D. Eugene Copeland

The salt absorbing cells in the gills of the blue crab (Callinectes sapidus Rathbun) with notes on modified mitochondria.

SummaryA modified, glandular epithelium lining the respiratory platelets of gills in crabs known to be absorbing salt is described. The cell surface adjacent to the surface cuticle is thrown into folds whose spaces are filled with flocculent material that is subject to pinocytosis. The lateral surface areas of neighboring cells are thrown into narrow, flat sheets that deeply interdigitate with one another on a one to one alternating basis. There is considerable spacing between the interdigitating plasma membranes that communicates with the haemolymph surface of the epithelium. Tremendously flattened mitochondria with modified cristae are seen. Both flattened mitochondria and more normally shaped mitochondria are seen to form mitochondrial pumps.

Fine structural study of gas secretion in the physoclistous swim bladder of Fundulus heteroclitus and Gadus callarias and in the euphysoclistous swim bladder of Opsanus tau

SummaryThe Haldane-Koch-Scholander-Kuhn-Steen theory of salting out countercurrent multiplication effect of the rete mirabile now accounts for release of most gases in the fish swim bladder. Evidence presented here indicates that final release is by microbubbles from the secretory epithelium. There is only one specific cell type in a highly vascularized epithelium. It is characterized by complex folds in the paravascular zone and by “gas” forming bodies which seem to form from plentiful Golgi material. The bodies are formed with dark amorphous matrix that becomes patterned (tubular or lamellar), finally froths and then is released to the gas surface. Residual material may form myelin-like layers on the lumenal surface. Active cells are also characterized by surface villi and subsurface, parallel cisternal spaces. Gas may be formed by cells not touching the gas surface and released through intercellular spaces. There are discontinuous desmosomes (maculae adhaerentes) near the gas surface and there are no tight junctions (zonulae occludentes). Gas release as bubbles would explain Wittenbergs observations that the gases found in swim bladders have ratios more closely related to their solubility coefficients in water than to ambient partial pressures. A surfactant may be present to lower the surface tension of the microbubbles. The carrier in the cytoplasm would have to be an iron-protein (or perhaps peroxidase) compound capable of binding molecular oxygen.

Ultrastructural study of the neurosecretory granules in the sinus gland of the blue crab, Callinectes sapidus

SummarySeven morphologically different types of neurosecretory granules have been found in the axon terminals of the sinus gland of the blue crab, Callinectes sapidus. They differ from each other in size, shape, staining characteristics, solubility characteristics, core matrix characteristics, axon terminal matrix characteristics, presence or absence of space between the granule membrane and granule core matrix, and frequency of occurrence. Five of the types are segregated in different axon terminals and are believed to represent different hormone-protein complexes. Two of the types, which have lost part or all of their granular contents, are thought to be variants of the other five types. The differences in granular morphology are better revealed by some fixation procedures than others. Palades acetate-veronal buffered osmium tetroxide, in particular, reveals striking differences. The following observations suggest that different hormone-protein complexes are segregated in different axon terminals and that these complexes may be morphologically distinguished at the level of the electron microscope.

Fine structure of the pseudobranch of the flounder Paralichthys lethostigma

SummaryThe free or “non-glandular” pseudobranch of the flounder Paralichthys lethostigma was studied with the electron microscope. Cells typical of glandular type pseudobranchs are found. This indicates that, at least in the flounder, the free pseudobranch should be called “glandular”. In addition, the chloride-type cells, commonly found in the gill, buccal epithelium, and surface epithelium of other fish, have been found in the pseudobranch, where they have not been described previously. The fine structure of both the chloride-type and the pseudobranch-type cell has been characterized and contrasted. We have not been able to confirm previous reports that the specific cells in both pseudobranch and gill are identical in the flounder.

The anatomy and fine structure of the eye of teleost. I. The choroid body in Fundulus grandis

Abstract The choroid body of fish eye is a rete mirabile whose function, as a counter-current system, is to elevate the oxygen tension in the retina by many fold. In Fundulus it is a “Y”-shaped organ straddling the optic nerve just beneath the sclera of the eyeball. Blood flows from the choroid body to the choriocapillaris and returns. There is no vascularization of the internal (vitreous) surface of the retina. Detailed anatomy and fine structure of the body is described. Comparison is made to the rete mirabile of the swim bladder where gases are also concentrated.

The anatomy and fine structure of the eye in teleosts. V. Vascular relations of choriocapillaris, lentiform body and falciform process in rainbow trout (Salmo gairdneri).

Abstract The lentiform body is a counter-current system based on two sets of interdigitating capillaries (rete mirabile). It and the much larger rete mirabile of the choroidal body are implicated in the elevation of oxygen in the retina of many teleosts. The arterial blood comes to the lentiform body independently of the choroidal body and passes to the inside of the eye (to hyaloid vessels in Fundulus and to a falciform process in rainbow trout). Arterial blood to the choroidal body passes to the choriocapillaris. It has been shown recently that the choriocapillaris provides counter-current blood to condition the incoming systemic blood of both the lentiform and choroidal rete in Fundulus . This report gives a detailed analysis of the vascular connections in the rainbow trout eye.

The anatomy and fine structure of the eye in teleost. IV. The choriocapillaris and the dual vascularization of the area centralis in Fundulus grandis

Abstract The eye of Fundulus grandis possesses both external (choriocapillaris) and internal (hyaloid) circulations which with the rete mirabile of the choroidal body and lentiform body provide an elevation of oxygen tension in the retina. Both the choriocapillaris and the hyaloid vessels are arranged in three distinet regional patterns. Spatially the external and internal regions closely match each other, particularly in regard to the area centralis. The rete mirabile of the choroidal body has a dual set of efferent vessels that receive blood from different areas of the choriocapillaris. Although the lentiform body is independent of the choroidal body for incoming systemic blood, it is dependent on the choriocapillaris-choroidal body complex for blood to run counter-current in its rete mirabile. Conditioned blood from the lentiform body supplies the hyaloid system inside the eye. Part of the blood in the hyaloid system returns to one set of the efferent vessels in the choroidal body. The total circulation is complex but makes functional sense when studied in detail.

Layered membranes: A diffusion barrier to gases in teleostean swimbladders

Flattened cells are dispersed in an overlapping fashion within the submucosa of closed (physoclistous) swimbladders. Within the cells are located round platelets best seen by phase or interference type microscopy. At the electron microscope level the platelets are revealed as repeated, numerous layers of membranous discs. Each disc is a bilayer with an enlarged rim. The bilayer is strongly and preferentially reactive to osmium tetroxide. Swimbladder walls are known to be highly resistant to passage of gases. The randomly disposed platelets with the highly ordered layering of membranes may provide that physical resistance to gas movement.

The anatomy and fine structure of the eye in teleost. II. The vascular connections of the lentiform body in Fundulus grandis

Abstract The lentiform body is found in association with the choroid body in the back of teleost eyes. It probably helps to maintain the elevated oxygen tension which has already been produced by the choroid body-choriocapillaris complex. The body contains interdigitating afferent and efferent capillary beds (rete mirabile) which, by counter-current exchange, could have such a conservation effect. It has been reported that lentiform bodies are found only in connection with falciform processes. However, in Fundulus there is no falciform process and the body connects to the hyaloid vessels which in turn supply blood to the retractor lentis muscle and to the vitreous humor at the retinal surface. The lentiform body delivers no blood to the choriocapillaris, but, oddly enough, its venous counter-current blood is supplied by the choriocapillaris.

The anatomy and fine structure of the eye in teleost. III. The structure of the lentiform body in Fundulus grandis

Abstract The lentiform body in conjunction with the much larger choroidal body is concerned with the elevation of oxygen tensions in the eyes of some teleost fishes. The lentiform body of Fundulus grandis is a counter-current system of afferent capillaries interspaced with irregular efferent sinusoids. It is significantly smaller than the choroidal body and much less efficient in that the vascular components are shorter in length and larger in diameter, reducing the exchange capability. The fine structure of the vessels in the lentiform body is much like that of the choroidal body.