Intersexual allometry differences and ontogenetic shifts of coloration patterns in two aquatic turtles,Graptemys oculifera and Graptemys flavimaculata

Coloration can play critical roles in a species' biology. The allometry of color patterns may be useful for elucidating the evolutionary mechanisms responsible for shaping the traits. We measured characteristics relating to eight aspects of color patterns from Graptemys oculifera and G. flavimaculata to investigate the allometric differences among male, female, and unsexed juvenile specimens. Additionally, we investigated ontogenetic shifts by incorporating the unsexed juveniles into the male and female datasets. In general, male color traits were isometric (i.e., color scaled with body size), while females and juvenile color traits were hypoallometric, growing in size more slowly than the increase in body size. When we included unsexed juveniles in our male and female datasets, our linear regression analyses found all relationships to be hypoallometric and our model selection analysis found support for nonlinear models describing the relationship between body size and color patterns, suggestive of an ontogenetic shift in coloration traits for both sexes at maturity. Although color is critical for many species' biology and therefore under strong selective pressure in many other species, our results are likely explained by an epiphenomenon related to the different selection pressures on body size and growth rates between juveniles and adults and less attributable to the evolution of color patterns themselves.     

Migratory constraints on yolk precursors limit yolk androgen deposition and underlie a brood reduction strategy in rockhopper penguins

Hormonally mediated maternal effects link maternal phenotype and environmental conditions to offspring phenotype. The production of lipid-rich maternal yolk precursors may provide a mechanism by which lipophilic steroid hormones can be transported to developing yolks, thus predicting a positive correlation between yolk precursors in mothers and androgen levels in eggs. Using rockhopper penguins (Eudyptes chrysocome), which produce a two-egg clutch characterized by extreme egg-size dimorphism, reversed hatching asynchrony and brood-reduction, we examined correlations between circulating concentrations of the primary yolk-precursor vitellogenin (VTG) and levels of yolk androgens. Previous work in Eudyptes penguins has shown that egg-size dimorphism is the product of migratory constraints on yolk precursor production. We predicted that if yolk precursors are constrained, androgen transport to developing yolks would be similarly constrained. We reveal positive linear relationships between maternal VTG and androgens in small A-eggs but not larger B-eggs, which is consistent with a migratory constraint operating on the A-egg. Results suggest that intra-clutch variation in total yolk androgen levels depends on the production and uptake of yolk precursors. The brood reduction strategy common to Eudyptes might thus be best described as the result of a migratory constraint.     

Functional changes in the anatomy of the pharyngeal jaw apparatus of Astatoreochromis alluaudi (Pisces, Cichlidae), and their effects on adjacent structures

Organisms are tightly packed with structures so architectonic interdependency of structures is an obvious aspect of integration. This aspect of functional morphology, however, has received remarkably little attention. The present paper presents an example of the spatial relations among several apparatuses in the head of the cichlid fish, Astatoreochromis alluaudi. It investigates the transformations of these apparatuses and their functions due to a change in the pharyngeal jaw apparatus resulting from a functional shift (insect eating to snail crushing or vice versa ). The volume of the pharyngeal jaw apparatus differs 55% between the insect eating- and the snail eating morph. The increase in volume of the pharyngeal jaw apparatus has an impressive number of spatial effects, both direct and indirect, on other structures. Reallocation of space within the pharyngeal jaw apparatus occurs. Total head volume increases 31% but a reallocation of space is still necessary as the increase of the opercular compartment where the pharyngeal jaw apparatus is situated compensates for only 59% of the volume increase of that. Not all spatial effects do impose constraints. Spatial constraints are avoided when one of the apparatuses can use a topographically different volume of space. The respiratory apparatus shows internal reallocations of space without loss of total volume. The same solution occurs for elements of the expansion apparatus and the buccal savity. The eyes are not influenced. Finally spatial effects can have positive repercussions. The muscles of the oral jaw apparatus increase in size. This may be an example of an epiphenomenon.     

Fighting During Suckling: Is it Really an Epiphenomenon?

Suckling by piglets and kittens is accompanied by intense fighting among littermates. There are strong arguments that support the fighting for teats as an epiphenomenon, such as there being a sufficient number of mammary glands (teats) that are of equal quality for littermates, as suggested by Hudson and Distel (Ethology, 119, 2013, 353). However, this article presents a possible adaptive explanation for fighting during suckling. To substantiate the adaptive function of suckling fights, the disposability and limitations of colostrum are first considered. Other aspects are also discussed, such as the potential role of social thermoregulation, the stimulation of mammary glands (massage) and milk composition. Adaptive explanations for the absence/presence and intensity of suckling fights across species consider differences in the colostrum and mature milk composition, mechanisms of transferring immunoglobulin that supply passive immunity to neonates, strategies used to compete for teats and litter size. However, agonistic behaviours in the context of suckling should not be simply categorised as an epiphenomenon.     

Female-solicited extrapair matings in Humboldt penguins fail to produce extrapair fertilizations

The study reported in this paper demonstrated that Humboldtpenguins at Punta San Juan, Peru, despite forming pair-bonds,are not strictly monogamous in their mating behavior: 19.2%of the study males and 30.7% of the study females (21 nests)engaged in extrapair copulations. The total number of completedmatings observed during the course of this study was 106, ofwhich 17.9% were extrapair copulations. Using DNA fingerprintingwe demonstrated that none of these extrapair copulations resultedin extrapair fertilizations; all 49 offspring were attributedto the putative father. Location of copulations suggested thatfemales solicited these extrapair copulations because 89.2%of Humboldt penguin within-pair copulations occurred at thehome burrow, yet extrapair copulations took place at a differentlocation based on the sex of the penguin. Extrapair copulationsby males occurred at their nest, whereas females conducted 92%of their extrapair copulations away from the nest. These resultsare most consistent with mate-appraisal and epiphenomenal hypotheses.