Bau und funktionen der blutzellen des mehlk�fers Tenebrio molitor L.

Abstract

The morphology and the functions of the blood cells of the mealworm beetle Tenebrio molitor L. are investigated with various methods in histological preparations and in unharmed, living pupae under completely natural conditions with timelapse and slow-motion microcinematography. Thus it is possible to immediately observe their normal shape and funktions. It was found that conventional methods of obtaining haemolymph from live or dead insects extensively change the behaviour and shape of the blood cells. A method for gaining haemocytes of unaltered morphological appearance for histological investigations is described. The fine structure in light and electron microscopy, histochemistry of inclusions and some enzymes, behaviour in the pupa, locomotion, cell division, clotting, phagocytosis, histolysis, wound healing, encapsulation of foreign bodies, behaviour in tissue culture and death of the blood cells are studied in detail. Two main groups of blood cells with clear differences in shape, inclusions, and functions are distinguished. The first group consists of oval or disc-like blood cells with rounded outline. They contain many mucopolysaccharide granules, little RNA, and few mitochondria. In the haemocoel of the normal animal, they show no recognizable changes or activities, but remain ready in a state of high reactivity to explode in the process of clotting in fractions of seconds at injuries at contact with the outer atmosphere or with foreign bodies. The second group is chiefly concerned with functions within the body and comprises spindle-shaped cells with pointed processes, or polymorphous cells, containing much RNA, many mitochondria, some reserve material, but only few or no mucopolysaccharide granules. The polymorphous amoeboid forms; devoid of mucopolysaccharide granules and often loaded with reserve materials and cell fragments, are capable of active movement, phagocytosis; and secretion. They are engaged in several functions in the normal animal and undergo characteristic changes under pathological influences. Spindle-shaped cells are able to transform into polymorphous pseudopodial forms. The clotting of the haemolymph consists of three combined components, 1. formation of a meshwork of strands, 2. coagulation of the lymph, 3. formation of pseudopodial cells; it is an immediate activity of the blood cells and no sole reaction of the haemolymph. The single actions of the three components are demonstrated by inhibiting the other two ones respectively, and can be correlated to certain types of blood cells or inclusions: coagulation of the haemolymph to the cells with round outline, formation of strands to the mucopolysaccharide granules from which they arise, and transformation into amoeboid forms to the spindle-shaped cells. The haemocytes arise by mitosis and differentiation from small original forms. Comparison with the conditions in some other insect species reveales that the strict separation into two different haemocyte groups as in Tenebrio does not generally occur; however the basic functional patterns remain the same in alle observed cases. A new nomenclature is proposed and discussed which is not based on morphological but on physiological characteristics of blood cells.