Energetics of larval swimming and metamorphosis in four species of Bugula (Bryozoa)

The amount of energy available to larvae during swimming, location of a suitable recruitment site, and metamorphosis influences the length of time they can spend in the plankton. Energetic parameters such as swimming speed, oxygen consumption during swimming and metamorphosis, and elemental carbon and nitrogen content were measured for larvae of four species of bryozoans, Bugula neritina, B. simplex, B. stolonifera, and B. turrita. The larvae of these species are aplanktotrophic with a short free-swimming phase ranging from less than one hour to a maximum of about 36 hours. There is about a fivefold difference in larval volume among the four species, which scales linearly with elemental carbon content and, presumably, with the amount of endogenous reserves available for swimming and metamorphosis. Mean larval swimming speeds (in centimeters per second) were similar among species. Specific metabolic rate and larval size were inversely related. For larvae of a given species, respiration rates remained similar for swimming and metamorphosis; however, because metamorphosis lasts about twice as long as a maximal larval swimming phase, it was more energetically demanding. Larger larvae expended more energy to complete metamorphosis than did smaller larvae, but in terms of the percentage of larval energy reserves consumed, swimming and metamorphosis were more "expensive" for smaller larvae. A comparison of the energy expended during larval swimming calculated on the basis of oxygen consumption and on the basis of elemental carbon decrease suggests that larvae of Bugula spp. may not use significant amounts of dissolved organic material (DOM) to supplement their endogenous energy reserves.     

Early development of milkfish: effects of salinity on embryonic and larval metabolism, yolk absorption and growth

During embryogenesis of Chanos chanos , more than half of the yolk was consumed and the majority of it was converted into larval tissue. Salinity affected both yolk absorption and embryonic and larval growth. Larvae hatched in 20% had larger yolk reserves but were smaller and grew more slowly than larvae in 35 and 50%. Larvae hatched in 35 and 50% had equal amounts of yolk but those from 35% were larger. Oxygen consumption rates increased during development (from 0.06 ± 0.01 μl O₂ egg^–1 h^–1 by blastulae to 0.37 ± 0-01 μl O₂ egg^–1 h^–1 by prehatch embryos and 0–43 ± 0–03 μl O₂ larva ^–1 h ^–1 by newly-hatched larvae) and were significantly affected by salinity. Eggs and yolk-sac larvae incubated in 35% consumed more oxygen than those in the low and high salinities. Salinity affected both the rate and pattern of yolk utilization but salinity-related differences in metabolism, yolk absorption, and growth were not related directly to the osmotic gradient. Low salinity retarded yolk absorption while high salinity reduced yolk utilization efficiencies. Differences in oxygen consumption rates were probably related to variations in the relative amounts of metabolically active embryonic and larval tissue and/or higher activity levels rather than differential osmoregulatory costs. 35% is probably the most suitable salinity for incubation and larval rearing of milkfish.     

Comparative larval energetics of an ophiuroid and an echinoid echinoderm

The morphologically convergent larvae of the echinoderm classes Ophiuroidea and Echinoidea have been suggested to be functionally dissimilar when it comes to their capacities to feed, but little is known about whether these larvae are similar in terms of energetics. Here, we compare the energetics of early development of a tropical ophiuroid, Ophiocoma alexandri, and a temperate to tropical echinoid, Arbacia punctulata, two species with similarly sized eggs. Measurements of respiration and constituent analyses were performed on eggs and unfed larvae of both species. Members of both species showed an increase in oxygen consumption during morphogenesis followed by a lower, static rate once morphogenesis was complete (3 d for O. alexandri and 1.3 d for A. punctulata). Compared to the echinoid larvae, the ophiuroid larvae developed more slowly and had peak respiration rates that were 3.1× lower. Eggs of O. alexandri contained significantly more protein and significantly less triacylglycerol than eggs of A. punctulata. Energy utilization, as calculated via respiration measurements, closely matched decreases in energy content from the eggs to larvae as measured with biochemical constituent assays. Larvae of A. punctulata used 1.4× more energy to reach the pluteus stage than larvae of O. alexandri, and used 4× more energy during the first 9 d of larval life. These data suggest that echinoid larvae require more energy to develop to the feeding stage than ophiuroid larvae, and likewise have higher requirements for maintenance metabolism. Ophiuroid larvae may be more tolerant of low food levels due to their very low metabolic rates, but this advantage may be offset by their slower rate of development.     

Growth and respiration of embryos and larvae of the rabbittish Siganus randalli (Pisces, Siganidae)

Growth and respiration of larval rabbitfish from Guam were examined. Larvae were reared from eggs in 2- to 10-ton tanks and were fed rotifers, Anemia , and artificial feed in succession as development proceeded through metamorphosis. Growth in length was rapid during the 12 h after hatching, then slowed until the larvae began to feed. The yolk sac was usually absorbed by 36 h after hatching. Rates of respiration of larvae and eggs were determined with a dissolved oxygen electrode at various times through development. Larval metabolism increased steadily during the embryonic stages culminating in a metabolic burst immediately after hatching. Respiration rates remained relatively stable from shortly after hatching until the onset of exogenous feeding, after which respiration rates increased with larval size. The respiration rates of post-yolk-sac larvae scaled isometrically with larval dry mass. Daily growth of feeding larvae was 27 to 28% of larval dry mass.     

Rapid declines in metabolism explain extended coral larval longevity

Lecithotrophic, or non-feeding, marine invertebrate larvae generally have shorter pelagic larval durations (PLDs) than planktotrophic larvae. However, non-feeding larvae of scleractinian corals have PLDs far exceeding those of feeding larvae of other organisms and predictions of PLD based on energy reserves and metabolic rates, raising questions about how such longevity is achieved. Here, we measured temporal changes in metabolic rates and total lipid content of non-feeding larvae of four species of reef corals to determine whether changes in energy utilization through time contribute to extended larval durations. The temporal dynamics of both metabolic rates and lipid content were highly consistent among species. Prior to fertilization, metabolic rates were low (2.73–8.63 nmol O₂ larva^?1 h^?1) before rapidly increasing to a peak during embryogenesis and early development 1–2 days after spawning. Metabolic rates remained high until shortly after larvae first became competent to metamorphose and then declined by up to two orders of magnitude to levels at or below rates seen in unfertilized eggs over the following week. Larvae remained in this state of low metabolic activity for up to 2 months. Consistent with temporal patterns in metabolic rates, depletion of lipids was extremely rapid during early development and then slowed dramatically from 1 week onward. Despite the very low metabolic rates in these species, larvae continued to swim and retained competence for at least 2 months. The capacity of non-feeding coral larvae to enter a state of low metabolism soon after becoming competent to metamorphose significantly extends dispersal potential, thereby accruing advantages typically associated with planktotrophy, notably enhanced population connectivity.     

Function of Ventral and Lateral Processes in Larvae of Chironomus (Diptera, Chironomidae)

Oxygen consumption by larvae of five Chironomus species from the Plumosus group belonging to different larval forms was studied. Larvae of C. agilis ( f. l. reductus) were unable to utilize oxygen at its concentrations lower than 1 mg/l. Larvae of C. plumosus ( f. l. plumosus) used oxygen from water at concentrations higher than 0.7 mg/l; pupas of this species and larvae of C. borokensis ( f. l. plumosus) utilized oxygen at concentrations lower than 0.4 mg/l. C. entis and C. muratensis (both-- f. l. semireductus) utilized oxygen from water at its concentrations up to 0.05 mg/l. The lack of correlation between the rate and ability of larvae to use oxygen at low concentrations and the degree of development of processes allows suggesting that these structures are not additional respiratory organs, as is commonly accepted. At the same time, ability of species to inhabit under conditions of oxygen deficiency correlates directly with the size of the processes. Therefore, ventral and lateral processes are suggested to perform a function of excretion of anaerobic metabolism metabolites.     

The energetic costs of case construction in the caddisfly Limnephilus rhombicus: direct impacts on larvae and delayed impacts on adults

Caddisflies, whose aquatic larvae build a portable case with silk, are a suitable model organism to test the impacts of resource allocation trade-off during development and examine the evolution of life-history strategies. In the caddisfly Limnephilus rhombicus, adult feeding is minimal. Therefore, the whole resources are acquired during the larval phase and must be allocated to case construction, growth and reproduction. In this study, the larval energetic reserves of L. rhombicus were manipulated by forcing larvae to rebuild their cases in the final larval stage. This allowed us to measure the physiological cost of construction. First, we recorded oxygen consumption during case reconstruction. Second, we measured the sugar, protein and lipid contents of larvae forced to rebuild their case and of larvae required only to re-enter on their case. Larvae had their sugar, protein and lipid content measured after the rebuilding event and 72 h later. The same analyses were carried out with adults immediately after emergence. We found that larvae forced to rebuild a case consumed 1.5 times more oxygen than control larvae. This energy expenditure generated a cost that was estimated to be a loss of larval protein of approximately 35%. Insects were unable to compensate for this loss of proteins during the end of the larval stage, and their metamorphosis to adults was also impacted. Therefore, we suggest that loss of larval protein is linked to silk production and may alter fitness.     

Lipid content in the early life stages of three mesopelagic fishes

Changes in lipid concentration during early ontogenetic stages were determined in three mesopelagic fish species, Benthosema glaciale , Hygophum benoiti and Maurolicus muelleri . Total lipid content per larva was related to size and mass and increased over the course of development. In all three species, the dry mass : total lipid ratio displayed a better fit than the standard length : total lipid ratio. Larvae of B. glaciale had a higher amount of lipid content, at a given mass, than the other two species. The rate of lipid accumulation with increasing larval development was similar in B. glaciale and H. benoiti , and both were higher than in M. muelleri larvae. Furthermore, total lipid concentration values, as a proportion of dry mass, increased significantly from the larval to the juvenile stages in B. glaciale (from 16 to 55%) and M. muelleri (from 9 to 20%). The present study has allowed comparisons to be drawn of the ability on the early developmental stages of deep‐sea fishes to accumulate energy reserves, both within and among species.     

Temperature and food quality influences feeding behavior,assimilation efficiency and growth rate of arctic woolly-bear caterpillars

Summary The energy budget for feeding activity and growth of larval Gynaephora groenlandica was investigated on the tundra and in the laboratory. Larvae fed only in June when the buds and young leaves of Salix arctica, its principal host plant, contained the highest concentrations of macro-nutrients and total nonstructural carbohydrates (TNC). The mid-summer hiatus in larval feeding was coincident with an abrupt decline in the TNC content of leaves and a buildup of plant secondary metabolites in the leaves of S. arctica. Following cessation of feeding, the larvae remained concealed from the sun within crevices and vegetation mats. Growth rates of larvae incubated at 15 and 30°C were similar (4.7–5.0 mg/larva/day), but the assimilation efficiency at 15°C was four times greater (40%) than at 30°C. Growth rates were lowest at 5°C (0.22mg/larva/day) as was the assimilation efficiency (6.6%), because of the extended residence time of food in the gut. The high rate of ingestion and excretion at 30°C was caused by elevated maintenance metabolism. Changes in metabolic state influenced oxygen consumption, which was highest for feeding larvae (0.29 ml/g/h) and significantly lower for each, digesting, moving, starved larvae, and lowest for inactive larvae (0.06 ml/g/h). An influence of temperature and leaf quality on digestion rate and maintenance metabolism is the most likely cause of the feeding behavior pattern in G. groenlandica. The larvae may undergo voluntary hypothermia in order to avoid an energy, deficit resulting from high maintenance metabolism during mid-season when the energy content and food quality declines. The restriction of growth and development to a very short period prior to mid-summer may have contributed, to the extended 14-year life cycle of this species.     

Proteomic and metabolomic analysis reveals rapid and extensive nicotine detoxification ability in honey bee larvae

Despite potential links between pesticides and bee declines, toxicology information on honey bee larvae (Apis mellifera) is scarce and detoxification mechanisms in this development stage are virtually unknown. Larvae are exposed to natural and synthetic toxins present in pollen and nectar through consumption of brood food. Due to the characteristic intensive brood care displayed by honey bees, which includes progressive feeding throughout larval development, it is generally assumed that larvae rely on adults to detoxify for them and exhibit a diminished detoxification ability. We found the opposite. We examined the proteomic and metabolomic responses of in vitro reared larvae fed nicotine (an alkaloid found in nectar and pollen) to understand how larvae cope on a metabolic level with dietary toxins. Larvae were able to effectively detoxify nicotine through an inducible detoxification mechanism. A coordinated stress response complemented the detoxification processes, and we detected significant enrichment of proteins functioning in energy and carbohydrate metabolism, as well as in development pathways, suggesting that nicotine may promote larval growth. Further exploration of the metabolic fate of nicotine using targeted mass spectrometry analysis demonstrated that, as in adult bees, formation of 4-hydroxy-4-(3-pyridyl) butanoic acid, the result of 2′C-oxidation of nicotine, is quantitatively the most significant pathway of nicotine metabolism. We provide conclusive evidence that larvae are capable of effectively catabolising a dietary toxin, suggesting that increased larval sensitivity to specific toxins is not due to diminished detoxification abilities. These findings broaden the current understanding of detoxification biochemistry at different organizational levels in the colony, bringing us closer to understanding the capacity of the colony as a superorganism to tolerate and resist toxic compounds, including pesticides, in the environment.     

Simultaneous measurements of oxygen consumption and ammonia-N excretion in embryos and larvae of marine invertebrates

The quantification of oxygen consumption and ammonia-N excretion rates is essential in determining energy requirements for development of larval invertebrates. In larval energetics, there is a need for accurate and uncomplicated techniques to quantify metabolic rates. A method for simultaneous measurements of oxygen and ammonia-N concentrations is presented. It employs sealed respirometric chambers (ca. 30 ml) in which embryos and larvae are incubated. Analysis is carried out in end-point samples by Winkler's titration and indophenol-blue for oxygen and ammonia-N, respectively. Water is sampled into volume-calibrated glass syringes and oxygen consumption and ammonia-N excretion rates were determined by the difference between experimental and control (no animals) units. The method was successfully used to measure metabolic rates in embryo and larval stages of the shrimp Farfantepenaeus paulensis and in veliger of the mussel Perna perna. The accuracy denoted by the coefficient of variation is comparable to previous results on larval metabolic rates. A biomass: volume (microg ml(-1)) is proposed to extend its application to further species of marine invertebrates. The method is simple to operate, involves non-expensive material and is portable enough for field work. A substantial number of replicates can be analyzed at the same time and O:N ratio, an indicator of the catabolized substrate, can be calculated.     

Observations on ventilatory and net-spinning activities of larvae of the genus Hydropsyche Pictet (Trichoptera, Hydropsychidae) under experimental conditions

Larvae of three species of the genus Hydropsyche with distribution patterns indicating they are associated with increasing ranges of flow rate and temperature in the sequence H. instahilis, H. pelhicidula, H. angustipennis, were selected for study. Experiments on frequency of ventilatory movements indicated that the larvae were increasingly tolerant to dissolved oxygen concentration, flow rate and temperature in the same sequence of species. Experiments on net-spinning indicated a corresponding order of preference for higher temperatures and a general preference for higher flow rates. During experiments on net-spinning the number of larval casualties, ascribed to encounters between individuals, showed marked contrasts between species. The significance ofthe behaviour ofthe larvae under experimental conditions is discussed with reference to their distribution in the field.     

Influence of starvation on larval development of Carcinus maenas L. (Decapoda : Portunidae)

Lethal and sublethal effects of particular starvation events were investigated in larvae of Carcinusmaenas L. Mean survival times of continuously starved zoeae-1 were approximately twice the normal stage duration (12, 18, 25°C), and both increased with falling temperatures. At 6°C zoea-1 was unable to develop to stage-2. No larva retained the ability for successful further development if starved for half the stage duration time and was then refed. The zoea-1 larvae had to feed for at least 20 % of the normal stage duration for some larvae to moult to zoea-2. Some initial feeding was necessary to start zoea-1 development. Beyond a certain point of energy and accumulation of reserves development of the larvae seems to continue regardless of feeding rates. The demands for larval feeding correspond very well with the larval moulting cycle. Larvae of C. maenas proved to be well adapted to natural shortage of food.     

The influence of food plants on food utilization by Orthosia gothica (Lepidoptera, Noctuidae) larvae

Malus domestica, Salix caprea L. and Betula pubescens Ehrh. are host plants for Orthosia gothica L. The influence of the three plant species on time of larval development, mortality, and weight gain, and of adult fecundity, was studied. M. domestica was the most suitable food plant for the O. gothica larvae, and there was a positive correlation between the live weights of the females and their fecundity. The consumption, digestion and respiration of O. gothica larvae reared on foliage of S. caprea and B. pubescens were compared. Larvae fed on S. caprea had a shorter time of development, a higher weight gain, and a lower mortality, consumption, digestion and respiration compared with larvae reared on B. pubescens . Larvae reared on B. pubescens used a greater part of metabolism for maintenance than those on S. caprea . The different effects of the two food plants on the larvae were due to nutritional and/or physical conditions.     

不同食料植物对美国白蛾生长发育和繁殖的影响

2010年6月至7月,在室内研究了美国白蛾Hyphantria cunea(Drury)第1代幼虫对洋白蜡、欧美107号杨、法桐和白榆的取食量及不同的食料种类对美国白蛾生长发育和繁殖的影响。结果表明,美国白蛾对受试的各树种的取食量以洋白蜡为最多,完成一代平均每头可以取食2.21 g,其次为欧美107号杨1.95 g,再次为法桐和白榆,分别为1.85 g/头和1.68 g/头。3龄后幼虫对不同的寄主呈现出一定的偏好性,特别是5龄和6龄幼虫对不同的寄主的取食量表现出显著差异。不同的食料植物对美国白蛾幼虫和蛹的发育历期、存活率、蛹重、成虫寿命、产卵量等有显著影响。取食法桐对其生长发育和繁殖表现出明显的不利性,主要表现为幼虫期延长、蛹重减轻、单雌产卵量降低。     

A PROPOSAL FOR A NEW RED ALGAL ORDER, THE THOREALES

Two abalone species: green Haliotis fulgens and yellow Halioti corrugata represent nearly 97% of the total production in the Mexican abalone fishery. It has been assumed that abalone feed on the kelp algae Macrocystis pyrifera. Regional hatcheries use this species as a main source of natural food. M. pyrifera does not occur at the southern limit of the distribution of abalone species along the Baja California Peninsula. In this study, growth rates of juveniles H. fulgens , 17.3 ± 2.2 mm shell length and 0.4 ± 0.2 g body weight, were evaluated. Juveniles were fed with common species in the benthic environments inhabited by abalone along the western coast of Baja California during 191 days. Three diets were based on algae: palm kelp, Eisenia arborea , giant kelp, M. pyrifera and Gelidium robustum , and one on seagrass, Phyllospadix torreyi. Shell length and body growth rates varied between 21.5 μm day⁻¹ and 2.2 mg day⁻¹ for E. arborea and between 45.9 μm day⁻¹ and 6.7 mg day⁻¹ for M. pyrifera. Higher specific growth rates (SGR) in length and weight were determined for M. pyrifera : 0.2% and 0.7% day⁻¹. Significant differences between values of juveniles fed M. pyrifera with the rest of the diets were found. The highest mortality (21%) was in juveniles fed the red algae G. robustum.     

Trophic ecology of Atlantic bluefin tuna Thunnus thynnus larvae

Feeding intensity, diet composition, selectivity, energy ingestion and dietary niche breadth of larval Atlantic bluefin tuna Thunnus thynnus were studied on the eastern (Mediterranean) spawning grounds of the species. Larval T. thynnus were collected in the Balearic Archipelago (north-west Mediterranean Sea) during 2004 and 2005 using surveys specific for larval scombrids. Larvae between 2·6 and 8·7 mm standard length (L(S) ) are diurnal feeders, and 94% of the guts collected during daylight hours were full. The mean ±s.d. number of prey per gut was 7·1 ± 5·7, with mean ±s.d. ranging from 3·0 ± 1·6 in the smallest T. thynnus larvae to 11·1 ± 5·8 in 5·0-6·0 mm L(S) larvae. Up to 21 prey were found in a single larval gut (5·0-6·0 mm L(S) ) at the end of the day. Larvae progressively selected larger prey and exhibited increased carbon content concurrent with preflexion development of feeding and locomotory structures. Larvae of 5·0-6·0 mm L(S) exhibited positive selection of cladocerans over other prey (Chesson's index), whereas copepod nauplii dominated the diets of earlier stages. The dietary niche breadth measured increased initially but decreased at c. 5·5 mm L(S) . Appendicularians were found in the diet of larger larval sizes, but no piscivory was observed. Results are discussed in light of the sparse existing data for larval T. thynnus and other larval tuna species.     

Assessment of biochemical composition and energy reserves in larvae of the scallop Patinopecten yessoensis

Larvae of Patinopecten yessoensis increased in dry weight from ≈ 150 to 1000 ng per larva during the larval development period of 28 days. Microanalytical procedures were developed to determine the lipid, protein, carbohydrate, and ash contents from which energy levels and condition indices were derived. Replicate analyses of two sizes of P. yessoensis larvae gave coefficients of variation at or <5% for the biochemical analyses. Lipid and protein were identified as major components, and carbohydrate as a minor component providing 56.6,37.6, and 5.8 %, respectively, of the calculated energy content. The energy content of the eggs of P. yessoensis was 2.4 and 3.1 times higher than the larvae of P. yessoensis and Crassostrea gigas, respectively, derived from 20.6% lipid, 54.6% protein, and 7.2% carbohydrate. The carbohydrate in the eggs was stored principally as a glucan, considered to be glycogen, which was absent in the developing larvae. Changes in biochemical composition of P. yessoensis larvae during development showed that lipid and protein reserves were lost for ≈ 20 days and then lipid accumulated as the larvae reached premetamorphic condition.     

皱纹盘鲍的个体能量收支

对皱纹盘鲍的呼吸、摄食、生长及能量收支等实验研究表明, 鲍的耗氧率与壳长、体重、温度及昼夜变化有关, 耗氧率与壳长、体重均呈幂函数关系, 一天中16~4时(夜间)耗氧率高于4~16时(白天)且在18~20时达峰值.同温度下鲍日摄食率与体重呈幂指数关系, 日(相对)摄食率随温度升高而增加, 而日相对摄食率、日相对生长率均随壳长、体重增加呈下降趋势.鲍在14~20℃内对海带的总转化效率为53%.鲍软体部、海带及鲍粪便干品的比能值分别为19.2、8.57和7.23kJ·g^-1.14~20℃皱纹盘鲍摄入能量的34.6~48.6%为粪能, 22.0~38.2%的能量用于自身代谢, 5.6~28.2%用于贝体软体部的生长.     

皱纹盘鲍的个体能量收支

对皱纹盘鲍的呼吸、摄食、生长及能量收支等实验研究表明, 鲍的耗氧率与壳长、体重、温度及昼夜变化有关, 耗氧率与壳长、体重均呈幂函数关系, 一天中16~4时(夜间)耗氧率高于4~16时(白天)且在18~20时达峰值.同温度下鲍日摄食率与体重呈幂指数关系, 日(相对)摄食率随温度升高而增加, 而日相对摄食率、日相对生长率均随壳长、体重增加呈下降趋势.鲍在14~20℃内对海带的总转化效率为53%.鲍软体部、海带及鲍粪便干品的比能值分别为19.2、8.57和7.23kJ·g^-1.14~20℃皱纹盘鲍摄入能量的34.6~48.6%为粪能, 22.0~38.2%的能量用于自身代谢, 5.6~28.2%用于贝体软体部的生长.