Jatinderpal Singh the STRUCTURE and CHEMICAL COMPOSITION
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J.Bio.Innov 1(6), pp: 250-263, 2012 ISSN 2277-8330 (online) www.jbino.com THE STRUCTURE AND CHEMICAL COMPOSITION OF THE BODY WALL OF ANIMAL-PARASITIC NEMATODES Jatinderpal Singh Department of Zoology, Baring Union Christian College, Batala-143505 Punjab (India) Email: [email protected] ABSTRACT The nematode body is enclosed by a body wall comprising of three different layers. The outermost being a thick multilayered cuticle underlined by the middle hypodermal layer pronounced at four regions in the form of dorsal, ventral and a pair of lateral hypodermal cords. The innermost layer is constituted by a single layer of longitudinal muscle cells. Although the outer envelope of nematodes has been studied by a host of workers yet the controversy regarding certain aspects of its structure, chemical composition and function still prevail. The presence of proteins, carbohydrates, lipids, acid mucopolysaccharides and a variety of enzymes have been detected by various workers in different species of larval and adult nematodes. Since the mere survival of a nematode parasite in the body of its host is mainly attributed to the uniqueness of its body covering, hence the study of its nature and chemical composition is of paramount importance in parasitic nematology. The present paper briefly reviews the histological and histochemical studies on the body wall of animal nematodes parasitic animals. JBINO (6th Issue) Jatinderpal Singh J.Bio.Innov 1(6), pp: 250-263, 2012 ISSN 2277-8330 (online) www.jbino.com INTRODUCTION two-layered cuticle characterized the adult females of the family Heterodidae ( Bird Nematodes are the most numerous and Rogers, 1965; Kampfle, 1966) and the multicellular animals present on the earth parasitic larvae of Trichinella spiralis (Maggenti, 1981). They parasitize man, (Beckett and Boothroyd, 1961). This two- livestock, crops and have a deleterious layered structure was believed to be due to effect on all. Not only is the economics of rapid periods of growth at some stages in nematode parasitism important but nema these animals. However, in pre-parasitic themselves are a fascinating subject for the larvae and males of Heterodidae and in the study of morphology, biology and host- adults of Trichuroidae the normal three- parasite relationship. Morphologically the layered cuticle prevailed (Sheffield, 1963 Nematode is an exceedingly variable and Wright, 1968). group and there hardly exists any statement that could be made regarding RESULTS AND DISCUSSION their histomorphology, which would apply to all forms. Different types of anatomical Structurally, the nematode cuticle is quite features are present in different species of diverse, not only in different genera and parasitic nematodes which are the result of families, but also within species. There adaptation influenced by their particular may even be marked differences in the type of habitat (Chitwood and Chitwood, cuticle of male and female worms and in 1950). the different body regions of the same individual. These differences in the cuticle Some recent studies on the body wall of can be more marked in parasitic animal parasitic nematodes have been nematodes. ( Cano-Martil et al, 2006). performed by Johal (1995), Johal and In Oxyuris equi, the cuticle Shivali (1996), Page (2001), Cano-Martil consisted of an outer and an inner cortical et al (2006), Rahemo and Hussain (2009) layers, a fibrillar layer consisting of two and Lalchhandama (2010). The distinct layers of fibres, a homogenous multilayered nature of the cuticle had long layer and two distinct layers of fine fibres, been established with the number of layers a homogenous layer and two fibre layers ( varying from two in the larva of Martini, 1912). Bird (1958) studied the Trichinella spiralis (Beckett and cuticle of Oxyuris equi and described an Boothroyd 1961) to eight in adult Oxyuris additional fibrillar layer under the cortical equi (Bird, 1958). Since then there has layer which was not mentioned by Martini been a general agreement on the basic (1912). The cuticle of O. equi, thus terminology for the nematode cuticle as a comprised eight layers, starting from the three-layered structure consisting of outermost layer inwards: (1) an external cortical, median and basal layers. The cortical layer; (2) an internal cortical layer; nematode cuticle has been (3) a fibrillar layer; (4) a part of comprehensively reviewed from time to homogenous layer; (5) and (6) two outer time by Maggenti (1981), Bird (1980 and fibrous layers; (7) and (8) two inner 1984), Wright (1987), Bird and Bird fibrous layers. There was no indication of (1991) and Page (2001). The nematode presence of any bounding layer or a basal cuticle nearly always consists of at least layer. two major layers, the cortical and the basal. However, an exception to this Lee(1965) reported that the cuticle of general rule was found in the insect adults of Nippostrongylus brasiliensis had parasitic nematode Bradynema spp. where three main layers, an outer cortex, a the normal cuticular structure has been middle matrix and an inner fibre layer. The replaced by microvilli (Riding, 1970). The cortex appeared to be a single layer which th Jatinderpal Singh JBINO (6 Issue) J.Bio.Innov 1(6), pp: 250-263, 2012 ISSN 2277-8330 (online) www.jbino.com varied in thickness, being thin at the apices epicuticle ; a narrow electron dense outer of the longitudinal ridges and much thicker cortical layer; an inner cortical layer a between the ridges. The cortex was matrix layer; three fibre layers and an separated from the fibre layer by a fluid inner fibrous basal lamella. The basal filled region, the middle layer. The fibre lamella possessed local areas associated layer was found to be composed of two with hemi-desmosomes on the hypodermal fibre layers and a basement membrane. membrane. The cuticle of the anterior half Using light and scanning microscopy, of the body of female was found to be Anya (1966) observed that the cuticle of similar to the male while the posterior half Aspiculuris tetraptera had three basic was enveloped by seven-layered structure layers namely, the cortex consisting of an consisting of an outer membrane like outer and inner cortical layer, middle layer, a narrow outer cortex, an inner matrix and inner fibre layer which in turn cortex, a thin matrix layer, two fibre layers is made of three layers. In addition, a thin and a fibrous basal lamella. osmiophillic superficial membrane on the surface of the cuticle, discernible only with Based on their ultrastructural and the electron microscope, was reported. cytochemical studies, some authors (Lee, 1965 and Bird, 1980) considered that the Tomita (1975) described the cuticle of outer covering of the cuticle was a “cell Thelazia callipaeda to be composed of two membrane” and referred to it as an layers, an external layer consisting of three epicuticle. Since then the use of terms such sub-layers forming the transverse body as “membrane”, “membrane-like”, striations and an internal layer composed “modified membrane” for different regions of six sub-layers. Franz (1980) made of the cuticle’s surface have created certain scanning and transmission electron confusions and implied various concepts microscopic studies on the cuticle of regarding its composition and function. Onchocerca volvulus and found it to be Zuckerman et al (1979) and Bird (1985) consisting of a cortical, a median and a used the term “glycocalyx” for the basal layer. The outer limitation of the carbohydrate moieties on the outermost cuticle was an irregularily folded surface surface of the cuticle which sometimes membrane, which showed a regular honey appeared as a fuzzy coating. The presence comb pattern and covered the entire worm of carbohydrate moieties and use of the with the exception of anterior and posterior term “glycocalyx” for the surface ends. Lee and Nicholas (1983) used membrane of the cuticle gave rise to the plasma etching to reveal the structure of impression of epicuticle being a cell the cuticle of adult Nippostrongylus membrane. This concept of the outside brasiliensis. The cuticle revealed an outer layer being a cell membrane had been membrane like layer, a single cortical discussed by Wright (1987) who pointed layer, a fluid filled layer, two fibre layers out that the surface structure was likely to and a basement lamella. vary considerably in different nematode species as a result of different functional Martin and Lee (1983) described the and anatomical requirements. To solve this structure of body wall of adult problem and minimize further confusion, Nematodirus battus. The cuticle of the he suggested that, it will be much male Nematodirus battus was divided into appropriate to use the term surface coat for three main layers namely, an outer cortex, the outer carbohydrate component of the a middle layer and an inner fibre layer. cuticle rather than the glycocalyx. He also These three major layers were further suggested that the epicuticle was not a cell divided into eight distinct layers, membrane, however, with studies it could namely,an outer membrane like layer or th Jatinderpal Singh JBINO (6 Issue) J.Bio.Innov 1(6), pp: 250-263, 2012 ISSN 2277-8330 (online) www.jbino.com be seen as a surface trilaminate The P-face of the epicuticle outer fracture differentiation containing lipids. plane presented a large number of densely- packed small particles and many Nevertheless, the term epicuticle now protuberances. appears to be accepted for the outside layer. Regarding remaining layers of the Neuhaus et al (1996) investigated the cuticle, there seems to be a consensus that ultrastructure, development and a generalized cuticle would consist of an morphogenesis of the body cuticle of adult epicuticle, a cortical layer, a median layer and juvenile Oesophagostomum dentatum and a basal layer (Bird and Bird, 1991). by light microscopy, scanning electron Fok et al (1992) described the cuticle of microscopy and transmission electron Nippostrongylus brasiliensis as a three microscopy.