The relationship between plasmodium gallinaceum density and the fecundity of Aedes aegypti

The relationship between parasite density and host fecundity was examined using a Plasmodium gallinaceum-Aedes aegypti model system. A reduction in host fecundity was observed at very low parasite densities. No further change in the level of reduction was seen at high parasite densities.     

The relationship between fecundity and adult body weight in Homeotherms

Summary Bythotrephes cederstroemii Schoedler, a predatory freshwater zooplankter (Crustacea: Cladocera), was first found in the Laurentian Great Lakes in December 1984. The first individuals were from Lake Huron, followed in 1985 with records from Lakes Erie and Ontario. By late August, 1986 the species had spread to southern Lake Michigan (43°N). Bythotrephes has not previously been reported from North America, but has been restricted to a northern and central Palearctic distribution. Its dramatic and widespread rise in abundance in Lake Michigan was greatest in offshore regions. Bythotrephes appears to be invading aggressively, but avoiding habitats presently occupied by glacio-marine relict species that became established in deep oligotrophic North American lakes after the Wisconsin glaciation. Because it is a voracious predator its invasion may lead to alterations in the native zooplankton fauna of the Great Lakes. It offers the chance to study how invading plankton species join an existing community. Judging from its persistence and success in deep European lakes, Bythotrephes may now become a permanent member of zooplankton communities in the Nearctic.     

The relationship between egg load and fecundity among Trichogramma parasitoids

1. The relationships between parasitoid egg load, size, and age (3–72 h) for Trichogramma minutum, T. platneri, and T. pretiosum, reared from two factitious hosts, Ephestia kuehniella and Sitotroga cerealella, were evaluated to test the hypothesis that 24‐h egg load can be used to estimate the fecundity of Trichogramma parasitoids. 2. Egg load increased in relation to female age over the first 3 days of adult life for all three Trichogramma species to a mean egg storage capacity of 46.7 eggs for T. minutum, 41.1 for T. pretiosum, and 35.7 for T. platneri. At 24 h of age, T. minutum had matured enough eggs to fill 67% of its storage capacity, in comparison with 74% for T. pretiosum and 91% for T. platneri. There was a positive relationship between egg load and parasitoid size for all ages of the three Trichogramma species reared from both hosts (with the exception of T. platneri at 3 h post emergence), accounting for 14–69% of the variance in egg load. 3. The potential fecundity, realised (3 day cumulative) fecundity, and oviposition rate (potential fecundity/longevity) of T. platneri were all related linearly to size‐dependent variation in 24‐h egg load, but only the realised fecundity of T. pretiosum, and none of the reproductive characteristics of T. minutum. It is suggested that 24‐h egg load may not be an accurate measure of egg storage capacity in parasitoids and should be used cautiously to represent fecundity. 4. The potential fecundity of seven Trichogramma species reared from E. kuehniella varied from 55 to 150, but neither potential fecundity nor oviposition rate was related significantly to egg load (represented by eggs laid during first 24 h). Selection to avoid egg depletion in the attack of gregarious hosts appears most likely to account for the variation in potential fecundity among Trichogramma species.     

The relationship between fecundity and fertility in the mouthbrooding cichlid fish Tilapia leucosticta

The development of fry in the mouth of the female mouthbrooder Tilapia leucosticta Trewavas is described. The egg production by fish of various lengths is plotted and a curvilinear regression for standard and total length fitted. The number of eggs produced is approximately equal to the square of the total length in centimetres of the parent fish. The brood numbers of 460 females are plotted against length, and linear regressions for mean brood number and mean fry number fitted. The relationship between the expressions for numbers of fry brooded and egg production gives an estimate of brooding efficiency that decreases with increasing parent length. Individual female fish show signs of reripening and the timing of this process is estimated from gonad state and from the length of fry brooded in the mouth. The relationship between fecundity (egg production) and fertility (fry brooded) is considered and the effect of maturation size, growth rate and spawning frequency assessed.     

The relationship between fecundity and fertility in the mouthbrooding cichlid fish Tilapia leucosticta

The development of fry in the mouth of the female mouthbrooder Tilapia leucosticta Trewavas is described. The egg production by fish of various lengths is plotted and a curvilinear regression for standard and total length fitted. The number of eggs produced is approximately equal tothe square of the total length in centimetres of the parent fish. The brood numbers of 460 femalesare plotted against length, and linear regressions for mean brood number and mean fry number fitted. The relationship between the expressions for numbers of fry brooded and egg production gives anestimate of brooding efficiency that decreases with increasing parent length. Individual female fish show signs of reripening and the timing of this process is estimated from gonad state and from the length of fry brooded in the mouth. The relationship between fecundity (egg production) and fertility (fry brooded) is considered and the effect of maturation size, growth rate and spawning frequency assessed.     

The curvilinear relationship between worm length and fecundity of Teladorsagia circumcincta.

The variation among sheep in fecundity of Teladorsagia (Ostertagia) circumcincta was estimated by dividing the faecal egg count by the worm number following deliberate infection of mature Scottish Blackface lambs. Fecundity was skewed and ranged from 0 to 350 eggs per worm per day. Most animals had relatively low worm fecundities, but a small number of individuals had relatively high worm fecundities. However, as fecundity is a ratio of two imprecise estimates, extreme values may be statistical artefacts. Following both deliberate and natural infection, differences in worm fecundity were associated with differences in adult female worm length. In both infections, fecundity varied with worm length to the power 0.4. This relationship should assist the measurement of fecundity in studies of host immunity, in epidemiological modelling and in estimating the influence of density-dependent relationships.     

The relationship between intestinal location and fecundity in adult Trichinella spiralis.

Adult female worms recovered from the jejunum of rats infected per os with 1000 larvae of Trichinella spiralis were significantly more fecund (peak jejunal fecundity = 35.7 +/- 3.1 newborn larvae per female) than females recovered from the terminal ileum (9.3 +/- 4.1 larvae per female) in the same infections. The majority of the adult worms were established in those sections of the small intestines that produced the most fecund females (r = 0.92; P less than 0.05). Worm fecundity is believed to be location-specific because adult females that were surgically implanted into the jejunum were significantly more fecund that were implanted into only the ileum. It is concluded that the physico-chemical conditions of the anterior small intestines are optimal for the parasites' reproductive fitness and this exerts a strong selective pressure on habitat selection behavior.     

玉米螟赤眼蜂雌蜂繁殖力与年龄的关系

以米蛾卵作为繁育寄主,通过系统解剖不同发育期（0～144 h）玉米螟赤眼蜂的卵巢,探讨了雌蜂抱卵量、繁殖力与其年龄和个体大小之间的关系。结果表明,玉米螟赤眼蜂在羽化初期（0～3 h）,卵巢中只有部分卵处于成熟状态,随着雌蜂年龄的增加,其抱卵量不断增加,至72 h时接近其卵巢容纳量。抱卵量与雌蜂年龄之间的关系可以用以下公式来表示：y =a｛1-exp［-b(x+c)］｝。用后足胫节长度（HTL）来表示雌蜂个体大小时,HTL短于0.150 mm、介于0.150～0.159 mm之间以及长于0.160 mm的个体羽化后24 h的平均抱卵量分别为40.4、50.5和58.2粒,各占其卵巢容纳量的72.8%、79.3%和86.9%,占整个成虫期总产卵量的49.4%、47.9%及51.9%。玉米螟赤眼蜂羽化后24 h内的产卵量接近于羽化后24 h的抱卵量。雌蜂个体大小与抱卵量及总产卵量之间关系密切,抱卵量与总产卵量随着雌蜂个体的增大而不断增加,呈线性正相关。个体大小可以作为评估玉米螟赤眼蜂生殖潜能高低的一个良好的指标。     

The relationship between fecundity and oocyte resorption in field populations of Lucilia cuprina

In the Australian sheep blowfly, Lucilia cuprina, the number of ovarioles, and hence the maximum number of eggs developed in each ovarian cycle, is a linear function of adult size (headwidth). Field females have a mean headwidth of 3.0 mm (range=2.30–3.50 mm) and a mean potential fecundity/cycle of 232 eggs (range=111–318 eggs). Realised fecundity is influenced by the quality and amount of protein in the adult diet. All field females appear to have the same minimum protein requirement for egg maturation, i.e., whatever their size (potential fecundity) females must obtain sufficient protein to mature at least 110 eggs in order to become gravid. Females whose protein intake exceeds this minimum but falls short of the amount needed for maturation of their full egg complements resorb some of their oocytes and mature the remainder. Since potential fecundity increases with fly size, large females resorb more oocytes than small females under suboptimal protein regimes, i.e., the proportion of oocytes resorbed increases with fly size. Under field conditions, females rarely matured full complements of eggs, which indicates a general shortage of protein-rich material. The mean reduction in fecundity of field females during these studies was 53.4 eggs/cycle (23.2%).

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Résumé Chez Lucilia cuprina Wied., le nombre d'ovarioles, et ainsi le nombre maximum d'oeufs développés au cours de chaque cycle ovarien, est une fonction linéaire de la taille de l'adulte (largeur de la tête). La largeur moyenne de la tête des femelles de la nature est 3 mm (2,3 à 3,5) et la fécondité potentielle moyenne par cycle de 232 oeufs (111 à 318).La fécondité réelle est influencée par la qualité et la quantité de protéines dans le régime alimentaire. Toutes les femelles de la nature semblent avoir les mêmes exigences minimales en protéines pour la maturation des ovocytes, c'est à dire que quelle que soit leur taille (fécondité potentielle) les femelles doivent obtenir les protéines suffisantes à la formation d'au moins 110 ovocytes pour devenir gravides. Les femelles dont l'absorption de protéines dépasse ce minimum, mais est insuffisant pour permettre la maturation de la totalité de leurs ovocytes, en résorbent quelques uns et conduisent à maturité le reste. Puisque la fécondité potentielle augmente avec la taille des mouches, les grosses femelles résorbent plus d'ovocytes que les petites avec un régime suboptimal en protéines, c'est à dire que la proportion d'ovocytes résorbés augmente avec la taille des mouches. Dans les conditions de la nature, la totalité des ovocytes parvient rarement à maturité, ce qui indique une limitation générale en aliments riches en protéines. La réduction moyenne de la fécondité chez les femelles de la nature a été au cours de cette étude de 53.4 oeufs par cycle (23,2%).

     

Reproduction in the North Atlantic oceanic ichthyofauna and the relationship between fecundity and species' sizes

Synopsis The pelagic (589 spp.) and demersal (505 spp.) oceanic ichthyofaunas of the North Atlantic Basin have very different compositions at ordinal and family level. Yet the pattern of relationships between species' maximum size and maximum fecundity from data available (10% of the pelagic, 19% of the demersal species) was similar. A positive relationship between fecundity and weight was confirmed among most teleosts, but was not followed by the elasmobranchs represented. Species' reproductive styles are reviewed in ordinal groupings within a framework of the overall body size/fecundity distribution. Species size (maximum weight) spectra were synthesized for both pelagic and demersal assemblages to assess the allocation of potential reproductive effort throughout the North Atlantic oceanic ichthyofauna. The only available examples of species size spectra and biomass spectra from the pelagic and demersal ichthyofauna in this ocean basin imply geographic and bathymetric variation in overall reproductive effort among fishes whose fecundity is size dependent. Further implications concerning reproductive effort are discussed in the light of food availability.     

动物进化中神经肽样物质和神经系统关系之探讨

用免疫组织化学方法,研究和追踪神经肽样物质在原生动物、水螅及蝾螈胚胎发育过程中分布的变化,试图探索在动物早期进化过程中神经肽样物质和神经系统之间的关系。实验结果表明：（1）从系统发育看神经肽样物质比神经系统先出现并行使在细胞内的功能。（2）在随后的进化中神经肽样物质先分布于非神经系统部位,如肠道外缘及表皮,并逐渐进入神经系统,这无论从系统发育和个体发育中都能找到依据。（3）在神经系统,神经肽样物质先出现在周边神经,之后;才出现在中枢神经,实验中表明NPY是随着神经嵴细胞的迁移而进入周边神经系统,之后,随着胶质细胞的出现而出现在中枢神经系统。（4）原生动物和蝾螈胚胎均由皮膜或表皮细胞中囊泡状结构直接分泌神经肽祥物质进入胞质内或细胞外。     

The relationship between latitude,migration and the evolution of bird song complexity

For the past several decades it has been proposed that birds show latitudinal variation in song complexity. How universal this variation may be and what factors generate it, however, are still largely unknown. Furthermore, while migration is confounded with latitude, migratory behaviour alone may also be associated with variation in song complexity. In this paper we review the literature to assess current ideas on how latitude and migratory behaviour may drive large‐scale geographical patterns of song complexity. At least seven distinct hypotheses have been proposed in 29 studies of the topic. Four of these hypotheses posit that sexual selection pressures co‐vary with latitude and/or migration, resulting in concordant changes in song. Other hypotheses suggest that mechanisms other than sexual selection, such as large‐scale changes in environmental sound transmission properties, may be at play. Sixteen studies found support for increased song complexity with increased latitude and/or migration, whereas 13 did not. Relatively few studies exist on this topic, and methodological differences between them and variable definitions of ‘complexity’ make it difficult to determine whether results are comparable and concordant. At a minimum, it is possible to conclude there is no strong evidence that song complexity increases with latitude and/or migration in all birds. Future work should focus on examining multiple hypotheses at once to further advance our understanding of how latitude, migration and song complexity may or may not be related.     

The species-area relationship and evolution

Models relating to the species-area curve usually assume the existence of species, and are concerned mainly with ecological timescales. We examine an individual-based model of co-evolution on a spatial lattice based on the tangled nature model in which species are emergent structures, and show that reproduction, mutation and dispersion by diffusion, with interaction via genotype space, produces power-law species-area relations as observed in ecological measurements at medium scales. We find that long-lasting co-evolutionary habitats form, allowing high diversity levels in a spatially homogenous system.     

On the relationship between queen number and fecundity in polygyne colonies of the fire ant Solenopsis invicta

ABSTRACT. The reproductive status of individual queens in relation to the number of queens in polygyne colonies of Solenopsis invicta Buren was investigated under both field and laboratory conditions. In field colonies, the weight of individual queens is inversely related to the number of resident queens present. The weight of a queen is positively correlated with fecundity, as measured by the number of eggs laid in 5 h in isolation. Thus increasing queen number has a strong negative effect on the fecundity of individual queens in these colonies. A similar relationship was established in standardized laboratory colonies using queens from a single experimental population. Colony size by itself had no significant effect on queen weight in either the field or laboratory colonies, suggesting that the inverse relationship between queen number and fecundity results from mutual inhibition among queens, possibly involving pheromones, rather than reduced nutrition through lower worker/queen ratios. While uninseminated queens can comprise up to 50% of the functional (i.e. egglaying) queens in polygyne colonies of this ant, they tend to be less fecund than their inseminated nestmates; uninseminated queens within a given colony generally weigh 5–25% less.     

The relationship between the duration of food web evolution and the vulnerability to biological invasion

I conducted computer simulations of food web evolution and investigated the relationship between the duration of food web evolution and the vulnerability to biological invasion. Model food webs without evolution consisted of animal species with a limited number of prey species and producer species with small intrinsic growth rates. Because these species were not resistant to predation pressure, model food webs without evolution were vulnerable to invasion of powerful omnivores, which had a wide range of feeding preference and a high ecological efficiency. In model food webs without evolution, the number of animal species depending on producer species was small. Therefore, if a producer species invaded and disturbed the base of such food webs, few animal species became extinct. However, model food webs with a long time evolution had a structure that a small number of producer species supported a large number of animal species. When a producer species invaded and disturbed the base of such food webs in this state, many species became extinct by an indirect effect. The mean number of prey species of animal species and the mean intrinsic growth rate of producer species increased rapidly in the early stage of evolution. Therefore, in the early stage of food web evolution, food webs were temporarily resistant to invasion of powerful omnivores. However, this resistibility was not maintained for a long time. The result of this study strongly suggests that food webs change with time, and consequently the vulnerability to invasion changes with time.     

滇池金线鲃亲鱼培育、繁殖力以及卵径大小与胚胎存活率的关系

2007—2010年,对滇池金线鲃(Sinocyclocheilus grahami)进行了亲鱼培育、繁殖力和卵径(egg diameter,ED)大小的研究。滇池金线鲃的催产率、核偏位率和孵化率分别由2007年的25.2%、61.5%和30.4%到2010年的91.3%、85.2%和44.5%。四年间这3项指标均有不同程度提高,其中,催产率提高的幅度最大。提供适合滇池金线鲃营养全面的饵料可以保证亲鱼培育的最佳效果,获得高质量的鱼卵和鱼苗。滇池金线鲃绝对怀卵量与体长的关系是F=0.0004826SL3.166(R2=0.6424,P<0.05)。四年来滇池金线鲃的平均产卵量为(2118.4±899.1)粒,平均绝对怀卵量为(2402.9±881.9)粒,平均相对怀卵量为(70.4±20.8)粒。产卵量、绝对怀卵量和相对怀卵量都有随着体长增加而增加的趋势。卵的大小与胚胎存活相关,在胚胎发育的前两天,不同批次胚胎的死亡呈现一种稳定的或低的死亡率;而后5～7d不同大小的卵呈现不同的死亡率,即小的卵具有更高的死亡率;而卵径>2.0mm的胚胎死亡率趋于稳定;大的卵有更高的生存潜力,能保证仔鱼开口前继续完善身体器官的形成或发生所需要的能量。