Life history traits of Aedes caspius (Diptera: Culicidae): a laboratory study of larval stages

The larval survival and development times of Aedes caspius (Diptera: Culicidae) were examined in the laboratory. These life history traits were estimated using life tables constructed for two populations, one of which had been subjected to a long-term larvicide control program. Traits were evaluated for eight different population densities. The effects of population, larval stage and larval density were investigated using a general linear model. Density was positively correlated with larval survival but did not affect development time. The fourth instar and pupae had the lowest larval survival rates. First and fourth instar larvae had the longest development times. These traits were not significantly different between the two populations. The effect of larvicide control on these traits is discussed.     

The potential for mitten crab Eriocheir sinensis H. Milne Edwards, 1853 (Crustacea: Brachyura) invasion of Pacific Northwest and Alaskan Estuaries

Eriocheir sinensis H. Milne Edwards, 1853 is on the list of top 100 invaders compiled by the International Union for Conservation of Nature and Natural Resources. The recent establishment of a large Chinese mitten crab population in San Francisco Bay and the potential for introductions from California, Asia and Europe pose a significant invasion potential for estuaries and rivers from California to Alaska. This alien species would place at risk the catchment areas of the Pacific Northwest including the economic and social activities that depend upon intact aquatic systems. An analysis of ecological conditions that define the mitten crab’s native and introduced range suggests that large stable estuaries with long flushing times are necessary to sustain significant populations. Most Pacific Northwest estuaries have limited salinity intrusion, estuarine habitat and short flushing times and face a reduced risk of population establishment. Large, stable estuaries, such as the Puget Sound, may support significant populations. River-dominated estuaries, such as the Columbia River, have flushing times less than the duration of larval development and wouldn’t support populations. An application of a temperature based larval development rate to near-shore and estuary sea surface temperatures suggests that estuaries in Oregon and Washington have sufficient thermal regimes to support larval development. Most estuary systems in Alaska have limited periods where water temperatures are above the mortality threshold for the larval stages and are at a low risk for the establishment of populations. A potential sea temperature rise of two degrees Celsius would permit larval development in Alaskan estuaries, where sufficient estuarine and freshwater habitats exist.     

Early developmental stages of greasyback shrimp,Metapenaeus ensis (de Haan, 1844) (Crustacea, Decapoda, Penaeidae)

Metapenaeus ensis was spawned and laboratory cultured untilthe post-larval stage to illustrate and describe its embryonicand larval development. Fecundities ranged between 454 000 and689 000 eggs, and {small tilde}99.2% of spawned eggs hatchedafter 12 h and 40 min at 33.5 p.p.t. and 29.0-29.1°C. Sixnaupliar, three protozoeal, three mysis and one post-larvalstages were noted. A minimum of {small tilde}10 days (249 h20 min) from the time of hatching were required to completethe larval stages by subsisting only on Chaeioceros gracilisand Tetraselmis tetrathele at varying temperature and salinityof 28.1-29.8°C and 33.5—34.5 p.p.t., respectively.The embryonic and larval developmental stages of M.ensis aregenerally similar to those of other known penaeid species, exceptfor the size and structure of diagnostic characters, setationof appendages and duration of metamorphoses.     

Sensitivity to larval density in populations of Drosophila mojavensis: Influences of host plant variation on components of fitness

Summary Chromosomally polymorphic populations of Drosophila mojavensis from Baja California feed and breed on agria cactus, Stenocereus gummosus; whereas, monomorphic Arizona populations are associated exclusively with organ pipe cactus, S. thurberi. The effects of this host plant shift in expanding the kinds of feeding and breeding sites were assessed by manipulating larval density and recording differences in egg to adult development time and viability, and adult thorax size in both populations on artificially rotted substrates of both cactus species. Older agria rots increased development time but had no effect on viability. Organ pipe rots were qualitatively poorer substrates than agria rots for both monomorphic and polymorphic populations of D. mojavensis, especially at higher larval densities causing longer egg to adult development times, lower viabilities, and smaller thorax sizes than agria.The Baja population expressed shorter development times, higher viabilities, and smaller thorax sizes than the Arizona population on both cactus substrates. No evidence for cactus host race formation was found. The Baja population was less sensitive to increasing larval densities for all fitness characters studied on both cactus substrates indicating greater developmental homeostasis than in the monomorphic Arizona population. These data support the hypothesized central-marginal population structure within this species coincident with the distribution of host plants and lend insight into the process of adaptive divergence at different life history stages caused by host plant shifts.     

The effect of salinity and temperature on the larval development of Mithrax caribbaeus Rathbun, 1920 (Brachyura: Majidae) reared in the laboratory

Larvae of Mithrax caribbaeus were reared in the laboratoryin a factorial experiment employing three temperatures (22,25 and 28°C) and three salinities (32, 35 and 38). Survivaland duration of larval stages were recorded. Ovigerous femalesof M.caribbaeus were collected from the south-eastern coastof Margarita Island, Venezuela, and maintained in individualaquaria until hatching. Eggs from three of the females hatchedin the laboratory. Larvae from each hatching were subdividedinto groups of 10 and reared in plastic bowls containing 200ml filtered and UV-irradiated sea water at different temperature–salinitycombinations. Larvae were transferred daily to clean bowls withnewly hatched Artemia nauplii, and the number of molts and mortalitywithin each bowl was recorded. Complete larval development ofM.caribbaeus occurred under all experimental conditions. Salinityhad the greatest effect on percentage survival of each larvalstage and complete development up to the first crab stage. Thefirst zoeal stage exhibited the highest survival rate. Maximumsurvival for this stage occurred at 25°C, 32–35. Survivalin the second zoeal stage and the megalopa was affected onlyby salinity. Effects of temperature and salinity on survivaldecreased with advance in development. The duration of the twozoeal stages, the megalopa, and development to the first crabstage showed a gradual reduction with increasing temperature.Salinity showed an effect on the duration of zoeal stages butnot on the megalopal stage. Development from hatching to thefirst crab stage required 8–18 days, depending on thetemperature–salinity combination, and was inversely relatedto temperature, averaging 14.3 days at 22°C, 11.8 days at25°C and 9.2 days at 28°C.     

Modeling the effects of environmental variability on Balanus glandula larval development

Planktonic larvae encounter variability in the marine environmentas they develop, and rates of larval development are affectedby changes in certain environmental variables. We examine theeffects of variation in environmental parameters on the durationof the naupliar period of Balanus glandula larvae. Naupliardevelopment rate is modeled as a function of temperature andfood concentration. Simulations of the time course of developmentwere driven by time series of temperature and food concentrationcollected at two locations on the US west coast. Predicted naupliardurations are reasonable in comparison to previous observations.Simulations of larval development and dispersal were drivenby output of a three-dimensional physical circulation modeland remotely sensed chlorophyll. These simulations demonstratethe impact of spatial variation in current velocity, temperatureand chlorophyll on the duration of the larval period, the dispersaltrajectory of these organisms and ultimately on recruitmentsuccess. Our naupliar development model coupled with a physicalcirculation model is a useful tool for addressing questionsof intertidal population ecology.     

密度对大树蛙蝌蚪生长发育和存活率的影响

种群密度效应主要表现在影响和调节种群的死亡率、发育速率、繁殖率以及扩散、迁移等反应种群数量动态的重要参数。分析密度对大树蛙蝌蚪生长发育和存活率的影响,有助于探究外界环境因子导致大树蛙种群密度迅速下降的作用机制。设置了15、20、25只/L和30只/L 4个密度组,测量大树蛙蝌蚪的尾长、体长、发育时间和存活率。结果表明,在15—30只/L范围内,密度升高显著降低了大树蛙蝌蚪尾长和体长的生长速率,减小其变态期的尾长和体长大小,其中与15只/L相比,20、25只/L和30只/L 3组蝌蚪的尾长分别降低了11.6%、11.8%和13.9%,体长分别降低了11.1%、9.5%和12.9%;随着密度的升高,大树蛙蝌蚪发育至跗蹠部伸长期和前肢伸出期的所需时间显著延长;大树蛙蝌蚪生长后期的存活率随密度升高显著降低,但密度对蝌蚪生长早期的存活率影响不显著。因此,密度升高可显著减小大树蛙蝌蚪的尾长和体长、延长发育时间和降低其生长后期的存活率,可能影响大树蛙蝌蚪变态后的适合度。     

Polygenic Control of Drosophila Morphogenesis During the Stages of Determination and Specification of Adult Structures

There are three processes in the development of Drosophila whichmay be studied independendy but which are a manifestation ofinterdependent events which result in the formation of the adultphenotype. These processes are determination, specificationand differentiation. The mutant phenotype Abnormal-abdomen ischaracterized by a loss of abdominal tergites and is controlledby a major mutant gene,A^53g and a polygenic modifier system.The development of the abnormal phenotype is influenced by eventsin early embryogenesis and in mid-larval stages. These developmentallysensitive stages are correlated with the periods of determinationand specification of the cells which constitute the larval histoblastnests and which differentiate into the adult abdominal hypoderm.Evidence for gene control at these two development stages are1) a maternal effect of the genome correlated with changes inthe efficiency of enzymes catalyzing tRNA aminoacylating reactions,2) observations which relate histological defects of embryosat the blastoderm stage to the action of the mutant genotype,and 3) a temperature sensitive period for the expression ofthe abnormal phenotype which has defined limits in the latesecond and early third larval instars. Developmental eventswhich take place during oogenesis, early embryogenesis, andmid-larval stages are discussed with regard to their relationshipto each other and to the final differentiation of the adultphenotype.     

The duration of copepod life stages estimated from stage-frequency data

Current methods to determine the stage duration of copepodsfrom stage-frequency dataare often based on inappropriate distributionfunctions of the stage development time; they also lack a clearprobability model that describes the random noise in the data.This study aims to estimate the duration of copepod life stages,using an asymmetrical probability distribution function of developmenttime. Data on stage frequency were collected from cultured cohortsof Acartia clausi, Temora longicornis and Pseudocalanus elongatus.In addition, data from cultures of Calanoides carinatus andCalanus australis by Peterson and Painting (J. Plankton Res.,12, 283–293, 1990) were used. Following Landry(Limnol.Oceanogr., 20, 854–858, 1975), for each stage the numberof animals that did not yet pass that stage was plotted as afunction of time. A gamma distribution function appeared todescribe the expected proportion of these animals versus time.The number of animals is assumed to follow a binomial distributionand the model parameters are estimated by maximizing the likelihood.This method enables individuals with a retarded development,which are usually deleted from the data material, to be dealtwith. The median development time was estimated from the gammadistribution functions, from which the duration of the stageswas derived. Isochronal development was confirmed for most stages.However, the first feeding naupliar stage, as well as the lastcopepodite stage (CV), took longer in most species, whereasthe pre-feeding naupliar stages had a shorter duration, particularlyin P.elongatus. Differences betweensexes were not apparent.Contradicting results among cultures and with published resultsbyother workers suggest that part of the observed deviation fromnear-isochronal development may be due to the culture conditions.     

Natural development time of Eodiaptomus japonicus (Copepoda: Calanoida) in Lake Biwa

Seasonal and ontogenetic changes in natural development timewere studied for Eodiaptomus japonicus in Lake Biwa in 1986and 1987. Wild individuals in a certain developmental stagewere collected, fed on natural food and examined until theyhad moulted twice. Natural development times fluctuated irrespectiveof temperature from May to October. Food deficiency delayeddevelopment in all feeding stages, and food availability probablydetermined natural development time. Serious food limitationraised mortality in copepodid stage I. In November developmentwas delayed even with enough food. The development of E.japonicuswas almost isochronal except for a short prefeeding naupliarstage I and a long copepodid stage V.     

Exploring larval phenology as predictor for range expansion in an invasive species

Predicting range expansion of invasive species is one of the key challenges in ecology. We modelled the phenological window for successful larval release and development (WLR) in order to predict poleward expansion of the invasive crab Hemigrapsus sanguineus along the Atlantic coast of North America and north Europe. WLR quantifies the number of opportunities (in days) when larval release leads to a successful completion of the larval phase; WLR depends on the effects of temperature on the duration of larval development and survival. Successful larval development is a necessary requirement for the establishment of self-persistent local populations. WLR was computed from a mechanistic model, based on in situ temperature time series and a laboratory–calibrated curve predicting duration of larval development from temperature. As a validation step, we checked that model predictions of the time of larval settlement matched observations from the field for our local population (Helgoland, North Sea). We then applied our model to the North American shores because larvae from our European population showed, in the laboratory, similar responses to temperature to those of a North American population. WLR correctly predicted the northern distribution limit in North American shores, where the poleward expansion of H. sanguineus appear to have stalled (as of 2015). For north Europe, where H. sanguineus is a recent invader, WLR predicted ample room for poleward expansion towards NE England and S Norway. We also explored the importance of year-to-year variation in temperature for WLR and potential expansion: variations in WLR highlighted the role of heat waves as likely promoters of recruitment subsidising sink populations located at the distribution limits. Overall, phenological windows may be used as a part of a warning system enabling more targeted programs for monitoring.     

Temperature-dependent stage durations of Irish Sea Nephrops larvae

The relationships between temperature and stage duration ofthe three zoea stages of Irish Sea Nephrops norvegicus wereinvestigated by culturing individual larvae at five differenttemperatures. The relationships are required for estimatingdaily larval production from survey data on abundance. The survivalof cultured larvae was relatively high. Estimates of the temperature–stageduration relationships from data of individual larvae were differentfrom a previous Irish Sea study. However, using the averageduration at each temperature gave relationships that were notsignificantly different from previous studies in the Irish Seaand Clyde. No larvae were successfully reared to stage IV (post-zoea)at lower temperatures, so it was impossible to assess the relationshipbetween stage III larval duration and temperature.     

粟穗螟滞育的形成和解除与环境条件的关系

粟穗螟Manpava bipunctella Ragonot在川南地区为二化性兼性滞育的昆虫。光周期是诱发滞育的主导因素,在中位温度下,滞育与否主要取决于幼虫发育期间的每日光照时数。在2s℃恒温下,临界光周期为14小时38分。幼虫对光照刺激反应的敏感期为低龄期。 温度和食料效应只发生在每天14小时以上的长光照下,低温有抵销长光照抑制滞育的作用,高温影响不显著;取食玉米的幼虫滞育率比高粱的高,并随寄主生育阶段的发展而增高。该虫滞育解除必需每天14-15小时的长光照;不利于滞育发育和解除,适宜温度为10一25℃。本文最后讨论了该虫滞育形成和解除的特点对发生规律的作用及在测报上的意义。     

Complete larval and early juvenile development of the mangrove crab Perisesarma fasciatum (Crustacea: Brachyura: Sesarmidae) from Singapore, with a larval comparison of Parasesarma and Perisesarma

The complete larval development of the sesarmid crab Perisesarmafasciatum (Lanchester, 1900) from Singapore was obtained fromlaboratory culture. All four zoeal stages, the megalopa andthe first crab stage are described and illustrated. The morphologicalcharacteristics of the larvae of P. fasciatum are compared withthose of other known larvae of the genera Perisesarma and Parasesarma.The larval morphology of P. fasciatum clearly presents the typicalcombination of features that characterize sesarmid larvae. Overall,larval stages are very similar in Perisesarma and Parasesarmaand it is impossible to distinguish these two genera by larvalmorphology.     

Larval and early post-larval stages in the abbreviated development of Heterosquilla tricarinata (Claus, 1871) (Crustacea, Stomatopoda)

Heterosquilla tricarinata was laboratory-cultured through itscomplete larval development and found to have one propelagicand two pelagic larval stages prior to metamorphosis to thejuvenile. These larval stages, the first juvenile, and relevantportions of the second juvenile stage, are described and figured.Individual larvae do not change in size during intermoult periods.Larvae occurring in the plankton show a progressive decreasein mean size between early (September) and late (November) springtime.Reasons for this are suggested. The first pelagic stage of H.tricarinata is anatomically very advanced in development, andthe number of pelagic stages very few, in comparison with otherknown stomatopod life-histories. Ecological implications ofthis are discussed in relation to the high-latitude distributionof the species. Comparison is made between the final pelagicstage of H. tricarinata and that of its congenor H. brazieri. ^*Permanent address: Zoology Department, University of Queensland,Brisbane, Australia     

The development and mortality of the free-living stages of Haemonchus contortus in laboratory culture.

Haemonchus contortus eggs were cultured in intact fecal pellets at various temperatures (5-35 degrees C) for 22 days. Temperature and relative humidity were kept constant throughout the incubation period. Nl larval development occurred at 5 degrees C; peak third-stage larval recovery occurred at 20 degrees C. Egg mortality was an age-dependent phenomenon, whereas larval mortality remained constant irrespective of larval age. Development was characterized by a minimum development time followed by a transition to the next stage which occurred at a constant rate. All rates were temperature dependent. The minimum development times reported here are much less than those previously reported. Based on these results a mathematical model was used to describe the demography of the free-living stages of H. contortus at various temperatures.     

Adaptation to freshwater in the palaemonid shrimp Macrobrachium amazonicum: comparative ontogeny of osmoregulatory organs

The ontogeny of osmoregulatory organs was studied in two geographically isolated populations of the palaemonid shrimp Macrobrachium amazonicum, one originating from the Amazon estuary (A) and the other from inland waters of the Pantanal (P) in northeastern and southwestern Brazil, respectively. A previous investigation had shown that the estuarine population is able to hypo-osmoregulate in seawater, whereas the hololimnetic inland population has lost this physiological function. In the present study, the structural development of the branchial chamber and excretory glands and the presence of Na⁺/K⁺-ATPase (NKA) were compared between populations and between larval and juvenile stages after exposure to two salinities representing hypo- and hypertonic environments. In the newly hatched zoea I stage of both populations, gills were absent and NKA was localized along the inner epithelium of the branchiostegite. In intermediate (zoea V) and late larval stages (decapodids), significant differences between the two populations were observed in gill development and NKA expression. In juveniles, NKA was detected in the gills and branchiostegite, with no differences between populations. At all developmental stages and in both populations, NKA was present in the antennal glands upon hatching. The strong hypo-osmoregulatory capacity of the early developmental stages in population A could be linked to ion transport along the inner side of the branchiostegite; this seemed to be absent or weak in population P. The presence of fully functional gills expressing NKA appears to be essential for efficient hyper-osmoregulation in late developmental stages during successful freshwater adaptation and colonization.     

Determination During Early Embryogenesis in Drosophila melanogaster

Ligation of developing embryos of Drosophila melanogaster wasperformed at three different stages of nuclear multiplicationand at the cellular blastoderm stage. Egg fragments of variablesizes are able to continue development up to the hatching stage.Partial embryos differentiate larval structures, anterior fragmentsforming larval head and posterior fragments larval abdominalstructures. These fragments differentiate a variable numberof the twelve larval cuticular bands formed by intact embryos.We found that ligation at cellular blastoderm can lead to anteriorand posterior fragments which differentiate together all thetwelve bands, indicating that at this stage the embryo developsthese patterns in a mosaic fashion. Ligation of younger embryosprevents the differentiation of some intermediate larval cuticularbands, while the terminal ones are consistently differentiated.The number and position of the deleted bands is correlated withthe time and position of ligation. This indicates that the mosaicpattern present in the egg at blastoderm is not fully formedat earlier stages in development.     

孤雌生殖长角血蜱的哈氏器超微结构与发育

为阐明长角血蜱Haemaphysalis longicornis孤雌生殖种群的哈氏器结构及发育特征, 用扫描电镜对其各虫期哈氏器进行了观察, 分析了血餐对哈氏器发育的影响。结果表明： 该种群幼蜱、 若蜱和成蜱哈氏器形态结构基本相同, 均由前窝和后囊构成。幼蜱前窝感毛6根, 位于同一基盘; 若蜱和成蜱哈氏器相似, 前窝感毛7根, 其中1根孔毛位于外侧基盘, 另6根感毛位于内侧基盘。各虫期饱血后哈氏器大小均比饥饿状态下显著增大（P<0.05）。幼蜱前窝与后囊面积比值与若蜱相比无显著差异（P>0.05）, 若蜱前窝与后囊面积比值与成蜱相比差异显著（P<0.05）。各虫期哈氏器均在发育, 且血餐对哈氏器发育有重要影响。幼蜱至若蜱期哈氏器前窝与后囊的发育速度相似, 若蜱至成蜱期哈氏器前窝发育快于后囊。本研究结果在一定程度上揭示了孤雌生殖长角血蜱的哈氏器发育规律。