A Comparative Morphometrical Examine of the Pecten Oculi in Completely different Avian Species

On this research was investigated the construction of pecten oculi within the ostrich, duck, pigeon, turkey, and starling. The pecten oculi of the ostrich was vaned kind and made up major, secondary, and few tertiary lamellae. Nonetheless, duck, pigeon, turkey and starling had a pleated-type pecten oculi which displayed folded construction. The numbers of pleats of the pectens have been 12, 13-14, 21-22, and 17 in duck, pigeon, turkey, and starling, respectively. Gentle microscopic investigation demonstrated that pecten oculi is principally composed of quite a few capillaries, massive blood vessels, and pigment cells in all investigating avian species. Capillaries have been 20.23, 14.34, 11.78, 12.58, and 12.78 μm in diameter in ostrich, duck, pigeon, turkey, and starling, respectively. The capillaries are surrounded by thick basal membrane, and pigmented cells have been noticed across the capillaries.

1. Introduction

The pecten oculi is a extremely vascular and pigmented construction peculiar to the avian eye [13]. It’s located over the optic nerve head and initiatives from the retina into the vitreous physique [4, 5].

Three morphological kinds of pecten oculi are acknowledged as conical, vaned, and pleated sorts. The conical kind is just reported within the brown kiwi (Apteryx mantelli); the vaned kind is current in ostriches (Struthio camelus) and rheas (Rhea americana) [6]; and pleated type is broadly reported in most birds (neognathae) reminiscent of quail [5], black kite [1], galah [7], frequent buzzard [3], mallard [8], pigeon [4], and jungle crow [9]. The scale of the pecten is dependent upon the visible necessities of the chook, in order that day by day lively chook species have a comparatively massive and extremely advanced pecten oculi with many folds whereas evening lively chook species can have a comparatively small and easy pecten oculi [6].

Histologic research have proven that the pecten oculi consists of blood vessels, extravascular pigmented cells, and superficial overlaying membrane [1]. Birds have thicker retinas in comparison with mammals however haven’t retinal blood vessels [10]. Due to this fact it has been urged that the principle operate of pecten oculi is to provide diet to the avascular avian retina [1]. One in every of capabilities of pecten is the formation of a blood-retina barrier [11]. The endothelia of the pectinal capillaries are steady, possessing elaborate tight junctions. Additionally two barrier-specific proteins, that’s, the HT7-antigen and the glucose transporter isoform GluT-1, are expressed by the endothelial cells [12].

Vital variations within the pecten oculi reminiscent of kind and variety of pleats exist throughout the avian species because of the conduct of birds in relation to their common exercise and visible sample. Within the current research we studied the anatomical and histological particulars of the pecten oculi within the ostrich (Struthioniformes), duck (Anseriformes), pigeon (Columbiformes), turkey (Galliformes), and starling (Passeriformes) which belong to completely different orders of the avian species.

2. Supplies and Strategies

The eyeballs have been obtained from grownup ostrich, duck, pigeon, turkey, and starling. Six animals from every species have been used on this research. The animals have been anaesthetized and decapitated and the attention quickly enucleated. The eyeballs have been minimize on the equator, and the posterior half which contained the pecten oculi was photographed utilizing digital digicam hooked up stereomicroscope (Nikon SMZ- 2T, Nikon Corp., Tokyo, Japan). The variety of pleats of duck, pigeon, turkey, and starling pecten oculi was counted in stereomicroscope pictures.

The pecten oculi and its underlying retinal tissue have been painstakingly dissected out, then they have been mounted in 10% buffered formalin for histologic examination. After the fixation, the samples dehydrated in rising concentrations of ethanol, cleared with xylene, and embedded in paraffin. The serial sections from the apex to the bottom of pecten have been minimize in 6 μm thick, and the sections have been stained utilizing Crossman’s triple approach [13] and periodic-acid Schiff (PAS) response for basement membrane composed of glycoconjugates [14].

All specimens have been examined underneath gentle microscope (Leica DM-2500 mannequin with DFC-320 digicam attachment giving digital pictures). The diameter of the capillaries and thickness of capillary basement membrane of pecten oculi have been measured with IM-50 picture evaluation program. The parameters have been analyzed with one-way ANOVA (SPPSS 9.0; SPSS Inc. Corp., USA). Outcomes have been thought-about vital at .

3. Outcomes

The pecten oculi was positioned over the optic disc and was projected out into the vitreous physique. Because of the pigmentation pecten oculi was noticed in darkish brown to black (Figures 1 and 2).


The pecten oculi of the ostrich was vanned kind (Determine 3(a)) and made up major, secondary, and few tertiary lamellae (Determine 3(b)). Centrally positioned major lamellae have been the thicker lamellae, and the thinner secondary lamellae have been originated from the first lamellae. The tertiary lamellae arose from the distal a part of the secondary lamellae have been not often. In major lamellae, there have been the massive blood vessels having thick basement membrane. The blood capillaries have been particularly positioned within the distal a part of the secondary lamellae (Determine 3(c)). The wall of those capillaries consists of a single layer of excessive endothelial cells surrounded by a thick basement membrane (Determine 3(d)). Excessive diploma of pigmentation distributed between the capillaries was probably the most salient function of the distal a part of the secondary lamellae (Determine 3(c)).

In duck, pigeon, turkey, and starling the pecten oculi consists of the a number of skinny folds which confluence one another on the apex have been very delicate (Figures 4(a), 4(b), 4(c), and 4(d)). In serial transverse sections it was revealed that every fold has a big blood vessel surrounded by many capillaries having excessive endothelium and thick basement membrane (Determine 5). The distribution of the pigmentation was much like ostrich pecten oculi between the capillaries. The variety of pleats and the opposite morphometric parameters of pecten oculi have been illustrated in Desk 1.

Animals The numbers of pleats Diameter of capillaries (µm)
( ± Sd)
Thickness of capillary basement membrane (µm)
( ± Sd)
Ostrich 20.23 ± 2.98a 2.67 ± 0.32
Duck 12 14.34 ± 2.56b 2.11 ± 0.55
Pigeon 13-14 11.78 ± 2.71b 2.24 ± 0.37
Turkey 21–22 12.58 ± 2.67b 2.08 ± 0.56
Starling 17 12.78 ± 1.50b 2.00 ± 0.32
Values inside a column with no frequent superscripts are considerably completely different ().

4. Dialogue

The placement of the pecten oculi in all avian species used on this research conformed to that reported in different chook species. We noticed that duck, pigeon, turkey, and starling had a pleated-type pecten oculi which displayed folded construction. Nonetheless the pecten oculi of the ostrich was vaned kind and made up major, secondary, and few tertiary lamellae as cited by Kiama et al. [2].

Pleated-type pecten oculi has comparable buildings in numerous avian species as on this research. Nonetheless some appreciable variations between the species could be noticed in variety of the pleats, dimension, form and thickness of the capillary basal lamina of the pecten oculi. These variations rely upon the diurnal exercise and visible necessities of the species. Typically, day by day lively birds (diurnal) have larger and extra plated pectens in comparison with evening lively birds (nocturnal) [7, 15]. On this the research variety of pleats of the pectens was 12, 13-14, 21-22, and 17 in duck, pigeon, turkey, and starling, respectively. Earlier research have demonstrated that different diurnal species reminiscent of home fowl has 16–18 [15], black kite has 12-13 [1, 15], quail has 19 [5], frequent buzzard has 17-18 [3], jungle crow has 24-25 [9], mallard has 12–14 [8] folds in pectin. Nonetheless nocturnal birds have small pectens reminiscent of barred owl that has 8–10 [16] and noticed eagle owl that has 5-6 [15] folds in pecten.

Though practical morphology of the pecten oculi correlates with the life-style of the chook [15], histologic findings obtained from this research and former research [2, 5, 8] in numerous chook species demonstrated that pecten oculi is principally composed of quite a few capillaries, massive blood vessels, and pigment cells. Excessive vascular construction and specialised capillary morphology is essential attribute for nutritive operate of this organ. The capillaries are surrounded by thick basal membrane in pecten oculi of all investigated species on this research as described in pervious research [4, 7, 8, 17]. It’s urged that thickened basal laminae could help the delicate endothelial cells which have very skinny cell our bodies and quite a few microfolds [7, 17].

The pigmented cells are the second outstanding cell kind of the pecten oculi [18]. Pigmented cells have been noticed across the capillaries on this research. The shut affiliation between the pigmented cells and the capillaries has been additionally reported within the black kite [1], quail [5], ostrich [2], and jungle crow [9]. It has urged that pigmented cells present the structural reinforcement to pecten oculi for protecting it firmly erectile throughout the gel-like vitreous and in addition shield the blood vessels in opposition to harm from ultraviolet gentle [1, 7, 17]. As well as the absorption of sunshine by the pigmented cells in all probability raises the temperature throughout the pecten and therefore the speed of metabolism inside it [19].

This analysis gives information in regards to the anatomical and histological traits of pecten oculi of various avian species. These findings reveal that pecten oculi within the ostrich was vaned kind, and duck, pigeon, turkey, and starling had pleated-type pecten oculi. Histologic buildings have been fairly comparable in pecten oculi of all investigated species.

Battle of Pursuits

The authors haven’t any battle of pursuits.

Source

Leave a Reply