Experimental evidence for the relationship between food supply, parental effort and chick survival in the Lesser Black-backed Gull Larus fuscus

We studied breeding success, chick growth, parental effort and chick behaviour in two groups of Lesser Black-backed Gulls Larus fuscus whose chicks were provided with additional food until 7 days after hatching or until fledging. These data were compared with those from control pairs which we studied simultaneously to test the hypotheses that food was in short supply during the chick stage at the colony site and that in such circumstances the behaviour of adults and young is mainly responsible for the low success. Pairs whose chicks were fed with additional food until fledging showed a higher fledging success than control pairs (intermediate for pairs of first experimental group). During the first week after hatching, experimental adults of both groups were present together at the territory for longer than control pairs. In adult females of experimental pairs, the length of feeding trips was shorter than in females of control pairs, whilst the rate of chick feeding was more frequent in the experimental broods. After the chicks were 7 days old, differences were significant only for the experimental pairs whose chicks were provided with additional food until fledging. Chicks fed until fledging showed a higher daily mass and wing-length increments and reached a higher fledging mass at an earlier age than both control chicks and chicks which were provided with additional food until day 7. Starvation occurred only in control chicks and in chicks of the first experimental group after we had stopped providing food. When food was in short supply, fledging success of gulls was adversely affected as a result of both starvation (because of the lower feeding rates of chicks) and a higher predation rate (arising from changes in behaviour of both adults and chicks).     

The relationship between ovulation rate and embryonic survival in gilts

Norwegian Landrace gilts were inseminated on the second day of their second oestrus and slaughtered 28 to 34 days after insemination. The number of corpora lutea (ovulation rate) and normal embryos was counted and the embryonic survival rate was calculated for the 306 pregnant gilts. Mean (+/-S.D.) ovulation rate, number of normal embryos and embryonic survival rate were 14.17+/-2.48, 10.55+/-3.30 and 74.8%+/-20.7%, respectively. The significant (P<0.001) curvilinear regression of embryonic survival rate on ovulation rate gives a maximum embryonic survival rate at 13.2 ovulations. Increased ovulation rate gives increased number of normal embryos up to 18.1 ovulations. Ovulation rate should be considered when assessing factors affecting embryonic survival in pigs.     

Tits and their caterpillar food supply

In this paper I review what is known about the relationship between the tits' clutch-size and the timing of their breeding season and the numbers of their caterpillar prey. The results come from the Edward Grey Institute's long-term study of Great and Blue Tits in Wytham Wood, near Oxford. This study was started in 1947 by Drs D. Lack and J. A. Gibb (Lack 1966, Perrins 1979)- These results could only have been obtained from a long-term study and emphasize the value of such studies for our understanding of certain aspects of ecology. In addition, they could not have been obtained by a study of the birds alone, being dependent on a knowledge of their insect food; most of this information was made available as a result of a parallel long-term study of the insect fauna of the oak trees, made by a number of people from the Hope Department of Entomology, University of Oxford.     

On the relationship between food, reproduction and survival of two carabid beetles: Calathus melanocephalus and Pterostichus versicolor

Abstract.

• 1 The relative influences of temperature and availability of food on reproduction, survival and growth of all developmental stages of two carabid beetle species are discussed with special reference to the suggested relationship between availability of food, size of egg production and survival of adults from one breeding season to the next.
• 2 Temperature as well as food supply influence the length of larval growth and adult body size. Beetles grown at low temperatures and low amounts of food are smaller than those grown at higher temperature and with more food.
• 3 The number of eggs laid per female was correlated with the amount of food gathered. There was no inverse relationship (trade-off) between reproductive output and survival in the field until the next breeding season.
• 4 In 1980 no significant relationship was found between winter mortality and the amounts of food gathered by beetles in the period after reproduction and before winter diapause. However, in 1981 in C. melanocephalus a lower number of starved beetles survived the winter than the fed ones and‘field’beetles.
• 5 Only in the first part of the feeding activity period in autumn can enough food be gathered by C.melunocephalus for successful hibernation. In the second part of this period there is not enough food to build up the fat reserves needed to survive the winter.
• 6 Difference in population fluctuations of both species are discussed in relation to their life histories.

     

Moulting diving ducks and their food supply

Numbers of moulting diving ducks at Myvatn, north Iceland, were monitored over a period of 25 years; aquatic insects (Chironomidae and Simuliidae), a major food resource, were monitored with window traps for 23 years. The response of the duck populations to changes in the food situation during the moulting period varied between species. Histrionicus histrionicus and Melanitta nigra invariably go to the sea to moult. Three species (Aythya fuligula, Clangula hyemalis and Mergus serrator) have shown long term variation in moult migration habits. Aythya marila and Bucephala islandica stay for moulting, their numbers supplemented by birds from elsewhere. A. marila is a generalist feeder and therefore at low risk of starving, the strategy of Bucephala islandica is to move within the water system where the food situation tends to alternate between the lake and the river. Numbers of Bucephala islandica males moulting on Lake Myvatn were strongly and positively correlated with chironomid numbers and those moulting on the river Laxá with Simulium vittatum, the main food resource there. We did not find convincing evidence that numbers of moulting A. marila and C. hyemalis responded to variation in the food supply during the study period. This applied also to A. fuligula in the South Basin of Myvatn, but numbers in the North Basin were positively associated with chironomid numbers. M. serrator moulting on Myvatn showed negative correlations with the chironomids, perhaps reflecting a negative association between chironomids and its main food, Gasterosteus aculeatus. Apart from safety considerations for a flightless bird, the choice of a moulting site is apparently influenced by the local food conditions on one hand and by the opportunities and risks involved in migrating to distant moulting sites with an unknown food situation on the other hand.     

On the food of the freshwater eels and their feeding relationship with the salmonids

Following the results of the cursory investigations made by Jones & Evans (1960,1962) into the predatory habits of eels we decided to enlarge on this work. Consequently we looked at the stomach contents of about 5000 eels. In addition and at the same time two Welsh streams carrying salmonids were selected and sampled specifically to try to determine the relationship in the feeding habits of eels and salmonids.
The food of eels consisted mainly of trichopteran and dipteran larvae and plecopteran and ephemeropteran nymphs, though at times Gastropoda, Annelida, Crustacea and fish were common in the stomachs. Fish was not an important dietary item but, when eaten, the fish most commonly taken were elvers and eels.
In the River Dwyfach the salmonids ate more or less the same type of food as the eels, but the trout ate more surface food than the young salmon.
The similarity in feeding between the eels and salmonids resulted in apparent competition during the warmer months. In winter when the eels ate little the competition was thus almost negligible. Even though we speak of competition for the food available in the summer months we feel that before this can be accepted as fact we must know the relative abundance of each food organism eaten at this time.     

The relation between dispersal and survival of Lobesia botrana larvae and their density in vine inflorescences

Dispersal and survival of Lobesia botrana Den. & Schiff. (Lepidoptera: Tortricidae) larvae in a simulated first generation and the relationship with their density on vine inflorescences were studied under field conditions. Artificial infestations with neonate larvae were conducted at densities of 5, 10, 15, 20 and 25 individuals per vine inflorescence. Larvae had a considerable dispersal capacity on the vine espalier and were able to reach several inflorescences around those artificially infested. Dispersal downwards (63.1%) was significantly more frequent than upwards (36.9%), probably because larvae move down the vine plant using silk threads. However, the fact that there was upwards dispersal provides evidence that larvae are capable of active locomotion upwards on the vine plant structure. Mean distances covered by larvae ranged between 10 and 30 cm, with a maximum as far as 45 cm. The longest displacements were not associated with the downward dispersal. The maximum distance covered by larvae was positively correlated with larval density. Mean distance and larval density were not correlated, but mean distances covered at high larval densities were significantly higher than at low densities. At higher larval densities, the proportion of larvae which established in the artificially infested inflorescences decreased whereas the proportion of dispersing individuals increased. However, as a result of the balance between establishment and dispersal, larval survival did not differ significantly among larval densities (26–44%). The results obtained suggest that larval dispersal must be taken into account when preimaginal stages are sampled to determine whether damage thresholds are reached in an integrated pest management program.     

The relationship between nectar supply and the rate of capture of a nectar-dependent small marsupial Tarsipes rostratus

The influence of mild temperature (20 C) combined with different photoperiods (natural day length; 16L: 8D; 8L: 16D) on the testis of Gambusia affinis holbrooki during the early (Experiment I) and late (Experiment II) phases of the testicular quiescence period was studied by histologic quantitative methods. In Experiment I (October-January), spermatogenic development was not found in either the initial and final control fishes or the experimental groups. In Experiment II (January-March), neither initial nor final controls showed spermatogenic development. The group subjected to the short photoperiod showed development of secondary spermatogonia but no spermatocytes. Complete spermatogenesis was observed in both the group exposed to the natural day length photoperiod and the group exposed to the long photoperiod. These results indicate that a mild temperature combined with a long photoperiod induces spermatogenesis in G. affinis in the late phase of quiescence.     

二化螟蚁螟在不同类型水稻品种上的存活率及寄主选择性

二化螟Chilo suppressalis Walker是我国主要水稻害虫之一,近年来发生量呈上升趋势.本文研究表明二化螟蚁螟在不同类型水稻品种上3d的存活率不同.在两优培九上,3d的存活率最高,为60.8％.其次为南京11,其存活率为45.8％;在南粳44、武运粳7号、常优3号、武育粳3号和香糯8333上3d的存活率与南京11差异不显著,为40.0％ ～45.0％.在Ⅱ优084上蚁螟3d的存活率最低,只有25.8％.蚁螟对不同类型水稻品种的选择性也有差异.在8个水稻品种中,蚁螟对杂交籼稻两优培九的选择性最高,圆盘法测定其选择率为21.0％;Y型嗅觉仪法测定结果与圆盘法一致,在所有组合中蚁螟对两优培九的选择率均大于50.0％,明显高于常规籼稻和粳稻.蚁螟对南粳44(16.5％)和南京11(15.5％)的选择性仅次于两优培九,其后为常优3号(13.5％).对香糯8333的选择性最低,圆盘法测定其选择率仅有5.6％.进一步利用SPSS软件回归分析蚁螟在不同水稻品种上3d的存活率和对该品种的选择性,发现二者间存在明显的正相关关系.     

The relationship between female body size and survival rate of the malaria vector Anopheles arabiensis in Ethiopia

Abstract. The relationship between female mosquito body size and survival rate was studied in field populations of Anopheles arabiensis in the Awash valley, central Ethiopia. Body size was quantified by measuring the wing-length. Highly significant correlations were found between size, parousness and insemination. It was concluded that larger An.arabiensis females have a higher probability of survival, being inseminated and producing more egg batches than smaller adults. Implications for vectorial capacity and vector competence of mosquitoes are discussed.     

On the relationship between reproduction,age and survival in two carbid beetles:

Summary In this study the inverse relationship between the amount of reproduction in female carabid beetles and their survival until the next breeding season, suggested by Murdoch (1966), was examined in Pterostichus coerulescens L. and Calathus melanocephalus L.This was tested with individual and differently reproducing females, kept at the same temperature, as well as with groups of females kept at different temperatures, i.e. with very different overall levels of reproduction.No relationship was found between the numbers of eggs laid by individual females and their survival until the next breeding season.The numbers of eggs laid by individual females varies greatly, even under constant and optimal conditions,. In contrast to this, an individual female continues to lay a characteristic number of eggs over several succeeding weeks. The amount of reproduction is highly correlated with temperature when food is optimal. In P. coerulescens there was a positive correlation between the amount of reproduction of the same individuals in two succeeding years, whereas in C. melanocephalus no relationship could be found.Both in the field and in our experiments individuals of P. coerulescens generally live for 3 to 4 years, longer than C. melanocephalus which usually only lives for 2 years. The 3–4 year-old individuals of P. coerulescens die during the breeding season or shortly afterwards, but also during the winter, whereas the 2–3 year-old individuals of C. melanocephalus die during the winter. Males and females show a similar mortality after breeding. The level of reproduction of a population depends on the proportion of old beetles, since especially the very old ones die before the end of the breeding season.We reject the hypothesis of Murdoch because of these data. However, in a different way from that of Murdoch, we also suggest that old beetles are of great importance for the survival of a population, namely that this form of heterogeneity of a population may enhance its stability under varying environmental conditions.Communication No. 204 of the Biological Station, Wijster     

Withdrawn food rate for larvae of Siberian moth on conifers of Siberia

Experimental evaluation of the mass of food withdrawn by larvae of the Siberian moth during their development on larch, cedar pine, fir, spruce, and common pine was carried out. The obtained dependences between the masses of larvae and food withdrawn by them can be directly used to determine the withdrawn food rate of Siberian moth on each of the Siberian conifer species.     

生物钟信号调控的营养学

近日节律是生物界普遍存在的一种生理现象,而内源性生物钟是产生近日节律的物质基础,它能使生物体感知并适应环境中的光、温度和食物等周期信号,从而使生物体与外界环境保持周期同步。研究表明,葡萄糖、胆固醇、腺苷、咖啡因、维生素A和视黄酸等营养物质能通过各自不同的方式调控哺乳动物的生物钟,影响其近日节律的信号输出。本文概述了至今为止研究发现的各类与生物钟信号调控相关的营养物质及功能的相关研究进展。     

On the relationship between dissipation and the rate of spontaneous entropy production from linear irreversible thermodynamics

When systems are far from equilibrium, the temperature, the entropy and the thermodynamic entropy production are not defined and the Gibbs entropy does not provide useful information about the physical properties of a system. Furthermore, far from equilibrium, or if the dissipative field changes in time, the spontaneous entropy production of linear irreversible thermodynamics becomes irrelevant. In 2000 we introduced a definition for the dissipation function and showed that for systems of arbitrary size, arbitrarily near or far from equilibrium, the time integral of the ensemble average of this quantity can never decrease. In the low-field limit, its ensemble average becomes equal to the spontaneous entropy production of linear irreversible thermodynamics. We discuss how these quantities are related and why one should use dissipation rather than entropy or entropy production for non-equilibrium systems.     

Influence of the growth rate calculation on the relationship between growth rate and temperature

Three calculations of the growth rate (e.g. slope of a plot of the log10 of cfu ml-1 vs time, mum of the Gompertz equation and the reciprocal of time to obtain 108 cfu ml-1) were compared for Escherichia coli TG1 growing in tryptone soy broth medium at temperatures ranging from 14 to 39 degrees C. Up to now, the influence of using such different definitions on the relationship between microbial growth rate and temperature has never been investigated. In order to compare these calculation procedures, a dimensionless analysis based on the following normalized variables, mudim = mu/muopt and Tdim = [T-Tmin]/[Topt-Tmin], was used (Dantigny 1998). The influence of suboptimal temperatures on the growth rate was represented by means of a Belehràdek-type model based on a power function law: [mudim] = [Tdim]alpha. The influence of the different growth rate calculations on the model constants was assessed. Despite the great dependence of the raw growth rate values on the calculation procedure, the dimensionless analysis demonstrated that the alpha-value is independent of the growth rate definition. This result suggests that any definition for the growth rate can be utilized in studies aimed at determining the influence of temperature on microbial growth and highlights the interest of using dimensionless variables to overcome differences in the order of magnitude of the growth rate data and to avoid confusion between definitions.