Body Condition Index Research Articles

Associating physiological functions with genomic variability in hibernating bats

The challenges of surviving periods of increased physiological stress elicit selective pressures that drive adaptations to overcome hardships. Bats in the Palearctic region survive winter in hibernation. We sampled single nucleotide polymorphisms (SNPs) in hibernating Myotis myotis bats using double-digest restriction site-associated DNA sequencing and we associated the genomic variability with the observed phenotypes reflecting hibernation site preference, body condition and bat health during hibernation. We did not observe genotype associations between the detrended body condition index, representing fat reserves, and functional genes involved in fat metabolism. Bat body surface temperature, reflecting roost selection, or roost warmth relative to the climate at the site did not show any associations with the sampled genotypes. We found SNPs with associations to macroclimatic variables, characterising the hibernaculum, and blood biochemistry, related to health of the bat. The genes in proximity of the associated SNPs were involved in metabolism, immune response and signal transduction, including chaperones, apoptosis and autophagy regulators and immune signalling molecules. The genetic adaptations included adaptation to tissue repair and protection against tissue damage.

Variation in Species Composition, Size and Fitness of Two Multi-Species Sea Turtle Assemblages Using Different Neritic Habitats

The neritic environment is rich in resources and as such plays a crucial role as foraging habitat for multi-species marine assemblages, including sea turtles. However, this habitat also experiences a wide array of anthropogenic threats. To prioritize conservation funds, targeting areas that support multi-species assemblages is ideal. This is particularly important in the Gulf of Mexico where restoration actions are currently ongoing following the Deepwater Horizon oil spill. To better understand these areas in the Gulf of Mexico, we characterized two multi-species aggregations of sea turtles captured in different neritic habitats. We described species composition and size classes of turtles, and calculated body condition index for 642 individuals of three species captured from 2011 to 2019: 13.6% loggerheads (Caretta caretta), 44.9% Kemp’s ridleys (Lepidochelys kempii) and 41.4% green turtles (Chelonia mydas). Species composition differed between the two sites with more loggerheads captured in seagrass and a greater proportion of green turtles captured in sand bottom. Turtles in sand bottom were smaller and weighed less than those captured in seagrass. Although small and large turtles were captured at both sites, the proportions differed between sites. Body condition index of green turtles was lower in sand habitat than seagrass habitat; there was no difference for Kemp’s ridleys or loggerheads. In general, smaller green turtles had a higher body condition index than larger green turtles. We have identified another habitat type used by juvenile sea turtle species in the northern Gulf of Mexico. In addition, we highlight the importance of habitat selection by immature turtles recruiting from the oceanic to the neritic environment, particularly for green turtles.

Macroinvertebrate Communities and Body Condition of Larval Eastern Hellbender Salamanders (Cryptobranchus alleganiensis) in North Carolina.

Salamanders are important biological indicators of freshwater aquatic ecosystems. The Eastern Hellbender, Cryptobranchus alleganiensis, is found primarily in streams across the southeastern, midwestern, and eastern portions of the United States. However, this unique large aquatic salamander is facing numerous threats and declines across its geographic range, including in Appalachia. Moreover, little is known regarding the early life history stages (gilled larvae), particularly regarding food availability (aquatic insects present in streams) and body condition. In this study, we assessed the macroinvertebrate communities of streams sampled for larval C. alleganiensis and report on the body condition index within western North Carolina streams. We found varying levels of diversity across sample locations for macroinvertebrates (total sampled = 3,619, representing over 30 genera), with the most prevalent insects from Trichoptera order, with an overall high percent of Ephemeroptera, Plecoptera, and Trichoptera (EPT) in all streams, ranging from 68.5% to 90.7%. Functional Feeding Groups included 40.5% filterers, 24.3% predators, 17.6% gatherers, 10.7% shredders, and 6.9% scrapers. Shannon Diversity Index in sample streams ranged from 2.101 to 2.698. Body condition or SMI (scaled mass index) ranged from 1.5 to 3.3 2 across sites with a largely consistent and strong linear relationship between log mass and total length (r = 0.910). Our results add to the body of knowledge on the larval ecology of this North American salamander and may aid in future management of hellbender stream habitats.

Rodent helminths in fragmented Atlantic Forest areas in the western region of the state of Paraná.

Rodents are small mammals that can be parasitized by various helminths. This study aimed to identify and describe the ecological indicators of infection in rodents captured in fragments of the Atlantic Forest in the western region of Paraná State, Brazil. Sixty-eight specimens of five rodent species were collected, necropsied, and inspected in search of helminths. The parasites were stored in 70% ethanol, morphologically identified, and counted for calculation of infection indicators. Fourteen species of helminths and one species of Crustacea were recorded: ten in Akodon montensis, four in Mus musculus, two in Thaptomys nigrita, two in Oligoryzomys nigripes, and one in Euryoryzomys russatus. The registered species of parasites were: Rodentolepis akodontis, Angiostrongylus sp., Protospirura numidica criceticola, Trichuris navonae, Syphacia alata, Syphacia criceti, Syphacia evaginata, Trichofreitasia lenti, Stilestrongylus aculeata, Stilestrongylus eta, Stilestrongylus gracielae, Stilestrongylus franciscanus, Stilestrongylus moreli, Stilestrongylus sp., and Pentastomida gen. sp. A positive correlation between the intensity of infection of T. navonae and T. lenti was observed with the body condition index of the host A. montensis. For all species, this study represents a new register of locality, and for eight of them a new host.

Feeding ecology of juvenile green turtles in food-poor habitats of the Persian Gulf

The Persian Gulf hosts marine mega-herbivores that forage in its coastal habitats. Some areas, mainly along its southern coast, contain abundant benthic plants; however, marine plant resources are limited throughout most of this warm sea, which presents nutritional challenges for large herbivores. We measured curved carapace length (CCL) for 102 green turtles (Chelonia mydas) from foraging grounds with relatively limited plant resources surrounding Qeshm Island at the eastern Persian Gulf. The mean CCL was 41.8 cm (SE = ± 1.3 cm; range = 18.5–99), and 93 turtles (91%) had CCL < 65 cm, indicating the area is primarily a juvenile developmental habitat. To study feeding ecology of green turtles in the area, we analyzed esophageal lavage samples from 36 individuals captured in muddy-bottom (n = 23) and sandy/rocky-bottom (n = 13) habitats. Diet data showed a generalist foraging population with dietary niche variation among individuals that targeted mixtures of macroalgae, seagrasses and mangrove. Green turtles showed a slight preference for green algae (Ulva sp.) at both sites. The mean Fulton’s body condition index for juvenile turtles was 1.14 (SE = ± 0.03; n = 72), which is comparable to values reported elsewhere, and indicates that these turtles were not under-nourished. This is intriguing in light of the paucity of local food resources, and perhaps due to the absence of large sub-adults and adults with higher food demand, and/or individual dietary niche variation among resident turtles, both of which reduce competition among local green turtles for the region’s available resources.

Seasonal changes in maturational status, body condition, and population structure in the Moroccan Atlantic Sardine Sardina pilchardus (Teleostei: Clupeidae) from Safi fishing area

Aspects of reproduction and population structure were investigated between June 2017 to May 2018 in sardines, Sardina pilchardus (Walbaum, 1792) from the Safi fishing area. The sex ratio was generally in favor of males (χ2=19.50). Out of 3252 total specimens sampled, 1404 were females (46.00%), 1648 males 50.68%) and 200 immatures (6.15%). The immatures were best represented in the small size classes, between 8 and 12 cm. This study showed that sardines can breed throughout the year with a peak breeding season between November and February. The gonado-somatic index (GSI) and the condition coefficient (CC) evolved almost invariably. The volumetric absolute body condition index [kv= Fresh total body mass (g)/total body volume (cm3)] showed two peaks, which are discriminately sex dependent. For females, the peaks are concomitantly observed in September and April while for males, these are shown in June and February. Moreover, the morphometric index (kn) showed a single peak in January and September for reproductive males and females, respectively. As regards the non-reproductive individuals the males have two peaks in June and December or females, they have one peak in November. Additionally, the GSI showed a single peak in February. The size at first sexual maturity in males and females was 16.1 cm and 16.5 cm, respectively.

An alternative method for determining the body condition index of the free-living South American coati

Assessing and monitoring the welfare of free-living mammals is not a usual process due to the logistical complications associated with their capture and sedation, collection and storage of biological samples and their release. In this context, non-invasive methods for monitoring wildlife constitute a good alternative approach for in situ conservation. Body condition index, as a measurement of health status, has been used in free-living mammals; its low value may be associated with negative effects on reproduction and survival. The present study aimed to generate an alternative and reliable non-invasive method and then determine the body condition index, based on previously-collected biometric measurements, without the need to capture and immobilise the animals. A total of 178 free-living Nasua nasua Linnaeus, 1766 were trapped, weighed and measured. Statistical methods were used, based on Boosted Regression Trees (BRT) using body mass, biometric measurements (body length, height and chest girth) and gender as explanatory variables. To assess the agreement between the real Body Condition Indices (BCIs) and the predicted values of BCIs, we explored the correlation between each model using the Bland-Altman method. This method showed a strong agreement between the predictive BRT models proposed (standardised residuals from a linear regression between body length and chest girth) and standardised residuals (linear regression between body mass and body length). The results obtained herein showed that BRT modelling, based on biometrical features, is an alternative way to verify the body conditions of coatis without the need to capture and immobilise the animals.

Leukocyte profile of the helmeted manakin, Antilophia galeata (Passeriformes: Pipridae) in a Cerrado forest fragment

Changes in the amounts and proportions of leukocytes, known as leucocyte profiles, have been documented for several bird species and have been used to measure stress levels in these animals. The present work ascertained the biological and ecological attributes that influence the leukocyte profile of Antilophia galeata (Lichtenstein, 1823), the helmeted manakin. This species has been deemed useful in ecological studies because it responds to environmental changes. Blood samples drawn from 89 individuals of A. galeata captured in a Cerrado forest fragment were subjected to analysis under optical microscopy to identify and quantify leukocytes and micronuclei. The number of lymphocytes was greater for males, non-reproductive individuals and individuals infected with ticks. None of the leukocyte components differed in relation to age, molting or body condition index. The amount of micronuclei was correlated with values for total leukocytes, H/L ratio, heterophils, basophils and monocytes. The results suggest that reproduction may be an immunosuppressive factor for the species, producing sexual differences in lymphocyte availability. In addition, biomarkers of genotoxic damage (micronuclei) were related to the amount of leukocytes, indicating that individuals may be sensitive to environmental disturbances. Leukocyte profiles can be considered a useful tool for addressing ecological questions that are relevant to the conservation of species in degraded environments.

Demographic drivers of Norway rat populations from urban slums in Brazil

The Norway rat is a globally distributed pest, known for its resilience to eradication and control programs. Efficient population control, especially in urban settings, is dependent on knowledge of rat demography and population ecology. We analyzed the relationship between four demographic outcomes, estimated by live-trapping data, and fine-scale environmental features measured at the capture site. Wounds, a proxy for agonistic interactions, were associated with mature individuals. Areas with environmental features favorable to rats, such as open sewers and unpaved earth, were associated with more mature individuals with a better body condition index. The control measures (environmental stressors) are likely to be disrupting the social structure of rat colonies, increasing the frequency and distribution of agonistic interactions, which were common in both sexes and maturity states. The relationship between the favorable environmental conditions and the demographic markers analyzed indicate possible targets for infestation control through environmental manipulation, and could be incorporated into current pest management programs to achieve long-term success. Our study indicate that urban interventions focused on removal of potential resources for rats could be potential long-term solutions by reducing the carrying capacity of the environment.

Tasas de crecimiento somático de tortuga carey, Eretmochelys imbricata, en el Parque Nacional Natural Gorgona, Colombia, entre 2004 y 2018

La tortuga carey, Eretmochelys imbricata, se encuentra a nivel global en peligro crítico de extinción, y la información demográfica en el Océano Pacífico Oriental es limitada. Por esta razón, esta investigación evalúa las tasas de crecimiento somático en una agregación de individuos inmaduros de tortuga carey empleando el método de captura-marca-recaptura en los arrecifes coralinos de Playa Blanca y la Azufrada en el Parque Nacional Natural Gorgona, Colombia. Entre 2004 y 2018 se realizaron 89 capturas de 49 individuos de tortuga carey. El largo curvo del caparazón promedio (LCC) obtenido fue de 41,6 cm (rango 32-58 cm) y el largo recto del caparazón promedio (LRC) fue de 39,1 cm (rango 30,0-54,1 cm), lo que muestra que estos arrecifes son áreas de forrajeo importantes para individuos inmaduros de esta especie. El índice de condición corporal promedio fue de 1,3 (rango 1,0-1,5). Esto sugiere que las condiciones ambientales mantienen en buen estado la salud de esta agregación. Usando el modelo de crecimiento de von Bertalanffy y estableciendo una talla máxima (L∞) de 63 cm de LCC (donde se obtiene el menor coeficiente de variación), se estimó una k de 0,081 y una tasa anual de crecimiento promedio de 1,5 ± 1,8 cm/año. Esto indica que los individuos en esta agregación estarían alcanzando una LCC de 63 cm entre los 33 y 34 años, talla cercana a la de madurez sexual en la región del Pacífico oriental (aproximadamente 66 cm LCC). Lo anterior ratifica la vulnerabilidad de esta especie debido a las lentas tasas de crecimiento somático y madurez sexual tardía. Se sugiere que los esfuerzos de conservación para esta especie deben ser a largo plazo para procurar su recuperación, en vista de que especies con estas características tienden a expresar tasas de crecimiento poblacional muy bajas.

Effects of Season, Gravidity, and Streamflow on Body Condition from Tail Width in Two Federally Listed Salamanders, Eurycea sosorum and E. tonkawae

In population studies, individual physiological metrics can reveal important aspects of ecology and act as indicators of overall population health. Body condition is frequently used as a metric of physiological status and commonly quantified as some function of mass relative to structural size. In this study, we examined the natural variation in body condition of two central Texas spelerpines (Eurycea sosorum and E. tonkawae: Plethodontidae) to understand their nutritional status as a function of environmental variability and reproductive condition. Rather than using a mass-based metric to generate a body condition index (BCI), we used residuals from a linear regression of tail width vs. body length measured from subject photographs taken from the dorsal perspective. Overall, mean BCI for both species was lowest in the winter and generally higher in spring and summer. Streamflow had a small positive effect on E. tonkawae BCI and a negative effect on E. sosorum BCI. Gravid individuals for both species had lower BCI during autumn and winter (when the proportion of gravid individuals was the greatest) than nongravid individuals. By contrast, the few gravid E. sosorum we observed in summer had higher BCI than nongravid individuals. Our results provide important baseline information on the ecology of these federally protected salamanders and demonstrate the utility of a BCI based on width instead of mass.

Exposure to natural ultraviolet B radiation levels has adverse effects on growth, behavior, physiology, and innate immune response in juvenile European seabass (Dicentrarchus labrax)

Solar ultraviolet B radiation (UVB) has been underestimated as a stressor in fish species that grow in confined cages, especially in species cultured in oligotrophic waters that receive high levels of UVB. In this context, the present study aims to assess UVB radiation's adverse effects on European seabass (Dicentrarchus labrax), which is a cultured species in the Mediterranean and the Red Sea. Seabass juveniles were exposed for six weeks to four experimental conditions that simulated natural underwater conditions: (1) high dose - UVB-H, 11.86 kJ m−2 d−1; (2) moderate dose - UVB-M, 6.28 kJ m−2 d−1; (3) low dose - UVB-L, 2.55 kJ m−2 d−1; and (4) no UVB exposure as the control. Specimens were collected after 3, 15 (short-term), and 43 (long-term) days and effects of exposure on growth, behavior, physiology, and immune system were investigated. Overall, data showed that short- and long-term exposure to UVB resulted in detrimental effects in European seabass, and some of these effects were cumulative and dose-dependent. High mortality (around 50%) was observed in the seabass juveniles after 3 days of exposure to the highest daily dose (UVB-H). No significant mortality was observed in UVB-M, UVB-L, or control throughout the experiment. Reduction in growth and changes in animal body condition indices were evident in UVB-M exposed fish after 15 and 43 days of exposure. The swimming activity was reduced in the UVB-M treatment, and most of the fish from this treatment tried to avoid the exposure while showing a stationary behavior with slow caudal and dorsal fins movements. A lack of appetite was observed during the experiment, and the reduced total protein, glucose, lactate, and total cholesterol plasmatic levels in UVB exposed fish reflected physiological impairment. Furthermore, several changes in the humoral parameters suggest that an immune system modulation can occur in seabass exposed to the three UVB treatments (UVB-L, UVB-M, UVB-H), and during the different exposure periods (3, 15, and 43 days). Overall, our data provide evidence that, in the case of confinement in cages, European seabass juveniles are sensitive to UVB exposure, especially in oligotrophic waters with high UV radiation incidence such as the Red Sea. Hence, seabass' growth, resistance to pathogens, and survival may be affected by UVB exposure. Further research is recommended to understand how fish growth and survival may be affected by future increases in underwater UVB and when combined with other environmental stressors.

Pathology findings and correlation with body condition index in stranded killer whales (Orcinus orca) in the northeastern Pacific and Hawaii from 2004 to 2013.

Understanding health and mortality in killer whales (Orcinus orca) is crucial for management and conservation actions. We reviewed pathology reports from 53 animals that stranded in the eastern Pacific Ocean and Hawaii between 2004 and 2013 and used data from 35 animals that stranded from 2001 to 2017 to assess association with morphometrics, blubber thickness, body condition and cause of death. Of the 53 cases, cause of death was determined for 22 (42%) and nine additional animals demonstrated findings of significant importance for population health. Causes of calf mortalities included infectious disease, nutritional, and congenital malformations. Mortalities in sub-adults were due to trauma, malnutrition, and infectious disease and in adults due to bacterial infections, emaciation and blunt force trauma. Death related to human interaction was found in every age class. Important incidental findings included concurrent sarcocystosis and toxoplasmosis, uterine leiomyoma, vertebral periosteal proliferations, cookiecutter shark (Isistius sp.) bite wounds, excessive tooth wear and an ingested fish hook. Blubber thickness increased significantly with body length (all p < 0.001). In contrast, there was no relationship between body length and an index of body condition (BCI). BCI was higher in animals that died from trauma. This study establishes a baseline for understanding health, nutritional status and causes of mortality in stranded killer whales. Given the evidence of direct human interactions on all age classes, in order to be most successful recovery efforts should address the threat of human interactions, especially for small endangered groups of killer whales that occur in close proximity to large human populations, interact with recreational and commercial fishers and transit established shipping lanes.

Lice community structure infesting Trinomys iheringi (Thomas, 1911) - Ocurrence, sex bias and climatic variables on tropical island.

Few studies have provided information on parasitological indexes or other ecological characteristics of lice populations that parasitize small mammals in the Neotropical region. We used lice parasitizing a rodent species, Trinomys iheringi, as a study model to investigate the effect of parasite occurrence and intensity on the body condition of rodents and the effect of climatic conditions, sex and age class of T. iheringi. We also provide information on prevalence, mean intensity, aggregation, sexual ratio of adult lice, and proportion between life stages and lice parasitizing T. iheringi. The study was conducted in Ilha Grande, an island in southeastern Brazil. We used a logistic regression to run a model of lice occurrence using climatic variables (rainfall, temperature, humidity), and then adding sex and age classes. A total of 39 T. iheringi individuals were captured with 17 parasitized (43.58%). These animals hosted Gyropus (martini) martini (n = 94), Gliricola sp. (n = 8), and Pterophthirus wernecki (n = 2). The model with humidity and sex variables showed that the occurrence of lice was negatively associated with humidity. There are more males than females infested with lice, while most of the young individuals are not infested. The higher lice occurrence in the low humidity coincides with the birth period of T. iheringi. The contact among individuals are higher during the reproductive period of the host species, but males are more suscetible to the lice parasitism due to higher testosterone levels that reduce the immunocompetence. The distribution pattern of lice was aggregated, but there was no correlation between body condition index and lice infestation intensity. We highlight that the major occurrence of lice occurs in the driest period of the year, that males are more prone to parasitism by lice than females, and adults more prone than young.

Head-started Agassiz’s desert tortoises Gopherus agassizii achieved high survival, growth, and body condition in natural field enclosures

We measured survival, growth, and body condition of 8 hatchling cohorts of desert tortoisesGopherus agassizii(living in predator-resistant outdoor pens in the Mojave Desert, California, USA) over 11 yr to evaluate head-starting methods. At 11 yr of age, 7 times as many of the first cohort had survived than if they had been free-living tortoises. Subsequent improvements in predator control, food and water supplementation, and pen structure increased survival from 7 to 10 times that under wild conditions in younger cohorts. Annual survival averaged 96%. Carapace length (CL) increased 6.95 mm yr-1, similar to that of free-living tortoises. Annual growth rates varied with calendar year (possibly reflecting food and water supply), age, cohort (year hatched), mother, and in 4 dry years, with crowding. Most of the first cohort grew to a releasable size (CL &gt;100 mm) by their 9th year. Body condition indices remained high, indicating little dehydration despite droughts in 8 of the 11 years, because irrigation offered drinking opportunities. Head-started tortoises developed fully hardened shells (≥98% of adult shell hardness) earlier (10.1 vs. 11.6 yr), but at a larger CL (117 vs. 104 mm) than did free-living tortoises. Selective feeding in head-start pens decreased subsequent germination of favored wildflower species, apparently by reducing the natural seedbank. Consequently, we reseeded and irrigated each autumn to promote subsequent spring food supply. We irrigated in early summer to enable drinking and ensuing consumption of dry, dead plants and Bermuda grass hay, a supplement. These procedures can greatly improve juvenile survivorship, and increase numbers of hard-shelled, midsized juveniles to help augment wild populations.

Long-term capture and handling effects on body condition, reproduction and survival in a semi-aquatic mammal

In long-term individual-based field studies, several parameters need to be assessed repeatedly to fully understand the potential fitness effects on individuals. Often studies only evaluate capture stress that appears in the immediate weeks or breeding season and even long-term studies fail to evaluate the long-term effects of their capture procedures. We investigated effects of long-term repeated capture and handling of individuals in a large semi-aquatic rodent using more than 20 years of monitoring data from a beaver population in Norway. To investigate the effects, we corrected for ecological factors and analysed the importance of total capture and handling events, years of monitoring and deployment of telemetry devices on measures related to body condition, reproduction and survival of individual beavers. Body mass of dominant individuals decreased considerably with number of capture events (107 g per capture), but we found no statistically clear short or long-term effects of capture and handling on survival or other body condition indices. Annual litter size decreased with increasing number of captures among older individuals. Number of captures furthermore negatively affected reproduction in the beginning of the monitoring, but the effect decreased over the years, indicating habituation to repeated capture and handling. By assessing potential impacts on several fitness-related parameters at multiple times, we can secure the welfare of wild animal populations when planning and executing future conservation studies as well as ensure ecologically reliable research data.

Sex-based trade-offs in the innate and acquired immune systems of Sternotherus minor.

Longevity patterns in most vertebrates suggest that females benefit most from maintenance investment. A reversed longevity pattern in loggerhead musk turtles (Sternotherus minor) allowed us to test trade-offs between maintenance and survivorship. We tested the hypothesis that the sex with greater longevity has greater maintenance than the sex with shorter longevity. We also compared the following parameters between sexes: Bactericidal ability (BA) and heterophil:lymphocyte ratios (HLR). Baseline blood samples were collected from turtles in the field; a subset of turtles was returned to a laboratory for experiments of acquired immune responses to sheep red blood cells (SRBC). We found no support for the original hypothesis of reversal in sex-dependent immune trade-offs (difference between sex SRBC titers: p = .102; interaction between treatment and sex: p = .177; difference between treatments: p < .001; effect of sex on BA: p = .830; effect of sex on HLR: p = .717). However, we did find support for sex-dependent differences in immunity in the relationship between HLR and body condition (BCI) (effect of BCI on HLR: p = .015). In field conditions, we found that males with higher body condition indices express stressed phenotypes more than males with lower body condition indices (p = .002). However, females expressed similar stress loads across all body conditions (p = .900). Testosterone concentrations were assayed in free-living turtles and were not related to any of the immune parameters. Our results suggest that the immune systems play an important role in balancing sex-specific responses to different selective pressures in S. minor.

Resource‐use, body condition and parasite load metrics indicate contrasting health of stocked and native game fishes in Canadian prairie lakes

AbstractThis study evaluated the status of native and stocked fish species in 13 prairie lakes in central Canada over eight years (2007–14) using three metrics: resource‐use (benthic versus pelagic carbon via stable isotopes); body condition (relative weight index Wr); and parasite load (cestode gut enumerations). Analyses included game and non‐game fishes, like naturally occurring northern pike, Esox lucius L., and yellow perch, Perca flavescens Mitchill, but focused on stocked walleye, Sander vitreus (Mitchill) because it supports a robust recreational fishery. Walleye and northern pike were significantly more reliant on benthic carbon than yellow perch or forage fishes (p &lt; 0.05), but this reliance was not associated with any measured environmental variables for any species. In lakes with game fishes, forage fishes exhibited higher reliance on benthic energy, possibly due to predator avoidance strategy, particularly yellow perch. Walleye body condition index was consistently lower (&lt;95–105) than values exhibited by the other two game fishes (81–139), and parasites were only common in walleye and associated with lake‐water salinity (r2 = 0.93, p &lt; 0.05) and sex (p &lt; 0.05). Based on the results, the most desirable game fish, walleye, appears less resilient to environmental variability than northern pike and yellow perch, making this species more susceptible to impacts of future climate change.

Lipid metabolites as indicators of body condition in highly contaminant-exposed belugas from the endangered St. Lawrence Estuary population (Canada)

The endangered St. Lawrence Estuary (SLE) beluga population is declining and has shown no sign of recovery over the past decades despite several protective measures. Changes in the availability of food resources and exposure to organohalogen contaminants have been suggested as potential factors limiting the recovery of this population. Studies on SLE belugas have suggested that contaminant exposure may perturb energy metabolism, however, whether this translates into changes in energy reserves (lipid composition) and body condition is unknown. The objective of this study was to investigate the relationships between body condition and concentrations of organohalogens (polychlorinated biphenyls, organochlorine pesticides, and flame retardants) and a range of lipid metabolites (fatty acids, acylcarnitines, lysophosphatidylcholines, phosphatidylcholines, and sphingomyelins) in blubber samples collected from 51 SLE beluga carcasses recovered between 1998 and 2016 for which the cause of mortality was documented. Blubber Σ9fatty acid concentrations in SLE belugas significantly decreased between 1998 and 2016, suggesting a decline in energy reserves over the past two decades. Concentrations of several phosphatidylcholine analogues were greater in blubber of beluga males and/or females that were in poor body condition compared to those in good body condition. Moreover, concentrations of phosphatidylcholine acyl-alkyl C32:2 were greater in females that died from primary starvation (poor body condition). Greater concentrations of Σ12emerging flame retardants were also found in blubber of SLE beluga females that were in poorer body condition. This study suggests that the use of membrane lipids including phosphatidylcholine concentrations may be a good indicator of body condition and energy reserve status in blubber of marine mammals.

The effect of short-term fasting on the oxidative status of larvae of crested newt species and their hybrids

In nature, animals often face periods without food caused by seasonal fluctuations and/or prey scarcity. An organism's physiological response to imposed energetic limitations is followed by changes in mitochondrial functioning (adjustment of energy metabolism) and a reduction of non-essential processes. However, this energy-saving strategy can have its costs. In this study, we examined oxidative stress as one of the possible physiological costs of short-term, two-week-long food deprivation on developing amphibian larvae of the crested newts Triturus macedonicus and Triturus ivanbureschi and their hybrids. We investigated whether this exogenous factor additionally affected the oxidative status (fitness-related trait) of hybrid individuals. The fasting treatment led to lower growth and a lower body mass and body condition index of individuals. The results revealed that the antioxidant system (AOS) of food-deprived larvae could not cope in a proper manner with reactive oxygen species production under limited energy availability, leading to higher lipid oxidative damage. The lowest AOS response was observed for H2O2 scavenging parameters (catalase, glutathione peroxidase, and total glutathione), which together with the elevated activity of superoxide dismutase suggested increased H2O2 concentrations. Comparison between parental species and their hybrids showed that hybrid individuals suffered greater oxidative damage (as demonstrated by higher concentrations of lipid peroxides), indicating that they were more susceptible to fasting-induced oxidative stress. Overall, this study illustrates that: (i) an oxidative event is one of the costs amphibian larvae face during short-term periods of fasting, (ii) hybrids are less capable of dealing with this stressful condition, which can lower their chances of survival in a changing environment.