Utilisation of prey by antlion larvae (Neuroptera: Myrmeleontidae) in terms of energy and nutrients

Prey utilisation at low prey densities was determined for third instar Cueta sp., Furgella intermedia (Markl) and Palpares annulatus (Stitz) larvae in terms of wet weight, dry weight, energy and nutrients. Prey utilisation was similar to other insects on a wet weight (42-47%), dry weight (46-49%), energetic (40-58%) and nutritive basis (62-79%). Lipids (33-36%) provided energetically the highest contribution of the nutrients ingested. The quantities of water, proteins, nucleic acids, lipids and carbohydrates extracted by the antlion larvae were in proportion to their availability in their prey, the Hodotermes mossambicus larvae. The quantities of nutrients extracted by the antlion larvae at low prey densities were not significantly influenced by the differences in mandible size, antlion body weight or the trapping method (building a pit or not) of the antlion species. It is proposed that a low metabolic rate and the accumulation of fat reserves, and not the extent of prey utilisation, enable P. annulatus larvae to tolerate a 123-d starvation period in which 22.3% of their body weight is lost.     

入侵早期食蚊鱼仔幼鱼食物组成、摄食策略及营养状况分析

饥饿是影响鱼类仔鱼早期存活的关键因素,入侵鱼类仔鱼耐饥饿能力对其种群增长与扩散意义重大。本文对滇池流域食蚊鱼Gambusia affinis奠基种群仔幼鱼摄食及仔鱼营养状况进行深入分析,初步了解了饥饿因素在食蚊鱼入侵早期种群增长中的影响。研究结果显示,该种群食蚊鱼仔幼鱼主要以枝角类、桡足类为食物,同时能够广泛利用栖息地食物资源,包括种类较为丰富的水生昆虫幼体、弹跳虫等,具有广食性的摄食策略,许多个体食物多样性指数>1。这些特点与其口裂较大、发育较为完善的特点密切相关。尽管如此,仍有高达73.27%的食蚊鱼仔鱼存在饥饿胁迫问题,可能与奠基种群自身生物学特点、仔鱼群体内部竞争、行为特点及环境资源差异化分布格局等因素密切相关。对奠基种群而言,入侵早期仔幼鱼面临陌生的栖息地生境,其摄食与营养状况对种群的定殖有关键影响。     

Digestive enzyme profiles reveal digestive capacity and potential energy sources in fed and starved spiny lobster (Jasus edwardsii) phyllosoma larvae

The impact of starvation on the digestive enzyme (protease, trypsin, lipase and amylase) activities of Stage I and IV Jasus edwardsii phyllosoma larvae was used to identify the nutrients metabolised or conserved during food deprivation, highlighting the most critical energy reserves. Protease activities increased significantly in both Stages I and IV phyllosoma, suggesting that protein catabolism provided energy during food deprivation. Lipase activity decreased significantly in starved Stages I and IV larvae indicating that lipid may be spared for fuelling later developmental moults. The use of protein, while sparing lipid, may provide immediate energy but not at the expense of long-term lipid energy stores which are known to be important during their lengthy larval phase. The preferential use of protein during short-term periods of starvation suggests that particular attention must be given to providing sufficient protein in artificial diets at all times. Amylase activity in starved Stage I larvae was lower than in fed animals, suggesting that the starved animals are not gaining sufficient carbohydrate. However, amylase activity was similar in fed and starved Stage IV larvae, possibly due to the catabolism of accumulated glycogen stores that were not sufficiently developed in Stage I animals.     

The effect of starvation on RNA: DNA ratios and growth of larval striped bass, Morone saxatalis

Hatchery reared larval striped bass, Morone saxatilis , 8-days-post-hatching were subjected to various feeding/starvation regimes over a period of 14 days.
Batches of larvae from each treatment were sampled over the 14-day period and subdivided for determination of notochord length and RNA:DNA ratio. The best growth was found in fully fed F1000 larvae (exposed to 1000 Artermia nauplii l⁻¹), which reached 8.2 mm after 11 days and 9.6 mm after 14 days. Starved animals after 11 days had notochord lengths of 4.9 mm. Growth curves from feeding-delayed larvae indicated that animals fed after up to 5 days starvation were capable of complete recovery. F100 larvae (exposed to 100 Anemia nauplii 1^−l) had a slower growth rate than F1000 larvae, reaching a notochord length of 7.3 mm after 14 days. RNA:DNA ratios over time closely followed notochord growth curves, with clear differences between starved, F100 and F1000 larvae being established after only 2 days. Equilibrium RNA:DNA ratios of 3.0 and 2.25 were established in F1000 and F100 larvae, respectively, 6.8 days after the beginning of the experiment. The average lag time between a change from the starved to the fed condition and a change in RNA:DNA ratio as determined by the divergence of the nucleic acid curve from the starved condition was 0.66 days.
In treatments where starvation followed various periods of feeding, larvae regressed in notochord length such that the final length at 14 days reflected the degree of feeding. RNA:DNA ratios in these animals again closely followed growth curves with a lag time of 0.81 days.
It was concluded that RNA:DNA ratios provided very accurate indices of growth in striped bass larvae which were highly sensitive to feeding status.     

低温和饥饿对华贵栉孔扇贝幼虫生长和存活的影响

为了弄清我国南方低温季节能否利用自然水温进行华贵栉孔扇贝人工育苗以及饵料缺乏对幼虫的影响,于2008年10月上旬和11月下旬,分别在水温25.5—28.0℃和18.2—22.5℃条件下,研究了低温和饥饿对幼虫生长、存活的影响。实验分两次设置常温、低温和饥饿3个组进行。结果表明,低温情况下,幼虫摄食较少,活力差、绝大部分沉入水底,生长缓慢,发育迟缓,但存活率仍较高;饥饿不但抑制幼虫的生长和发育,同时也显著地降低幼虫的存活率。此外,低温和饥饿的结合会加剧对幼虫生长、发育、存活等的抑制作用。这些结果说明在我国南方水温低于23℃的季节利用自然水温已不适合进行华贵栉孔扇贝苗种生产。     

Feeding ability and survival during starvation of marine fish larvae reared in the laboratory

The larvae of Clyde and Baltic herring (Clupea harengus L.), cod (Gadus morhua L.) and flounder (Platichthys flesus L.) were reared and fed to examine the changes in feeding ability and survival during progressive starvation. The time to initial feeding for yolk-sac larvae and to the point-of-no-return (PNR, when 50% of the larvae, although still alive, are no longer strong enough to feed) for both yolk-sac and older larvae were determined. The yolk-sac larvae of Clyde and Baltic herring, cod and flounder begin to feed on days 6, 3, 5 and 6 post-hatching at rearing temperatures of 7.5, 9.2, 6.9 and 9.5°C, respectively. The time to reach the PNR for yolk-sac larvae of these species is only 3–5 days after yolk resorption. From the onset of starvation in older larvae the time to reach the PNR is 6–7 days for 36-and 60-day-old Clyde herring at 9.6 and 10.5°C and for 46-day-old Baltic herring at 13.1°C but it is 23 days for 32-day-old flounder at 12.3°C. In yolk-sac larvae the peak of feeding rate and intensity usually occurred on the day that the yolk became exhausted, or 1 day later. Older larvae could withstand longer periods without food than yolk-sac larvae, especially in flounder. While the feeding rate during starvation of older larvae slowly decreased the feeding intensity first increased significantly and then decreased. Survival of larvae remained high up to the PNR.     

Larval life history responses to food deprivation in three species of predatory lady beetles (Coleoptera: Coccinellidae)

We studied life history responses of larvae of three coccinellid species, Coleomegilla maculata (DeGeer), Hippodamia convergens Guerin-Meneville, and Harmonia axyridis (Pallas), when deprived of food for different periods of time during the fourth stadium. The coccinellid species did not differ in starvation resistance when larvae were starved throughout the stadium; however, for larvae fed only on day 1 of the stadium, H. convergens had the highest starvation resistance, followed by H. axyridis and then C. maculata. Percentage weight loss of larvae was affected by food deprivation period and coccinellid species. Both C. maculata and H. axyridis lost significantly more weight than H. convergens when starved throughout the fourth stadium. When deprived of food for 4 d of the stadium, C. maculata lost a higher percentage of initial body weight than H. axyridis. Percentage weight loss of H. convergens did not differ from that of C. maculata or H. axyridis. The weight of fourth instars and adults declined in an accelerating pattern as food deprivation period increased. However, food deprivation period had no significant effect on pupal development time for any of the three species or on larval development time for C. maculata and H. convergens. The increase in H. axyridis larval development time as a result of an increase in food deprivation period was curvilinear. Based on this laboratory study, it would seem that H. convergens is better able to cope with acute nutritional stress than either C. maculata or H. axyridis.     

Effect of starvation on the nutritional condition of early zoea larvae of the red squat lobster Pleuroncodes monodon (Decapoda,Munididae)

Abstract

One of the key factors affecting larval survival is food availability. This study investigated the influence of starvation on the nutritional condition of zoea I larvae of Pleuroncodes monodon. Experimental treatments with differential periods of starvation and subsequent feeding (point of no return: PNR) in addition to treatments with differential periods of feeding and subsequent starvation (point of reserve saturation: PRS) were used to quantify larval survival and the occurrence of lipid droplets in the hepatopancreas. Larval survival differed significantly depending on the starvation and feeding treatment administered. A high percentage of survival was found for the starvation treatment until day 1 (S1-PNR), for the feeding treatment until day 4 (F4-PRS), and for the continuously fed control groups (FC). Survival was minimal for the starvation treatment lasting until day 7 (S7-PNR) and for the continuously starved control groups (SC). In turn, similar tendencies were observed in the utilization of energy reserves; the lipid droplets significantly decreased throughout the PNR treatment, while the presence of lipid droplets gradually increased during the PRS treatment. All these larval condition parameters can be used in fishery models of population dynamics, which estimate the nutritional status of the offspring and their effects on survival.     

The flow of food in colonies of the fire ant, Solenopsis invicta: a multifactorial study

ABSTRACT. A study was conducted to determine the interaction of several factors in the trophallactic distribution of food in colonies of Solenopsis invicta Buren. Radioactive iodine (¹²⁵I) was used to quantify both the ingestion of test foods by foragers and the distribution of this food to nestmates. A multifactorial design tested the simultaneous effects of: (1) food-type (sugar water, casein hydrolysate, or oil), (2) temperature during foraging and food-sharing (25, 30 or 35°C), and (3) starvation period (colonies deprived for 0, 3, 7 or 14 days). The amount of food consumed by foragers was influenced by the interaction of food-type and starvation. Foragers from severely starved colonies ingested more aqueous foods than did those from slightly starved colonies, but oil was always taken in smaller quantities and its ingestion was least affected by starvation. Ingestion was generally lowest at 35°C, probably because of mutual interference of workers while feeding. Within the colony, food sharing varied with food type and increased with starvation. The sugar solution was utilized primarily by workers. Amino acids were shared throughout the colony, but were directed preferentially to the growing larvae. Soy oil was equally shared among workers and larvae and reached more colony members per initial unit volume than did the other foods. The test factors also interacted in their influence on trophallaxis. Starvation stimulated the dispersal of labelled foods, but at different intensities for different foods. The probability of the queen's receiving food increased when the labelled food was widely exchanged among her nestmates. Casein hydrolysate reached the queen in more cases than did the other tested foods.     

Biology of Lutzomyia intermedia Lutz & Neiva, 1912 and Lutzomyia longipalpis Lutz & Neiva, 1912 (Diptera, Psychodidae), under experimental conditions. I. Feeding aspects of larvae and adults

To improve our knowledge on the breeding and behaviour of sandflies in captivity, we established closed colonies of Lutzomyia intermedia and Lutzomyia longipalpis. Data are here presented on the feeding preferences of larvae and adults and their influence on the development and survival of each species. Fish food is accepted by the larvae of both species; it is easily available, unexpensive and does not encourage the growth of fungi. The larvae of both species, in all stages accepted food of vegetal and mixed origin, but the 1st and 2nd stage larvae of L. intermedia preferred vegetal food, while the 3rd and 4th stage larvae of L. longipalpis showed a discreet preference for mixed food. Previous feeding on sugar was not necessary to induce a blood meal. Both species can feed on man, dog, hamster and bird, but better development was obtained when the females was fed on hamster. The female of L. longipalpis were more resistant to the absence of blood meal than those of L. intermedia, although 70% of both were able to survive on a sugar meal up to seven days.     

Digestion and excretion of nitrogen and carbohydrate by the cranefly larva Tipula paludosa (Diptera: Tipulidae)

The nitrogenous and carbohydrate components of ryegrass and faeces from larvae of Tipula paludosa Meigen, fed on ryegrass (Lolium perenne L.), were compared. Proteins in ryegrass were efficiently digested and uric acid was the major nitrogenous excretory product. The alkaline midgut (pH 9.1) was considered to enhance the digestibility of hemicellulose, by removing inhibitory acetyl groups, and of cellulose by altering its crystallinity. T. paludosa larvae assimilated 50% of ryegrass cellulose, and 50% of an isolated ¹⁴C-labelled cellulose, whereas 86% of hemicellulose was digested.     

The abundance and trophic biology of Clarias albopunctatus Nichols & LaMonte, 1953 (Osteichthyes: Clariidae) in a tropical floodriver basin

The abundance, food and feeding biology of Clarias albopunctatus was studied over a period of 17 months in the lower River Anambra, Nigeria. The catfish was more abundant in late dry season (January–March) and early rainy season (April–June) than in other periods of the year in the small-sized Akwu pond than in other habitats. Feeding intensity was higher at night and at dawn (20.00–05.00 h) than during the day (08.00–17.00 h) in the 151–200 mm TL size class and during the rainy season (April–September). There was no sex-dependent variation in feeding intensity. Insects were the predominant food, followed by crustaceans. Of primary importance were Chironomidae (mainly Chironomus spp. and Tanypus sp.), Odonata nymphs, Dytiscus sp., mosquito larvae and pupae, Gyrinus sp., Daphnia sp., Ostracoda and Tilapia fry. Qualitative food composition and food richness were size, but not sex – or season-dependent. Diet breadth increased with catfish size and during the rainy season. The feeding behaviour of the catfish include foraging, shovelling and surface feeding. Abundant food and ability to switch to more available items enable C. albopunctatus to maintain its abundance in the River Anambra. This revised version was published online in July 2006 with corrections to the Cover Date.     

Starvation induced stress and the susceptibility of the Colorado potato beetle,Leptinotarsa decemlineata,to infection by Beauveria bassiana

Starvation of second instar Colorado potato beetle larvae for 24h immediately after treatment with Beauveria bassiana conidia increased susceptibility to the pathogen and subsequent sporulation of cadavers but decreased time to larval death. In feeding studies, B. bassiana-treatment had no effect on subsequent larval development, and mortality occurred 5-6 days after treatment. Twenty-four hours of starvation alone retarded subsequent larval development but did not affect mortality. Mortality of B. bassiana-treated starvation stressed larvae occurred 4-5 days after treatment. Both B. bassiana treatment and 24h starvation significantly reduced total foliage consumption and daily weight gains. On the day of treatment, B. bassiana had no effect on the efficiency with which food was converted to biomass (ECI). ECI was not affected by B. bassiana or starvation alone on the day following treatment but was significantly affected by a combination of both. When larvae were exposed to a range of limited food quantities, ECI decreased with decreasing food availability but only extreme stress (starvation for 24h) increased susceptibility to B. bassiana. Topical application of Dacryodes excelsa resin (an antifeedant) to potato leaves caused a concentration dependent reduction in foliage consumption and weight gain by second instar larvae but did not affect larval mortality. When larvae were exposed to a fixed concentration of B. bassiana and a range of antifeedant concentrations there were significant linear relationships between 24h larval weight gain and mortality and 24h larval weight gain and sporulation. The interaction between starvation stress and the susceptibility to B. bassiana infection is discussed and its possible implications in pest management considered.     

Effects of various environmental conditions on growth and reproduction of the sea hareAplysia oculifera (Adams and Reeve, 1850)

We studied the influences of food type, food quantity, water currents, starvation and light on growth and reproduction of the sea hareaplysia oculifera (Adams and Reeve, 1850) under laboratory conditions. Out of five species of algae served as food,Enteromorpha intestinalis promoted the fastest growth ofA. oculifera, Ulva spp. slower growth,Cladophora sp. allowed maintenance spp. slower growth,Cladophora sp. allowed maintenance of steady body mass, and the brown algaeColpomenia sp. andPadina pavonia were rejected by the sea hares. When sea hares were exposed to four levels of water currents, growth rates decreased as water currents increased. Sea hares fed on 50% ration grew slower than those fed on 100% ration (ad libitum). During 10 days of starvation sea hares lost weight, but when subsequently fed 100% ration they recovered and grew at a rate similar to those fed continuously with 100% ration. Under shade and under natural sunlight sea hares grew at the same rates. Whenever growth rates decreased, sea hares began to spawn at a smaller body size.A. oculifera demonstrated physiological plasticity that adapted them to varied and unpredictable environmental conditions. At different conditions of food availability they applied different tactics of resource allocation between growth and reproduction.     

The impact of food type, temperature and starvation on larval development of Balanus amphitrite Darwin (Cirripedia: Thoracica)

The impact of diatom food species (Chaetoceros calcitrans and Skeletonema costatum), temperature and starvation on the larval development of Balanus amphitrite was evaluated. Starvation threshold levels for different ages of larvae (0- to 5-day-old) fed with C. calcitrans and S. costatum and then starved at 5, 15 and 25 °C temperature were estimated as ultimate recovery hour (URH; denoting the starvation point in hours at the end of which larvae can recover and continue development). Effect of temperature on starvation threshold varied significantly with larval age and food species. The URH declined with larval age at 5 °C, but not at 15 and 25 °C. The URH and grazing rates were high for early instars fed on C. calcitrans, and for advanced instars fed on S. costatum. Carbon gain through feeding was maximum for 2-day-old larvae when fed with C. calcitrans and decreased with larval age. However, when fed with S. costatum carbon gain increased with larval age. This confirms that with development the utility of food types changes. The differences in the carbon gain can be attributed to differences in grazing rate due to variations in the size of the diatom cells, larval intersetular distance, diatom sinking rate and the photo-taxic behavior of larvae. Molting was observed at times when larvae were undergoing starvation and this could be viewed as stress-induced molting, and it differed with the larval age and food organisms.     

Feeding habits of larval Mirogrex terraesanctae (Steinitz, 1952) in Lake Kinneret (Israel) II. Experimental study

Interactions between the larvae of Mirogrex terraesanctae (Steinitz, 1952) in Lake Kinneret, Israel, and their zooplankton prey were studied experimentally. Prey species preference and size selectivities were measured. Larvae were hatched in the lab from eggs collected in the field, and fed different food items in various concentrations. The food items included lake zooplankton, algae, and commercial pellets. It was shown that small, first feeding larvae (7–8.5 mm SL) prefer small bodied zooplankters (< 180 µ). The effect of these food sources on larval growth was measured. It was found that larval Mirogrex grew at a higher rate when fed zooplankton prey sized from 63 µ–250 µ. Food items smaller than 63 µ, larger than 250 µ and Scenedesmus sp., produced less than optimal growth rates. The importance of Mirogrex feeding habits and their potential influence on the Kinneret ecosystem is considered.     

Comparison of nutritional status of field and laboratory reared Balanus amphitrite Darwin (Cirripedia: Thoracica) larvae and implication of starvation

Experiments were carried out to evaluate the influence of rearing temperature and food concentration (20 and 30 °C, 1×10⁵ and 2×10⁵ cells ml⁻¹) on the starvation threshold and nucleic acid content of the larvae of Balanus amphitrite. The larvae were also field-reared using micro-enclosures. Laboratory-reared larvae were larger in size than the field-reared larvae. An increase in size, DNA content and instar index of the starved II instar larvae was observed indicating that the absence of food may not be fatal to this early instar. The temperature at which larvae were raised and the food concentration had variable influence on the capacity to withstand starvation. Exposure to increased temperatures during starvation eliminated the effect of doubling food concentration during their feeding period prior to starvation. The larvae reared at 20 °C had comparatively lower nucleic acid content. The laboratory-reared larvae had ca. 1.7 times greater RNA:DNA ratio than larvae raised at comparable temperature in the field.     

LC–MS/MS-Based Metabolome Analysis of Biochemical Pathways Altered by Food Limitation in Larvae of Ivory Shell, <Emphasis Type="Italic">Babylonia areolata</Emphasis>

Ivory shell, Babylonia areolata, is one of the commercially important mariculture species in China and South East Asia. Survival varies in the artificial hatching and larval rearing of B. areolata. Food deprivation may be involved in rearing mortality, and so, a better understanding of how larvae respond and adjust to starvation is needed. In this study, the metabolite profiles of newly hatched larvae with yolk (I), larvae with yolk exhaustion (II), larvae suffering 24 h starvation after yolk exhaustion (III), and larvae fed with exogenous nutrients after yolk exhaustion (IV) were analyzed by LC–MS/MS. Principal component and cluster analyses revealed differential abundance of metabolite profiles across groups. When compared to metabolite levels of the I group, significantly up-regulated metabolites included polyunsaturated fatty acids, phospholipids, nucleotide, amino acids, and their derivatives were found in the II group, indicating that organisms relied predominantly on glycerophospolipid metabolism and protein-based catabolism for energy production during this stage. During starvation after yolk exhaustion, the levels of all energy related metabolites were significantly reduced, but an increase in products of purine and pyrimidine metabolism indicated an insufficient energy supply and an increase in cellular disintegration. Larvae fed exogenous nutrients can have significantly improved metabolism compared to starved larvae. These findings suggest that metabolomics, using LC–MS/MS, can be used to assess the physiological status and food-affected metabolic changes affecting B. areolata larvae.     

Uric acid excretion in larval Manduca sexta

The characteristic coating of frass of last-instar tobacco hornworms, Manduca sexta, reared on artificial diet, proved to be uric acid. Results indicated that uric acid is the major nitrogenous excretory product; during most of the larval feeding stage, 5–7% of the excreta (dry weight basis) was uric acid; only minute quantities of allantoic acid were present. The rate of uric acid excretion was linear for the periods when coated pellets were observed. Abrupt increases in uric acid resulted from delays in pellet expulsion associated with delays in feeding activity. A distinctive coating was not generated by penultimate instar larvae, but abrupt changes in uric acid content did occur, which suggests that the phenomenon of coated frass is directly related to a differential in uric acid concentration. The source of uric acid in the frass was the Malpighian tubule system. The transition period between feeding and the wandering stage was a time of rapid decrease in uric acid excretion; there were only low levels in the last fecal pellets and none in Malpighian ampullae of wandering-stage larvae. Since the first appearance of coated fecal pellets preceded the release of ecdysone by about 24 hr, the involvement of this hormone was not indicated.     

Effects of food availability on larval development in the slipper limpet Crepidula onyx (Sowerby)

Effects of food availability on the larval survival and development of Crepidula onyx were studied in four experiments by feeding the larvae with different concentrations of the chrysophyte Isochrysis galbana and by starving the larvae for different periods of time. Food concentration had a clear impact on the survival, growth and development time of C. onyx veligers. Larval development occurred only at 10⁴ cells ml⁻¹ and higher algal concentrations. No shell increment was detected in the veligers cultured for 12 days at 10² cells ml⁻¹I. galbana or the blank control. At 10³ cells ml⁻¹, there was only a slight increase in shell length over 12 days. At 10⁴ cells ml⁻¹, about 40% of the larvae became competent in 18 days. At 10⁵ and 10⁶ cells ml⁻¹, more than 90% of the larvae reached competence in 7 days. Initial starvation negatively affected the larval development, but the sensitivity differed among parameters measured on day 5: lower survivorship was detected only for larvae that had suffered 3 days or longer initial starvation, whereas one-day initial starvation caused shorter shells and lower percentage of competent larvae. Three days of continuous feeding was required for 50% of the larvae to reach competence. After feeding for 3 days, most larvae could become competent to metamorphose even under starvation. The time of starvation was also critical: larvae that suffered 1-day food deprivation in the first 2 days of larval release had shorter shells and lowered percent competent larvae than those that suffered the same length of food deprivation in later stages of development. Our study thus indicates that both food concentration and short-term starvation have detrimental effects on the larval development of this species, and that once the larva has consumed certain amount of food, starvation may induce metamorphosis.