THE CELLULAR STRUCTURE OF LYMPHOMYELOID TISSUES IN CHIMAERA MONSTROSA (PISCES, HOLOCEPHALI)

Abstract

The ultrastructure of the main lymphomyeloid organs of the holocephalan fish, Chimaera monstrosa, is presented.The thymus is well developed even in adults. It is densely packed with small and large lymphocytes, the former predominating. The ultrastructure of C. monstrosa's lymphocytes is similar to that of mammalian ones. The lymphocytes show intimate connections with large epithelial reticulocytes, which infiltrate the cytoplasm of the lymphocytes with long processes.The lymphomyeloid tissues around the orbit are mainly granulocytopoietic. Two types of granulocytes occur: eosinophilic and heterophilic. The latter is found in excess. The granulocytes are ultrastructurally similar to those of elasmobranchs such as Etmopterus spinax and have similar characteristic granules. In addition to granulocytes in various stages, lymphocytes, plasma cells, blast cells, and solitary macrophages are scattered throughout the tissue.The suprapalatal region also has a similar supply and variety of cells, but most heterophilic granulocytes have modified granules.In the spleen, erythrocytes in different developmental stages are common. This confirms earlier studies which suggested that the spleen functions primarily as an erythrocytopoietic organ.

Occurrence of lymphohaemopoietic tissue in the meninges of the stingray Dasyatis akajei (Elasmobranchii, Chondricthyes)

“…However, in other primitive fishes (Stahl, 1967;Fange and Sundell, 1969;Mattisson and Fange, 1986) in Holocephali (Chandler, 1911;van der Horst, 1925;Tilney, 1927;Vialli, 1932;Scharrer, 1944), in Chondrostei and Holostei, formerly Ganoidei, and in the urodeles Ambystoma (Dempster, 1930) and Megalobatrachus japonicus (Sano and Imai, 19611, lymphohaemopoietic masses occur in association with the meninges and choroid plexuses of various regions of the central nervous system. According to our results, the histological organization of the lymphohaemopoietic tissue found in the meninges of the stingray Dasyatis akajei resembles that reported by light (Stahl, 1967;Fange and Sundell, 1969) and electron microscopy (Mattisson and Fange, 1986) for the cranial lymphoid tissues of holocephalans and for the lymphomyeloid aggregates present in the meninges of the fourth ventricle of ganoids (Chandler, 1911;Scharrer, 1944). In all these locations, a reticular stroma has been recognized where lymphoid cells and developing and mature granulocytes reside and differentiate.…”

“…Likewise, Mattisson and Fange (1986) describe lymphocytes, monocytes, macrophages, and clusters of plasma cells in the lymphoid masses associated with the cranium in Chimaera monstrosa. Close association between macrophages and lymphoid cells in the meningeal lymphohaemopoietic tissue is a striking fact that may be important from an immunological point of view.…”

“…Furthermore, as mentioned above, antigenic stimulation elicits increased numbers of free cells in the subarachnoid space in a situation resembling that found (both in this study and by other authors) in the meningeal lymphohaemopoietic tissues of primitive fishes. On the other hand, various authors studying the structure of the meningeal lymphomyeloid tissues in Holocephali (Kolmer, 1923;Mattisson and Fange, 1986) and Ganoidei (Scharrer, 1944) have considered these tissues to the phylogenetic equivalents of the bone marrow of higher vertebrates. Our results regarding the histological organization and cell components of the stingray meningeal lymphohaemopoietic aggregates also suggest a phylogenetic relationship with bone marrow.…”

“…Especially interesting is the presence in primitive fishes of lymphohaemopoietic tissue in areas unlike those of other vertebrates. Thus, the holocephalans (Chimaera, Hydrolagus) contain a granulopoietic and lymphopoietic tissue (Mattisson and Fange, 1986) in depressions and cavities of the cartilaginous skeleton, mainly in the orbit, in the preorbital canal, suprapalatally, and in the coracoid area (Fange, 1984). This finding has moved some authors (Bjerring, 1984;Fange, 1984) to speculate that certain extinct Devonian fishes have meningeal lymphomyeloid tissue.…”

The Adult Hematopoietic Niches — Cellular Composition, Histological Organization and Physiological Regulation

“…The brain and cranium are also suitable sites for haematopoiesis. It occurs in the meninx primitive of some elasmobranches [139] and in the orbit and subcranium of the holocephali, Chimaera monstrosa [140,141]. An analogous tissue occurs in the meninges of ganoids [142] and in the brain of the urodeles Ambystoma [143] and Megalobatrachus japonica [144].…”