Summer reproduction of the planktonic copepod Calanus sinicus in the Yellow Sea: influences of high surface temperature and cold bottom water

We have observed that Calanus sinicus retreated from neriticareas in the Yellow Sea and concentrated in the Yellow Sea ColdBottom Water (YSCBW) area in summer. To investigate the summerreproductive strategy of C. sinicus in this situation, effectsof high temperature on reproduction and hatching, as well asgeographical variation of in situ egg production rate, werestudied by onboard incubation in August 2001. Diel verticalmigration (DVM) of females was investigated within and outsidethe YSCBW, respectively. Onboard incubation at 27°C (i.e.surface temperature) resulted in lower fecundities than thatat 9.8 and 12°C (i.e. bottom temperature inside and outsidethe YSCBW) together with decreased hatching rates and increasednaupliar malformation. Egg production was more active at stationsoutside the YSCBW than inside, where chlorophyll-a concentrationwas also relatively low. Females inside the YSCBW underwentDVM although they rarely entered the surface layer, but DVMwas not observed outside the YSCBW. We conclude that surfacetemperature in summer has deleterious effects on C. sinicusegg production and hatching, and that it cannot reproduce successfullyover the whole area. Inside the YSCBW, egg production is depressedby low food availability, while females outside suffer fromhigh temperatures because of strong vertical mixing.     

Pigment ingestion and egg production rates of the calanoid copepod Temora longicornisr. implications for gut pigment loss and omnivorous feeding

We examined the relationship between egg production rate (E)and pigment ingestion rate (I, from gut content corrected for33% loss) for adult female Temora longicornis in Long IslandSound on 47 occasions. Linear regression of E on I [both variablesexpressed in mass of nitrogen (N) female^–1 day^–1]was: E_N = 0.0016 + 0.770 x I_N. The slope, 0.77, is the apparentgross efficiency of egg production, equivalent to the grossgrowth efficiency (GGE) assuming that females partition allnitrogen for growth into egg production. Published work suggeststhat a GGE of 0.37 would be expected for herbivorous copepods.The discrepancy between the expected value of 0.37 and observedvalue of 0.77 could result from unquantified losses of gut pigmentor because T.longicomis ingested a significant amount of nitrogenby feeding as a carnivore. We suggest that if T.longicomis femalesderive all of their nitrogen for growth by feeding on phytoplankton,and if no correction for pigment loss is employed, then thegut pigment method underestimates pigment ingestion by no morethan a factor of two.     

Measuring production and viability of eggs in Calanus helgolandicus

The effect of several biotic and abiotic factors on the fecundityand hatching success of Calanus helgolandicus was tested duringshort- and long-term incubations. The results show that thevariations of the reproductive responses of C.helgolandicusare time dependent and rely on the type of factor tested. Whenstandardized over a 24 h incubation period, estimates ofin situproduction and egg viability can be obtained with good accuracy.     

Egg production and hatching success in the calanoid copepods Calanus helgolandicus and Calanus finmarchicus in the North Sea from March to September 2001

Spatial and seasonal egg production rates (E_r) and egg hatchingsuccess in the copepods Calanus finmarchicus and Calanus helgolandicuswere measured in the North Sea from March to September. Foodavailability was monitored by chlorophyll and protist concentrationsand three size fractions of seston fatty acids. Seasonal andspatial distribution and production differed between the species.Calanus finmarchicus was found only offshore of the 50-m isobath,with decreasing E_r (37–28 eggs female^–1 day^–1)from March to July. Calanus helgolandicus had two abundancepeaks, in spring and autumn, with a low in May during whichtime the highest E_r were observed (38 eggs female^–1 day^–1).At other times, E_r in C. helgolandicus remained lower than inC. finmarchicus (     

THE RELATIONSHIP OF BODY SIZE AND GROWTH TO EGG PRODUCTION IN THE HERMAPHRODITIC FRESHWATER SNAIL, HELISOMA TRIVOLVIS

Among several other factors, body size has been found to influenceegg production in several species of hermaphroditic snail. Wetested whether this relationship between body size and egg productionexists in Helisoma trivolvis, a freshwater hermaphroditic species.We isolated 50 H. trivolvis from a laboratory population, measuredshell diameter, and monitored egg production for seven weeks.We found a positive relationship between body size and totalnumber of eggs produced, as well as body size and number ofeggs per egg mass. When body size and egg production are linked,it should be adaptive for larger individuals to act as femalesand smaller individuals as males. Since body size is relatedto female fecundity in this species, the relative size of snailsshould determine, at least in part, which individual acts asmale and which as female during copulation. However, the relationshipbetween body size and egg production is not nearly as strongas it is in other snail genera. Other factors such as age, genotypeand previous experience may be important in determining egg-layingcapacity and therefore gender choice in this species. In addition,we found a negative relationship between growth during thisperiod and egg production. This relationship has been foundin other pulmonates, and is evidence of resource allocationtradeoffs. (Received 3 August 2004; accepted 2 August 2005)     

Measuring the precision of estimates of total egg production based on plankton surveys

Methods are given to measure the effects of spatial and temporaldifferences in egg production on the precision of estimatesof total seasonal egg production derived from ichythyoplanktonsurveys. The techniques are applied to the results of largescale plankton surveys conducted in 1977 and 1979 off the northeasternUSA. For the three species analyzed (Atlantic mackerel, Scomberscombrus; silver hake, Merluccius bilinearis and yellowtailflounder, Limanda ferruginea). the surveys produced estimatesof total egg production having an average coefficient of variationequal to 31%. Estimates of spawning stock size based on theegg production estimates compared favorably with other independentassessments of stock size. ^*MARMAP Contribution MED/NEFC 83–39.     

An intermediate in the phytylation of chlorophyllide a in vivo

The chromatogram of the extract from etiolated bean leaves illuminatedfor 1 min showed a single peak of chlorophyllide a. On subsequentdark incubation of the leaves for 5 min, an intermediate bandappeared in the chromatogram. During 2 hr of incubation, thecontent of the intermediate first increased, then decreasedand was finally transformed completely to chlorophyll a. (Received September 30, 1974; )     

Production of 2n Gametes in Diploid Subspecies of Dactylis glomerata L. 2. Occurrence and Frequency of 2n Eggs

Whereas polyploidy has been found in more than half the Gramineae,the occurrence of 2n gametes, a potentially major mechanismof polyploid production, has been rarely studied. In the presentwork, the frequency of 2n egg production in nine diploid (n= 2x = 14) subspecies of the polyploid complex Dactylis glomeratahas been estimated by determining the ploidy level of the progenyin 98 2X-4X crosses. The 2n egg origin of the 4X offspring wasverified using enzyme markers. The frequency of 2n egg productionin each subspecies was estimated from the number of 4X offspring,the number of florets in the seed plant and the fertility ofthe subspecies. The ploidy level of the progeny was determinedby chromosome counts or nuclear DNA quantification using flowcytometry. Plants producing 2n eggs were detected in 47% ofthe fertile crosses, involving eight subspecies. Variabilitywas related to individuals and not to subspecies. Average 2negg frequency was 0·49% for all crosses, and 1·53%for crosses where 2n egg production was detected. Individualfrequencies did not exceed 3·5%, with the exception of26% in one plant. Triploid block was higher and fertility, frequencyof high 2n gamete producers and average 2n gamete frequencywere lower in the 2X-4X crosses than in the opposite 4X-2X crossesinvolving the same plants, previously studied. Diplogynous anddiplandrous gamete production were not correlated with eachother. However, the widespread occurrence of plants producingboth kinds of 2n gametes in almost all the studied subspecies,as well as the presence of several individuals able to producehigh rates of 2n eggs or 2n pollen, support the hypothesis thattetraploids can be formed anywhere and anytime by sexual polyploidizationin diploid populations of Dactylis glomerata L. 2n eggs, polyploidy, Dactylis glomerata L., flow cytometry, sexual polyploidization     

Seasonal and fine-scale spatial variations in egg production and triacylglycerol content of the copepod Acartia tonsa in a river-dominated estuary and its coastal plume

We measured egg production rates of the estuarine calanoid copepodAcartia tonsa in Mobile Bay, an estuary in the northern Gulfof Mexico. Two stations were sampled approximately monthly,one at the mouth of the bay and the other just beyond the mouthin the salinity front between bay and coastal waters. Over thewhole year, temperature was the most important environmentalvariable controlling egg production. Rates increased with temperatureup to 30°C and 140 eggs female^–1 day^–1. We foundno evidence of food limitation. There was no correlation betweenegg production and phytoplankton abundance, nor increased eggproduction in response to supplements of phytoplankton addedto natural food, suggesting that non-phytoplankton food wasimportant in the diet. At the highest egg production rates,the amount of the storage lipid triacylglycerol (TAG) in adultfemales was greatly diminished, to <50 ng female^–1.This suggests that lipids in the diet can be very tightly coupledto egg production. Both egg production and TAG content of femalesshowed significant variability on spatial scales of 3–15km, especially in relation to the salinity front separat ingwater outwelling from the bay from open coastal water. For organismsthat are using copepods and their eggs as food, this variabilitywould result in a heterogeneous food environment, both in termsof the abundance of food and its nutritional content.     

Fitness costs and benefits of antipredator behavior mediated by chemotactile cues in the wolf spider Pardosa milvina (Araneae: Lycosidae)

Animals may exhibit a variety of defensive behaviors in thepresence of indirect predator cues. Such behavior offers immediatefitness benefits but may also incur substantial foraging andreproductive costs. We measured shifts in space use (verticalclimbing) by the wolf spider Pardosa milvina induced by chemotactilecues (silk and excreta) from a co-occurring predatory wolfspider Hogna helluo. We then measured foraging and reproductive costs, as well as survival benefits, of this behavior. For 2weeks, we maintained mated adult female Pardosa in plasticcontainers with one of three treated peat moss substrates:a container previously occupied by a conspecific for 3 days,a container previously occupied by an adult Hogna for 3 days,and a container devoid of either cue (control). We measuredprey capture efficiency, body condition, egg sac production,egg sac weight, and egg number for individuals in each treatment.We also counted the number of Pardosa that survived and exhibitedclimbing behavior in the presence of a live Hogna with andwithout silk and excreta cues. Pardosa climbed container wallssignificantly more often in the presence of Hogna silk andexcreta relative to other treatments. Pardosa exposed to Hognacues coupled with live Hogna survived significantly longerthan spiders that had no predator cues available. Pardosa placedin containers with Hogna cues, but no Hogna, lost weight morequickly, ate fewer prey, were in poorer body condition, producedlighter egg sacs, and produced fewer eggs than spiders in controlor conspecific treatments.     

空心莲子草叶甲室内大量繁殖研究

为了大量繁殖供环境释放的空心莲子草叶甲Agasicles hygrophila以实现空心莲子草区域减灾, 我们探索出室内大量饲养与繁殖空心莲子草叶甲的方法与流程, 包括用叶片法或苗水培法孵化卵粒、用盒养法饲养各龄幼虫与成虫并供成虫产卵、用栽培活苗笼养法化蛹羽化。在室内成虫终日均能取食、交配、产卵, 产卵前期约4～5 d, 产卵高峰期在羽化后第7～24 天, 每雌平均产卵21.08块, 约570粒。盒养法叶片平均可着卵4.28块, 叶背与叶面着卵量相近; 笼养法叶片平均着卵为1.46块, 卵主要产于叶背。盒养法与笼养法得到的卵孵化率分别为94.02%与92.50%。空心莲子草叶甲除化蛹需在栽培活苗上完成外, 各龄幼虫与成虫均可用离体新鲜苗盒养法密集饲养。初孵1龄幼虫转株（叶）期、3龄老熟幼虫转化蛹苗期是室内大量饲养与繁殖空心莲子草叶甲的关键时期, 高密度成功饲养与繁殖空心莲子草叶甲的最适化蛹接虫量是每株8头, 产卵期雌虫的最适密度是每株5头。     

Comparative Thermal Physiological Ecology of Syntopic Populations of Cacama valvata and Tibicen bifidus (Homoptera: Cicadidae): Modeling Fitness Consequences of Temperature Variation

SYNOPSIS. This paper develops a model based on egg-laying ratesand female oviposition temperature preferences in two speciesof cicada, Cacama valvata and Tibicen bifidus, from a centralNew Mexico desert grassland habitat. Output from the model indicatesthat C. valvata achieves maximal daily egg production (eggsfemale^–1 day^–1) on days when maximum shade ambienttemperatures reach 41°C; the corresponding value for T.bifidus is 33°C. These differences correlate with the thermalregime experienced by each species in its respective typicalhabitat. Simulations of the effects of variation in mean habitatambient temperature on egg production demonstrated that knowndistributional limits for T. bifidus correspond to thermal conditionsthat reduce daily egg production by only about 5–10% relativeto long-term means at the study site. The same is true for C.valvata only in lower-ambient temperature habitats. In higher-temperaturehabitats, C. valvata exhibits an unusual plasticity in the timingof adult activity and reproduction that allows it to occupya much wider geographic range than T. bifidus. Contrary to expectations,frequency distributions of predicted daily egg production rateswere negatively skewed in each species' respective ‘typicalhabitat’, and Gaussian only in thermally marginal habitats.The findings are discussed in the context of attempts to modelpopulation- and community-level effects of climatic change.     

Physiology and population structure of Calanus finmarchicus (Copepoda: Calanoida) during a Lagrangian tracer release experiment in the North Atlantic

A population of Calanus finmarchicus was followed in the opensea for a period of 10 days at the end of June 1996 using atracer release method. Gut fluorescence, egg production, carboncontent and stage specific abundance, together with phytoplanktonconcentration and composition, were measured during this period.Chlorophyll levels were less than 1 µg l^–1 and thephytoplankton population was dominated by coccolithophorids.Gut fluorescence decreased during a period with strong winds,whereas egg production remained constant. Estimated phytoplanktoningestion was too low to cover egg production requirements.However, the microzooplankton concentration seemed to be highenough to complement phytoplankton ingestion, enabling egg productioncarbon requirements to be covered. C/N ratios of adult femalesand stage CV were low, indicating low levels of lipid storage.The population was dominated by stage CIV, but shifted to adominance of younger stages during the study. Mortality calculatedfrom population structure indicates that higher death ratesoccurred at stage CV.     

THE LIFE-CYCLE AND REPRODUCTIVE ACTIVITY OF ACHATINA FULICA (BOWDICH) IN LABORATORY CULTURE

The life-cycle, growth characteristics and reproductive activityof Achatina fulica were studied in laboratory culture. Six generationshave been completed. Sexual maturity is reached as early as5 months of age, with a peak in egg production between 210–270days. Egg clutches contain 100–200 eggs which hatch synchronouslywithin a 24-hour period. The incubation period (days betweenoviposition and hatching) was determined exactly. The rangeof incubation times was 1–25 days, due to a variable degreeof ovoviviparity exhibited by the snail. The success of laboratoryculture provides a basis for experimental studies in developmentalneurobiology utilizing Achatina fulica. ^*Present address and to whom correspondence should be addressed:Jerry Lewis Neuromuscular Research Center, UCLA School of Medicine,Los Angeles, California 90025 U.S.A. (Received 14 February 1983;     

The evolution of egg size in the brood parasitic cuckoos

We compared genera of nonparasitic cuckoos and two groups ofparasitic cuckoos: those raised together with host young ("nonejectors")and those in which the newly hatched cuckoo either ejects thehost eggs or chicks, or kills the host young ("ejectors"). Nonejectorsare similar to their hosts in body size and parasitize largerhosts than do ejectors, which parasitize hosts much smallerthan themselves. In both types of parasite, the cuckoo's eggtends to match the host eggs in size. To achieve this, nonejectorshave evolved a smaller egg for their body size than have nonparasiticcuckoos, and ejectors have evolved an even smaller egg. Amongejector cuckoo genera, larger cuckoos have larger eggs relativeto the eggs of their hosts, and the relationship between cuckooegg volume (mass of the newly-hatched cuckoo) and host egg volume(mass to be ejected) did not differ from that predicted by weight-liftingallometry. However, comparing among Cuculus cuckoo species,the allometric slope differed from the predicted, so it is notclear that egg size is related to the need to give the cuckoochick sufficient strength for ejection. Comparing the two mostspeciose ejector genera, Chrysococcyx cuckoos (smaller and parasitizedome-nesting hosts) lay eggs more similar in size to their host'seggs than do Cuculus cuckoos (larger and parasitize open cup–nestinghosts). Closer size-matching of host eggs in Chrysococcyx mayreflect the following: (1) selection to reduce adult body massto facilitate entry through small domed nest holes to lay, and(2) less need for a large egg, because longer incubation periodsin dome-nesting hosts allow the young cuckoo more time to growbefore it need eject host eggs.     

Laboratory studies on egg and faecal pellet production of Centropages typicus: effect of age, effect of temperature, individual variability

The rates of egg production of individually reared females ofCentropager typicus have been observed from the moulting C5-adultto death under constant conditions of food (10 000 cells ml^–1of Hymenomonas elongara) and temperature (15 and 20°C).Preliminaiy experiments showed that virgin females could produceunfecunded eggs, but that the distinctive spines of the eggsof C.typicus were only obtained after fecundation occurred.High and continuous egg production needs several matings, andthe following experiments were run with a couple. In all experiments,both males and females fed and produced faecal pellets. Thefemales show a high variability in spawning life periods, inspawning rhythms, in daily rates and, consequently, in cumulatednumbers of eggs spawned during their life. The highest dailyrates of egg production were obtained in the first half of thefemale's life, and were as high at 20°C as at 15°C.Nevertheless, the females survived longer at 15°C than at20°C, and finally produced 47.6% more eggs during theirwhole life at 15°C than at 20°C, which can be partiallydue to the difference in size (almost 10% bigger at 15°Cthan at 20°C). The production of faecal pellets occurredduring the whole of life and was more regular than egg production,with a maximum daily rate in the first part of life, and showeda decrease until death. The decline in daily egg productionwith age was parallel to the decrease in daily faecal pelletproduction. The daily production of faecal pellets was higherat 15°C than at 20°C. At 20°C, a good correlationwas observed between the total egg production per female andthe total faecal pellet production per female. The individual-basedegg production rates of our experiments have been compared withrates obtained in different conditions by several authors, andwere lower than in other published studies, probably due tothe food offered. We emphasize the difficulties of comparingresults which have been obtained for the entire life of thefemales with those based on daily egg production. The totalegg production of a female is an important parameter in regardto the population d because it fixes the maximal rate of losses(mortality plus dispersion) for which a population can continueto develop.     

Reproductive biology of the planktonic copepod Paracalanus sp. in the Inland Sea of Japan

Egg production of the planktonic copepod Paracalanus sp. wasinvestigated both in the laboratory and in the Inland Sea ofJapan. Its spawning varied daily, but not always, being highestduring the night or around dawn. The egg size was correlatedpositively with female body size. Under food-satiated laboratoryconditions, the specific egg production rate increased exponentiallywith an increase of temperature from 5.0 to 17.5°C, beyondwhich the rate decreased. However, the egg production rate ofthe natural population did not decrease up to     

Temporal variability in copepod fecundity during two different spring bloom periods in coastal waters off Plymouth (SW England)

The temporal variation in egg production of the planktonic copepodsCalanus helgolandicus, Temora longicornis and Pseudocalanuselongatus was studied during two different spring bloom periodsin 1989 and 1990 by weekly sampling at two permanent stationsin coastal waters off Plymouth (SW England). Copepod egg productionwas estimated in situ by incubating individual adult femalesin filtered seawater for 24 h (72 h until hatching for P.elongatus)at the field surface temperature. The relationship between copepodegg production rates and: (i) chlorophyll a concentration (totaland >10 µm size fraction), (ii) temperature and (iii)initial copepod gut pigment content was investigated. The springbloom periods were very different in both years, with the occurrenceof a Phaeocystis sp. bloom in 1990, which negatively affectedthe feeding and fecundity of copepods. Egg production ratesin spring 1989 were significantly correlated with chlorophylla concentration (particularly with the >10 µm fraction),field temperature and copepod gut pigment contents. In spring1990, egg production rates were also correlated with copepodgut pigment contents, but no significant correlations were obtainedwith temperature or with chlorophyll a concentration, as a consequenceof the lower egg production rates obtained during the Phaeocystissp. dominance period. These results show that food availabilityis the factor which mainly affects the fecundity of neriticcopepods in short time periods.     

紫薇毡蚧种群生物学特性研究

该文报道紫薇毡蚧EriococcusLagerostroemiae Kuwana的种群生物学特性。该虫80年末传入贵州,在贵阳地区每年发生3-4代,世代重叠极重,越冬代是第3、4两代的混合群体,越冬虫态有卵、若虫和蛹。分别估测了卵、雄若虫、蛹、雌若虫和雌成虫的发育起点温度(T₀)和有效积温(K)。周年虫口变动有两个高峰：6月中旬至7月上旬和8月上旬至9月上旬。11月至翌年4月,因寄主休眠和低温导致虫口缓慢下降。雌成虫产卵量与寄主生长势好坏有关。控制紫薇毡蚧虫口最有效的天敌是红点唇瓢虫Chilocoruskuwanae Silverstri。药液涂干并辅之具内吸作用的杀虫药液灌根是目前较好的药剂防治方法。     

Egg production rates and stage-specific development times of Clausocalanus furcatus (Copepoda, Calanoida) in the northern Gulf of Mexico

The calanoid copepod Clausocalanus furcatus is widely distributedin tropical and subtropical oceans, yet knowledge of its reproductionand development remains limited. We estimated egg productionrates and stage-specific development times from laboratory incubationsand field samples collected at a petroleum platform in the northernGulf of Mexico. Egg production experiments were performed in2002 and 2003 at a laboratory on the platform using freshlycollected female copepods. Median stage development durationswere also measured during the incubations. Logistic regressionmodels were used to estimate median stage durations. The mediandevelopment times of Clausocalanus furcatus from hatching toadulthood ranged from 13 to 20 days. Field samples were collectedfrom waters beneath the platform at 12-h intervals using a 30-LNiskin water bottle during March–April and May–June2003, and the Edmonson egg ratio method was used to estimatethe mean in situ egg production rate. This field-derived meanegg production rate was significantly lower than the 12.08 eggsfemale^–1 day^–1 measured from incubation experiments,and this difference may reflect high in situ egg mortality.In situ egg production rates also showed high variability andwere almost five times higher during March–April comparedto May–June.