Fine structure of the pecten oculi of the common loon (Gavia immer)

1986 ◽  
Vol 64 (10) ◽  
pp. 2181-2186 ◽  
Author(s):  
C. R. Braekevelt
Keyword(s):  
Electron Microscopy ◽  
Basal Lamina ◽  
Light And Electron Microscopy ◽  
Gavia Immer ◽  
Common Loon ◽  
Luminal Surface ◽  
Pecten Oculi ◽  
The Common ◽  
Diving Bird ◽  
Region Form

The pecten oculi of a diurnally active diving bird, the common loon (Gavia immer), was studied by light and electron microscopy. In this species the pecten consists of a pleated, highly vascular, pigmented structure that is situated over the optic nerve head and projects into the vitreous chamber. Fourteen to 15 accordion folds are joined apically by a heavily pigmented bridge of tissue, which holds the pecten in a fanlike shape, widest at the base. A distinct basal lamina encloses the entire pecten. Within each fold are numerous capillaries, melanocytes, and larger blood vessels that are often difficult to differentiate as either arterioles or venules. The capillaries are surrounded by basal laminae separated from the endothelial cells by several fibrillar layers. Pericytes are often enclosed within the basal lamina. These capillaries display numerous microfolds on their luminal surface, with a slightly reduced number of processes on the abluminal border. The endothelial cell body is extremely thin and most organelles are in the paranuclear region. The melanocytes, which are most numerous in the bridge region, form an incomplete sheath around these capillaries. As in other species, the morphology of the pecten in the loon indicates a heavy involvement in the transport of materials.

Fine structure of the pecten oculi of the mallard (Anas platyrhynchos)

1990 ◽  
Vol 68 (3) ◽  
pp. 427-432 ◽  
Author(s):  
Charlie R. Braekevelt
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Endothelial Cell ◽  
Optic Nerve ◽  
Blood Vessels ◽  
Anas Platyrhynchos ◽  
Light And Electron Microscopy ◽  
Mallard Duck ◽  
Pecten Oculi ◽  
Region Form

The pecten oculi of the mallard duck (Anas platyrhynchos) has been examined by light and electron microscopy. In this species, the pecten is of the pleated type and 12–14 accordion folds are joined apically by a heavily pigmented bridge of tissue which holds the pecten in a fanlike shape, widest at the base. It is situated over the optic nerve head and extends out into the vitreous. The entire pecten is enclosed by a fine basal lamina and hyalocytes are often present on its outer surface. Within each fold are numerous capillaries, larger blood vessels, and melanocytes. The capillaries are surrounded by thick fibrillar basal laminae which often contain pericytes. These capillaries display extensive microfolds on both the luminal and abluminal borders. The endothelial cell bodies are extremely thin, with most organelles present in a paranuclear location. The melanocytes, which are most plentiful in the bridge region, form an incomplete sheath around the capillaries and other blood vessels. The morphology of the pecten in the mallard is indicative of a heavy involvement in the transport of materials.

scholarly journals Additional Data and Perspectives on Interspecific Aggression in the Common Loon, Gavia immer

2011 ◽  
Vol 125 (1) ◽  
pp. 61
Author(s):  
Martin L. Morton ◽  
Maria E. Pereyra
Keyword(s):  
Additional Data ◽  
Gavia Immer ◽  
Common Loon ◽  
Interspecific Aggression ◽  
Aythya Americana ◽  
The Common

We witnessed the killing of a female Redhead (Aythya Americana) by a male Common Loon (Gavia immer). The wound was delivered into the abdomen from below, and death occurred because of a torn, hemorrhaging liver. This same Common Loon also threatened a female Ring-necked Duck (Aythya collaris) with ducklings. We hypothesize that interspecific aggression by loons might be energetically costly but is sometimes adaptive because it deters predators.

Dynamics of an Aggressive Vocalization in the Common Loon (Gavia immer): A Review

Waterbirds ◽  
2014 ◽  
Vol 37 (sp1) ◽  
pp. 37-46 ◽  
Author(s):  
John N. Mager ◽  
Charles Walcott
Keyword(s):  
Gavia Immer ◽  
Common Loon ◽  
The Common

scholarly journals Plunging floater survival causes cryptic population decline in the Common Loon

The Condor ◽  
2020 ◽  
Author(s):  
Walter H Piper ◽  
Jason Grear ◽  
Brian Hoover ◽  
Elaina Lomery ◽  
Linda M Grenzer
Keyword(s):  
New England ◽  
Adult Population ◽  
Population Decline ◽  
Gavia Immer ◽  
Common Loon ◽  
Vital Rates ◽  
Geographic Ranges ◽  
The Common ◽  
Anthropogenic Threats ◽  
Territory Occupancy

Abstract Populations of many vertebrates are declining and geographic ranges contracting, largely as a consequence of anthropogenic threats. Many reports of such decline, however, lack the breadth and detail to narrow down its causes. Here we describe population decline in the Common Loon (Gavia immer), a charismatic aquatic bird, based on systematic resighting and measurement of a marked population. During our 27-year investigation, age-adjusted chick mass has fallen by 11%, mortality among young and old chicks has increased by 31% and 82%, respectively, and fledging success has declined by 26%. Meanwhile, the return rate of marked nonbreeders (“floaters”) has plunged by 53%, and the adult population overall has declined by 22%. Consistent with the thinning ranks of floaters, the rate of territory eviction has decreased by 52% during the study. Despite the decline in floaters, territory occupancy remains unchanged. However, a matrix model, updated with recent estimates for breeding success, juvenile survival, and senescence, yields a recalculated deterministic population growth rate (λ) of 0.94 for our study population, which suggests that declines in vital rates could lead to a loss of 52% of the current population and a decline of 37% in territory occupancy by 2031. Lack of data on floaters in other upper Midwest and New England loon populations leaves their status in doubt.

scholarly journals THE GOLGI APPARATUS IN NEURONS AND EPITHELIAL CELLS OF THE COMMON LIMPET PATELLA VULGATA

1957 ◽  
Vol 3 (5) ◽  
pp. 779-796 ◽  
Author(s):  
Dennis Lacy
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Golgi Apparatus ◽  
Light And Electron Microscopy ◽  
Neutral Red ◽  
Continuous Phase ◽  
Common Source ◽  
Patella Vulgata ◽  
Dense Substance ◽  
The Common

1. In view of widely diverse views held about the identity and structure of the Golgi apparatus in neurons of Mollusca, particularly gastropods, a study has been made on neurons of the common limpet, Patella vulgata, both by light and electron microscopy. A report is given also of observations made on epithelial cells of Patella by electron microscopy. 2. As revealed by Kolatchev's method, the Golgi apparatus in neurons consists basically of black filaments lying to one side of the nucleus. The filaments generally anastomose to form networks of various complexity. Rarely some cells contain only discrete filaments. Associated with some of the filaments is a weakly osmiophilic substance identified as archoplasm. Kolatchev's method also revealed spheroidal bodies (neutral red bodies, "lipochondria," etc.). 3. It has not been possible to demonstrate the Golgi apparatus using either iron-haematoxylin or Sudan black. 4. Examination of Kolatchev's preparations by electron microscopy has revealed that some of the Golgi filaments consist of chromophilic and chromophobic components. The chromophilic component consists of dense lamellae. 5. After fixation in buffered osmium tetroxide solution and examination by electron microscopy, it has been concluded that (a) the chromophilic component of the Golgi apparatus corresponds to a system of paired membranes (which usually enclose an inner dense substance), (b) the chromophobic component corresponds to a substance lying within small dilations of the paired membrane, and (c) the archoplasm corresponds to numerous small vesicles. 6. The paired membranes branch, anastomose, and can often be traced back to a common source. They are interpreted as lamelliform folds, and occasionally tubular processes, of essentially a single Golgi membrane. In cells containing a Golgi network it is suggested that the membrane extends through the whole of the apparatus in such a way that the substance it encloses may be regarded as being in a continuous phase. 7. Epithelial cells of Patella contain a juxtanuclear Golgi apparatus with an ultrastructure similar to that described for neurons.

Wildlife Criterion Value for the Common Loon (Gavia immer) in the Adirondack Park, New York, USA

Waterbirds ◽  
2014 ◽  
Vol 37 (sp1) ◽  
pp. 76-84 ◽  
Author(s):  
Nina Schoch ◽  
Allyson K. Jackson ◽  
Melissa Duron ◽  
David C. Evers ◽  
Michale J. Glennon ◽  
...  
Keyword(s):  
New York ◽  
Adirondack Park ◽  
Gavia Immer ◽  
Common Loon ◽  
The Common

Blood Supply and Function of the Tegmentum Vasculosum (Stria Vascularis) of the Duckling Cochlea

1999 ◽  
Vol 5 (S2) ◽  
pp. 1194-1195
Author(s):  
F.E. Hossler
Keyword(s):  
Electron Microscopy ◽  
Blood Supply ◽  
Carotid Arteries ◽  
Stria Vascularis ◽  
Light And Electron Microscopy ◽  
Corrosion Casting ◽  
The Common ◽  
And Function ◽  
Tegmentum Vasculosum ◽  
Common Carotid Arteries

On the basis of ultrastructural, biochemical, cytochemical, and electro-physiological evidence, the stria vascularis, a highly vascular epithelium of the mammalian cochlea, has been implicated as one site of endolymph synthesis. It would seem natural to suspect that its highly developed counterpart in the avian cochlea, the tegmentum vasculosum (TV), might have a similar function. This study utilizes routine light and electron microscopy, biochemistry, cytochemistry, and vascular corrosion casting to describe the structure and blood supply to the (TV) in the duckling and provide evidence for its involvement in endolymph synthesis.Four to 16 week-old ducklings (Anas platyrhyncos)were anesthetized and anticoagulated and perfused via the common carotid arteries with buffered, 2% glutaraldehyde for routine light microscopy or transmission or scanning electron microscopy, or with Mercox resin for vascular corrosion casting. Casts were macerated in 5% KOH and warm water to remove tissue, cleaned in formic acid and water, dried by lyophilization, mounted on stubs and viewed at 10-20 kv by SEM.

Specificity of a Black Fly, Simulium euryadminiculum Davies, toward its Host, the Common Loon

1964 ◽  
Vol 96 (6) ◽  
pp. 911-913 ◽  
Author(s):  
J. K. Lowther ◽  
D. M. Wood
Keyword(s):  
Head And Neck ◽  
Host Location ◽  
Herring Gull ◽  
Gavia Immer ◽  
Common Loon ◽  
Black Fly ◽  
Large Numbers ◽  
The Common ◽  
Common Merganser

AbstractThe attraction of large numbers of the ornithophilic black fly, Simulium euryadminiculum Davies, to its host, the common loon, Gavia immer (Brünnich), to the place where the loon skin had been washed, and to a dried museum skin of the loon, is described. The fly was not attracted to museum skins of a pied-billed grebe, common merganser and herring gull. The data suggest a system of olfaction in host location, probably involving volatile, air-borne substances. It is possible that the colour or pattern on the head and neck of the loon serves to attract the fly to this area of the host.

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