Measures Of Physiological Condition Research Articles

Juvenile hormone and temperature effects in the postzygotic parental investment of male waterbug Abedus ovatus (Belostomatidae)

AbstractParental investment is any expenditure of time or energy by parents that increases their offspring survival at the cost of future reproduction. The costs associated with parental investment can be reflected in a deterioration of their physiological condition. In insects, juvenile hormone has been identified as having a role in the control of parental care. However, its effects on parental investment remain unclear for many taxa, especially in species with exclusive paternal care. We evaluated whether juvenile hormone influences postzygotic parental investment in Abedus ovatus, a waterbug with exclusive paternal care. Males provide parental care by carrying eggs on their backs and ventilating them by generating water currents through push‐ups called brood pumping. In an experiment, we applied methoprene (an analog of juvenile hormone) to males at early and late parental care stages and quantified the frequency of brood pumping and the contents of energy reserves (lipids, carbohydrates, and glycogen) at the end of parental care as a measure of physiological condition. We found that methoprene increases the frequency of brood pumping only when the water temperature increases. However, there was no correlation between the parent's energy reserves and methoprene treatments. We found that males who cared for large egg pads had lower amounts of lipids and carbohydrates at the end of parental care, and both effects are greater as the water temperature increases. These results suggest that energy expenditure during parental care is high due to intense muscular activity during brood pumping, which depletes male energy reserves and could affect future reproduction.

Do oil palm plantations provide quality habitat for migratory birds? A case study from Mexico

Habitat loss and degradation represent a major threat to Nearctic-neotropical migratory birds in the tropics. Managed agroecosystems have the potential to mitigate some impacts of land conversion, however, we know little regarding the quality of expanding oil palm plantation habitat for migratory birds in the neotropics. In this study, we used sex and age ratios, body condition, fat deposition, and muscle mass to assess oil palm habitat quality for seven species of migratory songbirds. Specifically, we captured individuals in native forest fragments and oil palm plantations in the state of Tabasco, Mexico, during two winter seasons (2017–2018, 2018–2019), and compared differences in age and sex ratios, and condition indices between habitats. We found that, when differences occurred, most species exhibited indicators of better habitat quality in native forest (older males with higher body condition indices) when compared to oil palm. Our results suggest that age and sex ratios combined with measures of physiological condition can be used to assess habitat quality for Nearctic-neotropical migratory birds overwintering in modified landscapes. Importantly, determining a species’ territorial behavior is key when selecting a given indicator of habitat quality for each species, and in certain cases, more intensive approaches such as estimates of survival, territory size, and food availability may be needed. Our results suggest that management strategies that promote forest-like conditions in oil palm plantations will improve habitat quality for declining populations of Nearctic-neotropical migratory birds.

Hemolytic parasites affect survival in migrating red-tailed hawks.

Migrating birds face a myriad of hazards, including higher exposure to parasites and numerous competing energy demands. It follows that migration may act as a selective filter and limit population growth. Understanding how individual-level physiological condition and disease status scale up to population dynamics through differential survival of individuals is necessary to identify threats and management interventions for migratory populations, many of which face increasing conservation challenges. However, linking individual physiological condition, parasite infection status and survival can be difficult. We examined the relationship among two measures of physiological condition [scaled-mass index and heterophil/leukocyte (H/L) ratio], hematozoa (i.e. hemoparasites) presence and abundance, and constitutive immunity in 353 autumn migrating red-tailed hawks (Buteo jamaicensis calurus) from 2004 to 2018. Hematazoa (i.e. Haemoproteus and Leucocytozoon) were in the blood smears from 139 red-tailed hawks (39.4%). H/L ratio decreased with scaled-mass index. Adults had a significantly higher H/L ratio than juveniles. Our two measures of immune defences, hemolytic-complement activity and bacteria-killing ability, were highly positively correlated. Our most notable finding was a negative relationship between Haemoproteus parasitemia and survival (i.e. documented individual mortality), indicating that haemosporidian parasites influence survival during a challenging life stage. The effect of haemosporidian parasites on individuals is often debated, and we provide evidence that parasitemia can affect individual survival. In contrast, we did not find evidence of trade-offs between survival and immune defences.

The prevalence of avian haemosporidian parasites in an invasive bird is lower in urban than in non‐urban environments

Urbanization affects the ecology of wildlife diseases and although it has been suggested that there are lower risks of infection in urban areas, there have been no experiments to support this conclusion. We assessed haemosporidian prevalence and intensity in House Sparrows Passer domesticus using field and experimental data under contrasting conditions (i.e. urban vs. non‐urban). For experimental data, we kept 32 male House Sparrows in captivity as a proxy of stress, and for field data we sampled 49 House Sparrows (17 females). We made use of microscopy to determine the relative intensity and used the polymerase chain reaction to estimate infection prevalence. We obtained total leucocyte counts, leucocyte differentials, heterophil/lymphocyte ratio (H/L) as a measure of stress, and the Polychromatic Index as a measure of physiological condition (erythropoiesis). We identified a total of 10 haemosporidian lineages. For field samples (both males and females), we found a significantly higher prevalence of infection in non‐urban House Sparrows than in urban ones. Under experimental conditions, non‐urban House Sparrows showed a higher prevalence than urban ones both before and after captivity, with a significant increase in parasite intensity. The number of infected birds increased after captivity for both urban (~ 32%) and non‐urban House Sparrows (~ 19%), indicating either a recrudescence of chronic and relapses of latent infections or the appearance of infections that had been acquired earlier. The H/L ratio was significantly higher for non‐urban than for urban male House Sparrows before captivity. No difference in H/L was found for urban House Sparrows before and after captivity, indicating tolerance to city stressors. Our results showed a significant decrease in H/L for non‐urban birds after captivity, suggesting higher stress in the non‐urban agricultural environment. Haemosporidian infections were not associated with the H/L ratio. Our study provides evidence that highly urbanized areas within cities represent lower haemosporidian infection risks than do non‐urban areas for House Sparrows.

Scale-of-choice effect in the assortative mating by multiple ornamental and non-ornamental characters in the black-headed gull

Assortative mating is a tendency to mate with phenotypically similar individuals as a consequence of either selection acting on mate preferences or individual constraints resulting from temporal and spatial segregation. The aim of this study was to examine the patterns of assortative mating in a plumage-monomorphic bird species, the black-headed gull Chroicocephalus ridibundus. For this purpose, we captured 217 pairs of gulls breeding in two colonies in northern Poland over six years and assessed whether they mated assortatively based on morphology, condition, individual genetic diversity, and expression of ornaments. An analysis of raw data (colonies and years combined) provided support for assortative mating by specific structural characters (head and wing morphology) and condition (size-corrected body mass). However, these relationships lost significance after removing inter-colony and inter-annual variation in the traits, suggesting that they were primarily driven by spatial and temporal segregation of individuals. We also found support for assortative mating by the size, but not coloration, of two melanin-based plumage ornaments (hood and wingtip). These correlations were retained after removing variation between colonies and years, suggesting that they could be due to directional mate preferences. No evidence was found for assortative mating by physiological measures of condition (blood hemoglobin concentration and plasma metabolite concentrations) and heterozygosity of neutrally selected microsatellite loci. Our study provides rare evidence for the scale-of-choice effect in assortative mating, where different variants of a given trait are distributed non-randomly across spatial or temporal scales and pooling them into a single heterogeneous sample may produce false-positive results. Animals often choose their reproductive partners non-randomly, preferring to mate with individuals that are similar by certain phenotypic characters, which results in an assortative pattern of mating. However, similar patterns can occur as a result of non-random distribution of individuals across spatial and temporal scales. Here, we examined the patterns of assortative mating in a colonial waterbird, the black-headed gull Chroicocephalus ridibundus. We found that assortative mating by morphological characters and condition was apparent only in a heterogeneous sample, where data from different colonies and years were pooled together. In contrast, assortative mating by the size of melanin-based plumage ornaments (hood and wingtip) was retained after removing inter-colony and inter-annual variation in these traits. Our study provides a rare example of the scale-of-choice effect in assortative mating of birds.

Relations between total gonad energy and physiological measures of condition in the period leading up to spawning: Results of a laboratory experiment on black sea bass (Centropristis striata)

Liver weight, relative condition (Kn), and somatic energy content have proven useful for predicting reproductive potential of fishes. Such proxy measures are advantageous in that they are easier to measure directly than fecundity and can often be measured in advance of spawning. We explored the utility of simple as well as more detailed measures of reproductive output in a laboratory experiment with black sea bass (Centropristis striata), an iteroparous, batch spawning protogynous hermaphrodite that may exhibit both determinate and indeterminate fecundity patterns within its geographic range. Wild fish were collected in fall, well ahead of spring-summer spawning, from two locations (Woods Hole, MA; Panama City, FL) representing mid-Atlantic and Gulf of Mexico stocks. To obtain a range in condition, fish were subject to either a high or low feeding regime for 4–5 months. During the experiment, length, weight, and bioelectrical impedance analysis (BIA) of individuals were monitored monthly. At the end of the experiment, additional individual measures taken included: relative gonad, liver, and viscera weights, absolute energy density, sex and maturity. As planned, these feeding treatments produced a range in sizes, fish of both sexes were developing or spawning capable, and the high ration group had higher Kn. This provided sufficient contrast to explore predictive relationships between total gonad energy (TGE) and terminal or prior biological measures. Examining multiple models with Akaike Information Criteria showed that final TGE was estimated with highest precision from a model including final sex, gonadosomatic index, length, Kn and liver energy density (89.1% deviance explained). The best model using nonlethal measures included BIA measured phase angle (PA) one month earlier, but much precision was lost (31.0% deviance explained). The explanatory power of PA, Kn, fish size, and stock also changed during the experiment, reflecting differences in the timing and magnitude of energy allocation and the difficulty in applying non-lethal measures to estimate TGE precisely in this species. Different energy allocation pathways were also apparent by stock. By the end of the experiment, mid-Atlantic black sea bass allocated more energy to liver and gonad whereas Gulf black sea bass allocated more energy to soma and viscera. We postulate that such intraspecific differences are adaptive in terms of the very different environmental conditions experienced by and the reported differences in spawning strategies by each stock, but this is rarely demonstrated in fishes and warrants further investigation.

Corticosterone stress response and plasma metabolite levels during breeding and molt in a free-living migratory songbird, the wood thrush ( Hylocichla mustelina)

Many birds face energetic trade-offs between different life history stages, such as reproductive effort, feather molt and the non-breeding period. Little is known about how physiological measures of condition (corticosterone, plasma metabolites) in free-living birds change from nesting stages to the post-breeding molt period or whether this is influenced by prior reproductive effort. We evaluated whether corticosterone (CORT) and plasma metabolite levels vary with date, nest stage and sex in a free-living migratory songbird, the wood thrush ( Hylocichla mustelina). We also tested whether (1) baseline CORT levels early in the season were predictive of subsequent reproductive success and (2) whether prior reproductive effort influenced CORT levels and blood metabolites during molt. Baseline CORT levels decreased with date during both the incubation stage and nestling stage, but did not vary significantly across stage of breeding season. Stress-induced CORT declined with date during incubation and varied significantly across breeding stage, with lower levels during feather molt. Profiles of the metabolites of β-hydroxybutyrate, glycerol, and triglyceride did not vary significantly with date or breeding stage. Only triglycerides varied significantly with sex, with females having higher levels than males. Reproductive output was highly variable (0–10 fledglings per season) but baseline CORT levels in females during the first incubation period of the season was not related to subsequent reproductive output. Prior reproductive effort, measured as the cumulative number of young hatched during the breeding season, was positively related to stress-induced CORT during molt. High reproductive effort in wood thrush appears to have physiological carry-over effects into the molt period which could potentially affect rate of molt and preparation for fall migration.

To fight, or not to fight: determinants and consequences of social behaviour in young red drum (Sciaenops ocellatus)

Abstract Social behaviour is critical for survival and fitness in many organisms. The aim of this study was to examine the effects of developmental state, physiological state and their differences between individuals on the intensities of aggressive and grouping behaviours in red drum (Sciaenops ocellatus) larvae. Body size was used as a proxy for developmental state and body condition (i.e., residual of wet weight from the relationship between body size and wet weight) as a measure of physiological condition. Social interactions between two fish were observed for 30 min in a 9-l tank. We found that the duration of grouping behaviour increased as body size increased, but aggressive behaviour was less frequent as body size and condition increased. The larger fish in a trial tended to be aggressive to the smaller one, and fish of similar sizes tended to show grouping behaviour. Fish that more frequently displayed aggressive behaviours tended to occupy the lower part of the water column. Body size and condition were important determinants of social interactions between red drum larvae. Our results suggest competitive disadvantage for the larvae from late cohorts when they recruit to the nursery habitats where larger larvae from early cohorts have already occupied.

Physiological condition and barnacle larval behavior:a preliminary look at the relationship between TAG/DNA ratio and larval substratum exploration in Balanus amphitrite

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 198:303-310 (2000) - doi:10.3354/meps198303 Physiological condition and barnacle larval behavior: a preliminary look at the relationship between TAG/DNA ratio and larval substratum exploration in Balanus amphitrite Gilles Miron*, Linda J. Walters**, Réjean Tremblay***, Edwin Bourget GIROQ, Département de biologie, Université Laval, Québec, Québec G1K 7P4, Canada Present addresses: *Département de biologie, Université de Moncton, Moncton, Nouveau-Brunswick E1A 3E9, Canada. E-mail: mirong@umoncton.ca **Department of Biology, University of Central Florida, Orlando, Florida 32816, USA ***Centre aquicole marin, Ministère de l¹Agriculture, des Pêcheries et de l¹Alimentation, Direction générale des Pêches et de l¹Aquiculture commerciales, Grande-Rivière, Québec G0C 1V0, Canada ABSTRACT: Behavior of laboratory-reared larvae of the barnacle Balanus amphitrite was examined in Beaufort, North Carolina (USA), in relation to their physiological condition. Cyprid substratum exploration was monitored by means of video endoscopy using various experimental surface types (clean, biofilm, 1 and 2 wk fouled) and 2 water flow regimes (still water and ca 5 cm s-1) at room temperature (21°C). We used the triacylglycerol/DNA (TAG/DNA) ratio of small batches of larvae as a measure of physiological condition in 0 to 12 d old cyprids. The physiological condition of cyprids decreased significantly with age (p < 0.001), ratios severely dropping between 5 and 8 d. Although exploration behavior did not show much variation with age, the overall number of active exploring cyprids appeared to be age dependent. Additionally, the relationship between surface exploration behavior and age also appeared to vary with substratum type as well as flow rate. For example, fewer young cyprids (0 to 5 d old) explored unfavorable substrata (clean and biofilm treatments) than older ones in still water. Exploration responses, however, appeared to differ in relation to flow regimes (still vs moving water trials). Time spent by cyprids on surfaces before returning to the water column (non-exploratory behavior) appeared to vary in relation to age and substratum type in still water trials. Duration of exploration and distance explored by cyprids in flow generally peaked with cyprids from the 3 d cohort. Overall, our results showed that habitat selection in barnacle cyprids results from a complex relationship involving substratum type, hydrodynamics and larval age (i.e. physiological condition and competency). KEY WORDS: Balanus amphitrite · Barnacle · Cyprid · Larval behavior · Larval ecology · Lipid condition · TAG/DNA ratio Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 198. Publication date: June 05, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.

Intertidal barnacle distribution:a case study using multiple working hypotheses

The roles of larval supply, selection of habitat, availability of space, larval physiological condition, and early post-settlement mortality in determining vertical distribution patterns of the barnacle Semibalanus balanoides (L.) were simultaneously examined in Passamaquoddy Bay, New Brunswick, Canada. Pump samples and settlement surveys showed that about 60% of planktonic cyprids were collected from 1.5 to 4.0 m depth, while over 90% of newly settled cyprids colonized low intertidal levels. Selection of habitat by cyprids and patterns of settlement were studied using precolonized planks that had been previously placed to obtain various periphyton gradients. These planks precolonized at the low, mid-, and high intertidal levels and placed in different orientations, induced variations in the distribution of newly settled cyprids. For example, vertical planks turned upside down had fewer settlers at low intertidal levels compared to surfaces maintained in the same orientation at the same level. When placed horizontally at the same level, sections precolonized at the low intertidal level collected more larvae than sections initially placed at the high and mid-intertidal levels. We used the triacylglycerol/cholesterol ratio (TAG/CHOL) as a measure of physiological condition in planktonic and newly settled cyprids, and newly metamorphosed spat. The TAG/CHOL ratio in planktonic cyprids decreased over the sampling period, but there was no variability with position in the water column. For newly settled cyprids and newly metamorphosed spat, the TAG/CHOL ratio increased with decreasing intertidal level. Quadrats freed of conspecific adults were colonized by more cyprids than were uncleared controls. Early post-settlement mortality was greater in uncleared than in cleared quadrats, but this effect varied with intertidal level. Early post-settlement mortality increased with increasing intertidal level in cleared quadrats, while it did not significantly vary in uncleared controls. The present study shows that the vertical distribution of S, balanoides on the shore results from a complex relationship involving larval supply, selection of habitat, availability of space, and early post-settlement mortality. We also present the first evidence of correlations between larval physiological condition and early vertical distribution in S. balanoides.

USE OF BODY MEASUREMENTS AND SERUM METABOLITES TO ESTIMATE THE NUTRITIONAL STATUS OF MALLARDS WINTERING IN THE MISSISSIPPI ALLUVIAL VALLEY, USA

We collected mallards (Anas platyrhynchos) from bottomland hardwood habitats on the Bayou Meto Wildlife Management Area and the White River National Wildlife Refuge, Arkansas County, Arkansas during the winter of 1990 to 1991 to determine if measures of physiological condition could be predicted from structural size, serum metabolite levels, or from direct measures of carcass composition. Serum triglyceride levels were correlated (r = 0.57, P = 0.007) with total body fat in males and slightly increased the value (from R2 = 0.64 to 0.76) of intact body mass alone for predicting total body fat in males. Overall, however, serum metabolites appeared to be poor indicators of the magnitude of nutrient masses in mallards. Three potential indices of nutritional status were developed from carcass composition data: protein/total ash, fat/ total ash, and fat/fat-free body mass. Protein masses of male mallards changed over winter (P = 0.02). Consequently, fat-free masses are not constant and represent poor indicators of structural size for mallards wintering in the Mississippi Alluvial Valley.

Evaluation of Water and Nitrogen Stress on Bromegrass Growth1

AbstractPercent stress [reduction in growth rate of bromegrass (Bromus inermis L.) due to deficiency] was calculated by the method of Greenwood et al. to evaluate the effects of deficiencies of N, water, and N plus water combined. Dry matter yields of bromegrass receiving either (a) 270 kg/ha of N, (b) complete irrigation, (c) N plus irrigation, or (d) no treatment 3 weeks earlier were determined at periodic intervals in the field at low, medium, and relatively high levels of N availability. Percent stress due to N deficiency was greatest where N availability was lowest, generally increased as the grass approached maturity, but was insignificant as long as a relatively large pool of inorganic N remained in the soil. Percent stress due to water deficiency was affected by precipitation, and was generally greatest for plots low in available N, even though soil water content (to 120 cm depth) was greater in those plots. Generally, percent stress due to deficiencies of water and N combined was approximately equal to the sum of stresses for the two measured separately. The concept of percent stress appears to be useful for quantifying the effects of both N and water deficiencies, alone and in combination, on growth rates of grass. In connection with other measures of physiological condition or activity, this concept may have considerable utility in agronomic research.