mitochondria and responsible for the secretion of sodium
chloride from the blood, they are prominent in fish living
in the marine environment and characteristic during
smoltification, but their number may also increase in several
pathological conditions. Other cells within the filament
interstitium include lymphocytes, eosinophilic granular
cells (EGCs) (see Fig. 4.15), macrophages, neuroepithelial
cells and rodlet cells. Granular and neuroepithelial cells
are obvious at the base of the lamella and more frequent
in marine than in freshwater fish. Intraepithelial lymphocytic
cell accumulations can be seen at the caudal edge of
interbranchial septum in Atlantic salmon, and shown to be a
lymphoid tissue and probably of significance for surveillance
of gill infections (Fig. 2.5).
Blood flow in the lamella capillaries is opposite to the
ventilatory water flow (‘counter current’) ensuring effective
gas exchange between blood and water across the respiratory
epithelium. Venous blood from the ventral aorta diverges to the
afferent arterioles and capillaries of the lamellae where gas
exchange takes place and becomes arterial blood. Arterial
blood is drained through the efferent branchial artery and into
the dorsal aorta. The water flow over the lamellae is continuous
and achieved by means of the buccal-opercular pump.
Dorsally, on the inner surface of each operculum is the
pseudobranch, a rudimentary first gill arch (Figs. 2.6 and 2.7).
The pseudobranchial cells are in close proximity to a network
of blood vessels and may play a role in the blood supply to the
retina and in osmoregulation and sensing.
Fig. 2.2 (a) Gills of an adult wild Atlantic salmon, left operculum is removed. The complete gill arch with its gill rakers can be seen.
(b) Transversal section of one holobranch showing the hemibranchs with the vertical rows of gill filaments
Fig. 2.3 Gill filament, central cartilage and lamellae from adult Atlantic salmon. Chloride cells are located near the base of the lamellae
Fig. 2.4 Goblet (mucous) cells on lamellae of farmed adult Atlantic
salmon
2.1 Respiratory System (including the operculum and pseudobranch)
7
chloride from the blood, they are prominent in fish living
in the marine environment and characteristic during
smoltification, but their number may also increase in several
pathological conditions. Other cells within the filament
interstitium include lymphocytes, eosinophilic granular
cells (EGCs) (see Fig. 4.15), macrophages, neuroepithelial
cells and rodlet cells. Granular and neuroepithelial cells
are obvious at the base of the lamella and more frequent
in marine than in freshwater fish. Intraepithelial lymphocytic
cell accumulations can be seen at the caudal edge of
interbranchial septum in Atlantic salmon, and shown to be a
lymphoid tissue and probably of significance for surveillance
of gill infections (Fig. 2.5).
Blood flow in the lamella capillaries is opposite to the
ventilatory water flow (‘counter current’) ensuring effective
gas exchange between blood and water across the respiratory
epithelium. Venous blood from the ventral aorta diverges to the
afferent arterioles and capillaries of the lamellae where gas
exchange takes place and becomes arterial blood. Arterial
blood is drained through the efferent branchial artery and into
the dorsal aorta. The water flow over the lamellae is continuous
and achieved by means of the buccal-opercular pump.
Dorsally, on the inner surface of each operculum is the
pseudobranch, a rudimentary first gill arch (Figs. 2.6 and 2.7).
The pseudobranchial cells are in close proximity to a network
of blood vessels and may play a role in the blood supply to the
retina and in osmoregulation and sensing.
Fig. 2.2 (a) Gills of an adult wild Atlantic salmon, left operculum is removed. The complete gill arch with its gill rakers can be seen.
(b) Transversal section of one holobranch showing the hemibranchs with the vertical rows of gill filaments
Fig. 2.3 Gill filament, central cartilage and lamellae from adult Atlantic salmon. Chloride cells are located near the base of the lamellae
Fig. 2.4 Goblet (mucous) cells on lamellae of farmed adult Atlantic
salmon
2.1 Respiratory System (including the operculum and pseudobranch)
7