Does nest predation pressure influence the energetic cost of nest guarding in a teleost fish?

The energetic costs of providing parental care are widely documented, but rarely do studies consider the role of environmental variation (e.g., predation pressure) in this context. Here, we tested if variation in nest predation pressure influenced the energetic costs of parental care in smallmouth bass (Micropterus dolomieu), a teleost fish species that provides lengthy paternal care. First, we documented that nest predation pressure varied among the six lakes studied and the relative predation pressure ranking was consistent across a three year period. We used a combination of traditional proximate body composition (PBC) analyses and electromyogram (EMG) telemetry to quantify activity costs of nesting fish across these populations. The traditional approach revealed declines in energy stores across the parental care period but showed no evidence of an increased energetic cost to parents from populations with higher nest predation pressure. Comparing the distribution of EMG data from the two extremes of predation pressure revealed that males from the site of highest predation spent more time at higher EMG levels relative to the parents from the lake of lowest predation pressure. Although not statistically significant, males from the site of highest predation pressure also spent 21?C24?% of their time burst swimming when guarding young offspring compared to 10?C11?% for males at the site of lowest predation pressure. These differences in overall activity, a large contributor to the energy use of fish, may translate into longer recovery times and decreased future reproductive opportunities.     

Does reproductive effort influence the metabolic rate of Tomodon dorsatus snakes?

In Squamate reptiles, vitellogenesis in females is marked by an increase in the number and size of follicles, leading to an increase in aerobic metabolism to support the rising energy demand during reproductive activity. Male gametes are smaller than female gametes, and spermiogenesis requires less energy than vitellogenesis. This investigation compares the relationship between aerobic metabolism and reproductive effort in male and female viviparous Tomodon dorsatus snakes. We evaluated the influence of the males' and females' reproductive stages, along with the masses of follicles and testicles, on their aerobic metabolic rate. Our findings show that females have higher maintenance cost of pregnancy than metabolic costs of vitellogenesis. In males, we found no evidence of the reproductive effort influencing aerobic metabolic rates. In T. dorsatus, females have a long period of development and high fecundity. Therefore, the metabolic costs of vitellogenesis represent a critical component in the reproductive effort. On the other hand, males of T. dorsatus maintain a similar mass of gonads throughout the year with constant energy demand. These results reflect the difference in reproductive efforts between females and males of T. dorsatus.     

Does the host matter? Variable influence of host traits on parasitism rates

Parasitism of mammals is ubiquitous, but the processes driving parasite aggregation on hosts are poorly understood, as each system seems to show unique correlations between parasitism and host traits such as sex, age, size and body mass. Genetic diversity is also posited to influence susceptibility to parasitism, and provides a quantifiable measure of an intrinsic unchanging host property, but this link has not been well established. A lack of consistency in host traits predicting parasite heterogeneity may derive from the contribution of environmental factors to parasite aggregation. To evaluate this question, a large dataset was leveraged to explore the relationship between unchanging, intrinsic host traits (heterozygosity and sex), variable host traits (age, length and body mass), and extrinsic factors (sampling date/year and population) and flea presence/absence, abundance and intensity on two species of social burrowing mammal, the black-tailed prairie dog (Cynomys ludovicianus) and the Gunnison’s prairie dog (Cynomys gunnisoni). Prairie dogs experience frequent parasitism by fleas, but the distribution of fleas among individuals is highly skewed. In these systems, intrinsic host traits were nuanced in how they predicted flea aggregation on individual prairie dogs, with sex unimportant to parasitism rates and heterozygosity increasing the probability of infection and influencing the number of fleas in divergent ways. Variable host traits interacted with each other and with environmental or geographic stochasticity to influence flea aggregation. Length and age tended to increase parasitism, whereas the effects of body mass and condition were mediated by date and other host traits to produce both positive and negative effects on parasitism. This finding suggests that the factors affecting ectoparasite infection on individuals are complex, even within species. Importantly, there was no correlation between the number of fleas on an individual in one year and the number of fleas on the same individual the next year, supporting the idea that flea aggregation is not driven by unchanging, intrinsic characteristics of the host. Rather, these findings indicate that host traits influence parasitism in nuanced ways, including interactions with environmental characteristics and stochastic factors.     

Does the skeleton of a sponge provide a defense against predatory reef fish?

Sponge tissue often contains two structural components in high concentrations: spicules of silica, and refractory fibers of protein (spongin). Some terrestrial plants contain analogous structures, siliceous inclusions and refractory lignins, that have been demonstrated to deter herbivory. We performed feeding experiments with predatory reef fish to assess the deterrent properties of the structural components of three common Caribbean demosponges, Agelas clathrodes, Ectyoplasia ferox, and Xestospongia muta. The concentrations of spicules and spongin in the tissues varied widely between the three species, but when assayed at their natural volumetric concentrations, neither spicules (all three species assayed) nor the intact spiculated spongin skeleton (A. clathrodes and X. muta assayed) deterred feeding by reef fish in aquarium or field assays using prepared foods of a nutritional quality similar to, or higher than, that of sponge tissue. Spicules deterred feeding in aquarium assays when incorporated into prepared foods of a nutritional quality lower than that of sponge tissue (15–19 times less protein), but spiculated spongin skeleton was still palatable, even in prepared foods devoid of measurable protein, and even though spicules embedded in spongin were oriented in their natural conformation. Based on comparisons of the nutritional qualities of the tissues of the three sponge species and of the prepared foods, sponge tissue would have to be much lower in food value (5 times less protein or lower) for spicules to provide an effective defense, and spicules in combination with the spongin skeleton would be unlikely to provide an effective defense regardless of the nutritional quality of the tissue. Unlike terrestrial plants, marine sponges may use silica and refractory fibers solely for structural purposes.     

Does the growth temperature of a prokaryote influence the purine content of its mRNAs?

The formation and breaking of hydrogen bonds between nucleic acid bases are dependent on temperature. The high G+C content of organisms was surmised to be an adaptation for high temperature survival because of the thermal stability of G:C pairs. However, a survey of genomic GC% and optimum growth temperature (OGT) of several prokaryotes revoked any direct relation between them. Significantly high purine (R=A or G) content in mRNAs is also seen as a selective response for survival among thermophiles. Nevertheless, the biological relevance of thermophiles loading their unstable mRNAs with excess purines (purine-loading or R-loading) is not persuasive. Here, we analysed the mRNA sequences from the genomes of 168 prokaryotes (as obtained from NCBI Genome database) with their OGTs ranging from -5 °C to 100 °C to verify the relation between R-loading and OGT. Our analysis fails to demonstrate any correlation between R-loading of the mRNA pool and OGT of a prokaryote. The percentage of purine-loaded mRNAs in prokaryotes is found to be in a rough negative correlation with the genomic GC% (r(2)=0.655, slope=-1.478, P<000.1). We conclude that genomic GC% and bias against certain combinations of nucleotides drive the mRNA-synonymous (sense) strands of DNA towards variations in R-loading.     

Is skipjack tuna the fastest-growing teleost fish on earth?

Using a genetic marker mitochondrial DNA control region, Nikolic et al. (Environ Biol Fish 99:171-178, 2016) recently reported the identification of two juveniles of tuna as skipjack (Katsuwonus pelamis) recovered from the mouth of dolphinfish in the vicinity of Reunion Island, western Indian Ocean. Based on the age estimates of the two specimens from opercular bones at about 16–20 days and the increased occurrence of skipjack in the catch of Japanese longliners during October–January, the authors indicate that their results suggest a specific seasonal spawning area of skipjack around Reunion Island. We challenge the validity of age estimates and the interpretation of the results published by Nikolic et al. (Environ Biol Fish 99:171-178, 2016). Current knowledge of skipjack tuna biology indicates that the paper of Nikolic et al. (Environ Biol Fish 99:171-178, 2016) contains misinterpretation of field observations that led the authors to misunderstandings on skipjack tuna ecology.     

Does sucrose influence the properties of DMPC vesicles?

Small-angle neutron and X-ray scattering, dynamic light scattering, X-ray diffraction coupled with differential scanning calorimetry, and Raman spectroscopy were applied to investigate unilamellar (ULVs) and multilamellar (MLVs) dimyristoylphosphatidylcholine (DMPC) vesicles in aqueous sucrose solutions with sucrose concentrations from 0 to 60% w/w. In case of ULVs, the addition of sucrose decreases the polydispersity of vesicle population. A minimum value of polydispersity was found at 20% sucrose. For sucrose concentration from 0 to 35% oligolamellar vesicles in the ULV population have a minimum presence. Vesicles with 5-10% sucrose exhibit the best stability in time. For the case of MLVs, sucrose influences the temperature of the phase transitions, but the internal membrane structure remains unchanged.     

Does nasal echolocation influence the modularity of the mammal skull?

In vertebrates, changes in cranial modularity can evolve rapidly in response to selection. However, mammals have apparently maintained their pattern of cranial integration throughout their evolutionary history and across tremendous morphological and ecological diversity. Here, we use phylogenetic, geometric morphometric and comparative analyses to test the hypothesis that the modularity of the mammalian skull has been remodelled in rhinolophid bats due to the novel and critical function of the nasal cavity in echolocation. We predicted that nasal echolocation has resulted in the evolution of a third cranial module, the ‘nasal dome’, in addition to the braincase and rostrum modules, which are conserved across mammals. We also test for similarities in the evolution of skull shape in relation to habitat across rhinolophids. We find that, despite broad variation in the shape of the nasal dome, the integration of the rhinolophid skull is highly consistent with conserved patterns of modularity found in other mammals. Across their broad geographical distribution, cranial shape in rhinolophids follows two major divisions that could reflect adaptations to dietary and environmental differences in African versus South Asian distributions. Our results highlight the potential of a relatively simple modular template to generate broad morphological and functional variation in mammals.     

Does menarche mark a period of elevated resting metabolic rate?

Resting metabolic rate (RMR) and body composition were measured in 44 initially nonoverweight girls at three time points relative to menarche: premenarche (Tanner stage 1 or 2), menarche (+/-6 mo), and 4 yr after menarche. Mean absolute RMR was 1,167, 1,418, and 1,347 kcal/day, respectively. Absolute RMR was statistically significantly higher at menarche than at 4 yr after menarche despite statistically significantly less fat-free mass (FFM) and fat mass (FM), suggesting an elevation in RMR around the time of menarche. The pattern of change in RMR, adjusted for FFM, log transformed FM, age, race, parental overweight, and two interactions (visit by parental overweight, parental overweight by FFM), was also considered. Adjusted RMR did not differ statistically between the visits for girls with two normal-weight parents. For girls with at least one overweight parent, adjusted RMR was statistically significantly lower 4 yr after menarche than at premenarche or menarche. Thus parental overweight may influence changes that occur in RMR during adolescence in girls.     

Does free-energy change of individual reactions alone determine the flux through a metabolic pathway?

Most text books of biochemistry present the concept of free energy change clearly under bioenergetics. However, some text books in trying to explain this in more detail later in the book, with more specific examples, often confuse the students. With the possibility of more accurate measurement of reactants and products by high pressure liquid chromatography or other modern techniques, and by selecting an appropriate tissue, it should be possible to avoid errors of this kind, which contradict the basic concepts taught to the students earlier in the course.     

Does moonlight influence the biting behaviour of Anopheles funestus?

The possible effect of moonlight on the biting behaviour of mosquitoes in southern Mozambique, in particular that of Anopheles funestus (Diptera: Culicidae), a primary vector of malaria, was investigated by comparing catches indoors and outdoors using CDC light traps and 'Furvela' tent traps, respectively, for 35 consecutive nights, from 9 September to 15 October 2008. Collections were separated into three 4-hourly samples each night. A total of 17 591 mosquitoes belonging to nine species were collected, 6747 in light traps and 10 844 in tent traps. Anopheles funestus (n = 7634) and Mansonia africana (n = 4859) were the most abundant species. Fluctuations in temperature and humidity were the two environmental variables associated with changes in relative abundance of mosquitoes. Most An. funestus were collected indoors, with the majority collected in the first 4 h of the night. This was most evident on nights when moonlight was present in the early part of the night. A total of 3488 An. funestus were dissected for gonotrophic age determination. Parous rates did not change with lunar phase, but estimated oviposition cycle length was significantly shorter on nights when moonlight was present at the time of oviposition. Moonlight at dusk did not, however, affect the proportion of newly emerged insects with mating plugs collected. Outdoor transmission of malaria, especially on moonlit nights, remains a problem for control programmes.     

Does the treatment of primary hyperaldosteronism influence glucose tolerance?

Primary hyperaldosteronism (PH) is frequently considered to be a secondary form of diabetes mellitus (DM). In our previous study we attempted to evaluate the prevalence of DM among patients with PH compared to control subjects with essential hypertension (EH). We have noted a relatively high prevalence of DM and impaired glucose tolerance in PH, but the differences between the PH and EH groups did not reach statistical significance. We performed this study to assess whether the effective treatment of PH (surgical and conservative) would improve the glucose tolerance. We have studied 24 patients with PH of the following two subtypes: aldosterone-producing adenoma (APA) treated with adrenalectomy and idiopathic hyperaldosteronism (IHA) treated with spironolactone. No significant changes of glucose levels were found in the 60th and 120th min of the oral glucose tolerance test (OGTT) in the APA group. On the other hand, fasting glucose levels were decreased significantly after adrenalectomy. Plasma glucose levels were significantly increased in the 60th min, but no differences were found in fasting values and in the 120th min in the IHA group. There was a significantly higher incidence of impaired glucose tolerance (36 per cent before, 45 per cent after treatment) and DM (9 per cent, 18 per cent) in the IHA group compared to the APA group (8 per cent, 32 per cent; DM 0 per cent, 0 per cent). In conclusion, the treatment of PH does not improve glucose tolerance. Mild worsening of glucose tolerance after treatment could be explained by an increase of the body mass index. These data, in accordance with our previous study, do not support the idea that PH is a secondary form of diabetes mellitus.     

Does food quality influence thermoregulatory behavior in the intertidal fish Girella laevifrons?

Algal and invertebrate species are less abundant towards higher zones of the intertidal, where the greatest variations in physical environmental conditions occur. Mobile predators such as fishes that inhabit high intertidal rockpools are thus exposed to wide variations in physical conditions and to a low abundance and quality of food. We used an aquarium with a temperature gradient in the laboratory to assesed whether dietary quality differences modify temperature preferences of Girella laevifrons, one of the most abundant transitory fishes inhabiting rocky shores along the coast of Chile. Our results indicate that food quality clearly modifies temperature preferences in this species. Animals fed on high quality bivalves selected intermediate temperatures (16–18°C) while those fed on lower quality algae selected lower temperatures (10–12°C). Control fish not subjected to the temperature gradient did not select portions of the aquarium differentially. The thermal selectivity of G. laevifrons in relation to the optimization of digestive processes and mechanisms of energy conservation are discussed.     

Does proximity to aquatic pollution affect reproductive traits in a wild‐caught intertidal fish?

How chronic exposure to aquatic pollution affects reproductive traits was assessed in nesting wild-caught plainfin midshipman Porichthys notatus in areas with low and high contaminant exposure on Vancouver Island, British Columbia. Males in high-exposure areas had a greater degree of testicular asymmetry, sperm with shorter heads and fewer live eggs in their nests. The results of this study provide important insights into the potential consequences of contaminant exposure on the reproductive physiology of wild-caught fishes.     

Can behavioral and personality traits influence the success of unintentional species introductions?

Unintentional species invasions are instigated by human-mediated dispersal of individuals beyond their native range. Although most introductions fail at the first hurdle, a select subset pass through each stage of the introduction process (i.e., transport, introduction, establishment and spread) to become successful invaders. Efforts to identify the traits associated with invasion success have predominately focused on deliberate introductions, which essentially bypass the initial introduction stage. Here, we highlight how behavior influences the success or failure of unintentional species introductions across each stage of the introduction process, with a particular focus on transportation and initial establishment. In addition, we emphasize how recent advances in understanding of animal personalities and individual-level behavioral variation can help elucidate the mechanisms underlying the success of stowaways.     

Does gender influence neuromotor control of the knee and hip?

Patellofemoral pain (PFP) is a common condition that occurs more frequently in females. Anatomical, hormonal and neuromuscular factors have been proposed to contribute to the increased incidence of PFP in females, with neuromuscular factors considered to be of particular importance. This cross-sectional study aimed to evaluate differences in the neuromotor control of the knee and hip muscles between genders and to investigate whether clinical measures of hip rotation range and strength were associated with EMG measures of hip and thigh motor control. Twenty-nine (16 female and 13 male) asymptomatic participants completed a visual choice reaction-time stair stepping task. EMG activity was recorded from vastus medialis oblique, vastus lateralis, anterior and posterior gluteus medius muscles. In addition hip rotation range of motion and hip external rotation, abduction and trunk strength were assessed. There were no differences in the timing or peak of EMG activation of the vasti or gluteus medius muscle between genders during the stepping task. There were however significant associations between EMG measures of motor control of the vasti and hip strength in both females and males. These findings are suggestive of a link between hip muscle control and vasti neuromotor control.     

Can floral consumption by fish shape traits of seagrass flowers?

Seagrasses are marine flowering plants with hydrophilous pollination. This abiotic pollination by water assumes absence of flower-animal interaction, but animals can interfere in this process through consumption of reproductive structures. We studied predation on male flowers by fish for three dioecious seagrass species (Thalassia testudinum, Syringodium filiforme and Halodule wrightii) in the Mexican Caribbean. Seagrass flowers have a highly reduced or absent corolla and florivores directly consumed the anthers with pollen. The foliar structures (tepals, bracts or sheaths) protecting the male flower buds were removed by hand in situ. The floral buds were followed by videos or taking pictures at regular intervals and most (56–100 %, depending on seagrass species and experimental setting) artificially denuded male flower buds were consumed within 24 h by juvenile fish of various species. Histochemical analysis showed that the pollen and embedding mucilage were rich in polysaccharides and proteins, thus potentially nutritious. The seagrasses had copious production of pollen (between 0.2 and 1.2 × 10⁶ pollen per flower, depending on the species). But T. testudinum and S. filiforme were often pollen limited, and the probability of fruit set was reduced ~50 % when the females were at the distance of 1 and 5–6 m from the males flowers, respectively. Under natural conditions, depredation on pre-anthesis male flowers in the three species was low because flower bud emergence (few hours) and pollen release (1–4 h) were ephemeral processes. In addition, the release of pollen of T. testudinum occurred at dusk when herbivorous fish became inactive. These life-cycle characteristics aid to avoid excessive pollen consumption by fish, however, whether they are anti-predator strategies or mere adaptations for submarine pollination remains to be established.