The retina of the harbour seal, Phoca vitulina

The structure of the retina of the harbour seal, Phoca vitulina richardii, is described. It is shown that the retina of the harbour seal is similar to that of the harp seal, in that it shows little zonation of the inner nuclear layer, possesses large horizontal cells, and has similar nuclear densities within the different retinal layers throughout the retina. The outer nuclear layer is also the thickest of all the retinal layers. Two types of photoreceptor cell, types B and C, were observed with a ratio of roughly 1:23 respectively. This ratio, along with a well-developed and extensive tapetum, indicates a highly light-sensitive retina. The existence of retinal folding in marine mammals is also questioned and discussed.

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Vitamin A physiology in the precocious harbour seal (Phoca vitulina): a tissue-based biomarker approach

Canadian Journal of Zoology ◽

10.1139/z02-152 ◽

2002 ◽

Vol 80 (9) ◽

pp. 1511-1519 ◽

Cited By ~ 19

Author(s):

Lizzy Mos ◽

Peter S Ross

Keyword(s):

Vitamin A ◽

Marine Mammals ◽

Relevant Information ◽

Phoca Vitulina ◽

Retinyl Palmitate ◽

Harbour Seal ◽

Natural Processes ◽

Reproductive Endocrine ◽

Positive Correlations ◽

Free Ranging

Vitamin A is a nutrient essential to all mammals for growth and development, as well as for the maintenance of reproductive, endocrine, and immune systems. Environmental contaminant-related disruption of vitamin A has been observed in many wildlife species and can therefore be used as a biomarker of toxic effects. However, the natural processes regulating vitamin A uptake, storage, and distribution among compartments are poorly understood in marine mammals. In this study, 20 young healthy harbour seals (Phoca vitulina) were captured to establish a compartment-based model providing a foundation for a mechanistic understanding of vitamin A physiology and disruption. Vitamin A (retinol, retinyl palmitate, and (or) retinoic acid) was quantified in blood plasma and in biopsy samples of liver, blubber, and skin. Although the highest concentrations of vitamin A were found in liver, blubber represents a more important storage depot, with an estimated 66% of the total retinoid content of the compartments measured. We suggest that vitamin A physiology in the precocious harbour seal has evolved to deal with high vitamin A availability during a short nursing period and to sustain growth during the postweaning fast. Positive correlations in vitamin A concentrations among liver, blubber, and skin support the use of less invasive biopsy sampling of just blubber or skin, which can provide physiologically relevant information in biomarker studies of free-ranging marine mammals.

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Livestock-associated meticillin-resistant Staphylococcus aureus in a young harbour seal (Phoca vitulina) with endocarditis

Veterinary Record Case Reports ◽

10.1136/vetreccr-2019-000886 ◽

2019 ◽

Vol 7 (3) ◽

pp. e000886 ◽

Cited By ~ 1

Author(s):

Ana Rubio-Garcia ◽

John W A Rossen ◽

Jaap A Wagenaar ◽

Alex W Friedrich ◽

Jan H van Zeijl

Keyword(s):

Staphylococcus Aureus ◽

Marine Mammals ◽

Aortic Wall ◽

Bacterial Culture ◽

Histopathological Examination ◽

Phoca Vitulina ◽

Antimicrobial Treatment ◽

Harbour Seal ◽

First Time ◽

Secondary Bacterial Pneumonia

A five-month-old male harbour seal was admitted for rehabilitation to the Sealcentre Pieterburen on November 16, 2015. During initial veterinary examination parasitic pneumonia and secondary bacterial pneumonia were suspected. Therefore, the seal received antiparasitic and antimicrobial treatment and appeared to recover but died unexpectedly after several weeks. Postmortem examination revealed a perforation in the aortic wall and histopathological examination of the aorta revealed mural necrosis with haemorrhage and suppurative to mixed inflammation. Bacterial culture resulted in isolation of a meticillin-resistant Staphylococcus aureus (MRSA) from the pericardial effusion. Subsequent culture of rectal swabs collected at arrival and during rehabilitation showed that the animal was already colonised with MRSA when admitted to the Sealcentre. MRSA has been isolated from marine mammals before, however, to our knowledge this is the first report of MRSA-associated endocarditis in seals and the first time that livestock-associated MRSA is reported in seals.

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Morphological and functional identifications of catfish retinal neurons. I. Classical morphology

Journal of Neurophysiology ◽

10.1152/jn.1975.38.1.53 ◽

1975 ◽

Vol 38 (1) ◽

pp. 53-71 ◽

Cited By ~ 57

Author(s):

K. Naka ◽

N. R. Garraway

Keyword(s):

Ganglion Cells ◽

Horizontal Cell ◽

Dendritic Tree ◽

Amacrine Cells ◽

Cell Types ◽

Bipolar Cells ◽

Inner Nuclear Layer ◽

Horizontal Cells ◽

Specific Cell ◽

Definition Of

The morphology of the catfish horizontal cells is comparable to that in other fish retinas. The external horizontal cells contact cone receptors and are stellate in shape; the intermediate horizontal cells are even more so and contact rod receptors. The internal horizontal cells constitute the most proximal layer of the inner nuclear layer and may possibly be, in reality, extended processes from the other two horizontal cell types. Bipolar cells resemble those in other teleost retinas: the size and shape of their dendritic tree encompass a continuous spectrum ranging from what is known as the small to the large bipolar cells. The accepted definition of amacrine cells is sufficiently vague to justify our originating a more descriptive and less inferential name for the (axonless) neurons in the inner nuclear layer which radiate processes throughout the inner synaptic layer. These starbust and spaghetti cells vary considerably in the character and extent of their dendritic spread, but correlates exist in other vertebrate retinas. Ganglion cells are found not only in the classical ganglion layer but displaced into the inner nuclear layer as well. Several types can be distinguished on the basis of cell geometry and by the properties of their dendritic tree. Not all of the categorization corresponds with previous descriptions; our findings suggest that some reorganization may be necessary in the accepted classification of cells in the proximal areas of the vertebrate retina. A subtle yet remarkable pattern underlies the entire structure of the catfish retina; there exists a definite gradient of size within a particular class of cells, and of configuration among the subclasses of a specific cell type. It remains to be seen if these morphological spectra bear any functional consequences. The fact that the structure of the catfish retina most closely resembles those of other phylogenetically ancient animals, such as the skate and the dogfish shark, testifies to its primitive organization; morphological and functional mechanisms discernible in this simple system may, therefore, be applicable to the retinas of higher ordered vertebrates.

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Developmental changes in circulatory vitamin A (retinol) and its transport proteins in free-ranging harbour seal (Phoca vitulina) pups

Canadian Journal of Zoology ◽

10.1139/z00-129 ◽

2000 ◽

Vol 78 (10) ◽

pp. 1862-1868 ◽

Cited By ~ 8

Author(s):

Wendy Simms ◽

Peter S Ross

Keyword(s):

Vitamin A ◽

Marine Mammals ◽

Environmental Contaminants ◽

Phoca Vitulina ◽

Transport Proteins ◽

Developmental Changes ◽

Harbour Seal ◽

Retinol Binding Protein ◽

Free Ranging ◽

The Impact

Although vitamin A (retinol) levels are highly regulated within individual organisms, natural (e.g., age, sex, disease) and anthropogenic (e.g., environmental contaminants) factors can affect the dynamics of this essential nutrient. In this study, we examined developmental changes in the circulatory vitamin A system of free-ranging harbour seal (Phoca vitulina) pups by collecting serial blood samples from healthy known-age animals throughout their nursing period. While harbour seal pups were born with relatively low levels of circulatory retinol (144.4 ± 13.9 µg/L), nursing animals more than doubled these levels within 2 days (385.0 ± 46.9 µg/L), and levels continued to rise more gradually until weaning (431.0 ± 35.8 µg/L). Animals that were not nursing, such as orphaned (184.4 ± 34.2 µg/L), fasted (347.0 ± 14.4 µg/L), and weaned (204.5 ± 38.5 µg/L) pups, had significantly lower circulatory retinol levels. Despite the developmental changes observed in total retinol, the concentration of retinol bound by its transport proteins, retinol binding protein and transthyretin, remained relatively constant throughout the nursing period. This suggests that, like most mammals, the delivery of retinol to target tissues is highly regulated in harbour seal pups. Furthermore, the high concentrations of circulatory retinol observed in harbour seal pups may serve to saturate transport proteins, ensuring a steady delivery of vitamin A to target tissues during a period of potentially variable supply. Understanding how natural factors affect circulatory retinol and its transport proteins is an important facet of assessing the impact of environmental contaminants on vitamin A dynamics in marine mammals.

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Laryngeal and soft palate valving in the harbour seal (Phoca vitulina)

Journal of Experimental Biology ◽

10.1242/jeb.230201 ◽

2020 ◽

Vol 223 (20) ◽

pp. jeb230201

Author(s):

Arlo Adams ◽

Wayne Vogl ◽

Camilla Dawson ◽

Stephen Raverty ◽

Martin Haulena ◽

...

Keyword(s):

Soft Palate ◽

Marine Mammals ◽

Vocal Folds ◽

Phoca Vitulina ◽

Harbour Seal ◽

Upper Aerodigestive Tract ◽

Laryngeal Inlet ◽

Harbour Seals ◽

Lateral Margins ◽

And Function

ABSTRACTEffective ‘valving’ in the upper aerodigestive tract (UAT) is essential to temporarily separate the digestive and respiratory pathways. Marine mammals are largely dedicated to feeding underwater, and in many cases swallowing prey whole. In seals, little work has been done to explore the anatomy and function of the UAT in the context of valving mechanisms that function to separate food and air pathways. Here we use videofluoroscopy, gross dissection, histology and computed tomography (CT) renderings to explore the anatomy of the larynx and soft palate in the harbour seal (Phoca vitulina), and generate models for how valving mechanisms in the head and neck may function during breathing, phonating, diving and swallowing. Harbour seals have an elevated larynx and the epiglottis may rise above the level of the soft palate, particularly in pups when sucking. In addition, the corniculate and arytenoid cartilages with associated muscles form most of the lateral margins of the laryngeal inlet and vestibule, and move independently to facilitate airway closure. The corniculate cartilages flex over the laryngeal inlet beneath the epiglottis to completely close the laryngeal vestibule and inlet. The vocal folds are thick and muscular and the medial margin of the folds contains a small vocal ligament. The soft palate has well-defined levator veli palatini muscles that probably function to elevate the palate and close the pharyngeal isthmus during feeding. Our results support the conclusion that harbour seals have evolved UAT valving mechanisms as adaptations to a marine environment that are not seen in terrestrial carnivores.

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Incidence of the Ascarid Porrocaecum decipiens in the Stomachs of Three Species of Seals along the Southern Canadian Atlantic Mainland

Journal of the Fisheries Research Board of Canada ◽

10.1139/f58-023 ◽

1958 ◽

Vol 15 (4) ◽

pp. 495-516 ◽

Cited By ~ 18

Author(s):

D. M. Scott ◽

H. D. Fisher

Keyword(s):

East Coast ◽

Atlantic Cod ◽

Atlantic Coast ◽

Phoca Vitulina ◽

The Other ◽

Harp Seal ◽

Harbour Seal ◽

Halichoerus Grypus ◽

Bay Of Fundy ◽

Harbour Seals

Identifications were made of ascarids collected from 1948 to 1956 from the stomachs of 318 harbour seals (Phoca vitulina), 812 harp seals (P. groenlandica), and 127 grey seals (Halichoerus grypus) killed in several localities along the Atlantic coast of Canada. Porrocaecum and 2 other genera of ascarids, tentatively identified as Anisakis and Contracaecum, were present in each species of seal. All 112 male Porrocaecum that were identified to species were P. decipiens.Almost all stomachs of harbour and grey seals at all seasons and in all localities contained P. decipiens. Considering all localities, the overall average incidence was about 20 adult P. decipiens in harbour seals and about 100 in grey seals.P. decipiens was normally much rarer in the stomachs of harp seals than in the other seals. It appeared most frequently in harp seals taken around the Magdalen Islands in April and May. The incidence of adult P. decipiens was much lower during the breeding season of the seals and during their southward and northward migrations within the Gulf of St. Lawrence. The incidence of P. decipiens in harp seals from the east coast of Newfoundland was very low.The relative importance of each species of seal as a vector of P. decipiens is as follows. The harbour seal is the most important in the Bay of Fundy and along the southwestern coast of Nova Scotia. Elsewhere harbour and grey seals occur in approximately equal numbers. In such localities the grey seal is probably more important than the harbour seal. The harp seal is about 100 to 200 times as numerous, while in the southwestern Gulf of St. Lawrence, as the combined populations of harbour and grey seals there. Despite this great numerical superiority the harp seal does not appear to be more important than the other seals as a host of P. decipiens.The relation between each species of seal and the incidence of larval P. decipiens in Atlantic cod (Gadus callarias) is discussed.

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The Regenerating Adult Zebrafish Retina Recapitulates Developmental Fate Specification Programs

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2020.617923 ◽

2021 ◽

Vol 8 ◽

Author(s):

Manuela Lahne ◽

Margaret Brecker ◽

Stuart E. Jones ◽

David R. Hyde

Keyword(s):

Photoreceptor Cell ◽

Outer Nuclear Layer ◽

Neuronal Cell ◽

Cell Types ◽

Developmental Competence ◽

Rod Photoreceptor ◽

Muller Glia ◽

Müller Glia ◽

Adult Zebrafish ◽

Cell Ablation

Adult zebrafish possess the remarkable capacity to regenerate neurons. In the damaged zebrafish retina, Müller glia reprogram and divide to produce neuronal progenitor cells (NPCs) that proliferate and differentiate into both lost neuronal cell types and those unaffected by the damage stimulus, which suggests that developmental specification/differentiation programs might be recapitulated during regeneration. Quantitative real-time polymerase chain reaction revealed that developmental competence factors are expressed following photoreceptor damage induced by intense light or in a genetic rod photoreceptor cell ablation model. In both light- and N-Methyl-D-aspartic acid (NMDA)-damaged adult zebrafish retinas, NPCs, but not proliferating Müller glia, expressed fluorescent reporters controlled by promoters of ganglion (atoh7), amacrine (ptf1a), bipolar (vsx1), or red cone photoreceptor cell competence factors (thrb) in a temporal expression sequence. In both damage paradigms, atoh7:GFP was expressed first, followed by ptf1a:EGFP and lastly, vsx1:GFP, whereas thrb:Tomato was observed in NPCs at the same time as ptf1a:GFP following light damage but shifted alongside vsx1:GFP in the NMDA-damaged retina. Moreover, HuC/D, indicative of ganglion and amacrine cell differentiation, colocalized with atoh7:GFP prior to ptf1a:GFP expression in the ganglion cell layer, which was followed by Zpr-1 expression (red/green cone photoreceptors) in thrb:Tomato-positive cells in the outer nuclear layer in both damage paradigms, mimicking the developmental differentiation sequence. However, comparing NMDA- to light-damaged retinas, the fraction of PCNA-positive cells expressing atoh7:GFP increased, that of thrb:Tomato and vsx1:GFP decreased, and that of ptf1a:GFP remained similar. To summarize, developmental cell specification programs were recapitulated during retinal regeneration, which adapted to account for the cell type lost.

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Distinct and Atypical Intrinsic and Extrinsic Cell Death Pathways between Photoreceptor Cell Types upon Specific Ablation of Ranbp2 in Cone Photoreceptors

PLoS Genetics ◽

10.1371/journal.pgen.1003555 ◽

2013 ◽

Vol 9 (6) ◽

pp. e1003555 ◽

Cited By ~ 21

Author(s):

Kyoung-in Cho ◽

MdEmdadul Haque ◽

Jessica Wang ◽

Minzhong Yu ◽

Ying Hao ◽

...

Keyword(s):

Cell Death ◽

Photoreceptor Cell ◽

Cell Types ◽

Cone Photoreceptors ◽

Cell Death Pathways

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Minocycline decreases CCR2-positive monocytes in the retina and ameliorates photoreceptor degeneration in a mouse model of retinitis pigmentosa

PLoS ONE ◽

10.1371/journal.pone.0239108 ◽

2021 ◽

Vol 16 (4) ◽

pp. e0239108

Author(s):

Ryo Terauchi ◽

Hideo Kohno ◽

Sumiko Watanabe ◽

Saburo Saito ◽

Akira Watanabe ◽

...

Keyword(s):

Cell Death ◽

Retinal Degeneration ◽

Photoreceptor Cell ◽

Fluorescent Protein ◽

Outer Nuclear Layer ◽

Inhibitory Effect ◽

Subretinal Space ◽

Photoreceptor Degeneration ◽

Retinal Inflammation ◽

Green Fluorescent

Retinal inflammation accelerates photoreceptor cell death caused by retinal degeneration. Minocycline, a semisynthetic broad-spectrum tetracycline antibiotic, has been previously reported to rescue photoreceptor cell death in retinal degeneration. We examined the effect of minocycline on retinal photoreceptor degeneration using c-mer proto-oncogene tyrosine kinase (Mertk)−/−Cx3cr1GFP/+Ccr2RFP/+ mice, which enabled the observation of CX3CR1-green fluorescent protein (GFP)- and CCR2-red fluorescent protein (RFP)-positive macrophages by fluorescence. Retinas of Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice showed photoreceptor degeneration and accumulation of GFP- and RFP-positive macrophages in the outer retina and subretinal space at 6 weeks of age. Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice were intraperitoneally administered minocycline. The number of CCR2-RFP positive cells significantly decreased after minocycline treatment. Furthermore, minocycline administration resulted in partial reversal of the thinning of the outer nuclear layer and decreased the number of apoptotic cells, as assessed by the TUNEL assay, in Mertk−/−Cx3cr1GFP/+Ccr2RFP/+ mice. In conclusion, we found that minocycline ameliorated photoreceptor cell death in an inherited photoreceptor degeneration model due to Mertk gene deficiency and has an inhibitory effect on CCR2 positive macrophages, which is likely to be a neuroprotective mechanism of minocycline.

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