Macroscopic
The Guinea fowl birds were possessed left and right reddish-brown coloured kidneys. Both the kidneys were placed retroperitoneally symmetrical on either side of the vertebral column in the depression of synsacrum and iliac fossa (Fig 1). The similar findings were reported by
Braun and Dantzler (1972) in desert quail,
Khadim and Dauod (2014) in barn owl and
Michalek et al., (2016) in breeding Emu. Each kidney had dorsal and ventral surfaces. The oblique groove was observed on the ventral aspect of each kidney which divided the kidneys into three divisions
viz. cranial, middle and caudal. The smallest cranial component of both kidneys was extended with the caudal segment of the lungs, however its caudal surface was largest. The present result was in accordance with close consent of
Mohammed et al., (2009) in steppe buzzard and
Batah (2012) in Coot bird. The impressions on the dorsal surface of the kidneys were identified as lumbosacral mass. These findings were not different with the mentioning of
Mohammed et al., (2009) in Seteppe buzzard and
Dhyaa et al., (2014) in harrier, mallard and chicken.
In male and female, the ventral surface of the cranial part was communicating with testis and ovary respectively and the middle and caudal component of both kidneys was related with gizzard, intestine, ureter, vas deferens and oviduct (Fig 1). The present findings were somewhat similar with the findings of
Batah (2012) in Coot bird and
Al-Agele (2012) in Golden eagle (
Aquila chrysaetos). The maximum length and width of the right and left kidney was measured with Vernier caliper which was on the tune of 54.23±1.206 mm and 53.21±1.226 mm and 12.73±0.514 mm and 13.39±0.37 mm respectively. Volume and weight of the right and left kidney was also measured and observed as 4.78±0.119 ml and 4.75±0.169 ml and 4.34±0.12 gm and 4.14±0.156 gm respectively (Table 1). However nobody has reported the micrometrical observations of kidneys in Guinea fowl.
Batah (2012) have reported this type of findings with different numerical in coot bird.
Histomorphology
Kidneys of the Guinea fowl were observed histologically with different structures from outside to inside
viz. capsule, cortex and medulla. Their microscopical findings have been observed as under.
Capsule
The very thin wrapper and protective cover of kidneys had a firm contact with parenchyma. It was composed after elastic, collagen and reticular fibers. These observations were corroborating with the observations revealed by
Mobini and Abdollahi (2016) in Japanese quail,
Gahaffor and Mohammed (2012) in racing pigeon,
Sreeranjini et al., (2010) in Japanese quail.
Cortex and medulla
It was discovered as the parenchyma of kidneys which was composed of pear-shaped lobules with larger the cortex and smaller the medulla. It was calculated in the proportion of 71% and 29% respectively. The cortex had a major segment of nephron without the loop of Henle. The central vein, numerous blood capillaries and infiltrated lymphocytes were seen in the region of cortex (Fig 2 and 3) which inclined towards its physiological conscientiousness to have the defense mechanism of the organ. These observations were not different from the findings of
King and McLelland (1975).
Numerous nephrons were seen in the cortical region but reptilian types of nephrons were predominantly located there. The mammalian type nephrons were observed at juxtamedullary. The medulla had shown medullary collecting duct, the thin as well as thick segment of the loop of Henle and blood capillaries-vasa recta. The medullary lobules were observed enclosing by a thin layer of collagen fibers as the connective tissue (Fig 2 and 3), such in-length observations were reported by
Schmidt-Nielsen (1979) in vertebrates and
Nicholson (1982) in starlings.
Nephron
It was observed with Renal corpuscles comprising Bowman capsule and tuft of glomerular capillaries, Proximal and Distal convoluted tubules, Loop of Henle, Collecting tubules, blood vessels
etc. The Guinea fowl kidney was observed with two types of nephron
viz. Reptilian type
i.e. without loop of Henle and mammalian type
i.e. with loop of Henle.
Numerous reptilian nephrons (R.N.) were at the cortical and mostly scattered towards the periphery. The small Bowman’s capsule, little of the tuft of glomerulus and also the short urinary space was observed in reptilian nephron. The macula densa in these nephrons was present at the vascular pole and tubules were started from the urinary pole of the glomerulus (Fig 2 and 4).
The Mammalian nephron (M.N.) was identified with the loop of Henle as the relatively larger than reptilian type of nephrons. These were situated close to the medullary lobules and characterized by large glomerulus surrounded by the visceral layer of cells. Distal convoluted tubules were also present on the vascular pole of the glomerulus. A large amount of urinary space was present in Bowman’s capsule (Fig 4). These findings were in accordance with the observation of
Sivakumar et al., (2012) in Guinea fowl and
Dhyaa et al., (2014) in mallard species. However, the intermediate type of nephrons were also reported by
Nicholsen (1982),
Wideman and Nissley (1992),
Islam et al., (2004) and
Mobini and Abdollahi (2016) in various species of birds, which were not observed in the present studies.
Renal corpuscles
These were seen as an initial part of the nephron. It consisted of a Bowman capsule and tuft of a glomerular capillaries. The Bowman capsule was made up of a parietal layer with simple squamous epithelium while its visceral layer was the cuboidal epithelium. The space between parietal and visceral layers
viz. urinary space was narrow towards the vascular pole and extensive towards the urinary pole. Some different types of cells with a large irregular nucleus were also seen in the center of the tuft which was recognized as the mesangial cell (Fig 4 and 5). Similar types of findings were noted by
Braun and Dantzler (1972) in desert quail,
Hodges (1974) in fowl and
Sreeranjini et al., (2010) in Japanese quail.
The parietal layer of renal corpuscles was composed of all three types of connective tissue fibers
viz. collagen, elastic and reticular fibers but in the visceral layer of it more elastic fibers and few reticular fibers were encountered (Fig 6). Partly collaborative observations were reported by
Islam et al., (2004) in Rhode Island Red and White leghorn and
Sreeranjini et al., (2010) in Japanese quail with the findings of collagen and reticular fibers in renal corpuscle.
Proximal convoluted tubule (PCT)
In the cortical region the PCT with other elements of the nephron were located. The wall of PCT had brush bordered high columnar cell which were along with the indistinct cell boundaries and centrally placed large nucleus. Their basement membrane showed collagen, elastic and reticular fibers (Fig 6). The PCTs were emerged from the urinary pole of Bowman’s capsule. The lumen was not visible or sometimes less visible due to which the PCT was observed in spherical shape. Comparable findings were brought on record by
Islam et al., (2004) in Rhode Island Red and White leghorn and
Sreeranjini et al., (2010) in Japanese quail and
Patil and Janbandhu (2012) in Indian false vampire bat exceptionally the cuboidal type of cells were reported by
Batah (2012).
Distal convoluted tubule (DCT)
It was observed within the cortex and as a continuation of the ascending limb of Henle. However, most DCTs were found near the collecting tubule and PCTs. These tubules were easily distinguished from the proximal tubules due to a wide lumen, darkly stained cytoplasm and centrally placed euchromatic nucleus. These tubules were lined by the simple cuboidal epithelium which was devoid of brush border unlikely to the proximal convoluted tubule (Fig 4). The lumen of the DCT was shown wider than that of PCT which was composed of all three types of fibers
viz. collagen, elastic and reticular fibers which were similar with the current investigations. This outcome of the present examination was in accordance to close consent of
Batah (2012) in coot bird,
Patil and Janbandhu (2012) in Indian false vampire bat and
Abdulla et al., (2014) in house sparrow.
Loop of henle
The mammalian type nephron possesses the loop of Henle in the medullary cone wherein numerous thick and thin limbs of the loop of Henle were combined with medullary collecting duct. The present study revealed the numerous thick limb of the loop of Henle at periphery of medullary cone but the thin limb were located in the center of the medullary cone. The thick and thin limb of loop of Henle has shown simple cuboidal epithelium with wider lumen and simple squamous epithelium with narrow lumen respectively (Fig 7). Similar findings were reported by
Wideman et al., (1981), Casotti and Richardson (1993),
Nabipour et al., (2009) and
Baragoth (2015) in different avian species. Loop of the Henle were composed of all three types of fibers
viz. collagen, elastic and reticular (Fig 8) fibers whereas
Islam et al., (2004) and
Sreeranjini et al., (2010) were reported the collagen and reticular fibers only.
Macula densa and Juxtaglomerular apparatus
The Guinea fowl kidney has shown Mammalian and Reptilian types of the nephron which were consisting of the macula densa and juxtaglomerular apparatus. The convoluted part of DCT came in contact with the vascular pole of renal corpuscles. The cells of Macula densa towards the vascular pole of renal corpuscles became taller and narrower with the closely packed nucleus. The lumen was also visible (Fig 4). The present investigations illustrated dark stained tall cells in both mammalian and reptilian types of nephrons. The same dark-stained macula densa tall cells were observed only in mammalian types of nephrons. These findings were very much similar to those reports given by
Dantzler and Braun (1980),
Morild et al., (1985b), C
asotti and Richardson (1993),
Sreeranjini (2010) and
Islam et al., (2004).
Collecting tubule (CT)
The last part of nephron was observed in the cortex and medullary regions. The cortical collecting ducts open into the medulla as the medullary collecting duct. The lining epithelium of the collecting tubules was cuboidal in cortical region (Fig 4) and columnar epithelium in the medullary region. The lumen was substantially more visible than PCT and DCT. No villi were seen on the apical part of cells. All three types of fibers
viz. collagen, elastic and reticular (Fig 8) which were in agreement with similar findings of
Sreeranjini (2010) in quail,
Casotti and Richardson (1993) in Honeyeater birds and
Archana et al., (2017) in Emu and Duck. However,
Mobini and Abdollahi (2016) have reported their studies of the renal collecting ducts in Japanese quail wherein they revealed distinctive brush border of interdigitations microvilli which were projected into the terminal web at luminal surfaces of the epithelial cells. The mentioned findings of them were not seen in presently undertaken studies.
Histochemistry
Periodic Acid Schiff (PAS) for glycogen was employed toward determining the secretion of neutral Mucopolysaccharides substances as per
Kiernan (2015). It has demonstrated a positive activity at mesangial cells of renal corpuscle and basement membrane of distal convoluted tubule (Fig 9). The findings which were encountered in present studies were corroborative with the findings of
Rovasio et al., (1974) who were reported the positive activity of PAS in the basement membrane of proximal convoluted tubule, intense positive reaction in distal convoluted tubule and the weak activity in collecting tubule.
The Alcian blue (AB) (pH 2.5) was used to find its determination on secretion of acidic mucopolysaccharide substances (
Kiernan, 2015). It has observed the positive reaction in capsule of kidney, parietal and visceral layer of renal corpuscle, proximal convoluted tubule, lumen of distal convoluted tubule, thin and thick loop of Henle, whereas the cortical collecting tubule, medullary collecting tubule were showed intensive activity (Fig 9 and 10). The findings were in agreement with the findings of
Casotti (2001) who has mentioned the presence of mucosubstances in renal tubules helps in the elimination of uric acid which were supporting the functioning of these kidney components.
The alkaline phosphatase activity in present investigations has shown moderate activity in capsule, parietal and visceral layer of the renal corpuscle, proximal convoluted tubule, distal convoluted tubule, cortical collecting tubule, medullary collecting tubule and loop of Henle (Fig 11). The capsule, brush border of proximal convoluted tubule and distal convoluted tubule has shown the positive activity of alkaline phosphatase. These findings were similar reporting made by
Sivakumar et al., (2012) in Guinea fowl. Lesser the alkaline phosphatase activity has indicated higher the active vigor of structural components. However, in the present investigation, the components were moderately active.
The present investigation on acid phosphatase activity has shown moderately in capsule, distal convoluted tubule, collecting tubule and loop of Henle whereas the parietal and visceral layer of renal corpuscle and lumen and basement membrane of proximal convoluted tubule were showing intense activity (Fig 12). Pertaining to the observations mentioned by
Sivakumar et al., (2012) in Guinea fowl that they reported intense activity of acid phosphatase in Capsule and brush border of proximal convoluted tubule and distal convoluted tubule. However, in the present investigation, the capsule, distal convoluted tubule, collecting tubule and loop of Henle were moderately activity components, while the visceral layer of renal corpuscle and lumen and basement membrane of proximal convoluted tubule were showing less activity. Lesser the acid phosphatase activity indicating higher vigor of activeness of structural components what we observed in present findings.
The present studies have shown intense bluish to the purple colour activity of Succinic dehydrogenase at proximal convoluted tubule, distal convoluted tubule and collecting tubule and renal corpuscle showed feeble activity (Fig 13). The comparable findings were reported by
Sivakumar et al., (2012) in Guinea fowl wherein proximal convoluted tubule and distal convoluted tubule had shown positive reaction. The higher succinic dehydrogenase activity in tissue demonstrated higher mitochondrial content and thereby the higher oxidative potential which agrees with the activity of enzyme of succinic dehydrogenase at the level of microscopical kidneys.
