Gross structure and dimensions of the gill in an air-breathing estuarine goby,Pseudapocryptes lanceolatus

The gills of the air-breathing estuarine goby,Pseudapocryptes lanceolatus, are reduced owing to the development of a specialized organ of O₂ uptake from air. In the first gill arch, the filaments of the outer hemibranch are reduced to nearly one-half in comparison to those of its inner hemibranch. A smaller number of secondary lamellae per mm (27.6) occurring on one side of the gill filament reduces the gill surface area. A bilogarithmic plot of the gill area and the body weight indicates a curve with two significantly different components, one (b = 0.924) related to the fish weighing up to 6 g and the other (b = 0.405) to the fish weighing 8 g and above.     

Gross structure of the respiratory organs and dimensions of the gill in the mud–skipper, Periophthalmodon schlosseri (Bleeker)

In Periopkrlialnwdon scldosseri the respiratory organs consist of the gills, the suprabranchial and opercular chambers. The gills are more suited for aerial than aquatic respiration as is shown by the presence of the vascular papillae, blood sinusesand dilated blood vessels in their lamellae. The gill lamellae possess a surface coat of sulphated mucopolysaccharides that prevents water loss during exposure to the air. The filaments of the outer hemibranchs in the first gill arch are reduced to nearly one quarter of those of its posterior hemibranch. The gill area in relation to body weight shows a high slope value ( b =0·93).     

Morphometric examination of the gills of walleye, Stizostedion vitreum vitreum (Mitchill) and rainbow trout, Salmo gairdneri Richardson

Observations on the gill morphology of individual gill arches of walleye, Stizostedion vitreum vitreum and rainbow trout, Salmo gairdneri suggest that the first two arches account for the highest proportion of gill filament number, secondary lamellae number, lamellae area, and gill surface area. Interspecific comparisons suggest walleye contain a larger number of gill filaments, with a lower secondary lamellae count, but a larger gill surface area than a trout of the same weight. This is partially attributed to the larger surface area of each lamella in a walleye than in a trout.
A detailed examination suggests the surface area of a lamella is dependent on its position on the gill filament, and the position of the gill filament on the gill arch.     

波纹唇鱼鳃丝的光镜、扫描和透射电镜观察

应用光学显微镜、扫描电镜和透射电镜对波纹唇鱼(Cheilinus undulatus)鳃的组织结构、表面形态特征及鳃小片超微结构进行了观察.结果表明,波纹唇鱼有3对全鳃,1对半鳃和1对伪鳃,鳃丝呈梳状紧密排列在鳃弓上,鳃小片紧密地镶嵌排列在鳃丝两侧,入鳃动脉、出鳃动脉和鳃小片毛细血管网组成鳃的血液系统.鳃丝非呼吸区分布...     

Vascular organization of the head and respiratory organs of the air-breathing catfish,Heteropneustes fossilis

Light and scanning electron microscopy of vascular replicas from the facultative air-breathing fish Heteropneustes fossilis show modifications in the macrocirculation of the respiratory organs and systemic circulation, whereas, gill microcirculation is similar to that found in typical water-breathing fish. Three and sometimes four ventral aortae arise directly from the bulbus. The most ventral vessel supplies the first pair of arches. Dorsal to this another aorta supplies the second gill arches, and a third, dorsal to, and larger than the other two, supplies the third and fourth arches and the air sacs. Occasionally a small vessel that may be the remnant of a primitive aortic arch arises from the first ventral aorta and proceeds directly to the mandibular region without perfusing gill tissue. The air sac is perfused by a large-diameter extension of the afferent branchial artery of the fourth gill arch and its circulation is in parallel with the gill arches. Blood drains from the air sac into the fourth arch epibranchial artery. A number of arteries also provide direct communication between the efferent air sac artery and the dorsal aorta. All four gill arches are well developed and contain respiratory (lamellar) and nonrespiratory (interlamellar and nutrient) networks common to gills of water-breathing fish. Air sac lamellae are reduced in size. The outer 30% of the air sac lamellar sinusoids are organized into thoroughfare channels; the remaining vasculature, normally embedded in the air sac parenchyma, is discontinuous. A gill-type interlamellar vasculature is lacking in the air sac circulation. Despite the elaborate development of the ventral aortae, there is little other anatomical evidence to suggest that gill and air sac outflow are separated and that dorsal aortic oxygen tensions are maintained when the gills are in a hypoxic environment. Physiological adjustments to hypoxic water conditions probably include temporal regulation of gill and air sac perfusion to be effective, if indeed they are so.     

Gill structure and morphometry of its respiratory components in the Baikalian golomyankas (Comephoridae; Cottoidei; Pisces)

All four pairs of gill arches in Comephorus baicalensis and C. dybowskii (Comephoridae) are well developed. In contrast to other Baikalian cottoids (Cottidae, Abyssocottidae), the slit behind the fourth arch is well preserved and two hemibranchs are present on this arch in the golomyankas. These anatomical details are considered to contradict the opinion that Comephoridae may be derived from other Baikalian Cottoidei. The arches in golomyankas are elongated and equipped with very strong spinous gill-rakers. The external sides of the upper and lower jaws are covered with numerous spinelike denticles, the apices of which are bent toward the mouth cavity. The denticles and the spinous gill-rakers are considered to be a specific adaptation in sluggish golomyankas for precise grasping of zooplankton of different sizes, as well as fish larvae. Respiratory components of the gill apparatus in the golomyankas are reduced considerably because of short gill filaments and the sparce distribution of small respiratory lamella on them. The allometry for the relationships between gill respiratory surface area (GRSA) and body mass (Y = aW^b) in both golomyankas is biphasic: in juvenile immature C. baicalensis Yj = 199.013 W^1.057 and in mature animals Ym = 322.354 W^0.731. In C. dybowskii the values for immature and mature animals are Yj = 95.736 W^1.190 and Ym = 199.609W^0.707, respectively. In the sluggish bathypelagic golomyankas (Comephorus) the GRSA per body weight unit is 5–6 times smaller than that found in more active secondarily pelagic Baikalian sculpins (Cottocomephorus) examined previously. © 1996 Wiley-Liss, Inc.     

Morphometry of gill respiratory area in the Baikalian deep-water sculpins Abyssocottus korotneffi and Cottinella boulengeri (Abyssocottidae,Cottoidei)

Abyssocottus korotneffi and Cottinella boulengeri are the deepest-living bottom species among freshwater teleosts. Both species have gill arches with nodulous gill-rakers equipped with sharp denticles. The gill-slit behind the fourth arch is reduced considerably and the hemibranch corresponding to this slit is absent, though some miniature structures resembling reduced filaments were occasionally observed there. The respiratory components of the gill apparatus in both species considered are much reduced, especially in A. korotneffi, because of the moderate number of relatively short gill filaments and the small number of respiratory lamella on them. The allometric relationship between the gill respiratory surface area (GRSA) and body mass (Y = aW^b) is expressed by Y = 328.55 W^0.724 for A. korotneffi (7–22 g) and by Y = 333.15 W^0.902 for C. boulengeri (3–24 g). In adult A. korotneffi, the GRSA index calculated per body weight unit is about 35% lower than that in C. boulengeri, but is 70% higher compared with the bathypelagic golomyanka Comephorus dybowskii previously examined. The data seem to correspond with the difference in biological activity of these species. J. Morphol. 233:105–112, 1997. © 1997 Wiley-Liss, Inc.     

Gross morphology and surface ultrastructure of the gills of Odontesthes argentinensis (Actinopterygii, Atherinopsidae) from a Southwestern Atlantic coastal lagoon

Odontesthes argentinensis was collected from Mar Chiquita Coastal Lagoon, the Southernmost coastal Atlantic Lagoon of Argentina. The morphology of the gills was analyzed by scanning electron microscopy. The morphology of the superficial structures of the gill filaments and pharyngeal region of the gill arch was discussed and related to their functional aspects. The gills arches are structurally similar to those of other teleosts and bring out the osmoregulatory capacity of this species. The epithelium that covers the surface of the filaments and the pharyngeal region of the gill arch is formed by polygonal pavement cells with conspicuous microridges. These folds in the membrane are not denoted in the epithelium of the respiratory lamellae. Apical crypts of chloride cells are present on the afferent and interlamellar filament surfaces, but are absent elsewhere on the gill arch. The highest density of mucous cells is observed into the gill filament and the pharyngeal region which indicates the existence of a protective strategy of the respiratory lamellae and the pharynx. The epithelium of the gill arches and the rakers is studded with spines. There are taste buds along the whole pharyngeal region that may be associated with their participation in tasting at this zone.     

Scanning electron microscopy of the gills of a freshwater catfish,Rita Rita

Variations in the gross morphology and surface architecture of the gill filaments and secondary lamellae of a freshwater catfish (Rita rita) have been investigated using scanning electron microscopy. Heterogeneity of the gill has been correlated with the distribution of lamellar water-flow at different regions of a gill filament. Higher lamellar water flow (cc/pore/cmH₂O/sec) was estimated for the middle region of the filaments. The filaments are covered with epithelial cells whose surface is provided with well-developed microridges. The lamellae are generally covered with microvillous epithelial cells. The variations in surface architecture of the gill filaments and secondary lamellae have been correlated with their probable functions.     

Quantitative histopathology of Oreochromis niloticus gills after copper exposure

In order to test whether histopathological changes of gills demonstrated a good dose–response relationship with water copper levels, juvenile Nile tilapia Oreochromis niloticus, of both sexes and similar mass (36·3 + 7·7 g), were kept in dechlorinated tap water (temperature 25° C, range ±1° C; pH 6·5–7·5; hardness 74·5 mg l^?1 CaCO₃) and exposed to 40 and 400 μg l^?1 of copper. Gill samples were collected after 3, 7, 14 and 21 days. Six major histopathological changes (oedema, lifting, changes in filament epithelium thickness, lamellar fusion, vasodilatation and aneurisms) and three minor ones (proliferation of the lamellar epithelium, necrosis and adjacent lamellar fusion) were found and their prevalence estimated. The extent and severity of each histopathological change were used to develop a severity gradation scale (SGS). Semi‐quantitative analysis of the histopathological changes and measurements of gill copper deposition levels revealed a good dose– and time–response relationship. Oedemas and aneurisms were significantly correlated with acute exposure periods and lamellar fusion with chronic exposure. Epithelial lifting and changes in filament epithelial thickness were seen at lower and higher metal concentrations, respectively. The data also revealed that the SGS profile of each lesion was dependent of gill copper burden.     

The biometry of gills of 0-group European flounder

The gill surface area of 0-group, post-metamorphic Pleuronectes flesus L. was examined using digital image analysis software and expressed in relation to body mass according to the equation log Y=loga+c logW ( a =239·02; c =0·723). The components that constitute gill area, total filament length, interlamellar space and unilateral lamellar area were measured. The measurement of the length of every filament on all eight arches showed that commonly used methods of calculation can lead to an under-estimation of up to 24% of total filament length. Direct measurements of unilateral lamellar area with digital image analysis showed that previously reported gill area data for the same species was over-estimated by as much as 58%. In addition, in this species the neglect of gill pouch asymmetry after metamorphosis, can bring about a 14% over-estimation of total gill area.     

Sublethal effects of endosulfan on the histology and protein pattern of Cyprinus carpio gill

Histological and protein pattern changes in the gill of the common carp, Cyprinus carpio were investigated following exposure to sublethal concentrations of the organochlorine insecticide, endosulfan. Hyperplasia, lamellar fusion, curling of the tips of primary lamellae, exudation of erythrocytes and bulging of the tips of primary lamellae were the histological lesions observed. Protein pattern of the gill varied at different sampling periods characterised by disappearance of certain fractions and occurrence of additional fractions. It was concluded that the severity of histological changes and protein pattern variations seen in the gill was dependent on both the duration of exposure and the concentrations of endosulfan used (over the range 5—25 % of the 96 hr LC₅₀ value, 5·199ppb).     

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 morphology of the gills of the shortfin mako,Isurus oxyrinchus,a lamnid shark

This study examines the functional gill morphology of the shortfin mako, Isurus oxyrinchus, to determine the extent to which its gill structure is convergent with that of tunas for specializations required to increase gas exchange and withstand the forceful branchial flow induced by ram ventilation. Mako gill structure is also compared to that of the blue shark, Prionace glauca, an epipelagic species with lower metabolic requirements and a reduced dependence on fast, continuous swimming to ventilate the gills. The gill surface area of the mako is about one‐half that of a comparably sized tuna, but more than twice that of the blue shark and other nonlamnid shark species. Mako gills are also distinguished from those of other sharks by shorter diffusion distances and a more fully developed diagonal blood‐flow pattern through the gill lamellae, which is similar to that found in tunas. Although the mako lacks the filament and lamellar fusions of tunas and other ram‐ventilating teleosts, its gill filaments are stiffened by the elasmobranch interbranchial septum, and the lamellae appear to be stabilized by one to two vascular sacs that protrude from the lamellar surface and abut sacs of adjacent lamellae. Vasoactive agents and changes in vascular pressure potentially influence sac size, consequently effecting lamellar rigidity and both the volume and speed of water through the interlamellar channels. However, vascular sacs also occur in the blue shark, and no other structural elements of the mako gill appear specialized for ram ventilation. Rather, the basic elasmobranch gill design and pattern of branchial circulation are both conserved. Despite specializations that increase mako gill area and efficacy relative to other sharks, the basic features of the elasmobranch gill design appear to have limited selection for a larger gill surface area, and this may ultimately constrain mako aerobic performance in comparison to tunas. J. Morphol. 271:937–948, 2010. © 2010 Wiley‐Liss, Inc.     

Structural organization of the gills in pipefish (Teleostei,Syngnathidae)

Summary The morphology and structural features of the gills of the two Western Baltic pipefish Nerophis ophidion and Syngnathus rostellatus were investigated using scanning electron microscopy. The general anatomy of the gills complies with the general pattern in fish. Several adaptations though, show the highly specialized nature of pipefish gills. The filaments are extremely short, few in number and carry only a few lamellae due to the limited space in the branchial cavity. The lamellae have a widely projecting form yet still have a small area in comparison to other fish. Gill irrigation is performed by a specialized pumping mechanism which forces respiratory water through the small but densely packed gill sieve. Although both species live in the same habitat and belong to the same family, differences in gill morphology were found and are related to different lifestyles. S. rostellatus is the more active species and therefore has more filaments per gill arch, more lamellae per filament, wider projecting lamellae and a more extreme utilisation of available space in the gill cavity through a very densely packed gill sieve. N. ophidion has a stationary mode of life and therefore has a less extreme gill anatomy.     

Surface ultrastructure of the gill arch of the killifish, Fundulus heteroclitus, from seawater and freshwater, with special reference to the morphology of apical crypts of chloride cells

The surface ultrastructure of the gill arches of the killifish, Fundulus heteroclitus, adapted to seawater or freshwater, was found to be similar to that reported for other euryhaline teleosts. Two rows of gill filaments (about 42 filaments per row) extended posterolaterally, and two rows of gill rakers (about 10 rakers per row) extended anteromedially from each arch. Leaf-like respiratory lamellae protruded along both sides of each filament, from its base to its apex. The distributions, sizes, and numbers of various surface cells and structures were also determined. All surfaces were covered by a mosaic of pavement cells, which measured about 7 X 4 microns and exhibited concentrically arranged surface ridges. Taste buds were especially prominent on the rakers and the pharyngeal surfaces of the first and second gill arches, but were often replaced by horny spines on the third and fourth gill arches. Apical crypts of chloride cells occurred mostly on the surfaces of the gill filaments adjacent to the afferent artery of the filament. In seawater adapted killifish, crypts resembled narrow, deep holes along the borders of adjacent pavement cells, had openings of about 2 microns2, and occurred at a frequency of about 1 per 70 microns2 of surface area. In freshwater fish, the crypts usually had larger openings (about 10 microns2), occurred less frequently (1 per 123 microns2), and exhibited many cellular projections in their interiors. Changes in crypt morphology may be related to the ion transport function of chloride cells.     

Gill remodelling during terrestrial acclimation in the amphibious fish Polypterus senegalus

Fishes are effectively weightless in water due to the buoyant support of the environment, but amphibious fishes must cope with increased effective weight when on land. Delicate structures such as gills are especially vulnerable to collapse and loss of surface area out of water. We tested the ‘structural support’ hypothesis that amphibious Polypterus senegalus solve this problem using phenotypically plastic changes that provide mechanical support and increase stiffness at the level of the gill lamellae, the filaments, and the whole arches. After 7 d in terrestrial conditions, enlargement of an inter-lamellar cell mass filled the water channels between gill lamellae, possibly to provide structural support and/or reduce evaporative water loss. Similar gill remodelling has been described in several other actinopterygian fishes, suggesting this may be an ancestral trait. There was no change in the mechanical properties or collagen composition of filaments or arches after 7 days out of water, but 8 months of terrestrial acclimation caused a reduction in gill arch length and mineralized bone volume. Thus, rather than increasing the size and stiffness of the gill skeleton, P. senegalus may instead reduce investment in supportive gill tissue while on land. These results are strikingly similar to the evolutionary trend of gill loss that occurred during the tetrapod invasion of land, raising the possibility that genetic assimilation of gill plasticity was an underlying mechanism.     

The linear cable theory as a model of gill blood flow

The vascular organization of the teleost gill suggests that blood flow distribution from the filamental artery to the respiratory lamellae is governed by relationships analogous to the cable conduction properties of a nerve axon. The space constant (λ) by definition is the distance along the gill filament at which the in-series resistance of the afferent filament artery equals the in-parallel resistance of the afferent lamellar arteriolar, lamellar, efferent lamellar arteriolar (ALA-L-ELA) segments. Constriction of the afferent filamental artery or uniform dilation of the ALA-L-ELA will decrease λ. As λ decreases, flow through the proximal (basal) lamellae greatly increases at the expense of distal lamellar perfusion. When λ increases in a system of finite length the flow profile must account for reflected pressures within the main vessel. The λ calculated from corrosion casts of gill vasculature is $\text{1}\text{4}$ to $\text{1}\text{2}$ the filament length. This favors blood flow through the proximal lamellae and when cardiac output increases, the proportion of cardiac output perfusing the proximal areas increases at the expense of distal lamellar blood flow. To offset these changes it is proposed that increased distal lamellar perfusion is achieved by simultaneous vasodilatation of distal and constriction of proximal ALA-L-ELA segments and dilation of the afferent filamental artery.     

Gills of the medaka (Oryzias latipes): A scanning electron microscopy study

The general morphology and surface ultrastructure of the gills of adult and larvae medaka (Oryzias latipes) were studied in freshwater and seawater using scanning electron microscopy. The gills of all examined fish were structurally similar to those of other teleosts and consisted of four pairs of arches supporting (i) filaments bearing lamellae and (ii) rakers containing taste buds. Three cell types, specifically pavement cells, mitochondria‐rich cells (MRCs), and mucous cells, constituted the surface layer of the gill epithelium. Several distinctive characteristics of medaka gills were noted, including the presence of regularly distributed outgrowth on the lamellae, enlarged filament tips, the absence of microridges in most pavement cells in the filament and lamellae and the presence of MRCs in the arch at the filament base. A rapid mode of development was recorded in the gills of larval fish. At hatching, the larvae already had four arches with rudimentary filaments, rakers, and taste buds. The rudimentary lamellae appeared within 2 days after hatching. These results suggest the early involvement of larval gills in respiratory and osmoregulation activities. The responses of the macrostructures and microstructures of gills to seawater acclimation were similar in larvae and adult fish and included modification of the apical surface of MRCs, confirming the importance of these cells in osmoregulation. The potential roles of these peculiarities of the macrostructures and microstructures of medaka gills in the major functions of this organ, such as respiration and osmoregulation, are discussed.     

Morphology and vascular anatomy of the gills of a primitive air-breathing fish,the bowfin (Amia calva)

Summary The morphology of the gills of a primitive air breather (Amia calva) was examined by light microscopy of semithin sections of gill filaments, and gill perfusion pathways were identified by scanning-electron microscopic analysis of corrosion replicas prepared by intravascular injection of methyl methacrylate. The arrangement of gill filaments and respiratory lamellae is similar to that of teleosts with the exception of an interfilamental support bar that is fused to the outer margins of lamellae on adjacent filaments. The prebranchial vasculature is also similar to that of teleosts, whereas the postbranchial circulation of arches III and IV is modified to permit selective perfusion of the air bladder. Gill filaments contain three distinct vascular systems: (1) the respiratory circulation which receives the entire cardiac output and perfuses the secondary lamellae; (2) a nutrient system that arises from the postlamellar circulation and perfuses filamental tissues; (3) a network of unknown function consisting of subepithelial sinusoids surrounding afferent and efferent margins of the filament and traversing the filament beneath the interlamellar epithelium. Prelamellar arteriovenous anastomoses (AVAs) are rare, postlamellar AVAs are common especially at the base of the filament where they form a dense network of small tortuous vessels before coalescing into a large filamental nutrient artery. Unlike in most teleosts, the outer vascular margins of the lamellae are embedded in the interfilamental support bar and become the sole vasculature of this tissue. Arterial-arterial lamellar bypass vessels were not observed. Previously observed decreases in oxygen transfer across the gills during air breathing can be explained only by redistribution of blood flow between or within the respiratory lamellae.Supported by NSF Grant No. PCM 79-23073The author wishes to thank Miss K. Drajus and D. Kullman for their excellent technical assistance and Dr. W. Gingerich, Mr. J. Crowther and D. Zurn for help in obtaining bowfin