INTRODUCTION:Many, but not all, bird taxa possess the ability to see ultraviolet (UV) light, but it is currently unclear the extent this ability exists among seabirds. Measuring retinal photoreceptor sensitivity presents many challenges, but the penetration of UV light through the ocular media (ocular transmittance) is a good proxy for UV vision. METHODS:Here, we document the ocular transmission of light wavelengths using spectrometry through the eyes of eight Procellariiform and Suliform seabird species found in Aotearoa New Zealand. RESULTS:We report that the eyes of most Procellariiformes, but not the Suliformes, can transmit UV wavelengths. Thus, there is the potential for those Procellariiformes to perceive UV. DISCUSSION:Both phylogeny and ecology could play a role in UV vision in seabirds and understanding the wavelengths that seabirds perceive can be crucial for conservation against visual threats.
INTRODUCTION:Star-nosed moles are renowned as the fastest foragers among mammals, able to identify and eat small prey in less than a quarter of a second. This ability stems in part from the mole's extraordinary mechanosensory star which has been the focus of many investigations. However, fast eating also requires a specialized motor system and associated structures. Here, the mole's unusual incisors are explored as a key adaptation for efficient foraging. METHODS:High-speed videos of foraging moles, including microscopic views at 1,000 frames per second, were used to measure prey handling time and tooth movements. Scanning electron microscopy was used to assess tooth structure. Specimens from Cornell Museum of Vertebrates were examined with light microscopy. Data from previous investigations were compared to the present results. RESULTS:A mole with worn front teeth was discovered, and this specimen often failed to secure small prey efficiently, thus doubling the mole's handling time compared to normal specimens. The manner in which the worn teeth failed suggested the mole's normal incisors are analogous to a specific type of man-made surgical forceps - so-called Yaşargil tumor forceps. CONCLUSION:The results reveal an example of serendipitous biomimicry by human surgeons in designing soft tissue forceps, highlight the importance of motor specializations in the star-nosed mole's fast foraging ability, and suggest some of the specific anatomical specialization that are the result of selection on the key variables (space clearance rate and handling time) in Holling's pioneering foraging theory equation.
Introduction: Ontogenetic brain growth in cetaceans is essential for understanding their development and evolution. This study investigates brain size changes relative to body growth in bowhead (Balaena mysticetus) and beluga (Delphinapterus leucas) whales in the framework of age estimates of pre- and postnatal specimens. Methods: We collected specimens in the field, determined brain size and endocranial volumes, as well as size of endocranial adnexa, either by direct measurement or by CT. We estimated age using baleen length (bowhead), growth layers in teeth (belugas), or fetal stages. We fitted Gompertz growth models to our data. Results: Our findings show that both bowhead and beluga whales reach nearly their full brain size by the end of weaning, unlike dolphins and humans, whose brains continue growing after weaning. Bowhead brains grow faster than those of belugas, and much faster than those of humans, and their rete mirabile occupies a much larger portion of the cranial cavity than in belugas. Encephalization quotients decline with age due to continued body growth after brain maturation. Conclusion: Brain growth in these cetacean species plateaus early, challenging the assumption that cetacean brains grow throughout life. In bowhead, the brain is significantly smaller than the cranial cavity, and this is not the case in beluga. If this observation can be generalized to all mysticetes and odontocetes, it implies that no single equation can capture the proportional volumes of the brain and cranial cavity across the entire cetacean clade.
INTRODUCTION:We reanalyzed data from Sobrero et al. [Brain Behav Evol. 2016;87:51-64] to evaluate dorsal dentate gyrus (dDG) folding or gyrification as a morphological proxy for neurogenesis and macrostructural plasticity in hippocampal or extracortical regions of wild rodents. METHODS:Using Zilles' (ZGI) and Vogeley's (VGI) indices, we quantified dDG gyrification across hemispheres in Octodon degus and Octodon lunatus, comparing populations that differ in habitat complexity and social behavior. RESULTS:Left dDG gyrification (ZGIL) showed a preliminary association with social group size, whereas right dDG gyrification (VGIR) was predicted by population differences. O. lunatus from shrub-dense environments exhibited greater dDG folding than O. degus from open habitats. Although not statistically significant, hemispheric asymmetries were suggested, consistent with previously reported right-lateralized DG cell numbers in O. lunatus and habitat-sociality effects on DG cell counts in O. degus from El Salitre. CONCLUSION:These results support dDG gyrification as an informative marker of neural plasticity shaped by habitat conditions and emphasize the value of wild models in brain-ecology research.
INTRODUCTION:Over the last century, sea surface temperatures have increased by more than 0.5°C, with predictions suggesting an increase of 1-4°C by 2100. Oceanic warming poses significant challenges to marine species, particularly those with physiological and developmental processes that are tightly linked to environmental conditions. In cartilaginous fishes, including sharks, the brain grows continually throughout life, supported by the capacity for lifelong neurogenesis. This feature suggests that the nervous system - both peripheral (sensory) and central (brain) - of sharks may be highly plastic and able to adapt dynamically to a changing environment. METHODS:We investigated the effects of elevated rearing temperature on brain development in the epaulette shark (Hemiscyllium ocellatum), a species known for its tolerance of environmental fluctuations in intertidal habitats. Eggs (n = 12) were sourced from a breeding stock at the New England Aquarium and reared in either ambient (27°C) or elevated (31°C, 4°C above ambient) seawater temperatures until 2 months post-hatch. Using histological analyses, we compared the relative volume of the nose (olfactory rosette), total brain, and major brain regions between treatment groups. RESULTS:Despite this species' natural exposure to temperature variability, generalized linear models revealed that elevated temperature significantly altered the volume of the olfactory sensory epithelium, olfactory bulbs, and medulla oblongata after accounting for overall brain size. Analyses of proportional brain region volumes also showed that elevated temperature was associated with reduced olfactory bulb size and increased subpallial volume relative to total brain size. These differences may suggest potential changes in cognitive capacity related to olfactory processing as well as sensory and/or motor functions at elevated temperatures. CONCLUSIONS:While short-term studies, such as this one, cannot capture long-term adaptive potential, understanding the impacts of elevated temperature on brain phenotypes provides critical insights into how elasmobranchs may cope with changing ocean conditions. Such knowledge will be vital for predicting the resilience of these ecologically important species to future environmental stressors.
