens. The examination of cytoplasmatic components of oocytes indicated that vitellogenin uptake in the ovary started when oocytes reached 14 mm in diameter. Only reproductive females displayed a significant relationship between plasmatic vitellogenin and gonadal development, suggesting that vitellogenesis in C. coelolepis is a discontinuous process. Oestradiol levels were tightly coupled with gonadal development, underlining the importance of this hormone in controlling vitellogenesis. All these findings suggest that vitellogenesis in this yolk-sac viviparous shark might occur with similar mechanisms of oviparous vertebrates.     

Weight comparisons and litter size manipulation in Columbian ground squirrels (Spermophilus columbianus) show evidence of costs of reproduction

I studied reproductive costs in the female Columbian ground squirrel (Spermophilus columbianus) using individually marked animals. I compared weight changes during the active season and over winter, and mortality for females that did and did not wean young. Females raising young were heavier at emergence in that spring than unsuccessful ones. Females that did not raise young gained more weight during summer, were heavier than successful females at the time of entry into hibernation, and were heavier emerging from hibernation the following spring. Over-winter mortality was higher for females that reared young compared to reproductively unsuccessful females. A food supplementation experiment showed that energy-rich food can accelerate individuals’ weight gain. Interactions between litter size, birth weight, weight at emergence from the natal burrow, survival of young to yearling age, and maternal fitness were also studied. Litter sizes were experimentally manipulated to evaluate how females cope with costs of rearing one additional young. Birth weight of juveniles was positively correlated with survival to emergence from the natal burrow and with survival to yearling age. Partial litter loss was higher in experimentally enlarged litters than in either experimentally decreased or control litters. Total litter loss, survival of adult females or the probability of weaning young the following year were not affected by the litter size manipulation. Females appear to adjust the size of their litter before birth, and to some extent during lactation, to their ability to wean young. Received: 20 January 2000 / Received in revised form: 12 March 2000 / Accepted: 18 March 2000     

The effect of sea-water submergence on rhizome bud viability of the introducedAmmophila arenaria and the nativeLeymus mollis in California

Ammophila arenaria, an invasive European beach grass, dominates most United States Pacific coast beaches north of San Francisco Bay, and it appears to severely reduce opportunities for regeneration of native plant species, including American beach grass,Leymus mollis. The knowledge of how longAmmophila rhizomes can survive in sea-water is important for long-tern management strategies, which must consider the probability of reinvasion of areas whereAmmophila has been eradicated. The bud viability of bothAmmophila arenaria andLeymus mollis remained high following submergence in sea-water for 7 days, andLeymus bud viability was still high after 13 days submergence. In fact,Leymus bud viability appears to be enhanced slightly by submergence for 7 days in sea-water. SinceAmmophila rhizomes retain a mean bud viability of >50% following submergence for 7 days, there is clearly the potential for long distance dispersal to other beaches. Even after 13 days of submergence,Ammophila rhizomes still had a mean bud viability of 8.5%. Assuming near-shore current speeds of 5–45 cm/sec, viableAmmophila rhizomes can be transported up to 505 km in 13 days.     

氯代阻燃剂得克隆对孔石莼(Ulva pertusa)繁殖及早期发育的影响

得克隆(Dechlorane Plus,DP)是一种在全世界范围内广泛使用的氯代阻燃剂,具有潜在的毒性效应。但目前已有的生态毒理学数据还十分有限。本文选择分布广泛的大型绿藻孔石莼(Ulva pertusa)作为研究对象,探讨不同浓度DP对孔石莼繁殖细胞转化及早期发育的影响。结果表明,低浓度(10-6~10-8mol·L-1)DP暴露不同程度地影响孔石莼繁殖细胞的形成、释放及附着,在试验浓度范围内呈现一定的剂量效应关系。与空白对照组相比,DP处理(10-6mol·L-1)分别使繁殖细胞的形成率、释放率和附着率显著降低了76.76%、46.26%和85.64%。在丝状幼体阶段,DP处理组(10-8和10-7mol·L-1)幼体体长分别比对照组显著减少了32.74%和38.98%。结果表明,DP暴露抑制了孔石莼的繁殖及早期发育。基于绿藻繁殖特性及早期发育的生物学指标对DP暴露较为敏感,能够为海洋环境的DP生物学效应研究提供数据。     

Long-Term Changes in the State of Gonads in Sea Urchins Strongylocentrotus intermediusfrom Amur Bay,the Sea of Japan

The state of gonads was analyzed in sea urchins Strongylocentrotus intermediuscollected in Amur Bay (Peter the Great Bay, the Sea of Japan) in August 1984, 1985, 1989, and 1997 at five stations: Skrebtsov Island (1), Sportivnaya Harbor (2), Cape Tokarevskii (3), Alekseev Bay on Popov Island (4), and Verkhovskii Islands (5). The first three stations were in the polluted inshore zone of Vladivostok; stations 4 and 5 were in the open (insular) part of the bay, remote from the main sources of pollution. The state of gonads of sea urchins collected in different years and areas strongly varied with respect to gonad index (GI), gonad maturity index, and indices of pathological changes in gonads. As compared with the data obtained in 1984, 1985, and 1989, the values of GI increased in sea urchins from stations 1–3 and decreased in sea urchins from stations 4 and 5. Although GI values were high, the indices of gonad maturity in animals from the coastal zone were very low. In general gonad maturity in sea urchins from the Amur Bay was lower in 1997 than in the previous years. The correlation analysis of long-term data revealed no positive correlation between the values of GI and gonad maturity index in sea urchins from stations 1–4. Histopathological changes were more serious in sea urchins from stations 1–3. In 1997, the indices of pathological changes in the gonads of sea urchins from the insular zone (stations 4 and 5) were higher than in the previous period (1984–1989). The influence of various ecological factors—temperature, salinity, environmental pollution, and food supply—on gametogenesis in sea urchins is discussed.     

海南地区国防仓储防霉研究

海南地区国防仓储霉变情况严重,经抽查部分国防仓库,发现同时生长有十几种孢子,约占5个属性,这在仓储界是罕见的,给物资存储质量带来极大的危害。因此,寻找茵类的生长特点、生活规律,进而采取措施有效地控制菌类的生长繁殖,成为提高仓储物资保管良好率的关键。     

双酚AF对大型溞生殖、生长等生态行为的影响

为了明确双酚AF（BPAF）对水生生物行为的影响,考察了BPAF对大型溞的急性毒性和慢性毒性（生殖、生长、发育、生理等）影响.结果显示,BPAF对大型溞的24h和48h半致死浓度（LC₅₀）分别为9.70mg/L和5.02mg/L.根据化学品分类和标签规范,BPAF属于毒性Ⅱ级.BPAF对大型溞生殖、生长、发育和生理的毒性影响结果表明,高浓度BPAF（100 μg/L）导致大型溞性成熟时间明显延迟,并显著降低了大型溞产卵频次、产卵总数等生殖行为,且对大型溞的生长、发育产生显著抑制现象,同时造成种群繁衍能力显著受损.本文旨在为BPAF对水生生物的生态行为影响提供理论依据.