ArticlePDF Available

Histology of the lingual vallate papillae of the dromedary camel (Camelus dromedarius)

Authors:

Abstract and Figures

The present study aimed at investigating the histological structures of the vallate papillae of the tongue of the dromedary camel. Samples were taken from the tongues of 5 healthy adult dromedary camels, then processed by standard routine histological technique. The vallate papillae were broad, encircled by a distinctive sulcus, and exhibited concave dorsal surfaces. The papillae were covered with stratified squamous epithelium which was made up of several layers of cells arranged from the basement membrane to the outer surface as follows: basal layer; spinosum layer; squamous layer; corneum layer. The lamina propria sub mucosa showed two well-defined layers. The first one was located beneath the epithelium and characterized by loose connective tissue. The second layer was much thicker and composed mainly of dense irregular collagenous fibres. Deep to the circumvallate papilla was a group of prominent tubulo-acinar glands (von Ebner’s glands). The main ducts of the glands opened directly into the surrounding sulcus at different levels. In general, the histological structures of the vallate papillae of the dromedary camel were similar to those of other domestic mammals. The well-developed von Ebner’s glands suggested their abundant serous secretion that reflected on the high capability of gustation.
Content may be subject to copyright.
RESEARCH ARTICLE
University of Bahri Journal of Veterinary Sciences 2022; 1(2):72-79
http://journal.bahri.edu.sd/index.php/ubjvs
*Corresponding Author
Email Address: mortadamahgoub@bahri.edu.sd
72
Histology of the lingual vallate papillae of the dromedary
camel (Camelus dromedarius)
M.M.O. Elhassan*, Lemiaa Eissa, Rasha B. Yaseen
Department of Anatomy, College of Veterinary Medicine, University of Bahri, Khartoum, Sudan
KEY W O R D S
Camel
Histology
Tongue
von Ebner’s glands
Elhassan et al.
Univ. Bahri J. Vet. Sci. 2022; 1(2):72-79
73
INTRODUCTION
Dromedary camel (Camelus dromedarius) is considered as an
important livestock species which adapted to live in regions
with high temperature and dry climate (Al-Dahash and Sassi,
2009). Large population of this unique animal is existed in the
arid lands of Eastern Africa including Sudan, Somalia,
Ethiopia, Kenya and Djibouti (Gebreyohanes and Assen,
2017).
Camel has developed several morphological adaptations to live
in harsh conditions. One of these adaptations is that the
dromedary camel has very sturdy mouth to maintain the
efficient feeding of thorny and rough-stem plants which
naturally grow in the arid regions (El Sharaby et al., 2012). In
addition, several studies on the mouth of camel have described
the anatomical features of camel tongue (Qayyum et al., 1988;
Takehana et al., 2001; Peng et al., 2008; Salehi et al., 2010; El
Sharaby et al., 2012; Thanvi et al., 2020). With regards to its
dorsal surface, similar to ruminants, the tongue of camel is
characterized by the presence of fungiform and vallate papillae,
and the lack of foliate papillae as well (Thanvi et al., 2020).
Generally, the vallate papillae are classified as gustatory
papillae with taste buds (Abou-Elhamd et al., 2018). Each
papilla is encircled by a papillary groove and an annular pad of
the surrounding lingual mucosa (Qayyum et al., 1988).
Although several studies have displayed the microstructure of
the vallate papillae of camel, it is believed that detailed
histological structures are much less documented. Therefore,
the present study was conducted to provide histological
information on the vallate papillae of the tongue of the
dromedary camel.
Figure 1: Photomicrograph of vallate papilla showing the concave dorsal surface with non-keratinized stratified squamous
epithelium (arrowheads), sulcus (stars), taste buds (arrow), lamina propria submucosa (LM), and von Ebner’s glands (G). Masson’s
trichrome stain.
MATERIALS AND METHODS
Five apparently healthy adult dromedary camels (aged 5 to 7
years) were used in this study. The animals were slaughtered at
a local abattoir in Omdurman city, Sudan. Histological samples
were taken from the dorsal surface of the animal tongues within
20 min after slaughter. Samples were fixed in 10 % neutral
buffered formalin (pH 7.4) for 5 days and then processed for
routine histological technique (Bancroft and Gamble, 2008).
Briefly, specimens were dehydrated in a series of alcohol
dilutions, cleared in xylene, and embedded in paraffin wax.
Elhassan et al.
Univ. Bahri J. Vet. Sci. 2022; 1(2):72-79
74
Sections of 4-5 µm were cut, deparaffinized in xylene, and
rehydrated in decreasing concentrations of alcohol. In the next
steps, sections were stained with heamatoxylin and Eosin
(H&E), or Masson’s trichrome stains.
The stained sections were examined using a light microscope
(Olympus BX63-Japan) connected to a digital camera
(Olympus DP72). Photomicrographs were captured using
video image software (Cell Sens 510- Olympus).
Fig. 2: Photomicrograph of vallate papilla (V) showing thick epithelium (E) at the dorsal surface and thin epithelium at the
lateral surface (e). H&E stain.
RESULTS
The vallate papilla was broad, encircled by a distinctive sulcus,
and exhibited a concave dorsal surface. It was covered by
stratified squamous epithelium. Immediately beneath the
epithelium was a well-defined lamina propria submucosa (Fig.
1).
The stratified squamous epithelium covered the papilla was
either non-keratinized or parakeratinized. The non-keratinized
epithelium was seen at the concave part of the dorsal papillary
surface (Fig. 1). The parakeratinized epithelium was observed
in the other regions of the papilla. The thickness of the
epithelium varied distinctively according to the region. The
greater thickness was seen on the upper surface of the papilla
whereas the lesser one was located at the lateral surface of the
sulcus (Fig. 2).
Elhassan et al.
Univ. Bahri J. Vet. Sci. 2022; 1(2):72-79
75
Fig. 3: Photomicrograph of the vallate papilla showing the layers of the stratified squamous epithelium. The basal layer of columnar
cells (arrow), spinosum layer (S) of stratified cells with prominent spinous processes, squamous layer (arrowhead), and corneum
layer (C). Taste bud within the epithelium (TB). Masson’s trichrome stain.
The epithelium was composed of several layers of cells
arranged from the basement membrane to the outer surface as
follows: basal layer; spinosum layer; squamous layer; corneum
layer. The basal layer consisted of a single layer of columnar
cells. Some of these cells showed tiny spinous processes in their
lateral and upper surfaces. The spinosum was composed of
multiple layers of cells which were predominantly polyhedral
in shape. They exhibited numerous well-developed spinous
processes, as compared to the cells of the basal layer, radiated
from their outer surfaces (Fig. 3). The squamous layer
comprised different layers of flattened cells which had small
spinous processes. The latter reduced gradually in the layers
towards the outer surface (Fig. 3).
Taste buds were located in the lateral side of the vallate papilla.
They were spherical in shape and connected to the groove by
taste pores (Fig. 4A). The taste buds presented two types of
cells, large spindle-shaped neuroepithelial cells with prominent
nuclei, and small sustentacular cells, some of which showed
mitotic activity (Fig. 4B, C). Nonmyelinated nerve was
observed emerging from the basal area of the taste buds (Fig.
4A).
The lamina propria sub mucosa showed two well-defined
layers. The first layer was located beneath the epithelium, and
characterized by loose connective tissue. The second layer was
much thicker and composed mainly of dense irregular
collagenous fibres (Fig. 5). Deep to the circumvallate papilla,
the lamina propria submucosa exhibited a group of small
tubulo-acinar glands (von Ebner’s glands). Each gland was
covered by a connective tissue capsule predominantly
composed of collagenous fibres. Many thin trabeculae were
observed extending from the capsule, and divided the gland
into lobules. Serous acini separated by collagenous fibres
existed within each lobule. The duct system included
intralobular and interlobular ducts, both of which were lined by
simple cuboidal epithelium, and the main duct was almost lined
with stratified cuboidal epithelium. The main ducts of the
glands opened directly into the surrounding sulcus at different
levels (Fig. 6).
Elhassan et al.
Univ. Bahri J. Vet. Sci. 2022; 1(2):72-79
76
Fig. 4: Photomicrograph of the lateral surface of a vallate papilla (V). A: gustatory sulcus (star), taste pore (arrowhead),
nonmyelinated nerve (arrow) arising from the base of the taste bud. B: spindle-shaped neuroepithelial cells with prominent nuclei
(arrowheads), sustentacular cells (arrows). C: sustentacular cell showing mitotic activity (arrow). A, H&E stain. B & C, Masson’s
trichrome stain
DISCUSSION
In the present study, the general histological structure of the
vallate papillae of the camel was similar to the findings reported
in camel by Qayyum et al. (1988) and El Sharaby et al. (2012),
as well as in other domestic animals (Kobayashi et al., 2005;
Eurell and Frappier, 2006).
In this study, the first three layers (basal, spinosum, and
squamous layers) of the stratified epithelium displayed cells
with spinous processes. However, such spinous processes were
less developed in the basal and squamous layers as compared
to the spinosum layer. Similar observation was indicated in
previous study carried out on donkey by Abd-Elnaeim et al.
(2002).
Taste buds in the current findings were located at the lateral
side of the vallate papillae but no buds were observed within
the dorsal surface of the papillae. Similar findings have been
reported by Takehana et al. (2001) in bactrian camel and El
Sharaby et al. (2012) in dromedary camel. However, taste buds
were reported in the dorsal surface of the tongue of camel
foetus during the third trimester of gestation (Abou-Elhamd et
al., 2018). The absence of the taste buds in the dorsal surface
Elhassan et al.
Univ. Bahri J. Vet. Sci. 2022; 1(2):72-79
77
of the tongue of adult camel might have been due to a postnatal
development as a result of cellular involution that may
accompany increasing depths of the papillary circular grooves
(Abou-Elhamd et al., 2018).
Fig. 5: Photomicrograph of a vallate papilla showing the lamina propria submucosa. Loose connective tissue (L) with fine
collagenous fibres located beneath the epithelium (E). Dense connective tissue (D) with irregular connective tissue fibres.
Masson’s trichrome stain
The histological structures of the taste buds in this study were
similar to previous investigations conducted in mammals (Abd-
Elnaeim et al., 2002; Shao et al., 2010; El Sharaby et al., 2012;
Mescher, 2018). Nonetheless, the taste buds of camel need
further electron microscopical investigations to identify their
fine cellular structures.
In this study, prominent von Ebner’s glands were observed in
the lamina propria submucosa deep to the circumvallate papilla.
Each gland emptied into the sulcus through a separate duct. It
is known that the continuous flow of the serous secretion over
the taste buds would wash away food particles and
subsequently the taste buds can receive and process new
gustatory stimuli (Mescher, 2018). Therefore, it is plausible
that the presence of well-developed von Ebner’s glands along
with their numerous ducts may indicate the abundant secretion
of the glands, resulting in effective gustation of the dromedary
camel.
The general histological structures of the vallate papillae of the
dromedary camel were similar to those of other domestic
mammals. The well-developed von Ebner’s glands suggested
their abundant serous secretion that reflected on the high
capability of gustation. Further electron microscopical studies
are suggested in camels to elucidate the fine structures of the
taste buds.
Elhassan et al.
Univ. Bahri J. Vet. Sci. 2022; 1(2):72-79
78
Fig. 6: Photomicrograph of vallate papilla showing von Ebner’s glands. A and B: main ducts (arrowheads) of the gland (G) open
into the gustatory sulcus (star). B: connective tissue capsule (arrow) surrounding the gland. C: Interlobular duct with simple
cuboidal epithelium (arrowhead), and the main duct with stratified cuboidal epithelium (arrow) of the serous gland (G). D: dense
collagenous fibres of the capsule (C) surrounding the gland; serous acini (A); intralobular duct (arrowhead) opens into the
intralobular duct (arrow). Masson’s trichrome stain.
CONCLUSION
The general histological structures of the vallate papillae of the
dromedary camel were similar to those of other domestic
mammals. The well-developed von Ebner’s glands suggested
their abundant serous secretion that reflected on the high
capability of gustation. Further electron microscopical studies
are suggested in camels to elucidate the fine structures of the
taste buds.
COMPETING OF INTERESTS
The authors declare that they have no competing interests.
REFERENCES
Abd-Elnaeim M.M.M., Zayed A.E., and Leiser R. (2002).
Morphological characteristics of the tongue and its papillae in
the donkey (Equus asinus): A light and scanning electron
microscopical study. Ann. Anat., 184: 473-480.
Abou-Elhamd A.S., Abd-Elkareem M. and El-Zuhry Zayed A.
(2018). Morphogenesis of lingual papillae of one-humped
camel (Camelus dromedarius) during prenatal life: A light and
scanning electron microscopic study. Anat. Histol. Embryol.,
47(1): 38-45.
Al-Dahash S. and Sassi M. (2009). A preliminary study on
management, breeding and reproductive performance of camel
in Libya. Iraq J. Vet. Sci., 23: 276-281.
Elhassan et al.
Univ. Bahri J. Vet. Sci. 2022; 1(2):72-79
79
Bancroft J.D. and Gamble M. (2008). Theory and Practice of
Histological Techniques. 6th edition. Churchill Livingstone.
Elsevier Limited.
El Sharaby A.A., Alsafy M.A., El-Gendy S.A. and Wakisaka
S. (2012). Morphological Characteristics of the Vallate Papillae
of the One-Humped Camel (Camelus dromedarius). Anat.
Histol. Embryol., 41: 402-409.
Eurell J.A. and Frappier B.L. (2006). The Digestive System.
Frappier B. L. (editor). In: Dellmann's Text Book of Veterinary
Histology. 6th edition. Blackwell Publishing, Iowa, Oxford,
Victoria.
Gebreyohanes M.G. and Assen A.M. (2017). Adaptation
mechanisms of camels (Camelus dromedarius) for desert
environment: a review. J. Vet. Sci. Technol., 8(6): 1000486.
doi: 10.4172/2157-7579.1000486
Kobayashi K., Jackowiak H., Frackowiak H., Yoshimura
K., Kumakura M. and Kobayashi K. (2005). Comparative
morphological study on the tongue and lingual papillae of
horses (Perissodactyla) and selected ruminantia (Artiodactyla).
Ital. J. Anat. Embryol., 110 (2/1): 55-63.
Mescher A.L. (2018). Janqueira’s Basic Histology: Text and
Atlas. 15th edition. McGraw-Hill Education. New York. ISBN:
978-1-26-002617-7.
Peng X., Ye W., Yuan G., Zhang H. and Wang J. (2008).
Morphology of the lingual papillae of Bactrian Camel
(Camelus bactrianus). J. Camel Pract. Res., 15: 95-101.
Qayyum M.A., Fatani J.A., and Mohajir A.M. (1988). Scanning
electron microscopic study of the lingual papillae of the one-
humped camel (Camelus dromedarius). J. Anat., 160: 21-26.
Salehi E., Pousti I., Gilanpoor H. and Adibmoradi M. (2010).
Morphological observations of some lingual papillae in
camelus dromedarius embryos. J. Anim. Vet. Adv., 9: 514-518.
Shao B., Long R., Ding Y., Wang J., Ding L. and Wang H.
(2010). Morphological adaptations of yak (Bos grunniens)
tongue to the foraging environment of the Qinghai-Tibetan
Plateau. J. Anim. Sci., 88: 2594-2603.
Takehana K.E., Yamamoto E., Kobayashi A., Cao G., Ueda
B.H. and Tangkawattana P. (2001). Characteristics of Dorsal
Lingual Papillae of the Bactrian Camel (Camelus bactrianus).
Anat. Histol. Embryol., 30: 147-151.
Thanvi P.K., Joshi S. and Palecha S. (2020). Gross anatomical
peculiarities of tongue of Indian dromedary camel. Journal of
Camel Practice and Research, 27(3): 323-328.
ResearchGate has not been able to resolve any citations for this publication.
Article
Full-text available
The present study was conducted on tongues obtained from 10 cadavers of adult camels (Camelus dromedarius). Gross anatomical features were studied. The tongue of camel was muscular and spatula shaped, comprised of 3 parts - the apex, body and the root. The mean length of tongue was 41.21 ± 0.527 cm. A median groove was present on the dorsal surface of tongue. The caudo-dorsal part had convexity and formed an elliptical dorsal prominence (torus linguae), and bounded rostrally by the fossa linguae. A median fibrous ridge like structure, “lyssa” was present on the rostral third of its ventral surface. Five types of papillae were identified on the tongue of camel.
Article
Full-text available
This study was made on 24 camel fetuses of crown-rump vertebral length (CVRL) ranging from 10.5 cm to 105 cm CVRL (94–352 days old). These camel fetuses were classified into three groups representing the three trimesters of prenatal life. During the first trimester (94–142 days), lingual papillae (circumvallate and lentiform papillae) were demonstrated on the lingual root, but lingual body and the apex were almost free of papillae except for some scattered epithelial projections especially near the lateral borders of the body. In the second trimester (152–229 days), the lentiform papillae covered the entire root of the tongue except for areas occupied by the circumvallate papillae. Taste buds with clear pores were observed for the first time in areas between the circumvallate gustatory furrow and surface epithelium of the tongue. In addition, short numerous filiform papillae were observed on the rostral part of the lingual body and the lateral parts of the apex. Fungiform papillae, however, were demonstrated amidst the filiform papillae. In this trimester, taste buds were also seen on the top of the fungiform papillae. In the third trimester (256–352 days), all lingual papillae were clearly demonstrated on the dorsum of the root, body and apex of the tongue. Both types of gustatory papillae (circumvallate and fungiform) had well-developed taste buds. Mechanical papillae (filiform and lentiform) were well developed. Lentiform papillae occupied most of the dorsal aspect of the Torus linguae; they were larger in size with semicircular apices. Filiform papillae, however, were numerous and demonstrated heavily on the lateral and rostral parts of the body as well as on the apex of the tongue.
Article
Full-text available
Using light and scanning electron microscopy, the morphological adaptations of the yak (Bos grunniens) tongue to its foraging environment in the Qinghai-Tibetan Plateau were studied. The tongue of the yak was compared with that of cattle (Bos taurus). Compared with cattle, yak tongues are on average 4 cm shorter (P < 0.001), and yak consume forages using the labia oris, rather than by extending the tongue into the harsh environment. The lingual prominence of yak is greater (P < 0.001) and more developed than in cattle. The conical papillae on the prominence surface of yak are slightly larger (diameter: P = 0.068 and height: P = 0.761) and more numerous (P < 0.001) than in cattle. The lenticular papillae on the prominence surface of yak are larger (diameter: P = 0.002 and height: P = 0.115) and more numerous (P = 0.007) than in cattle. Such characteristics may improve the digestibility of forage by the grinding of food between the tongue and the upper palate. Filiform, conical, lenticular, fungiform, and vallate papillae were observed on the dorsal surface of the tongues studied; no foliate papillae were observed. The papillae were covered by keratinized epithelium, which was thicker (P < 0.001) in the yak than in cattle. It is suggested that the development of characteristic filiform papillae, and more numerous lingual gland ducts and mucus-secreting pores in the lenticular, fungiform and vallate papillae, fungiform papillae, probably having mechanical functions, are all morphological adaptations by yak to diets with greater fiber and DM content as provided by the plants within the Qinghai-Tibetan Plateau environment. On average, yak has 26 vallate papillae and cattle have 28. In the vallate papillae of the yak, the taste buds are arranged in a monolayer within the epithelium, whereas they are multilayered (2 to 4) in those papillae in cattle. The number of taste buds in each vallate papillae was less (P < 0.001) in the yak than in cattle. Therefore, the gustatory function of the yak was weaker than in cattle. Yaks graze throughout the year on diverse natural grasslands and have evolved morphological characteristics enabling them to consume a wide variety of plant species, thereby better adapting them to the typically harsh characteristics of their pastures.
Article
Dromedary camels have a number of adaptation mechanisms that help them to survive successfully in dry and arid climates in which there is shortage of water and high environmental temperature. For survival in desert environment, camels have physiological, anatomical and behavioral adaptation mechanisms. Water conservation ability, the unique features of blood, thermoregulation, and efficient digestion and metabolism are among the physiological adaptations. Anatomically the nature of skin coat, eye, nostril and lips, large body size and long height and large foot pads contribute for their survival. Moreover the feeding, drinking, thermal and sexual behavior of camels also plays a major role in succeeding their existence in the desert environment. Despite of their great contribution for the livelihood of many pastoralists in different parts of the world in which other animals face difficulties, camels are the most neglected domestic animals by the scientific community. Therefore the value camels should have to get emphasis and awareness should have to be created to the community about health care and management of camels to improve their production and productivity.
Article
The lingual papillae of adult bactrian camel were studied using light and scanning electron microscopy (SEM). Five types of lingual papillae were found on the dorsal surface of the tongue. Two types of filiform papillae could be distinguished. The filiform papillae had a primary papilla and a few slender secondary papillae. Fungiform papillae were round in shape, and more densely distributed on the tip of the lingual apex. Only a few taste pores were recognisable on the free surface of the papillae. Conical papillae have a round base and a blunt tip without any projection. Lenticular papillae were positioned in a round or flat protrusion with the appearance of a papillae groove. Vallate papillae were encircled by a papillary groove and an annular pad of the surrounding lingual mucosa. Many taste buds were found in the papillary groove of the papillae. The taste buds, composed of several layers structure of appearing to be sponge shaped, looked like tree peony in shape. The irregular surface of all types of papillae revealed microplicae in the form of microridges and micropits.
Article
This study was carried out to investigate the morphological development of the tongue in the foetal stage of camelus dromedaries by light microscopy. In foetuses of about 60 days, the tongue tissues showed thickening of the epithelium into about 4-6 layers of cells. In foetuses of about 75 days, mesenchymal tissue was observed under the epithelium. Rudiments of some papillae were observed at this time. Collagenous fibre and blood vessels were scant in the lamina propria. In the 90 days old foetuses, their was further differentiation of the epithelium rudiments into some papillae and this continued to mature until in foetuses of about 105 days, were early rudiments of taste buds were observed and in 120 days old foetuses taste buds were developed well and taste buds cell were recognizable.
Article
In this study, the morphology of the vallate papillae of camel was investigated using gross, light and scanning electron microscopy as well as immunohistochemistry. Vallate papillae were arranged along an identical line on each side of the lingual torus and revealed remarkable individual differences. However, each papilla - round or flat, small or large, single or paired - was surrounded by a prominent groove and an annular pad. Based on our findings, postnatal development and formation of new papillae occur in camel. Microscopically, taste buds were constantly observed along the medial wall epithelium, and in the papillary wall epithelium on both sides of the secondary groove apparently separating the vallate papillae. In addition, an aggregation of taste buds was occasionally observed at the bottom of the lateral wall epithelium. Using SEM, we observed several pits and microplicae on the surface of papillae as well as distinct taste pores on the peripheral parts of the dorsal surface. We demonstrated immunoreactivity of α-gustducin only in mature taste buds. We conclude that the morphological features and microstructure of vallate papillae are a characteristic feature in camel compared to other ruminants. These features might have evolved to assist the camel in the manipulation and tasting of thin organic stiff plants that grow in its environment and therefore might have related to the feeding habits of the animal.
Article
The dorsum of the camel tongue shows filiform, fungiform, circumvallate and special (wart-like) papillae. Filiform papillae are conical in shape and show different heights and thicknesses at various levels. Fungiform papillae are rounded and are surrounded by robust filiform papillae. They can also be observed on the tip of the ventral surface. They have taste pores on their surfaces. Circumvallate papillae are encircled by a primary groove and an annular pad. Their taste pores open into the grooves. A special type of filiform papillae is wart-like and has been observed on the posterior portion. These do not show taste pores.
Article
The morphology of dorsal lingual papillae of the Bactrian camel (Camelus bactrianus) was studied by using light and scanning electron microscopy. Filiform and lenticular papillae were considered as mechanical papillae but fungiform and vallate papillae were considered as gustatory papillae. Filiform papillae were distributed mostly in the anterior two-thirds region of the tongue. Each filiform papilla consisted of one primary papilla and a few smaller secondary papillae. Lenticular papillae were distributed on the torus linguae. The larger papillae were arranged in two parallel lines medially whereas the smaller papillae were laterally located. Most of the fungiform papillae were found on the lateral margins of the anterior two-thirds of the tongue. These papillae were small and round. Intra-epithelial taste buds were located on the dorsal surface of each papilla. The vallate papillae were arranged in two rows on each rim of the torus linguae. Each round- and flat-shaped vallate papilla was surrounded by a prominent gustatory groove and an annular pad. A few taste buds were observed in the lateral epithelium of the papillae. The keratinization of the covering stratified squamous epithelium of the mechanical lingual papillae was relatively thicker than those of the gustatory papillae. The lingual papillae of the Bactrian camel exhibited some different characteristics from other domestic ruminants. These morphological characteristics of the tongue of the Bactrian camel might have evolved to assist the camel in prehension and manipulating of the inorganic stiff plants that grow in its environment and therefore might relate to the feed and feeding habits of the animal.