Erin M. Scott

Aggression in bottlenose dolphins: Evidence for sexual coercion, male-male competition, and female tolerance through analysis of tooth-rake marks and behaviour

Aggressive behaviour is rarely observed, but may have a large impact on the social structure, relationships and interactions in animal societies. Long-term behavioural study of Indian Ocean bottlenose dolphins in Shark Bay, Australia, suggests that males are more aggressive than females, and use sexual coercion during the breeding season, but age and sex-specific patterns of aggression have not been well documented. We analyzed tooth rake marks, an indirect measure of received conspecific aggression, to determine such patterns by age, sex, and adult female reproductive state. Photographs of 224 Shark Bay bottlenose dolphins were examined for tooth rakes and each rake was categorized as new (broken skin), obvious (white rake lines that are clearly visible) or faint (faint evidence of rakes). Rake lines were also coded by each body section visible in the photograph. Cycling females (those that became pregnant within 6 mos. of the photograph date) were significantly more likely to have new tooth rakes than non-cycling females (pregnant or with a dependent calf 2 years apart) suggests that the marks are not cumulative. Overall, 83% of the population has tooth rake marks, suggesting that agonistic interactions occur for most individuals at least every two years. Analysis of gonistic interactions for 55 adult focal females (observed for 1960 h) and their 88 calves (observed for 1876 h) show that female aggression is extremely rare (occurring every 490 h), but females receive aggression more often (every 61 h), and 84% of received aggression was from juvenile and adult males. Focal adult females were never observed acting aggressively towards juveniles or adults of either sex, suggesting that female bottlenose dolphins are highly tolerant. Of the four observed instances of adult female aggression, all were directed at their dependent offspring. Male calves are significantly more aggressive than female calves, and calves had higher rates of agonistic interactions than their mothers (every 18 h), even though calves had fewer tooth rakes than all other age classes. The patterns of tooth rake presence and prevalence likely result from sexual coercion of adult females by adult males and intra-sexual male competition.

Canine Retina Has a Primate Fovea-Like Bouquet of Cone Photoreceptors Which Is Affected by Inherited Macular Degenerations

Retinal areas of specialization confer vertebrates with the ability to scrutinize corresponding regions of their visual field with greater resolution. A highly specialized area found in haplorhine primates (including humans) is the fovea centralis which is defined by a high density of cone photoreceptors connected individually to interneurons, and retinal ganglion cells (RGCs) that are offset to form a pit lacking retinal capillaries and inner retinal neurons at its center. In dogs, a local increase in RGC density is found in a topographically comparable retinal area defined as the area centralis. While the canine retina is devoid of a foveal pit, no detailed examination of the photoreceptors within the area centralis has been reported. Using both in vivo and ex vivo imaging, we identified a retinal region with a primate fovea-like cone photoreceptor density but without the excavation of the inner retina. Similar anatomical structure observed in rare human subjects has been named fovea-plana. In addition, dogs with mutations in two different genes, that cause macular degeneration in humans, developed earliest disease at the newly-identified canine fovea-like area. Our results challenge the dogma that within the phylogenetic tree of mammals, haplorhine primates with a fovea are the sole lineage in which the retina has a central bouquet of cones. Furthermore, a predilection for naturally-occurring retinal degenerations to alter this cone-enriched area fills the void for a clinically-relevant animal model of human macular degenerations.

Canine Keratomycosis in 11 Dogs: A Case Series (2000–2011)

Keratomycosis is rarely reported in dogs. The purpose of this study was to review the signalment, clinical characteristics, predisposing factors, and outcome of 11 cases of canine keratomycosis. Medical records of included dogs were reviewed and follow-up information was obtained by re-examination of patients following their initial diagnosis. All 11 patients possessed predisposing factors for fungal keratitis, including an underlying endocrinopathy, pre-existing corneal disease, intraocular surgery, and/or prolonged use of either topical antibiotics or corticosteroids at the time of initial examination. Diagnostic techniques included corneal cytology demonstrating yeast or hyphae in 6 of 11 eyes, and fungal cultures with positive results in 7 of 11 eyes. Fungal organisms isolated included Cladosporium spp. (n = 1), Chrysosporium spp. (n = 1), Curvularia spp. (n = 2), Aspergillus spp. (n = 1), Penicillium spp. (n = 1), and Phialemonium spp. (n = 1). Of the 11 patients, 6 responded to medical management alone. Two resolved after a superficial keratectomy, and three were enucleated due to either endophthalmitis or progression of corneal disease. This study identified potential risk factors for developing fungal keratitis.

Overlap of abnormal photoreceptor development and progressive degeneration in Leber congenital amaurosis caused by NPHP5 mutation

Ciliary defects can result in severe disorders called ciliopathies. Mutations in NPHP5 cause a ciliopathy characterized by severe childhood onset retinal blindness, Leber congenital amaurosis (LCA), and renal disease. Using the canine NPHP5-LCA model we compared human and canine retinal phenotypes, and examined the early stages of photoreceptor development and degeneration, the kinetics of photoreceptor loss, the progression of degeneration and the expression profiles of selected genes. NPHP5-mutant dogs recapitulate the human phenotype of very early loss of rods, and relative retention of the central retinal cone photoreceptors that lack function. In mutant dogs, rod and cone photoreceptors have a sensory cilium, but develop and function abnormally and then rapidly degenerate; L/M cones are more severely affected than S-cones. The lack of outer segments in mutant cones indicates a ciliary dysfunction. Genes expressed in mutant rod or both rod and cone photoreceptors show significant downregulation, while those expressed only in cones are unchanged. Many genes in cell-death and -survival pathways also are downregulated. The canine disease is a non-syndromic LCA-ciliopathy, with normal renal structures and no CNS abnormalities. Our results identify the critical time points in the pathogenesis of the photoreceptor disease, and bring us closer to defining a potential time window for testing novel therapies for translation to patients.

Tapetal dysplasia in a Swedish Vallhund dog

OBJECTIVE To describe the gross, histopathological, and ultrastructural findings in a dog with bilateral tapetal dysplasia. PROCEDURES The globes of a 15-year-old neutered male Swedish Vallhund dog with a ventrally displaced tapetum in both eyes were fixed in 10% formalin and submitted to the Comparative Ocular Pathology Laboratory of Wisconsin for histological evaluation. Sections were stained with hematoxylin and eosin, Massons trichrome, and Melan-A immunohistochemistry (IHC), and tissues were subsequently processed for transmission electron microscopy. RESULTS Bilateral fundic and gross examination revealed a tapetal fundus inferior to the optic nerve head (ONH) and a nontapetal fundus with mild scattering of tapetal tissue superior to the ONH. Histologically, there was decreased pigmentation of the retinal pigment epithelium with only a few melanin granules in the peripheral retina. The affected tapetum was relatively acellular and fibrous with occasional tapetal cells scattered throughout the inner choroid or displaced into the vascular outer choroid. Special stains revealed that the tapetum was mostly composed of collagen (Massons trichrome) and failed to express Melan-A (IHC) unlike a normal canine control tapetum. Ultrastructurally, the tapetum was markedly dysplastic both superior and inferior to the ONH with no uniformly arranged tapetal cells. The few cells identified within the tapetum contained irregularly arranged and disorganized electron-dense structures within their cytoplasm, which were interpreted as dysplastic tapetal rodlets. CONCLUSIONS Based on microscopic and ultrastructural findings, this is the first report of tapetal dysplasia in a dog.