ABSTRACT Cetacean blubber is a multifunctional vital organ that serves as a diagnostic medium for assessing nutritional status, life history, and general health at both macro‐ and microscopic scales. In this study, we provide the first histological characterisation of adipocyte morphology in killer whales ( Orcinus orca ) using full‐depth blubber samples collected postmortem from 25 individuals (16 females, 9 males) from strandings in New Zealand. Specifically, we assessed the relationships between adipocyte area (AA), adipocyte index (AI), and biological covariates. Additionally, we tested the application of a novel blubber grading system to explore the impact of histological slide characteristics on adiposity metrics, confirming that decomposition state did not systematically bias morphological data. Linear mixed‐effects models identified distinct stratification across the blubber profile. Adipocyte area was predicted by both total body length and blubber thickness, indicating that blubber expansion is mediated by body size and cellular hypertrophy. In contrast, the AI was primarily driven by nutritional status. A significant interaction between cell size and depth revealed that the inner layer is the most dynamic stratum, indicating superior architectural plasticity. To improve diagnostic resolution, we further developed an integrated health ratio (AA/AI). This metric was significantly lower in emaciated individuals, as it accounts for the concurrent reduction in lipid stores and increase in structural fibre density. Our findings establish a baseline for killer whale blubber physiology and demonstrate that with rigorous quality control, stranded specimens yield reliable morphometric data for the assessment of body condition in cetaceans.
ABSTRACT Small cetaceans serve as sentinel species for monitoring marine ecosystem health due to their vulnerability to bioaccumulative contaminants that may disrupt reproductive development. Despite this, there is a lack of validated reproductive toxicity markers, most notably for sexually immature individuals. This study assessed the feasibility of assessing ovarian follicle quantification in stranded sexually immature female harbour porpoises ( Phocoena phocoena ) and common dolphins ( Delphinus delphis ), using ovarian assessment criteria commonly applied in reproductive toxicity studies in other species. Ovarian tissues from 29 stranded individuals were processed, of which only those with adequately preserved bilateral ovarian sections ( n = 18) were included in the follicle‐count and morphometric analyses. Ovarian follicle classes, including naked ova, primordial, and primary follicles, were identified, counted, and measured. Results revealed significant left–right ovarian asymmetry in harbour porpoises, with the left ovary containing more combined follicle‐class counts in both calves and juveniles, consistent with previously reported left‐sided asymmetry in genital morphology and lateralised mating behaviour in the species. In contrast, common dolphins showed no evidence of ovarian asymmetry in sexually immature individuals. In both species, combined follicle‐class counts declined sharply with increasing body length, while follicle diameter showed a positive association with somatic growth, indicating parallel patterns of early‐life follicular depletion and enlargement. Naked ova were consistently observed across all body length groups in harbour porpoises, while none were reported in the ovaries of common dolphins. These results demonstrate that harbour porpoises and common dolphins differ in patterns of ovarian asymmetry and early follicular development, supporting species‐specific baseline descriptions of ovarian morphology. Furthermore, quantification of ovarian follicle classes provides a reproducible histological endpoint that may help detect deviations from normal ovarian development associated with early‐life exposure to environmental contaminants in stranded small cetaceans, provided tissue is adequately preserved.
ABSTRACT The present study provides the first comprehensive account of the embryonic and larval ontogeny of Plesiopuntius bimaculatus , a smiliogastrine cyprinid distributed in peninsular India and Sri Lanka, together with observations on its reproductive biology. Captive spawning produced small, adhesive, demersal eggs (696.46 ± 23.72 µm) deposited on vegetation and gravel, with no parental care observed. Embryogenesis followed the characteristic teleost developmental sequence, including meroblastic cleavage, epiboly‐driven gastrulation, and sequential organogenesis, with hatching occurring approximately 16 h 15 min after fertilization at 27°C–28°C. Larvae hatched at 2.09 ± 0.08 mm total length and exhibited transient substrate adhesion, early swim bladder inflation, and the onset of exogenous feeding during the pre‐flexion stage. Regression analyses revealed strong linear relationships among selected cranial and body measurements ( R 2 = 0.944–0.99), indicating coordinated changes in these dimensions during ontogeny. An ontogenetic shift from a terminal to a subterminal mouth position was also observed during juvenile development. Comparison with published developmental data for other smiliogastrine cyprinids revealed a broadly conserved developmental sequence, alongside differences in egg size, hatching size, and reported embryonic duration. These comparisons provide a basis for investigating potential differences in developmental timing among smiliogastrine taxa; however, heterochrony cannot be established from the available data because incubation conditions and developmental‐stage criteria differ among studies. The findings expand knowledge of early development in P. bimaculatus and provide a foundation for further comparative research and captive‐breeding applications.
The morphology of the trigeminal nerve extending through the snout region in Archosauria has recently been the focus of extensive research, particularly in paleontology. However, the pathways of this nerve within cranial bones in extant birds have not been described in detail. Here, we describe trigeminal nerve pathways in the skull of nine avian species using a non-destructive soft-tissue imaging technique (diceCT) with a particular emphasis on osteological correlates, including intraskeletal neurovascular canals as well as foramina and grooves on the bony surfaces. In many species, a branch of the trigeminal nerve, the ophthalmic nerve, extends through the anterior premaxillary canal. Similarly, another branch of the trigeminal nerve, the maxillary nerve, passes through a bony canal in the maxillopalatine process at the posterior end of the snout in many species. However, apparently clade-specific unique pathways are also observed for the ophthalmic nerve around the external naris in Falconiformes and Psittaciformes and the maxillary nerve on the palatal surface in Anseriformes, the latter of which is likely associated with the specialized tactile sensation. Based on comparison with the condition in Crocodylia, the "reptilian-like" course of the maxillary nerve within the premaxilla is considered to have apomorphically been lost, whereas that of the ophthalmic nerve within the premaxilla has become extremely prominent in Aves. These changes in the intraskeletal nerve pathways in Aves have likely been associated with the enlargement of the premaxilla and the loss of teeth in the avialan lineage. The present observation of the trigeminal nerve pathway in Aves potentially contributes to the discussion of the homology of other associated soft-tissue structures and the presence of special sensory functions in fossil archosaurs.
ABSTRACT An animal's morphology directly influences its ability to perform fundamental tasks, which can be vital to its survival and reproduction. This is especially true in harsh or extreme environments, like the shifting‐sand desert of the Sahara. Additionally, sexes can differ in their morphology, performance, or in the relationship between morphology and performance, with implications for behaviors such as habitat selection, predator avoidance, and reproduction. Despite being common across a broad geographic range, little is known of the ecomorphology and sexual dimorphism of the sandfish skink ( Scincus scincus ). To investigate this, we first validated the uses of molecular sexing protocols and morphology (hemipene eversion) to identify the sex of our animals. We then tested for differences in body size, the multivariate morphological phenotype, and coloration between the sexes. While patterns generally suggested male bias in both body size and limb dimension in concordance with previous studies, these differences were not statistically significant. Additionally, we found several exceptions to the standard color‐based sex assignment of these animals, especially for females. We then conducted an experiment to test how body size and dimensions affect performance at optimum temperatures. We quantified three different types of movement: sprinting on top of sand (used in hunting behavior), swimming under sand (an undulatory form of locomotion used in thermoregulation), and diving into sand (an important escape behavior). Overall, skinks with larger body sizes sprinted faster and swam faster through sand. Female skinks sprinted faster than male skinks even after accounting for differences in body size. Larger heads, wider bodies, and longer limbs were negatively correlated with swim speed. Diving performance exhibited the lowest among‐individual variation, did not differ between the sexes, and was not dependent on body size or shape. Finally, we found no evidence of among‐individual correlations in performance measures, suggesting each performance is independent of the others. Overall, this experiment provides insight into morphology–performance relationships across a number of ecologically important aspects of locomotion for a species inhabiting an extreme desert environment.
