Changes In Food Level Research Articles

Quantification of Information Encoded by Gene Expression Levels During Lifespan Modulation Under Broad-range Dietary Restriction in C. elegans.

Sensory systems allow animals to detect, process, and respond to their environment. Food abundance is an environmental cue that has profound effects on animal physiology and behavior. Recently, we showed that modulation of longevity in the nematode Caenorhabditis elegans by food abundance is more complex than previously recognized. The responsiveness of the lifespan to changes in food level is determined by specific genes that act by controlling information processing within a neural circuit. Our framework combines genetic analysis, high-throughput quantitative imaging and information theory. Here, we describe how these techniques can be used to characterize any gene that has a physiological relevance to broad-range dietary restriction. Specifically, this workflow is designed to reveal how a gene of interest regulates lifespan under broad-range dietary restriction; then to establish how the expression of the gene varies with food level; and finally, to provide an unbiased quantification of the amount of information conveyed by gene expression about food abundance in the environment. When several genes are examined simultaneously under the context of a neural circuit, this workflow can uncover the coding strategy employed by the circuit.

Quantification of Information Encoded by Gene Expression Levels During Lifespan Modulation Under Broad-range Dietary Restriction in <em>C. elegans</em>

Sensory systems allow animals to detect, process, and respond to their environment. Food abundance is an environmental cue that has profound effects on animal physiology and behavior. Recently, we showed that modulation of longevity in the nematode Caenorhabditis elegans by food abundance is more complex than previously recognized. The responsiveness of the lifespan to changes in food level is determined by specific genes that act by controlling information processing within a neural circuit. Our framework combines genetic analysis, high-throughput quantitative imaging and information theory. Here, we describe how these techniques can be used to characterize any gene that has a physiological relevance to broad-range dietary restriction. Specifically, this workflow is designed to reveal how a gene of interest regulates lifespan under broad-range dietary restriction; then to establish how the expression of the gene varies with food level; and finally, to provide an unbiased quantification of the amount of information conveyed by gene expression about food abundance in the environment. When several genes are examined simultaneously under the context of a neural circuit, this workflow can uncover the coding strategy employed by the circuit.

Seawater pH Predicted for the Year 2100 Affects the Metabolic Response to Feeding in Copepodites of the Arctic Copepod Calanus glacialis.

Widespread ocean acidification (OA) is transforming the chemistry of the global ocean, and the Arctic is recognised as a region where the earliest and strongest impacts of OA are expected. In the present study, metabolic effects of OA and its interaction with food availability was investigated in Calanus glacialis from the Kongsfjord, West Spitsbergen. We measured metabolic rates and RNA/DNA ratios (an indicator of biosynthesis) concurrently in fed and unfed individuals of copepodite stages CII-CIII and CV subjected to two different pH levels representative of present day and the “business as usual” IPCC scenario (RCP8.5) prediction for the year 2100. The copepods responded more strongly to changes in food level than to decreasing pH, both with respect to metabolic rate and RNA/DNA ratio. However, significant interactions between effects of pH and food level showed that effects of pH and food level act in synergy in copepodites of C. glacialis. While metabolic rates in copepodites stage CII-CIII increased by 78% as a response to food under present day conditions (high pH), the increase was 195% in CII-CIIIs kept at low pH—a 2.5 times greater increase. This interaction was absent for RNA/DNA, so the increase in metabolic rates were clearly not a reaction to changing biosynthesis at low pH per se but rather a reaction to increased metabolic costs per unit of biosynthesis. Interestingly, we did not observe this difference in costs of growth in stage CV. A 2.5 times increase in metabolic costs of growth will leave the copepodites with much less energy for growth. This may infer significant changes to the C. glacialis population during future OA.

Modeling the eco-physiology of the purple mauve stinger, Pelagia noctiluca using Dynamic Energy Budget theory

Parameters for the standard Dynamic Energy Budget (DEB) model were estimated for the purple mauve stinger, Pelagia noctiluca, using literature data. Overall, the model predictions are in good agreement with data covering the full life-cycle. The parameter set we obtain suggests that P. noctiluca is well adapted to survive long periods of starvation since the predicted maximum reserve capacity is extremely high. Moreover we predict that the reproductive output of larger individuals is relatively insensitive to changes in food level while wet mass and length are.Furthermore, the parameters imply that even if food were scarce (ingestion levels only 14% of the maximum for a given size) an individual would still mature and be able to reproduce. We present detailed model predictions for embryo development and discuss the developmental energetics of the species such as the fact that the metabolism of ephyrae accelerates for several days after birth. Finally we explore a number of concrete testable model predictions which will help to guide future research. The application of DEB theory to the collected data allowed us to conclude that P. noctiluca combines maximizing allocation to reproduction with rather extreme capabilities to survive starvation. The combination of these properties might explain why P. noctiluca is a rapidly growing concern to fisheries and tourism.

Otolith increment width responses of juvenile Australian smelt Retropinna semoni to sudden changes in food levels: the importance of feeding history

To aid the interpretation of otolith microstructure in wild fishes, the present study assessed responses in daily otolith increment widths of early juvenile Australian smelt Retropinna semoni to sudden changes in feeding conditions. There was an almost immediate response in otolith increment widths (which can be interpreted as growth in length) to sudden changes in feeding conditions, with such changes being detected statistically after c. 4 days. Fish displayed compensatory growth when food supplies were increased following a period of limited food, indicating the magnitude of the response in growth appears highly dependant on feeding history. Additionally, fish size also appeared to influence increment widths suggesting that both fish size and feeding history are important factors that must be considered when interpreting otolith microstructure for the species.

EVOLUTIONARY RESPONSES TO ENVIRONMENTAL HETEROGENEITY IN CENTRAL AMERICAN ECHINOID LARVAE: PLASTIC VERSUS CONSTANT PHENOTYPES

Do changes in food resources lead to evolutionary changes in phenotypic plasticity or in different constant phenotypes? I addressed this question by studying plasticity of larval feeding arms for "geminate species pairs" in three echinoid genera. These closely related species were geographically isolated when the Panamanian Isthmus raised 2.8-3.1 million years ago, creating two different food level environments: high but variable food levels in the eastern Pacific versus chronically low food levels in the western Caribbean. I reared larvae of geminate species in different replicated food environments for 10 days postfertilization, collected morphological measurements of individual arm and body lengths, and calculated degrees of plasticity of relative arm length for each species. In contrast to previous studies with temperate echinoids, there was no significant plasticity of arm length in either the Pacific or Caribbean species considered here. Caribbean species, however, had significantly longer relative arm lengths than Pacific species, regardless of food levels. These results suggest that historical changes in food levels have led to the evolution of constant rather than plastic differences between Pacific and Caribbean echinoids. The evolution of plasticity may be limited by the timing of reproduction or by egg size in this system.

Size-dependent competition in a gregarious porcelain crab Petrolisthes cinctipes (Anomura: Porcellanidae)

Studies of competition in benthic marine organisms have focused on sessile filter-feed- ers and mobile grazers, to the neglect of mobile filter-feeders, including porcelain crabs. The present study demonstrates intraspecific competition in Petrolisthes cinctipes (Randall) (Porcellanidae: Anomura). P. cinctipes settles gregariously and lives in high-density, multi-size aggregations. Studies of gregarious species often identify the benefits of aggregation without quantifying the concomitant costs; this study quantifies these costs. In field and laboratory experiments, P. cinctipes growth rates declined with increasing conspecific density and this decline was more severe for smaller individuals. P. cinctipes also fed less frequently at high density, and this effect was more pronounced for smaller individuals. This indicates that size-dependent agonistic interactions in P. cinctipes have effects on feeding rate and, ultimately, on growth rate. Resource levels were manipulated in laboratory experi- ments by using filtered and unfiltered seawater. The effect of resource level also depended on size: smaller crabs were more sensitive to changes in food level. Thus, conspecific density and food avail- ability both affected growth rate in a size-dependent manner. Therefore, the costs of aggregation are more extreme for recruits than for adult crabs; recruits suffer more from competition, but may also benefit more if conspecific cueing results in settlement to sites with higher food availability.

Growth and seasonal energetics of the Antarctic bivalve Laternula elliptica from King George Island, Antarctica

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 257:99-110 (2003) - doi:10.3354/meps257099 Growth and seasonal energetics of the Antarctic bivalve Laternula elliptica from King George Island, Antarctica In-Young Ahn1,*, Jeonghee Surh2, You-Gyoung Park2, Hoonjeong Kwon2, Kwang-Sik Choi3, Sung-Ho Kang1, Heeseon J. Choi1, Ko-Woon Kim1, Hosung Chung1 1Polar Sciences Laboratory, Korea Ocean Research & Development Institute (KORDI), Ansan, PO Box 29, Seoul 425-600, Republic of Korea 2Department of Food and Nutrition, Seoul National University, Sillim-dong, Kwanak-ku, Seoul 151-742, Republic of Korea 3Department of Aquaculture, Cheju National University, Ara-1-dong, Cheju 690-756, Republic of Korea *Email: iahn@kordi.re.kr ABSTRACT: The Antarctic marine environment is characterized by extreme seasonality in primary production, and herbivores must cope with a prolonged winter period of food shortage. In this study, tissue mass and biochemical composition were determined for various tissues of the bivalve Laternula elliptica (King & Broderip) over a 2 yr period, and its storage and use of energy reserves were investigated with respect to seasonal changes in food level and water temperature. Total ash-free dry mass (AFDM) accumulated rapidly following phytoplankton blooms (with peak values immediately before and after spawning) and was depleted considerably during the spawning and winter periods. Most of the variation was in the muscle, gonads and digestive gland. Spawning peaked in January and February and caused considerable protein and lipid losses in the muscle, gonads and digestive gland. In winter (March to August), the muscle and digestive gland lost considerable mass, while gonad mass increased; this suggests that the muscle tissue and digestive gland serve as major energy depots for both maintenance metabolism and gonad development in winter. There were also marked year-to-year differences in the seasonal patterns of mass variation and reproduction. Overall, the relative and absolute tissue-mass values were positively correlated with chlorophyll concentration, and were not related to water temperature; thus, for the first time, this study clearly shows that food is an important factor governing growth and gonad maturation in this bivalve. It is also noteworthy that protein, constituting ~75% of AFDM, served as the major energy reserve throughout the study, closely following the AFDM variation. In particular, during the winter months, protein comprised >60% of AFDM loss, while lipids and glycogen served as minor (<20% each) reserves. Protein loss was most substantial in the muscle tissue, which comprised half of the body tissue. Thus, protein use, with muscle tissues as a depot for protein reserves, may be a result of selective pressure on Antarctic marine herbivores undergoing a prolonged period of food shortage in winter. KEY WORDS: Antarctic bivalve · Laternula elliptica · Growth · Energy reserve · Biochemical composition · Protein · Reproduction Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 257. Online publication date: August 07, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Maternal effects in Daphnia: what mothers are telling their offspring and do they listen?

Maternal effects can significantly impact offspring performance. Provisioning of offspring with energy stores can quantitatively alter their growth rates, survivorship, and future fecundity, and influence population regulatory mechanisms. In this paper, we show that maternal effects can also qualitatively affect offspring reproduction (i.e. their mode of reproduction). The freshwater herbivore Daphnia pulex can change the amount of energy allocated between asexual and ephippial egg production. Our experiments on individuals, experiencing “step‐up” or “step‐down” food manipulations, reveal that offspring qualitatively shift their energy allocation away from asexual reproduction to ephippial egg production when there is a simple mismatch between maternal and offspring food environments. We show that the response is asymmetric with respect to changes in food level, ephippial egg production is higher with a greater mismatch between environments, and that the effect can be observed in dynamic experimental populations. These results point to a “generational memory” that could challenge our interpretation of field patterns and mechanisms influencing population dynamics in Daphnia–algal systems.

Effect of changes in resource level on age and size at metamorphosis in Hyla squirella.

Recent experiments suggest that timing of metamorphosis is fixed during development in some anurans, insects, and freshwater invertebrates. Yet, these experiments do not exclude a growth rate optimization model for the timing of metamorphosis. I manipulated food resources available to larvae of squirrel treefrogs (Hyla squirella) to determine if there is a loss of plasticity in duration of larval period during development and to critically test growth rate models for the timing of metamorphosis. Size-specific resource levels for individual tadpoles were switched from low to high or high to low at three developmental stages spaced throughout larval development. The effects of changes in resource availability on larval period and mass at metamorphosis were measured. Switching food levels after late limb bud development did not significantly affect larval period in comparison to constant food level treatments. Therefore, developmental rate in H. squirella is better described by a fixed developmental rate model, rather than a growth rate optimization model. The timing of fixation of developmental rate in H. squirella is similar to that found in other anuran species, suggesting a taxonomically widespread developmental constraint on the plasticity of larval period duration. Mass at metamorphosis was not significantly affected by the timing of changes in food levels; the amount of food available later in development determined the size at metamorphosis. Larval period and mass at metamorphosis were negatively correlated in only one of two experiments, which contrasts with the common assumption of a phenotypic trade-off between decreased larval period and increased mass at metamorphosis.

Movement in a Zaprochiline Katydid (Orthoptera: Tettigoniidae): Sex-Specific Response to Food Plant Distribution

Movement in relation to local food levels was compared between the sexes of the zaprochiline katydid Kawanaphila nartee Rentz. Adults of both sexes were marked, and their departure rates were estimated (1) early in the season for two plots having high vs. low food density and (2) throughout the season for a single plot with changing food levels. Based on the between-plot comparison, movement of males was independent of food density, whereas females were less likely to leave the rich patch than the poor one. The within-plot comparisons revealed that, despite large changes in food levels, male departure rates did not vary over the season. Females showed increased movement over the season and by the end of the study had a departure rate similar to that of males.

The effect of providing a high fibre diet on foraging behaviour of outdoor sows and consequent pasture damage

Food restricted sows under extensive conditions forage for considerable periods of time and this can give rise to serious pasture damage. This pasture damage can be diminished by the reduction of rooting behaviours. In the past this has been achieved by nose ringing but, due to welfare implications, the emphasis has now been shifted onto alternative methods such as nutritional modification. This rooting behaviour is, in part, caused by hunger (feed motivation) and it has been demonstrated that this feed motivation can be manipulated by short-term changes in food level and type (Brouns et al 1994; Edwards et al, 1993; Ewbank, 1974).The objective of this experiment was to study the effects of feeding a fibrous diet (containing 600 g/kg unmolassed sugarbeet pulp) either at a restricted or ad libitum level, on foraging behaviour and the consequences of this for pasture damage.

The effect of providing a high fibre diet on foraging behaviour of outdoor sows and consequent pasture damage

Food restricted sows under extensive conditions forage for considerable periods of time and this can give rise to serious pasture damage. This pasture damage can be diminished by the reduction of rooting behaviours. In the past this has been achieved by nose ringing but, due to welfare implications, the emphasis has now been shifted onto alternative methods such as nutritional modification. This rooting behaviour is, in part, caused by hunger (feed motivation) and it has been demonstrated that this feed motivation can be manipulated by short-term changes in food level and type (Brouns et al 1994; Edwards et al, 1993; Ewbank, 1974).The objective of this experiment was to study the effects of feeding a fibrous diet (containing 600 g/kg unmolassed sugarbeet pulp) either at a restricted or ad libitum level, on foraging behaviour and the consequences of this for pasture damage.

Metamorphic Responses to Changing Food Levels in Two Species of Hylid Frogs

We investigate how changes in food availability during development affected the timing of and body size at metamorphosis in two closely related species of tree frogs that use different larval habitats. We raised tadpoles of Hyla gratiosa (a temporary—pond breeder) and Hyla cinerea (a permanent—pond breeder) at two different temperatures on either constant resources or a regime in which we altered food levels at one of three different times during development. For both species, larval period was affected only by early changes in food level; early increases shortened larval period, and decreases lengthened it. The timing of metamorphosis of Hyla gratiosa showed greater plasticity than that of Hyla cinerea, because of its greater overall response to any food—level change and not because of any difference between species in the duration of the sensitive period. The two species showed comparable levels of plasticity in body size at metamorphosis; increases in food level produced larger body sizes, and decreases produced smaller sizes. However, in contrast to the pattern seen in larval period, later changes in food level had the greatest effect on body size. These results force a reexamination of current ideas about the adaptive significance of plasticity in the timing of metamorphosis in response to food availability in larval anurans. We offer a model of dynamic allocation that accommodates the extant data on this issue.

The impact of two Chaoborus species on a zooplankton community

The responses of a zooplankton community to Chaoborus predation were studied in large in situ mesocosms in Peter Lake. Chaoborus flavicans, the native chaoborid, significantly reduced the density of the dominant grazer, Daphnia pulex, in relation to controls that lacked Chaoborus. Chaoborus americanus, a species found only in fishless bogs, reduced Da. pulex densities far more than the chaoborid found in Peter Lake, C. flavicans. Chaoborus americanus also significantly reduced the dominant copepod, Diaptomus oregonensis, in relation to both the control and the C. flavicans treatment. Chlorophyll a concentration did not differ among treatments, indicating that herbivore responses could not be explained by changes in food levels. Our results show that Chaoborus predation can greatly affect a zooplankton community, especially daphnids.

Feeding selectivity in relation to territory size in a herbivorous reef fish.

Territory size in the herbivorous reef fish, Parma victoriae, (Pisces: Pomacentridae) is primarily determined by local density patterns and is independent of changes in food levels (Norman and Jones 1984). However, while individual readily expand territories in response to having their neighbours removed, they appear not to increase total food consumption. Individuals with large territories may benefit from improved food quality. Here we test the hypothesis that expanded territories increase access to preferred food types.A preliminary comparison of the relative proportions of algal species consumed and those present in the field indicated that feeding was highly selective. Strong feeding preferences were indicated by a field 'cafeteria' experiment, in which algal species were presented to individuals in equal amounts. Selectivity indices calculated from diet and availability measures were positively correlated with the feeding preference rankings.Individuals examined from two territory size categories (<10 m2 and > 10 m2) did not exhibit significant differences in feeding prefernces. However, they differed greatly in terms of the makeup of their diets. Higher ranking algae such as Champia zostricola and Rhodoglossum sp. were consumed in greater proportions on large territories. Algal abundances within territories also differed for the two groups. Some of the less abundant, high ranking food species were found in greater quantities per unit area on large territories. The differences in diet were not solely explained by changes in availability. The appropriate comparison showed that whereas individuals on large territories fed in a highly selective manner, those on small territories consumed algae in proportion to their availability. A neighbour removal experiment supported the hypothesis that territory expansion results in an increase in the consumption of preferred algal species.