Morphological Observations on the Thrombocyte of Eastern Sarus Cranes (Grus antigone sharpii) in Northeastern Thailand
Blood samples from eastern sarus cranes housed at Nakhonratchasima
Zoo, Nakhon Ratchasima, northeastern, Thailand were collected in January,
2007. A morphological observation of the thrombocytes was examined using
scanning electron microscopy. The results revealed the following information:
The thrombocytes of the eastern sarus cranes are tiny cells and they display
a smooth, irregular, spherical and pseudopodic membrane surface with long
microfilament protrusions from their membrane. The thrombocytes of the
eastern sarus cranes use these microfilaments to attach to other blood
cells for movement and blood clumping. The long microfilaments were not
found in fish, reptiles and other domestic birds. The morphological structure
of the thrombocyte, the microfilaments and the activities of the eastern
sarus crane has not been reported previously.
The eastern sarus crane (Grus antigone sharpii) is the world`s
tallest flying bird (Jeltes, 2006). As one of three Grus antigone subspecies,
it formerly inhabited Indochina; however, it`s population there has been
greatly reduced in distribution and number. Flocks have been recently
located in Myanmar, Cambodia and Vietnam, but it appears as if the population
may now be fragmented into two separate sub-populations. Total numbers
are estimated to be between 1,000 and 1,600 birds (Zoo, 1997). Jeltes
(2006) reported that in this decade the total population of the eastern
sarus crane has been reduced to between 500-1,500 birds. At present, sarus
cranes are currently listed as vulnerable A1cde + 2cde on the IUCN red
list. Nakhonratchasima Zoo obtained their eastern sarus cranes from the
forests in Cambodia and keeps them in cages in the breeding section and
public viewing section of the Zoo. At present, Nakhonratchasima Zoo has
more than 40 eastern sarus cranes.
Thrombocytes have their origins in bone marrow and play a primary role
in hemostasis (Sturkie, 1965) clot promotion (Shepro et al., 1969)
and tendency to clump in peripheral blood films and may also have a phagocytic
function to aid in the removal of foreign material from the blood (Campbell,
1995). Whereas, documents about the thrombocyte`s characteristics in the
eastern sarus crane are limited, the objective of this preliminary study
was to examine the morphological aspect of the thrombocytes in eastern
sarus crane by using SEM. Basic knowledge from this examination is important
to any future in depth study of the hematology of this bird.
MATERIALS AND METHODS
Two eastern sarus cranes (male and female) were reared in the breeding
section of Nakhonratchasima Zoo, Nakhon Ratchasima Province northeastern
Thailand. Their blood samples were collected in January, 2007. Cranes
were restrained manually and five milliliters of blood sample were collected
from the wing vein (Rithchie et al., 1994) using a 10 mL syringe,
21 gauge needle and 1.5 inch of length then placed in plastic tube with
EDTA. The samples were cooled to approximately 4 °C (Campbell, 1995)
using icepacks and then taken to the Central Instrumentation Units, Faculty
of Science, Mahasarakham University within 12 h of blood collection.
Blood samples were dropped in 2.5% glataraldehyde in 0.1 M phosphate
buffer, pH 7.2 overnight at 4 °C then washed in the same buffer. Samples
were postfixed with 1% Osmium tetroxide for 2 h then rinsed with distilled
water, dehydrated in 20, 40, 60, 80 and 100% acetone and left to air dry.
Gold coated blood films were examined with a SEM (JSM 6460LV).
RESULTS AND DISCUSSION
Thrombocytes of the eastern sarus crane were examined by using SEM. The
results revealed the following information: The thrombocytes are tiny
cells (diameter = 2-3 μm); with a smooth, irregular and pseudopodic
membrane surface with long microfilaments protruding from the membrane
(Fig. 1A-H). The cell size of the thrombocytes in the
eastern sarus crane were smaller than that of the chickens by about 2
times. Daimon and Uchida (1978) found that mature thrombocytes of the
white leghorn chickens measured approximately 10 μm in length and
5 μm in width. Salakij et al. (2002) reported that the thrombocytes
of the king cobra had an elongated shape with a smooth membrane. Moreover,
Santos et al. (2003) and Sano-Martins et al. (1994) found
that the thrombocytes of snakes and the roadside hawk, normally ellipitical
in shape, become spheroid with cytoplasmic protrusions and adhere to one
another. This was accordant with the shape of the thrombocytes of the
eastern sarus cranes in this study.
The membrane surface of the thrombocyte of the eastern sarus crane was
similar to that reported by Shepro et al. (1969) and Maxwell (1974).
They found that under ultra-structural observation, the membrane surface
in dogfish and domestic birds had many forms: smooth, irregular, pseudopodia,
lobopodia and villi like; whereas, the long microfilaments, which were
found in the eastern sarus cranes, were not found in fish, reptiles and
other domestic birds. Figure 1 showed that the thrombocytes
of the eastern sarus cranes used their microfilaments to attach to other
blood cells. Moreover, the thrombocytes used these structures for blood
||SEM micrograph of thrombocyte in eastern sarus cranes
(Grus antigone sharpie) (A) normal thrombocyte with long microfilament,
(B) thrombocyte with microfilament attached to leukocyte and red blood
cell, (C) clumping of thrombocyte, (D) thrombocyte with microfilament
attached to mature and young red blood cell, (E) thrombocyte with
microfilament attached to red blood cell, (F) thrombocyte with microfilament
attached to red blood cell, (G) thrombocte with microfilament and
(H) clumping of thrombocyte (E, F and G = 1 μm; A, B and H =
2 μm; C and D =5 μm)
The thrombocytes of the eastern sarus cranes are small and their surface
membrane had several forms with long microfilament protrusions from their
membrane. They used the microfilaments for blood clumping and to attach
to other blood cells. No previous reports on the morphological structure
of the thrombocytes, the microfilaments or the activities of the eastern
sarus cranes have been published.
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Shepro, D., F.A. Belamarich, F.B. Merk and F.C. Chao, 1969. Changes in thrombocyte ultrastructure during clot retraction. J. Cell Sci., 4: 763-779.
Sturkie, P.D., 1965. Avian Physiology. 2nd Edn., Comstock Publishing Associates, Cornel University Press, New York, pp: 766.
Zoo, K.K.O., 1997. Eastern sarus cranes (Grus antigone sharpii): Population and habitat. Proceedings of the Viability Assessment Workshop, January 15-17, 1997, Khao Kheow Open Zoo, Chonburi, Thailand, pp: 2-2.