Histochemical mapping of certain enzymes in few fresh water teleosts. I. Acid phosphatase.

A detailed investigation of the distribution pattern of acid phosphatase in the different parts of alimentary canal and associated glands of Colisa fasciatus, Macrognathus aculeatus, Notopterus notopterus and Nandus nandus has been made. Though this enzyme shows its hydrolytic activity in all the parts of the digestive system yet its intense activity has been noted in the intestine, pyloric caeca, liver and pancreas of all the 4 fishes. Mucosal and submucosal layers of all the parts of the alimentary canal are the main seat of localization of this enzyme.     

Histo-chemical mapping of phosphomonoesterases in the gonads of Notopterus notopterus and Colisa fasciatus during different seasons. Part II. Adenosine triphosphatase and glucose-6-phosphatase

Histochemical techniques described by McManus (1960) have been applied in the fishes, Notopterus notopterus and Colisa fasciatus, for the study of Glucose-60phosphatase and adenosine triphosphatase in the four stages of gonads in different seasons. It has been observed that the activity of adenosine triphosphatase is more intense in comparison to the activity of Glucose-6-phosphatase in all the stages i.e. I (immature), II (maturing), III (mature) and IV (spent) of the gonads in both the fishes. The general tendency of the adenosine triphosphatase and Glucose-6-phosphatase distribution in the gonads are much more remarkable in stage II in comparison to stage I, III and IV. The stage I seems to be the stage of synthesis of these enzymes. In stage III and IV, these enzymes show the tendency of declination with the time period. The possible role of these enzymes seems to be the transport of glucose across the cell membrane involving phosphorylation and dephosphorylation which depend on the different stages of gonad maturation.     

The morphology of the gills of the freshwater African crab Potamon niloticus (Crustacea: Brachyura: Potamonidae): A scanning and transmission electron microscopic study

The gills of the African freshwater crab Potamon niloticus -Ortmann have been investigated by scanning and transmission electron microscopy. Potamon has seven pairs of phyllobranchiate gills contained in the branchial chambers. From the central axis of the gills arise bilaterally situated thin flaps, the lamellae. The afferent branchial vessel (the epibranchial vessel) is located on the dorsal aspect of the gill arch and the efferent vessel (the hypobrancial vessel) on the ventral side. Between these two blood vessels, the blood percolates through the lamellar vascular channels where it is oxygenated. The lamellae consist of an epithelial cell layer covered by a thin cuticle which consists of tightly fused but distinct layers. The epithelial cells approach each other at regular intervals and fuse in the middle of the lamellar sinus delineating the vascular channels. Apical profuse membranous infoldings and numerous mitochondria characterize the epithelial cells, features typical of cells involved in active transport of macro- and micromolecules. In Potamon , however, there were no distinct gas exchange and osmoregulatory regions of the gills. On average, the cuticle was 0.78 μm thick while the epithelial cell was 6 μm. Cells that were morphologically similar to the renal glomerular podocytes of the vertebrates were observed in the efferent gill vessel of Potamon. These cells have been said to be phagocytic and may play an important defensive role in the crustaceans. Although basically the morphology of the gills of Potamon is similar to that of the other decapods, fine structural differences were evident as would be intuitively expected in a group of animals that has undergone such remarkable adaptive radiation.     

Functional anatomy of the internal gills of the tadpole of Litoria ewingii (Anura,Hylidae)

Summary (1) Scanning electron microscopy and vascular casting were used to study the morphology and vascular anatomy of the fully developed internal gills of Litoria ewingii tadpoles. — (2) The four pairs of gills were located in two branchial baskets on either side of the heart. Each gill consisted of a branchial arch with gill tufts projecting ventrally and gill filters running dorsally. The gills bore a variable number of gill tufts in which a complex three-dimensional array of capillary loops, of varying lengths and diameters, was trailed in the path of the ventilatory current. — (3) The evidence presented in this paper suggests that the gill tufts have greater potential as gas exchangers than either the gill filters or skin. — (4) The study revealed structural and functional evidence for the existence of branchial shunts between afferent and efferent branchial arteries.     

Fish gill morphology: inside out

In this short review of fish gill morphology we cover some basic gross anatomy as well as in some more detail the microscopic anatomy of the branchial epithelia from representatives of the major extant groups of fishes (Agnathans, Elasmobranchs, and Teleosts). The agnathan hagfishes have primitive gill pouches, while the lampreys have arch-like gills similar to the higher fishes. In the lampreys and elasmobranchs, the gill filaments are supported by a complete interbranchial septum and water exits via external branchial slits or pores. In contrast, the teleost interbranchial septum is much reduced, leaving the ends of the filaments unattached, and the multiple gill openings are replaced by the single caudal opening of the operculum. The basic functional unit of the gill is the filament, which supports rows of plate-like lamellae. The lamellae are designed for gas exchange with a large surface area and a thin epithelium surrounding a well-vascularized core of pillar cell capillaries. The lamellae are positioned for the blood flow to be counter-current to the water flow over the gills. Despite marked differences in the gross anatomy of the gill among the various groups, the cellular constituents of the epithelium are remarkably similar. The lamellar gas-exchange surface is covered by squamous pavement cells, while large, mitochondria-rich, ionocytes and mucocytes are found in greatest frequency in the filament epithelium. Demands for ionoregulation can often upset this balance. There has been much study of the structure and function of the branchial mitochondria-rich cells. These cells are generally characterized by a high mitochondrial density and an amplification of the basolateral membrane through folding or the presence of an intracellular tubular system. Morphological subtypes of MRCs as well as some methods of MRC detection are discussed.     

Scanning electron microscopic evaluation of effects of low pH on gills of Channa punctata (Bloch)

Bioassay of Channa punctata (± 36 g) was carried out in acidic waters of different pH. A 96 h LC₅₀, value was obtained at pH 5.3. Scanning electron microscopy of gills of C. punctata showed fusion of adjacent secondary lamellae. At this low pH, dissociation of epithelium of branchial arches and gill filaments take place. At 360 h the branchial epithelium ruptures developing lesions in the gills exposing the efferent filament vessels. At pH 6.6 the tips of adjacent filaments belonging to both oral and aboral hemibranchs fuse in blocks.     

Morphology and ultrastructure of the gills of terrestrial crabs (Crustacea,Gecarcinidae and Grapsidae): Adaptations for air-breathing

Summary The terrestrial crabsGeograpsus grayi, Geograpsus crinipes, Cardisoma hirtipes andGecarcoidea natalis have a reduced number of gills and show a reduced planar gill surface (SA) compared to aquatic species. Gill lamellae are stiffened and thickened (increasing blood/gas (BG) diffusion distances) and nodules maintain wide spacing between lamellae. Haemolymph is directed through the gill lamellae by rows of pillar cells and in the afferent region an intralamellar septum splits the haemolymph into two parallel networks. Gaps in the lines of pillar cells allow movement of haemolymph between adjacent channels. The afferent vessel distributes haemolymph to the lamella via a number of direct channels including the marginal canal and in large gills with the aid of a long, forked sinus which supplies the ventral and central regions of the lamellae. The marginal canal functions in both distribution and collection of haemolymph; the role varies with species. Potential flow-control sites were identified at the junctions between afferent and efferent areas and where the efferent channels enter the efferent branchial vessel. Each gill receives a branch from the sternal artery which supplies all the lamellae. Transport epithelia is the principal cell type in the gills of all species examined though its location varies between species, either being confined to certain gills or specific parts of the lamellae.The gill lamellae of air-breathing crabs are clearly modified to breathe air (stiffening and presence of nodules), though the overall contribution of the gills to gas exchange has been reduced (smaller SA and longer BG diffusion distances). The role of the gills in air-breathing crabs thus appears to have switched from one of an efficient aquatic gas-exchanger (thin with large surface area) and transport tissue, to one that is predominantly set up for ion-regulation.Abbreviations a afferent branchial vessel - ac afferent channels - art arteriole - ass artifactual subcuticular space - bl basal lamina - c cuticle - col collagen - ct connective tissue - e efferent branchial vessel - ec efferent channels - epi epithelium - f folds - g Glycogen - h haemolymph - hc haemocyte - is intralamellar septum - m marginal canal - mi mitochondria - mt microtubules - n nucleus - p pillar cell - s shaft of efferent vessel - sd septate desmosome     

Haemodynamic effects of adenosine on gills of the trout (Salmo gairdneri)

Summary The haemodynamic effects of adenosine on gills of the trout (Salmo gairdneri) were studied with in vitro and in vivo preparations.On the isolated head preparation, adenosine induced a decrease of the ventral aortic inflow and of the dorsal aortic outflow. Simultaneously the venous outflow increased. These effects were antagonized by theophylline. Adenosine induced a vasoconstriction in gill arches without filaments perfused by the afferent or the efferent branchial arteries. The efferent vessels were more sensitive to adenosine than afferent vessels. The whole systemic circulation of the isolated trunk did not show any response to adenosine. When adenosine was infused into the ventral aorta of living trout, the gill resistance to blood flow was greatly increased.These results suggest that adenosine is able to control the arterious and venous blood pathways in the trout gills by modulating their vascular resistance.     

Gill microcirculation of the air-breathing climbing perch, Anabas testudineus (Bloch):relationships with the accessory respiratory organs and systemic circulation

The general macrocirculation and branchial microcirculation of the air-breathing climbing perch, Anabas testudineus, was examined by light and scanning electron microscopy of vascular corrosion replicas. The ventral aorta arises from the heart as a short vessel that immediately bifurcates into a dorsal and a ventral branch. The ventral branch distributes blood to gill arches 1 and 2, the dorsal branch to arches 3 and 4. The vascular organization of arches 1 and 2 is similar to that described for aquatic breathing teleosts. The respiratory lamellae are well developed but lack a continuous inner marginal channel. The filaments contain an extensive nutritive and interlamellar network; the latter traverses the filament between, but in register with, the inner lamellar margins. Numerous small, tortuous vessels arise from the efferent filamental and branchial arteries and anastomose with each other to form the nutrient supply for the filament, adductor muscles, and arch supportive tissues. The efferent branchial arteries of arches 1 and 2 supply the accessory air-breathing organs. Arches 3 and 4 are modified to serve primarily as large-bore shunts between the dorsal branch of the ventral aorta and the dorsal aorta. In many filaments from arches 3 and 4, the respiratory lamellae are condensed and have only 1-3 large channels. In some instances in arch 4, shunt vessels arise from the afferent branchial artery and connect directly with the efferent filamental artery. The filamental nutrient and interlamellar systems are poorly developed or absent. The respiratory and systemic pathways in Anabas are arranged in parallel. Blood flows from the ventral branch of the ventral aorta, through gill arches 1 and 2, into the accessory respiratory organs, and then returns to the heart. Blood, after entering the dorsal branch of the ventral aorta, passes through gill arches 3 and 4 and proceeds to the systemic circulation. This arrangement optimizes oxygen delivery to the tissues and minimizes intravascular pressure in the branchial and air-breathing organs. The efficiency of this system is limited by the mixing of respiratory and systemic venous blood at the heart.     

Functional Organization of the Teleost Gill

The circulation of the gills has been studied in the perch, trout and eel combining the conventional histological methods and casting techniques. The existence of two blood pathways in each gill arch was confirmed. 1 — An arterio-arterial pathway assuming the respiratory function. It includes the afferent branchial artery and in each primary lamella the afferent primary artery, the secondary lamellae capillaries and the primary and branchial efferent arteries. 2 — An arterio-venous pathway arising from both the branchial artery, in the gill arch, and the primary arteries in each primary lamella. This pathway includes the central venous sinus of the primary lamella, several small veins and is finally connected with the branchial veins. 3 — The lack of connections between afferent primary arteries and cvs in the trout and the perch makes impossible a direct blood flow from the afferent to the efferent artery (shunt). In the eel connections between cvs and both afferent and efferent arteries do not mean that a shunt is operating according to the pressure gradient.     

Arteriovenous anastomoses in the afferent region of trout gill filaments (Salmo gairdneri richardson,teleostei)

Summary Arteriovenous anastomoses (AVAs) in the afferent region of trout gill filaments originate from two small filament arteries (Fromm's arteries), which parallel the main afferent filament vessel on either side. As in the efferent filament arteries the origin of AVAs is bordered by specialized endothelial cells. Fromm's arteries originate from efferent filament or branchial arteries. A few extremely narrow connections between the afferent filament artery and Fromm's arteries (= afferent shunts) do exist in some gill filaments. Nevertheless, the AVAs in the afferent filament region carry mainly arterialized blood, or blood plasma, to the central venous sinus of the filament.Supported by the Deutsche Forschungsgemeinschaft (Vo 229/1)     

Observations of valve-like structures and evidence for rectification of flow within the gill lamellae of the crab Carcinus maenas (Crustacea,Decapoda)

Summary The isolated gills of Carcinus maenas, perfused at pressure drops of 1–10 cm of water, exhibited flow rectification, the resistance to perfusion via the afferent vessel being many times lower than that for efferent perfusion. The asymmetry was greater at the lower end of this pressure range.The overall afferent branchial resistance for Carcinus of weight 65 g, and with no ventilatory component in the transmural pressure difference, was estimated to be 0.05 cm of water. l^–1 · sec. The corresponding overall reverse (efferent) branchial resistance was 0.36 cm of water · l^–1 · sec.LM, TEM and SEM examination of the gills indicated that haemolymph leaves each gill lamella via several discrete parallel efferent channels which drain different regions of the lamella, and that each efferent channel is nearly closed, at its junction with the efferent branchial vessel, by a diaphragm of loosely interwoven and very elongated cells. It is concluded that these cells may constitute efferent valves and that narrow apertures between them may contribute a major component to the branchial resistance and be primarily responsible for the rectification of flow. Relatively wide apertures lead directly from the afferent vessel into the lamellae and are not asociated with valves of any kind.The valves may be important in enabling changes in transmural pressure associated with ventilatory reversals to pump haemolymph unidirectionally through the lamellae. Similarly valves may allow the oscillating venous pressures associated with locomotor activity to improve gill perfusion during exercise.The elongated tails of the cells of the efferent valve contain numerous microtubules. The wider cell bodies contain the nucleus and many mitochondria. Unusual organelles composed of many short (about 0.25 m long) microtubules and often lying close to the nuclear membrane may be microtubule organising centres. It is speculated that, in addition to their simple mechanical function, the valve cells may play a more dynamic role in regulating flow of haemolymph through different lamellar routes, or that they may monitor composition, pressure or flow of the efferent lamellar circulation.     

The structure of the gill of the trout,Salmo gairdneri (Richardson)

Summary A light and electron microscopic study was made of the structure of the gill arch, filament and secondary lamella of Salmo gairdneri R. Blood pathways through the gill were traced from serial histological sections, and from the examination of ink perfused tissue and perspex casts formed following resin injection of the circulatory system.The epithelium covering the gill consists of unspecialized, dark, chloride and mucous cells. The distribution of specialized cells appears to be related to gill function. The basement membrane underlying the epithelium consists of three layers, the inner collagen layer being continuous with the connective tissue core of the gills.Blood supply to the secondary lamellar respiratory surface is via branchial, filament and secondary lamellar arteries. Blood spaces of the secondary lamellae are delimited by pillar cells containing what appears to be contractile material. The marginal channel of each lamella is bounded distally by cells of endothelial origin. A network of lymph spaces within the filaments connects with efferent branchial arteries. Nutritionary capillaries within the filaments connect with afferent branchial arteries. No shunts between afferent and efferent filament arteries were found.Data from this study and previous physiological and histopathological studies suggest a mechanism for the control of blood flow to suit the respiratory requirements of the fish. This mechanism involves a system of recruitment of additional respiratory units and changes in overall blood flow patterns.This work formed part of a thesis submitted for the degree of Doctor of Philosophy in 1971 and for which M. M. was in receipt of a studentship from the Natural Environmental Research Council. The authors are grateful for the support given by research grants from the M.R.C (P.T.) and the N.E.R.C. (M.M.), and to Prof. G. M. Hughes in whose department the work was carried out.     

Aminergic cellular organization in the gills of Aplysia species

The constituent elements of the gills of Aplysia kurodai and A. juliana were examined for the presence of biogenic amines using histochemical, immunocytochemical, and HPLC techniques. Aminergic elements were revealed by glyoxylic acid-induced fluorescence in the branchial nerve, branchial ganglion, branchial vessels, and pinnules in both species. Three types of fluorescent cells were found in the neural plexus of the gill in each species. Two of them might be sensory neurons. Although HPLC analysis showed the presence of serotonin and dopamine in all gill structures including fluorescent neural elements, there were regional differences in concentrations of the monoamines. It was noted in the pinnules that there was a much higher concentration of dopamine than serotonin. Serotonin immunocytochemistry revealed neural processes which were immunoreactive to antiserotonin antibody, but serotonin immunoreactivity could not be found in a population of branchioganglionic neuron (BGN) somata. Serotonergic elements in the ganglion may be processes of the central ganglion, while dopaminergic elements may be processes of neurons in the neural plexus, located beyond the branchial ganglion. BGNs were activated by bath-applied dopamine and serotonin. These results suggest that dopaminergic sensory inputs from the neural plexus and serotonergic descending inputs from the abdominal ganglion may be among the inputs received by BGNs. It was found that serotonin depressed excitatory junctional potentials in muscle cells of the efferent branchial vessel, which were induced by an identified neuron of the abdominal ganglion. The aminergic cellular organization of the gill may involve serotonergic presynaptic-inhibitory fibers arising from the abdominal ganglion.     

The morphology and vasculature of the lungs and gills of the soldier crab,Mictyris longicarpus

The five gill pairs of Mictyris longicarpus have the lowest weight specific area reported for any crab. The cuticle of the gill lamellae is lined with epithelial cells which have structural features characteristic of iontransporting cells. Pillar cells are regularly distributed in the epithelium and serve to maintain separation of the two faces of the lamellae. The central hemolymph space is divided into two sheets by a fenestrated septum of connective tissue cells. The dorsal portion of the marginal canal of each lamella receives hemolymph from the afferent branchial vessel and distributes it to the lamella while the ventral portion of the canal collects hemolymph and returns it to the efferent branchial vessel. The lung is formed from the inner lining of the branchiostegite and an outgrowth of this, the epibranchial membrane. Surface area is increased by invagination of the lining which forms branching, blind-ending pores, giving the lung a spongy appearance. The cuticle lining the lung is thin and the underlyng epithelial cells are extremely attenuated, giving a total hemolymph/gas distance of 90–475 nm. Venous hemolymph is directed close to the gas exchange surface by specialised connective tissue cells and by thin strands of connective tissue which run parallel to the cuticle. Air sacs are anchored in position by paired pillar cells filled with microtubules. Afferent hemolymph is supplied from the eye sinus, dorsal sinus, and ventral sinus. Afferent vessels interdigitate closely with efferent vessels just beneath the respiratory membrane. The two systems are connected by a “perpendicular system” which ramifies between the airways and emerges to form a sinus beneath the carapace and then flows back between the air sacs to the efferent vessels. The afferent side of the perpendicular system is the major site of gas exchange. Efferent vessels return via large pulmonary veins to the pericardial cavity. P_aO₂ levels were high (95.5 Torr), indicating highly efficient gas exchange.     

Development of the pharyngeal arch skeleton in Catostomus commersonii (Teleostei: Cypriniformes)

Skeletal elements of the gill arches of adult cypriniform fishes vary widely in number, size, and shape and are important characters in morphologically based phylogenetic studies. Understanding the developmental basis for this variation is thus phylogenetically significant but also important in relation to the many developmental genetic and molecularly based studies of the early developing and hence experimentally tractable gill arches in the zebrafish, a cyprinid cypriniform. We describe the sequence of the chondrification and ossification of the pharyngeal arches and associated dermal bones from Catostomus commersonii (Catostomidae, Cypriniformes) and make selected comparisons to other similarly described pharyngeal arches. We noted shared spatial trends in arch development including the formation of ventral cartilages before dorsal and anterior cartilages before posterior. Qualitatively variable gill arch elements in Cypriniformes including pharyngobranchial 1, pharyngobranchial 4, and the sublingual are the last such elements to chondrify in C. commersonii. We show that the sublingual bone in C. commersonii has two cartilaginous precursors that fuse and ossify to form the single bone in adults. This indicates homology of the sublingual in catostomids to the two sublingual bones in the adults of cobitids and balitorids. Intriguing patterns of fusion and segmentation of the cartilages in the pharyngeal arches were discovered. These include the individuation of the basihyal and anterior copula through segmentation of a single cartilage rod, fusion of cartilaginous basibranchials 4 and 5, and fusion of hypobranchial 4 with ceratobranchial 4. Such “fluidity” in cartilage patterning may be widespread in fishes and requires further comparative developmental studies. J. Morphol., 2009. © 2008 Wiley‐Liss, Inc.     

Gill morphology and morphometry of the facultative air-breathing armoured catfish,Corydoras paleatus,in relation on aquatic respiration

The Neotropical armoured catfish Corydoras paleatus is a facultative air-breathing teleost commonly exported as ornamental fish. In this species, air breathing enables it to survive and inhabit freshwater environments with low oxygen levels. Therefore, it is important to analyse the gills from a morphological aspect and its dimensions in relation to body mass with reference to aquatic respiration. For that, the gills were analysed using a stereoscopic microscope for morphometric studies, and structural and ultrastructural studies were carried out to compare the four branchial arches. Furthermore, two immunohistochemical techniques were used to locate and identify the presence of a Na⁺/K⁺ pump. The characterization of the potential for cell proliferation of this organ was assessed using an anti-PCNA antibody. The results show that gills of C. paleatus present some characteristics related to its diet and lifestyle, such as the limited development of gill rakers and the abundance of taste buds. In addition, other special features associated with the environment and bimodal breathing were observed: scarce and absent mucous cells (MCs) in the gill filaments and branchial lamellae, respectively, and the localization of mitochondria-rich cells (MRCs) covering the basal third of the branchial lamellae, which reduces the gill respiratory area. A peculiar finding in the gill epithelium of this armoured catfish was the presence of mononuclear cells with sarcomeres similar to myoid cells, whose functional importance should be determined in future studies. Finally, in C. paleatus, the interlamellar space of gill filaments is an important site for cell turnover and ionoregulation; the latter function is also performed by the branchial lamellae.     

A morphological study on gills of the brown shrimp, Penaeus aztecus

The gills of Penaeus aztecus were examined by light and electron microscopy. They are dendrobranchiate, consisting of a central axis with biserially arranged branches that subdivide into bifurcating filaments. A septum divides the lumina of these structures into afferent and efferent channels. Hemolymph from the sternal sinus flows through the afferent channels into the filaments where it is directed into the efferent channels and finally to the pericardial cavity. In addition to these channels, numerous blood vessels permeate the gill. The cuticle covering the gill overlies a thin epithelium which is separated from hemolymph by a basal lamina. The epithelium, which is active in cuticle secretion, has a series of pillar processes that form subcuticular lacunae. The apical membranes of epithelial cells become folded in shrimp exposed to hypo- and hyperosmotic salinities. Granular cells that contain elaborate Golgi apparati and several types of granules are present throughout the gill. Nephrocytes resembling glomerular podocytes line the efferent channels. A large nerve traverses the septum in the axis.     

Adrenergic innervation of the gills of brown and rainbow trout,Salmo trutta and S. gairdneri

The adrenergic innervation of structures in the gills of brown and rainbow trout was studied with catecholamine fluorescence histochemistry. In the arterio-arterial vascular pathway, there was an innervation of the afferent and efferent lamellar arterioles, but the afferent and efferent filamental arteries and the secondary lamellae were devoid of any fluorescent nerve fibres. In S. trutta only, there was an additional innervation of the afferent and efferent branchial arteries and the base of the efferent filamental artery. The innervation of the arterio-venous vascular pathway was similar in both trout species. Many fluorescent nerve fibres were found on nutritive arterioles in the gill arch and interbranchial septum, and in the core of each filament between the surface epithelium and the wall of the filament venous sinus. No fluorescent nerve fibres were observed at the origins of the capillaries arising from the efferent filamental artery. The sympathetic nerve supply is provided to the gills mainly through the posttrematic nerve, with an occasional small contribution through the pretrematic nerve. The presence of adrenergic nerves in the gills is discussed in relation to the regulation of blood flow through the arterio-arterial and arterio-venous pathways.