THE GROWTH AND BREEDING CYCLE OF LITTORINA OBTUSATA (GASTROPODA : PROSOBRANCHIATA) FROM CARDIGAN BAY

The population structure of Littorina obtusata was for mostof the year bimodal, with a stable adult component and an activelygrowing juvenile component. Growth rate of the juvenile componentwas similar at different beach levels and there was a retardationof growth as the snails approached sexual maturity. There was little variation in the histology and external appearanceof the reproductive organs throughout the year and the breedingcycle has been characterized by the amount of spawn laid andthe presence of mature eggs in the oviduct of the female. ^*Present address: Portway School, Penpole Lane, Shirehampton,Bristol. (Received 7 September 1977;     

Endosulfan-enhanced crest induction in Daphnia longicephala: evidence for cholinergic innervation of kairomone receptors

Daphnia iongicephala were reared from early embryogenesis inthe presence or absence of crest-inducing kairomones releasedby Anisops gratus (Notonectidae) and from birth in one of fiveconcentrations of the organochiorine pesticide, endosulfan (0,0.1, 1.0, 10 or 100 g 1^–1 The morphologyof the daphnidswas measured 3 days after birth and on production of the firstbrood of eggs. The reproductive parameters, first brood size,age at first reproduction, mean egg volume and total egg volume,were also measured. Endosulfan significantly induced crest developmentin 3-day-old daphnids at 0.1, 1.0 and 10 g ^1– in thepresence and absence of Anisops kairomone, although crest sizein the absence of kairomone was only marginally greater thancontrols. A concentration of 10 pg 1^–1 endosulfan significantlyenhanced crest growth of kairomone-exposed daphnids at maturity.The Anisops kairomone alone induced a large crest in D.iongicephola,reduced first brood size, mean egg volume and total egg volume,and increased age at maturity. The coefficient of variationof mean egg volume was significantly reduced by Anisops kairomone.It is hypothesized that endosulfan enhances crest developmentbyinhibition of .     

Visualization of Membrane Calcium and Calmodulin in Embryo Sacs in situ and Isolated from Petunia hybrida L. and Nicotiana tabacum L.

We have used chlorotetracycline (CTC) and fluphenazine (FPZ)as fluorescent probes to visualize the distributional patternsof membrane calcium (mCa²⁺) and the Ca²⁺-receptor protein calmodulin(CaM) in various cell types of unfixed living isolated and unisolatedembryo sacs of Petunia hydrida L. and Nicotiana tabacum L. Ourresults indicate that in the young embryo sacs of Petunia, bothsynergids and the central cell sequester relatively higher amountsof mCa²⁺ and CaM than the egg cell and the antipodals. Much of the mCa²⁺ in the synergids is polarized in its distributionin that the mCa²⁺ is higher towards the micropylar end of thesynergids. Interestingly, in the mature embryo sacs of Petuniaonly one of the two synergids and the egg cell proper manifesta higher level of mCa²⁺. In vivo only one of the synergids inthe young as well as in the mature embryo sacs if Nicotianaconsistently show higher mCa²⁺. In the mature embryo sacs of Petunia the level of CaM is almostuniform in all the cell types except that one of the synergidsand the three antipodal cells show a slightly higher level ofCaM. The possible implications of these findings in the late eventsof vectorial orientation of pollen tube tip, pollen-tube-synergidinteractions and sperm delivery mechanism are discussed.Copyright1993, 1999 Academic Press Membrane-Ca²⁺, calmodulin, living embryo sacs, Petunia, Nicotiana, pollen tube-synergid interaction     

Food type induces different reproductive responses in the copepod Centropages typicus

Egg production and hatching success were determined for individualCentropages typicus fed two diatoms (Thalassiosira rotula andPhaeodactylum tricomutum) and two dinoflagellates (Prorocen-trumminimum and Gonyaulaxpolyedrd). Both reproductive responseswere strongly affected by food type. Females incubated withoutmales produced eggs with all diets, but fecundity was twiceas high with the larger T. rotula and G.polyedra cells. In contrast,hatching success was 2–3 times higher with the dinoflagellatediets. The presence of males did not enhance egg productionrates. Males also did not improve hatching success when thediet consisted of the diatom T.rotula. However, egg viabilitywas higher for couples fed the dinoflagellate G.polyedra, indicatingthat egg viability was possibly being controlled by both rematingand food type. Egg viability was artificially lowered by exposingnewly spawned eggs to high concentrations (10⁴–10⁹ pgC) of extracts from T.rotula, whereas the development of eggsproceeded normally at all concentrations of extracts from P.minimum.Blockage of egg development was not due to anoxia, but to thepresence of intracellular, deleterious chemical compounds indiatoms, suggesting that bottom-up prey control mechanisms underlieseasonal fluctuations in C.typicus populations at sea.     

家蚕保存系统红色卵的遗传分析

用遗传背景清楚的家蚕Bombyx mori红卵（re）、白卵(w-2、pe)、第4褐卵（b-4）的标志基因系统和正常型黑卵系统与我国家蚕基因库保存的20个红色卵系统杂交,进行顺反测验,分析了它们的卵色支配基因及遗传规律。结果发现：①在03-310系统中存在家蚕卵色新突变pink egg,与红卵re 等位,基因符号为re^p,表型特征为：卵淡红色,成虫蛾眼也为淡红色;②6个系统为红卵（re）的纯合系统,还有５个系统除具有re／re基因型外,还具有支配白色卵或浅红色或橙红色卵的突变基因;③２个系统为第4褐卵（b4）的纯合系统; ④6个系统的红褐色卵为母性影响遗传;⑤发现家蚕卵色基因b-4和r-e的互补关系,b-4/b-4 re/re基因型表现为新的卵色——橙黄色。     

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 (     

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.     

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.     

Distribution and species-specific egg production of Pseudocalanus in the Gulf of Alaska

Pseudocalanus species are important contributors to the secondaryproduction of the northern hemisphere mid- to high-latitudeoceans. In the coastal Gulf of Alaska, Pseudocalanus are presentyear round and are represented by three species. In 2001, Pseudocalanusmimus was the dominant Pseudocalanus species on the shelf duringspring and summer, comprising 30–100% of the total, whilePseudocalanus newmani dominated in Prince William Sound (10–90%).Pseudocalanus minutus were only abundant in Prince William Soundduring early spring. Egg production (by number and volume) wasa function of female prosome length and decreased from springto summer; however, significant variability was attributableto regional influences that were independent of size. For thesame sized female, P. newmani produced more eggs per clutchthan P. mimus. Pseudocalanus mimus, however, tended to havea larger mean egg size than P. newmani. Consequently, clutchvolumes of the two species were indistinguishable. Pseudocalanusegg production rates (EPRs) (eggs female^–1 day^–1)were lower in July and August (ca. 2–4) than April andMay (ca. 1–9), but total egg production by the population(eggs day^–1) was nearly equivalent for the two time periodsdue to higher female concentrations in summer.     

Primary structure of 12 neutral oligosaccharide-alditols released from the jelly coats of the anuran Xenopus laevis by reductive {beta}-elimination

The O-linked oligosaccharides of the jelly coat surroundingthe eggs of Xenopus laevis were analysed by ¹H-NMR spectroscopy.Among the 12 neutral oligosaccharide-alditols which have beencharacterized, three of them posses the following unusual structures,As previously observed for six other amphibian species, thecarbohydrate chains of the jelly coat of Xenopus eggs displaya high species specificity which could support a biologicalrole during the fertilization processes. amphibian egg jelly coats ¹H-NMR oligosaccharide structure Xenopus laevis     

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.     

Zooplankton community structure and copepod egg production in coastal waters of the central Great Barrier Reef lagoon

We describe zooplankton community structure and copepod eggproduction in the vicinity of the coastal boundary zone of theGreat Barrier Reef lagoon, Australia. The abundance and eggproduction rate of constituents of the zooplankton assemblagecharacteristic of the coastal zone rapidly increase subsequentto events such as flooding and upwelling. Our sampling spannedtwo summer monsoonal seasons, the first of which (1990-91) wasvery wet. The second monsoonal season (1991-92) was very dryand was characterized by intrusive upwelling events from theCoral Sea. Chlorophyll a concentrations did not rise in thewet year, probably because of light limitation, but did riseas a result of upwelling. Terrestrial run-off in the wet yearhad a greater apparent effect on zooplankton abundance patternsthan did upwelling in the dry year, except where coastal trappingallowed sufficient time for increases in zooplankton abundanceto occur. Egg production rates by the copepods Acrocalanus gibberand Acrocalanus gracilis showed haphazard spatial differences.Nitrogen-specific egg production ranged between 0.03 and 0.21day^–1 for A.gibber, and between 0.13 and 0.41 day^–1for A.gracilis. The egg production rate by A.gibber was foodlimited for most of the year and showed a poor correlation withtemperature. ³Present address: Department of Biological Sciences, FloridaTech, 150 W University Boulevard, Melbourne, FL 32901, USA     

Egg production, growth and development of the cyclopoid copepod Oithona similis

Egg production, growth and development rates of Oithona similiswere measured in the laboratory as a function of food concentrationand composition. On an optimum diet, development is isochronaland growth is near exponential. The maximum juvenile growthrate at 15C (0.2 day^–1) is similar to juvenile growthin calanoid copepods. The maximum weight-specific egg productionrate (0.1 day^–1), on the other hand, is substantiallyless than in free-spawning calanoids, but similar to that inegg-carrying calanoids. In the Kattegat, Oithona spp. egg productionis strongly limited by food during summer and controlled bytemperature during winter. The seasonal signal in fecundityand population biomass is much weaker than in the co-occurringfree-spawning calanoid genera, where fecundity and populationbiomass undergo dramatic seasonal viaration. ¹Present address: Instituto Nacional de Investigacin y DesarrolloPesquero, INIDEP, CC 175, Playa Grande, Mar del Plata, Argentina     

不同温度下的甜菜夜蛾实验种群生命表研究

组建了甜菜夜蛾Spodoptera exigua在5种温度下的实验种群生命表。结果表明：在20～32℃,甜菜夜蛾的发育速率随着温度的升高而加快,并符合Logistic模型;甜菜夜蛾卵、幼虫、蛹、产卵前期及世代的发育起点温度分别为13.73℃、15.68℃、15.09℃、12.83℃和15.06℃,有效积温分别为37.9、126.3、73.8、29.2和265.6日·度;甜菜夜蛾在26℃时世代存活率和种群增长指数最高,分别为55.2%和205.9,20℃时不利于种群增长;在26℃和29℃时,甜菜夜蛾的平均产卵量最高,分别为604.7和611.4粒/雌,26℃是甜菜夜蛾最适宜交配的温度,交配率为84.9%,平均精包数为2.46个/雌;高温条件下,甜菜夜蛾的成虫寿命、产卵前期和产卵期均缩短;甜菜夜蛾的世代存活率(S)和种群趋势指数(I)与温度（t）的关系均可用二次抛物线表示：S=-0.5056 t²+27.652 t-326.02 (r=0.91),I=-3.2532t²+178.45 t^-2 270.40 (r=0.94)。     

Seasonal variation of reproduction rates and body size of Calanus sinicus in the Southern Yellow Sea, China

Annual variations of egg production rate (EPR) and clutch sizeof Calanus sinicus, as well as body size of females (prosomelength and dry weight), were investigated at a series of stationsin the Southern Yellow Sea by onboard incubation. Calanus sinicuswas spawning in all the 11 cruises investigated, and the annualvariation of EPR was bimodal. Monthly average EPR was highestfrom May to July, respectively, 5.97, 5.36 and 6.30 eggs female^–1d^–1, then decreased dramatically to only 1.37 eggs female^–1d^–1 in August and attained the lowest 1.07 eggs female^–1d^–1 in October. In November, average EPR increased againto 4.31 eggs female^–1 d^–1. Seasonal variation ofclutch size was similar to EPR, except that it decreased graduallyafter August rather than dramatically as did EPR. Prosome lengthof females was maximum in May and minimum in October, but dryweight was highest in November. Monthly average EPR correlatedbetter with prosome length than dry weight, while clutch sizewas rather determined by dry weight of females. It is suggestedthat egg production of C. sinicus was active during two discontinuousperiods when both surface and bottom temperature fell into itsfavorite range (i.e. 10–23°C), and different reproductivestrategies were adopted in these two reproductive peaks: otherthan the highest EPR, longer prosome length was also achievedby C. sinicus from May to July, while females in November developedshorter bodies but accumulated more energy for reproduction.     

Herbivorous nutrition of Cyclops vicinus: the effect of a pure algal diet on feeding, development, reproduction and life cycle

Nutritional requirements, functional response, development andreproduction of Cyclops vicinus were studied with exclusivelyalgal food. Phytoflagellates were found to be adequate foodresources for both juvenile development and egg production.Ingestion measurements were performed with Chlamydomonas reinhardii.The functional response data give evidence for low feeding efficiency,especially for the naupliar stages. A difference between naupliiand older instars was also found in their quantitative foodneeds. A higher threshold food concentration was observed fornaupliar development (0.4 mg C l^–1) than for copepoditedevelopment (0.2 mg C l^–1). The calculation of assimilationefficiencies suggests that the high food requirements are dueto low specific ingestion rates rather than poor assimilationefficiency. Development time decreased as algal density increasedand males developed more quickly than females at all food concentrations.Body size and carbon content increased with increasing foodconcentration. Continuous egg production was observed abovea food concentration of 0.5 mg C l^–1. The results haveimplications for the life cycle of C. vicinus. Summer diapauseis interpreted as a strategy to avoid starvation of the juvenilestages. The facultative herbivory of the adults might be anadvantage when competing against other more carnivorous cyclopoidcopepods. ¹Present address: Agricultural University of Wageningen, Departmentof Mathematics, Dreijenlaan 4, NL-6703 HA Wageningen, The Netherlands     

Egg size and clutch size in two Daphnia species grown at different food levels

The effect of three different Scenedesmus food concentrations(0.04, 0.2 and 1 mg C l^–1) on maternal investment wasstudied in two cladoceran species of similar size, Daphnia pulicariaand D.hyalina. It was observed that as food concentration decreased(between 1 and 0.2 mg C l^–1), there was an increase insize, protein content, lipid content, carbon and mass of theegg, while, at the same time, the clutch size of the femalesbecame smaller. Such an increase in ‘per offspring investment’was reflected in an increase in body length, body carbon andbody mass of neonates as the food available for females decreased.However, in D.pulicaria this tendency was not maintained downat 0.04 mg C l^–1 in which there was a decrease of theegg characteristics mentioned above. Although, there are notavailable all the egg and neonate parameters of D.hyalina at0.04 mg C l^–1, the body length of the neonates was largerthan at 0.2 and 1 mg C l^–1. These results show that, asfood diminishes, these two cladoceran species are able to respondby decreasing clutch size, but increasing the size of egg, therebyincreasing the probability of neonate survival. This tendencyis probably maintained until the food concentration is too lowand the females have to reduce the energy allocated for reproduction.     

Calcium limitation in Daphnia magna

The role of ambient calcium concentrations on survival, moulting,growth and egg production was assessed in the cladoceran Daphniamagna. A threshold for survival was found in the range 0.1–0.5mg Ca l^–1, even when ionic strength of the medium waskept constant. Accumulated length and length specific dry weightwas retarded at low Ca (0.5–1.0 mg Ca l^–1) at foodconcentrations above incipient limiting level. For lower foodlevels, the effect of Ca on growth was less clear. The effectof low Ca on growth rate was most manifest during the firstdays after hatching, reflecting the higher Ca demands of theearly juveniles. Age-specific egg production was strongly reducedat Ca concentrations <10 mg Ca l^–1. This was partlyan indirect effect of reduced growth rates, but could also bean effect of higher energetic costs associated with Ca uptakein a Ca-poor medium. The high Ca demands in D.magna may notbe representative of other Daphnia species. Nevertheless, highspecific Ca content seems to be a common property of Daphniaspp. and Ca deficiency could be a major determinant of speciessuccess and community structure among crustacean zooplankton;it also puts constraints on carbon sequestration in the pelagicfood web of softwater lakes.     

Laboratory study of the spawning rate of the calanoid copepod Centropages typicus: effect of fluctuating food concentration

The spawning rate of laboratory-reared Centropages typicus fedHymenomonas elongala increases with food concentration, up toa value of {small tilde}2800 µg C (16 500 cells) ml^–1.An alternation of a low food (1000 cells ml^–1) and highfood concentration (16 500 cells ml^–1) is not favourableto egg release when its periodicity is 1 or 2 days, whereasit may be of advantage if it is longer (3–6 days). Inthe latter case, Centropages typicus will benefit best fromthe rich food diet if this coincides with (or just follows)the last moult.     

TENACITY OF ATTACHMENT IN TWO SPECIES OF LITTORINID, LITTORINA LITTOREA (L.) AND LITTORINA OBTUSATA (L.)

Here we present data concerning the ability of two littorinidsto remain attached to a slate substratum as a dislodging forceis applied vertically. Specimens of Littorina littorea (L.)and L. obtusata (L.) were attached to a simple pulley and sandflowsystem which applied force to the animals at a constantly increasingrate until the animals released from the substratum. Three aspectsof tenacity were measured: force required to remove the winklesfrom the substratum; time taken for removal; and final displacementat removal. For L. littorea the mean force required (1.09 N),the mean displacement (8.9 mm) and the mean time taken (185s) were all found to be significantly greater than those recordedfor L. obtusata (means = 0.60 N, 7.5 mm and 102 s, respectively).However, when animal size was taken into account there was nosignificant difference in either force or time required forremoval, although L. obtusata showed a greater displacementthan did L. littorea. Animal dry flesh weight was not a usefulpredictor of any of the tenacity variables. Rugosity of theslate substrata was shown to have a significant effect on alltenacity variables, greater forces being required to removeboth species of winkle from smooth substrata than from roughsubstrata. This also generally held true when animal size wasaccounted for. The results of these experiments, although insufficientto identify the mechanism(s) of attachment, do discount themechanism of ‘muscular grip’, since greater tenacitywould be expected on rough substrata. Whether winkles were immersedor emersed had no significant effect on any of the tenacityvariables. Recorded tenacities suggest that many L. littoreaand L. obtusata would be dislodged by the direct forces createdby breaking waves. (Received 5 August 1996; accepted 18 November 1996)