A comparative study of the relationship between host size and brood size in Apanteles spp. (Hymenoptera: Braconidae)

ABSTRACT. 1. Current models of insect oviposition predict that clutch size in parasitoids should correlate with host size, with a continuum from solitary species at one end to large gregarious broods at the other. This prediction is tested for the genus Apanteles (sensu lato).
2. The distribution of brood sizes in Apanteles is bimodal, with peaks at one (solitary species) and at about twenty (gregarious species).
3. Brood size of gregarious species correlates with host size, but when a measure of the total volume of a parasitoid brood is plotted against host size, solitary species do not lie on the same regression slope as gregarious species.
4. There is a relative shortage of gregarious species on small hosts, and a relative excess of solitary species on large hosts. Solitary species on large hosts do not fully consume the host resource.
5. The possible role of evolutionary constraints to adaptive progeny allocation in Apanteles is discussed.     

Correlation of tooth size and body size in living hominoid primates, with a note on relative brain size in Aegyptopithecus and Proconsul.

Second molar length and body weight are used to test the correlation between tooth size and body size in living Hominoidea. These variates are highly correlated (r= 0.942, p less than 0.001), indicating that tooth size can be used in dentally unspecialized fossil hominoids as one method of predicting the average body weight of species. Based on tooth size, the average body weight of Aegyptopithecus zeuxis is estimated to have been beteen 4.5 and 7.5 kg, which is corroborated by known cranial and postcranial elements. Using Radinsky's estimates of brain size, the encephalization quotient (EQ) for Aegyptopithecus was between 0.65 and 1.04. A similar analysis for Proconsul africanus yields a body weight between 16 and 34 kg, and an EQ between 1.19 and 1.96.     

Temporal and latitudinal comparisons of reproductive parameters in a heavily exploited shark,the bonnethead,Sphyrna tiburo (L. 1758), in the southern Gulf of Mexico

In the southern Gulf of Mexico, the bonnethead shark, Sphyrna tiburo, is one of the most frequently captured species in landings of small-scale fisheries. Based on the analysis of two fishery-dependent sampling periods (1993–1994 and 2007–2014), this study aimed to determine reproductive parameters and identify temporal differences between the two time periods. In the first sampling period, 776 males and 352 females with a size range of 28.0–120.0 cm total stretched length (L_T) were analysed, and in the second sampling period, 387 males and 432 females with a size range of 28.0–122.0 cm L_T were analysed. The size at 50% maturity in the second sampling period was significantly different between sexes, 82.6 cm L_T for females and 73.8 cm L_T for males (no estimation was possible for the first sampling period). The size at 50% maternity was not different between sampling periods, 97.3 cm L_T for the first sampling period and 99.0 cm L_T for the second sampling period. Litter size varied from 3 to 19 embryos and the average was not statistically different in both periods, 10.1 (S.D. = 3.8) for the first sampling period and 11.3 (S.D. = 3.5) for the second sampling period. The female reproductive cycle is asynchronous, and it seems to be annual, with a gestation period of 5–6 months, and a consecutive ovarian cycle and gestation period. Temporal (between sampling periods) and latitudinal (southern Gulf versus northern regions) variations occur in the synchronicity of the reproductive cycle, temporal variation in the relationship between maternal length and litter size, and latitudinal variation in average size of mature sharks.     

Temperature- and predator-induced phenotypic plasticity in Bosmina cornuta and B. pellucida (Crustacea: Cladocera)

SUMMARY 1. Clones of Bosmina cornuta and B. pellucida (B. longirostris species complex) were derived from samples collected from Scheuermühlenteich and Lake Windsborn(westernGermany). Experimental temperature change (to 10 °C and 20 °C) and exposure to Acanthocyclops vernalis copepods (12 L^?1) significantly altered external morphology in laboratory cultures of the two species. Morphological traits were derived from eight log₁₀‐transformed and standardised morphometric distances by factorial analysis: factor 1 represented body size, factor 2, size of appendages and factor 3, the head size. 2. Acclimation of clones to cold water (10 °C, >14 days) led to an increase in body, antennule and mucrone size in B. cornuta and B. pellucida. Moreover, at 10 °C, B. cornuta cultures usually collapsed within a few weeks. Compared to the trials at 10 °C, acclimation to 20 °C (the two species) and to 15 °C (B. pellucida only) left the size of body appendages unchanged. Individuals were unequivocally assigned to each species by discriminant functions. Conspecific individuals that were acclimated to different temperatures between 10 and 20 °C also differed in external morphology, but discriminant analysis yielded misclassification rates of 5.3–23.3%. 3. Morphological response to the presence of copepod predators was weaker than that caused by temperature change. Long‐term exposure of clones to copepod predators induced a significant increase in size of appendages in the two species but left body size unaffected. Again, species identification by discriminant functions could be made without any error, whereas conspecific controls and experimentals were misclassified at rates between 19.4 and 29.5%. 4. It is suggested that temperature is the main proximal cue for Bosmina cyclomorphosis. The distinct response to temperature of B. pellucida and B. cornuta may also account for seasonal differences in abundance observed in field.     

Lessons from the size efficiency hypothesis II. The mire of complexity

Over the years, models and concepts developed to explain the behaviour of lake plankton have been generalized and extended to most parts of the limnetic community. This development has now fused with parallel research programs into stream and marine benthos and fish, to yield an imposing literature dealing with complex interactions in aquatic communities. Although the size of this literature has grown, its basic elements, i.e. the allometries of organismal capacity and environmental opportunity, remain those associated with the seminal size efficiency hypothesis. Unfortunately, the difficulties that eventually buried that hypothesis in a welter of detail and special cases were not resolved, so the newer, broader concepts associated with complex interactions remain difficult or impossible to test. Those concepts are so subjective, poorly defined, and variably interpreted that they are more effective in explaining our observations after the fact than in predicting them before-hand. Despite predictive failure, such explanatory models have achieved wide acceptance. Once accepted as substitutes for predictive theory, they mire the advance of science by hiding its deficiencies. One solution to this cloying complexity is insistence that the theories of ecology specify simple, observable response variables so that theories may be evaluated by their predictive power. Components of a general refuge concept illustrate the point. This policy has implications for environmental science well beyond the confines of plankton ecology.Dedicated to Dr Karl Banse, School of Oceanography, University of Washington on his 60th Birthday.     

An analysis of cercopithecoid odontometrics. I. The scaling of the maxillary dentition.

The relations between two tooth indices, post-canine area and incisor width in the upper jaw, and three variables, diet, body weight and body weight dimorphism, were examined separately for the males and females of 29 cercopithecoid species. Each species was assigned to one of three diet classes (folivore, frugivore, omnivore). Data on the other variable consisted of species means (log-transformed) obtained from published sources. The analytic techniques used were bivariate and multiple regression, the tooth indices being the dependent variables. All tooth indices scaled isometrically within diet classes, and all except female incisor width scaled with positive allometry across diet classes. In both sexes, the body weight adjusted mean incisor width of folivores was significantly smaller than that of either frugivores or omnivores. In the females, the body weight adjusted mean post-canine areas did not differ significantly across diet classes, while in the males the omnivores had a larger body weight adjusted mean post-canine area than either the folivores or frugivores. Female post-canine area was the only tooth index for which body weight dimorphism was a significant predictor. Extrapolations of these findings to other extant and to fossil primate species are discussed.     

The effective number of a population that varies cyclically in size. II. Overlapping generations

We consider haploid and dioecious age-structured populations that vary over time in cycles of length k. Results are obtained for both autosomal and sex-linked loci if the population is dioecious. It is assumed that k is small in comparison with numbers of haploid individuals (or of numbers of males and females) in any generation of a cycle. The inbreeding effective population size N(e) is then approximately given by the expression [T summation operator (k-1)(j=0)1/[N(e)(j)T(j)]](-1), where N(e)(j) and T(j) are, respectively, the effective population size and generation interval that would hold if the population was at all times generated in the same way as at time j. The constant T, which is the effective overall generation interval, is defined to be k times the harmonic mean of the quantities T(j). Our expressions for T and N(e), in terms of N(e)(j) and T(j), are general, but the N(e)(j)s are derived under the assumption that offspring are produced according to Poisson distributions.     

Census vs. effective population size in chinook salmon: large- and small-scale environmental perturbation effects

Population viability has often been assessed by census of reproducing adults. Recently this method has been called into question and estimation of the effective population size (Ne) proposed as a complementary method to determine population health. We examined genetic diversity in five populations of chinook salmon (Oncorhynchus tshawytscha) from the upper Fraser River watershed (British Columbia, Canada) at 11 microsatellite loci over 20 years using DNA extracted from archived scale samples. We tested for changes in genetic diversity, calculated the ratio of the number of alleles to the range in allele size to give the statistic M, calculated Ne from the temporal change in allele frequency, used the maximum likelihood method to calculate effective population size (NeM), calculated the harmonic mean of population size, and compared these statistics to annual census estimates. Over the last two decades population size has increased in all five populations of chinook examined; however, Ne calculated for each population was low (81-691) and decreasing over the time interval measured. Values of NeM were low, but substantially higher than Ne calculated using the temporal method. The calculated values for M were generally low (M < 0.70), indicating recent population reductions for all five populations. Large-scale historic barriers to migration and development activities do not appear to account for the low values of Ne; however, available spawning area is positively correlated with Ne. Both Ne and M estimates indicate that these populations are potentially susceptible to inbreeding effects and may lack the ability to respond adaptively to stochastic events. Our findings question the practice of relying exclusively on census estimates for interpreting population health and show the importance of determining genetic diversity within populations.     

Variation in female life-history traits among Alaskan populations of the threespine stickleback, Gasterosteus aculeatus L. (Pisces: Gasterosteidae)

Life-history characteristics of female threespine stickleback (Gasterosteus aculeatus) were examined in 12 populations, 11 freshwater and one anadromous, within the Cook Inlet region of Alaska. Because this area has been deglaciated during the last 20 000 years, the freshwater populations are recently derived, probably independendy, from the local marine or anadromous stickleback. Freshwater threespine stickleback have undergone considerable morphological evolution within this region, apparently in response to environmental factors including predatory regimes and environmental productivity. Our freshwater study populations were selected to sample this range of morphological variation in order to determine whether life-history traits and morphologies have followed similar evolutionary trajectories. Freshwater populations could be categorized generally into one of three ecomorphotypes: those inhabiting relatively productive lakes having one or more piscivorous fishes present, and in which the stickleback exhibit a fully developed pelvic girdle; those inhabiting low-calcium lakes that lack piscivorous fishes, and in which the pelvic structures are incomplete; those living in streams with piscivorous fishes, in which the stickleback have fully developed pelvic girdles. The anadromous population constituted a fourth ecomorphotype that lives in marine waters, and is robusdy armored. The freshwater populations showed considerable variation in all life-history traits assessed, and this variation generally corresponded to our ecomorphological classifications. Nevertheless, within each ecomorphotype there was sufficient variation to suggest that morphological and life-history traits may not always respond in the same manner in response to the same selective regime.     

Zur numerischen Auswertung von Schnittflächenverteilungen. IV

In this paper a general integral equation is given for the connection between the size distribution of similar formed objects and the size distribution of their sections with zero thickness. The spherical problem is enclosed in this solution. The integral kernels for six simple polyhedrons are numerically given. The integral geometry is the theoretical basis for this paper, and the computer simulation of the section process is the practical method for the numerical calculation of integral kernels.     

Significant physiographic disturbances in the Ebro basin reservoirs (N.E. Spain) reflected by Oligochaeta size spectra

Benthic fauna size distribution, water and sediment composition, and physiographic features of catchments were used to classify ten reservoirs in the Ebro basin, Spain. Three reservoirs (Alloz, Urrunaga and Barasona) diverged from the rest. Environmental factors (water and sediment characteristics) that accounted for the separation of these three reservoirs were directly linked to minor features of the watersheds (high chloride water concentration in Alloz reservoir, iron loading in Barasona reservoir, and Na-rich silicates in sediments from Urrunaga reservoir).     

Cryptosporidium apodemi sp. n. and Cryptosporidium ditrichi sp. n. (Apicomplexa: Cryptosporidiidae) in Apodemus spp.

Faecal samples from striped field mice (n = 72) and yellow-necked mice (n = 246) were screened for Cryptosporidium by microscopy and PCR/sequencing. Phylogenetic analysis of small-subunit rRNA, Cryptosporidium oocyst wall protein and actin gene sequences revealed the presence of C. parvum, C. hominis, C. muris and two new species, C. apodemi and C. ditrichi. Oocysts of C. apodemi are smaller than C. ditrichi and both are experimentally infectious for yellow-necked mice but not for common voles. Additionally, infection by C. ditrichi was established in one of three BALB/c mice. The prepatent period was 7–9 and 5–6 days post infection for C. apodemi and C. ditrichi, respectively. The patent period was greater than 30 days for both species. Infection intensity of C. ditrichi ranged from 4000–50,000 oocyst per gram of faeces and developmental stages of C. ditrichi were detected in the jejunum and ileum. In contrast, neither oocysts nor endogenous developmental stages of C. apodemi were detected in faecal or tissue samples, although C. apodemi DNA was detected in contents from the small and large intestine. Morphological, genetic, and biological data support the establishment of C. apodemi and C. ditrichi as a separate species of the genus Cryptosporidium.     

菜薹种质内不同大小群体问遗传多样性的RAPD鉴定和比较

为了了解菜薹种质内的遗传多样性,确定适宜的更新群体,从一份菜薹地方品种的200株群体中随机抽取10、15、20、25、30、35和．40株组成不同的群体,利用RAPD技术分析各自的多态位点数、计算多态位点百分率、遗传多样性指数和缺失位点数。通过对各参数的比较结果表明,该种质内单株间的遗传差异较大,大于30株的群体能代表200株群体的遗传多样性。在满足其完全随机交配的前提下,可视为更新的有效群体。根据更新时繁种群体应为有效群体2倍的原则,认为不小于60株的群体为菜薹种质更新比较适宜的群体。     

The influence of prey size and abundance, and individual phenotype on prey choice by the three-spined stickleback, Gasterosteus aculeatm L.

Prey selection behaviour of three-spined sticklebacks, Gasterosteus aculeatus L., was studied in two experiments. Where possible, the experimental apparatus satisfied the assumptions of the simplest optimal diet model (the basic prey model); prey were presented sequentially, the fish could not search for and handle prey at the same time, and net energy gain, handling time and encounter rate were fixed. Experiment 1 presented fish with a range of Asellus sizes so that pursuit ( p ) and handling ( h ) time could be related to prey size. Published energy values of Asellus together with pursuit and handling times were used to calculate E /( p+h ) for Asellus measuring 3,4,5,6,7 and 9 mm. Pursuit times did not differ with prey size but handling times did. E /( p+h ) was very variable particularly at the larger prey sizes. Experiment 2 presented fish with two sequences of prey differing in the encounter rate with the most profitable prey sizes. Fish did not select the diet predicted by the basic prey model tending to always ignore the largest prey even when net energy gain would have been maximized by including them in the diet. Further analysis showed that the probability of a prey size being taken was a function of prey size, fish stomach fullness and encounter rate. It is concluded that the basic prey model is too simple to capture the behaviour of the fish. One of its main faults is that the changing state of the fish through the feeding bout is ignored.     

Relative genome-size differences among populations of Spartina alterniflora Loisel (Poaceae) along East and Gulf Coasts of U.S.A.

Flow cytometric analysis of mithramycin-stained rhizome nuclei was used to compare relative amounts of DNA among 18 populations of Spartina alterniflora Loisel (Poaceae) from the East and Gulf Coasts of the U.S.A. The DNA amount increases, significantly with increasing latitude. These findings support the general model of genome size change with latitude.     

异速生长模型研究概述

最近,关于异速生长模型的讨论再次成为焦点,讨论热点为异速生长指数的取值及其理论解释.本文综述了WBE 97、BMR(99)模型的相关研究,重点介绍了MGL模型及由此模型得到的结果:个体整体的新陈代谢率与个体的质量没有明显依赖关系,其标度指数不是一个固定的值,而是一个区间[2/3,1].考虑的视角从个体整体的新陈代谢率转到单位质量的新陈代谢率,通过对不同物种、不同环境的单位质量新陈代谢率的研究,发现对大多数物种,其值落在一个具有普适性的上、下界的区间内;认为存在单位质量的新陈代谢率最小值确定了个体的大小,并建立基于该最小值的描述个体大小与温度关系的数学模型,该模型得到实验数据验证.     

Size distributions and trophic relationship of the pelagic ecosystem in the Oosterschelde (S.W. Netherlands)

The theory of SHELDONet al. (1972), stating that in marine pelagic communities biomass is distributed equally over logarithmic size classes, is tested for the inland part of the Oosterschelde. It is shown that none of the data on total particulate matter (including phytoplankton and non-phytoplankton particles), phytoplankton separately and zooplankton abundance and size, on a yearly basis, are distributed equally over the size range in which they occur. Using experimentally determined predation efficiency values for zooplankton grazing on phytoplankton, it is shown that the ratio of zooplankton-to phytoplankton biomass found is nevertheless rather consistent with the model of SHELDONet al. (1977).Communication no. 539 of the Delta Institute for Hydrobiological Research.     

Clinical efficacy of a GnRH-agonist implant containing 4.7 mg deslorelin, Suprelorin, regarding suppression of reproductive function in tomcats. Sandra.Pesch@vetmed.uni-giessen.de

The aim of the present study was to test for the efficacy of a slow release GnRH-agonist implant (4.7 mg deslorelin, Suprelorin®) in the male cat. Ten toms were implanted sc in the neck. Changes in testosterone (T) secretion, testicular size, body weight and behaviour (mounting, mating, urine marking) were monitored. T concentrations were significantly decreased (P < 0.0001) to basal levels (< 0.1 ng/mL) in 5 of 10 cats after 4 weeks and in all but one tom after 11 weeks (T < 0.1 ng/mL). In this respective tom only partial downregulation with T-values from 0.2 to 0.1 ng/mL was achieved until week 27. In weeks 28 and 32, T concentrations were below 0.1 ng/mL. Compared to pretreatment values, testicular volume was significantly decreased by about 60% in week 12 and about 73% after 36 weeks (P < 0.001). Penile spines disappeared 9.4 ± 1.0 weeks after treatment. Food intake was significantly increased during treatment period (P < 0.001). In all tomcats libido, mating behaviour and urine marking were significantly reduced (P < 0.0001) after an initial stimulation. In one tom, mating an oestrous queen on day 20 after implant administration resulted in pregnancy. Mating of another tom that had T-values between 0.1 and < 0.1 ng/mL since day 24 in week 8 revealed the presence of spermatozoa; however, this mating did not result in pregnancy.Subcutaneous implant administration was well tolerated by all tomcats without sedation or anaesthesia and no treatment related negative effects were observed.These results demonstrate the clinical efficacy of the 4.7 mg deslorelin implants (Suprelorin®) in the tom inducing all castration related effects.