what is the importance of haemocoel during moulting
Answers
Answer:
Molting, which usually requires 5–10 days, occurs periodically throughout the life of the tardigrade. The entire cuticular lining of the foregut, including the buccal tube, placoids, stylets, and stylet supports, is ejected through the expanded buccal opening. The mouth opening closes, and the animal cannot feed. This is the “simplex” stage, characterized by the absence of the sclerified buccal–pharyngeal apparatus (Figure 17.26(a)). The buccal glands reform the cuticular structures of the buccal tube, stylets, and stylet supports (Figure 17.26(b)). The posterior part of the apparatus is reconstructed by the pharynx and by the epithelia of the esophagus. Concomitantly, new body cuticle, including the hindgut lining, is synthesized by the underlying epidermis, and the new claws are produced by claw (pedal) glands in the legs. When cuticular production is complete, a new set of claws and a complete buccal–pharyngeal apparatus (Figure 17.26(c)) are visible. The molt ends with the abandonment of the old (external) cuticle (including the lining of the hindgut); this exuvium is used as a container for the eggs in many species of tardigrades. In some heterotardigrades, defecation can also be associated with molting. Generally, body length increases with each molt until maximum size is attained, although lack of food can result in a decrease in size. Although growth is more rapid during the earlier molts, molting and growth continue even after sexual maturity.
Explanation:
Answer:
Explanation:The exoskeleton or cuticle of arthropods is an important feature that contributes to their great success in colonising numerous habitats on earth. It has numerous functions among which to provide protection against parasites. Whereas often regarded as a simple physical barrier to the outside world, the immune protection of the cuticle is slightly more complex than that. Here, we provide an overview of the cuticle defensive traits against parasites and examine their variation as a response to parasitism. It appears that the cuticle is an efficient line of defense, which includes physical, biochemical and physiological defensive components that are potentially subject to genetic and plastic variation in response to parasitism. It also appears that the cuticle defense systems are relatively understudied despite it may determine for large part the success of parasitic attacks.
Physical component of the cuticle defense
Intuitively, the protective function of the cuticle of arthropods relies on boundary defense, which consists of a tough and flexible integument covering the animal surface. This protection even extends to the digestive system, where a protective cuticular membrane called the peritrophic membrane, covers the midgut. (Peters, 1992). Despite this physical barrier, parasites, can invade directly through the exoskeleton. Parasites that penetrate the cuticle are mainly bacteria, fungi and parasitoids. For instance, the entomopathogenic fungi such as Metarhizium anisopliae and Beauvaria bassiana, or bacteria responsible for the shell disease syndrome (e.g., Vibrio sp., which induces characteristic black-spot lesions on the exoskeleton of marine crustaceans) use a combination of physical and enzymatic processes, such as chitinase and protease, to breach the cuticle