Livial: an economic appraisal.
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Anabolic Agents↗
Biomedical subjects
C J Phillips
Publications and source records attributed to C J Phillips.
Effect of hoof characteristics on the propensity of cattle to slip.
Bovine hooves were assessed for their linear and volumetric characteristics and ranked in sets of four for hoof volume. An artificial cow was constructed with the hooves set into metal cylinders underneath a platform containing a known weight. The device was connected via a strain gauge to a pulling handle operated by two people, and the horizontal force required to move each set of hooves was determined three times. The coefficient of friction, calculated as the horizontal force divided by the fixed vertical force, was positively correlated with hoof volume. The same exercise was repeated with the hooves ranked for toe angle, and the hooves with steep toe angles had a lower coefficient of friction than the hooves with shallow toe angles. However, since both hoof volume and toe angle were related to toe length, the relationship between friction and toe angle was believed to derive from the larger size of claws with shallow toe angles. The results indicate that young cattle that have small claws with smooth surfaces and steep toe angles are more likely to slip.
Accidental Falls↗
Ultrastructure of the binary parotid glands in the free-tailed bat, Tadarida thersites. I. Principal parotid gland.
BACKGROUND: Many species of bats have two sets of submandibular glands, principal and accessory. The accessory gland may resemble the principal one but more often shows wide morphological divergence. The free-tailed bat, Tadarida thersites, is very unusual in that it has two sets of parotid glands rather than binary submandibular glands. We studied the ultrastructure of the principal parotid gland to establish a baseline for comparison with the accessory parotid. METHODS: Two specimens of adult free-tailed bats, one male and one female, were live-trapped in western Kenya. Parotid glands were fixed for electron microscopy using a protocol expressly designed for field fixation and then embedded by conventional means. RESULTS: Histologically, the principal parotid is a typical serous gland. The secretory granules of the endpiece cells have an unusual substructure in that they contain variable numbers of lucent halos and one or several spherules. Intercalated duct cells contain a significant number of dense, serous-like granules. Striated ducts have the usual basal configuration of mitochondria and folded plasma membranes, but the supranuclear cytoplasm contains many small, dense granules, so that these ducts resemble the granular convoluted tubules found in the submandibular glands of many families of rodents. The apices of the duct cells have a peculiar contour--the luminal surfaces obliquely invaginate into the apical cytoplasm, so that in thin section the luminal membranes appear to be underlaid by a layer of vacuoles. CONCLUSION: Although the principal parotid gland of the free-tailed bat shows some distinctive, species-specific ultrastructural features, it basically is similar to the parotid gland in two other molossid bats, Tadarida brasiliensis and Molossus molossus. The distinctive features in the principal parotid gland of T. thersites might relate to its feeding on hard-bodied insects and perhaps to the production of lysozyme.
Animals↗
Ultrastructure of the binary parotid glands in the free-tailed bat, Tadarida thersites. II. Accessory parotid gland.
BACKGROUND: Many bat species have an extra set of major salivary glands. In some species, the accessory glands are quite similar to the principal one, but in others they may be radically different. Accessory glands usually are associated with the submandibular gland, but the free-tailed bat, Tadarida thersites, also has an accessory parotid gland. In the present study, we compared the accessory parotid gland with its principal counterpart. METHODS: Salivary glands were removed from two specimens of free-tailed bats, one of each sex, that had been live-trapped in western Kenya and immersion-fixed in a specially formulated mixture designed for field fixation. Once back in the laboratory, the tissue was further prepared for electron microscopy by conventional means. RESULTS: The secretory endpieces consist of serous tubules composed of typical serous cells that contain numerous dense granules. In contrast, the intralobular duct system shows a radical departure from normal. These ducts are enormous in caliber, their lumina measuring greater than 100 microm in diameter. They appear to arise by amalgamation of the homologues of intercalated and striated ducts into macroducts. The walls of the macroducts consist of intermingled patches of simple cuboidal and simple columnar epithelia that occasionally include a tuft cell and are underlaid by an almost continuous layer of myoepithelium. A few cells have some modified basal striations, but most cells display a cytological organization that differs radically from either of their two putative ancestral cell types. Both tall and short epithelial macroduct cells have a paranuclear collection of ovate mitochondria and aggregates of what presumably are peroxisomes. Macroduct cells in both the female and male are pervaded by a system of tubular smooth endoplasmic reticulum (SER). In the female, the SER gives rise to membranous whorls that consist of numerous plies. As the macroducts approach their termini, a single row of small dense secretory granules appears just beneath their luminal surface. At the lobular periphery, the ducts taper down to become excretory ducts of normal dimensions. CONCLUSIONS: An accessory parotid gland occurs in T. thersites, but apparently is absent in the related species, T. brasiliensis. The ultrastructural data are consistent with a possible steroidogenic function, although other features of the gland might relate to the elaboration of a secretory product associated with feeding on chitinous beetles. The macroducts conceivably function as reservoirs of preformed saliva.
Animals↗
Intercellular material in the basal and lateral folds of parotid serous cells in four species of bats.
BACKGROUND: Basal folds are slender plications at the basal surface of acinar cells in the salivary glands of many mammalian species. These largely organelle-free folds increase the surface area of the basal plasmalemma manyfold and are unquestionably involved in the translocation of organic and inorganic molecules and water into the acinar cells. METHODS: Specimens of salivary glands were obtained from over 230 species of live-trapped bats from major areas of the globe. Tissues for electron microscopy were fixed and processed by conventional means. RESULTS: A number of the bat species examined had dense material in the intercellular spaces between basal and lateral folds of serous cells in the parotid gland. This intercellular material was particularly prominent in three species of New World bats, viz., Pteronotus parnellii, P quadridens, and Phyllostomus latifolius, and in one species of Old World bats, Chalinolobus argentatus. This dense material, which has a farinaceous texture, appears not to pass through tight junctions, so it is excluded from the lumina of intercellular canaliculi and acini. The dense material originates in the acinar cells--it is carried to the membranes of the folds via coated vesicles, which empty their dense content by exocytosis into the intercellular space. Similar dense material is present in the intercellular spaces of the basal labyrinth of striated ducts in the two species of Pteronotus. The manner in which this material accumulates in the striated duct is unclear. CONCLUSIONS: Although the function of the intracellular dense material is undetermined, it appears to be placed strategically to influence molecular traffic into acinar cells or to modulate the paracellular pathway. From a comparative evolutionary perspective, we hypothesize that, in bats, the combination of basal folds and extracellular densities is associated with insectivory. Similar morphologies appear to be lacking in frugivorous or nectarivorous species.
Animals↗
Comparative ultrastructure of intercalated ducts in major salivary glands: a review.
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Animals↗
An unusual parotid gland in the tent-building bat, Uroderma bilobatum: possible correlation of interspecific ultrastructural differences with differences in salivary pH and buffering capacity.
The tent-building bat, Uroderma bilobatum, is a small, frugivorous phyllostomid bat with a broad neotropical distribution. Generally found in humid forest, this bat lives in small groups that create daytime "roosts" from large leaves of a variety of tropical plants. Fruit eating engenders a variety of ecological and physiological challenges for bats, some of which could require adaptive features in their salivary glands. The parotid salivary glands of Uroderma bilobatum were prepared for transmission electron microscopy by using methods that have become standard for field work. The parotid gland is extremely unusual in structure. Although the secretory endpieces still produce serous granules with a complex substructure, they are modified into quasi striated ducts. Their basal folds, which are extensive, occasionally harbor some vertically oriented mitochondria, imparting a resemblance to striated ducts. Other evidence for the endpiece origin of these parenchymal components is a well-developed system of intercellular canaliculi, structures that never occur in bona fide striated ducts. The long but sparse intercalated ducts consist of two types of cells, each of which elaborates a modest number of secretory granules of differing substructure. Striated ducts are of conventional morphology, except that a few dark cells shaped like wine glasses are present in their walls. The striated duct cells produce no secretory granules, but their apical cytoplasm may contain some small, empty vesicles. Capillaries lie in longitudinal grooves in the base of the duct cells, an arrangement that might enhance electrolyte exchange. Excretory ducts consist of simple cuboidal epithelium composed of cytologically unspecialized cells that sometimes includes a dark cell. It was concluded that salivary glands could have a major role in adapting species to acquire nutrients from marginal sources, such as tropical fruits, which have a low protein and sodium content. The unusual parotid acinar cells in Uroderma bilobatum are discussed in the context of salivary pH and buffering capacity. Comparisons are made with four other bat species, including an insectivorous species with a salivary pH > 8.0 and a very high buffering capacity, an intermediate species, and a fruit bat with acidic-stimulated saliva and very low buffering capability. Such interspecific comparisons provide a foundation for hypothesizing that ultrastructural features of the acinar cell basolateral membranes and intercellular canaliculi correlate with differences involving Na/H+ exchangers and release of HCO3- and, thus, are associated with the species differences that are important to diet and nutrient acquisition.
Animals↗
Complete mitochondrial genome of a neotropical fruit bat, Artibeus jamaicensis, and a new hypothesis of the relationships of bats to other eutherian mammals.
The complete mitochondrial genome was obtained from a microchiropteran bat, Artibeus jamaicensis. The presumptive amino acid sequence for the protein-coding genes was compared with predicted amino acid sequences from several representatives of other mammalian orders. Data were analyzed using maximum parsimony, maximum likelihood, and neighbor joining. All analyses placed bats as the sister group of carnivores, perissodactyls, artiodactyls, and cetaceans (e.g., 100% bootstrap value with both maximum parsimony and neighbor joining). The data strongly support a new hypothesis about the origin of bats, specifically a bat/ferungulate grouping. None of the analyses supported the superorder Archonta (bats, flying lemurs, primates, and tree shrews). Our hypothesis regarding the relationship of bats to other eutherian mammals is concordant with previous molecular studies and contrasts with hypotheses based solely on morphological criteria and an incomplete fossil record. The A. jamaicensis mitochondrial DNA control region has a complex pattern of tandem repeats that differs from previously reported chiropteran control regions.
Animals↗
Habitat islands, genetic diversity, and gene flow in a Patagonian rodent.
The effects of terrestrial habitat islands on gene flow and genetic diversity in animal populations have been predicted and discussed in theoretical terms, but empirical data are needed to test these predictions and provide an understanding of the relationships of life-history characteristics to genetics of insular species. We studied saxicolous mice (Phyllotis xanthopygus) in Patagonia to explore genetic structure, phylogeography, and gene flow in a species inhabiting natural habitat islands. Phylogeographic analyses based on mtDNA sequences revealed two haplotype clades, which presumably reflect early Pleistocene factors that temporarily separated the mice into two geographically isolated groups. The Río Chubut, which lies within a glacial drainage basin bisecting northern Patagonia, might have affected gene flow in the species. Although we anticipated isolation by distance and founder phenomena associated with habitat islands, in some habitat patches we found evidence of high local genetic diversity. The amount of divergence in the mitochondrial cytochrome b gene (approximately 3.4%) in animals at a single locality could best be explained through a combination of historical factors and metapopulation source-sink theory. Demographic shifts, dispersal, and episodic recolonization are important in the life history and genetic population structure of P. xanthopygus.
Animals↗
Cytomegalovirus infection in the submandibular and parotid salivary glands of an African grass mouse (Arvicanthus dembeensis).
The submandibular and parotid glands of one of five specimens of African grass mice (Arvicanthus dembeensis) were found to be infected with cytomegaloviruses, producing a profound cytomegaly in certain cells at the juncture of secretory endpieces and intercalated ducts. These cytomegalic cells tended to have multiple nuclei, many of which contained a characteristic reticular inclusion. The viruses appeared to arise in association with the intranuclear inclusions, then passed through the nuclear envelope to the cytoplasm where they budded into Golgi saccules or into small vacuoles, presumably of Golgi origin. Fusion of small virus-carrying vacuoles led to the formation of large vacuoles containing a plethora of viruses. Viruses were liberated into gland lumina via fusion of the vacuoles with the luminal plasmalemma. Fusion of vacuoles with dehiscent ones resulted in a form of chain exocytosis. The development of cytomegaloviruses in salivary glands may differ in details in a species-specific manner.
Animals↗
Plasticity and patterns of evolution in mammalian salivary glands: comparative immunohistochemistry of lysozyme in bats.
Salivary gland plasticity was a significant adaptive feature in the mammalian radiation. This plasticity is reflected in remarkable and well-documented interspecific phenotypic variation in gland ultrastructure and in the chemical components of saliva. However, comparative data are still too sparse for determination of evolutionary trends that combine phenotypic patterns with evolutionary history and the actual secretory products. Although our theoretical approach assumes that natural selection has taken advantage of salivary gland plasticity in gene regulation, gland development, and secretory cell organelles and processes, it still is difficult to delineate the biological roles of secretory products in the context of ecological adaptation. In the present investigation we used immunohistochemical techniques and a polyclonal antiserum against lysozyme to compare the parotid and principal submandibular glands in a set of 12 species of microchiropteran bats. With this data set we used comparative methods and phylogenetic trees to develop the foundations for testable hypotheses about the molecular genetics and adaptive significance of lysozyme production in bats. By comparing immunohistochemical results with ultrastructure, lysozyme-like immunoreactivity was associated with serous secretory granules in parotid gland acinar calls, parotid gland intercalated duct cells, and submandibular gland demilune cells. Lysozyme production in submandibular gland demilune cells marks a point of evolutionary divergence between three families of insectivorous bats and four families composed of species with diverse diets (ranging from carnivory to nectarivory). In terms of diet, lysozyme-like immunoreactivity corresponded most strongly with feeding on hard-bodied insects, leading to the hypothesis that lysozyme serves as an important chitinase in bat saliva.
Adaptation, Physiological↗
Ultrastructure of major intraglandular ducts in the parotid gland of the African mole-rat.
The parotid gland of a female African mole-rat, Tachyoryctes splendens, was examined by light and electron microscopy. A pure seromucous gland of conventional histology, its striated and excretory ducts contain prominent cytoplasmic inclusions that are lightly stained with toluidine blue. At the ultrastructural level, the inclusions are seen to consist of a light to moderately dense structureless matrix in which are suspended scattered, randomly oriented filaments that either are 4-7 nm or approx 14 nm thick. A few multivesicular bodies or putative lipid droplets are sparsely distributed in the inclusions. Even though the inclusions lack an encompassing membrane, all other formed cytoplasmic structures are excluded. These inclusions are not present in the ducts of the submandibular gland of the mole-rat. The inclusions may confer special properties on the parotid gland of this fossorial animal that permit it to cope with the exigencies of a subterranean existence.
Africa↗
Megamitochondria in the serous acinar cells of the submandibular gland of the neotropical fruit bat, Artibeus obscurus.
BACKGROUND: As part of a continuing investigation of the comparative ultrastructure of chiropteran salivary glands, we examined the submandibular glands of eight species of neotropical fruit bats in the genus Artibeus. We previously described secretory granules of unusual substructure in the seromucous demilunar cells of this organ in some species in this genus. In the present study, we turned our attention to the serous acinar cells in the same glands. METHODS: Specimens of eight species of Artibeus were collected in neotropical localities. Salivary glands were extirpated in the field and thin slices were fixed by immersion in triple aldehyde-DMSO or in modified half-strength Karnovsky's fixative. Tissues were further processed for electron microscopy by conventional means. RESULTS: In contrast to seromucous cells, which exhibit species-specific diversification in bats of this genus, the secretory apparatus and secretory granules in the serous acinar cells are highly conserved across all seven species. The single exception involves the mitochondria in one species. In this instance, some of the serous cell mitochondria in Artibeus obscurus are modified into megamitochondria. Such organelles usually have short, peripheral cristae; a laminar inclusion is present in the matrix compartment of every outsized organelle. Inclusions of this nature never are present in normal-size mitochondria in the serous cells. None of the megamitochondria were observed in the process of degeneration. CONCLUSIONS: The giant mitochondria in A. obscurus have a matrical structure that is radically different from that of the only other megamitochondria reported to occur in bat salivary glands. The factors that lead to variation in megamitochondrial substructure in different species, as well as the functional capacities of such giant organelles, are unknown.
Animals↗
Ultrastructure of the unusual accessory submandibular gland in the fringe-lipped bat, Trachops cirrhosus.
BACKGROUND: The phyllostomid fringe-lipped bat, Trachops cirrhosus, is sui generis (in a family of ca. 138 species) in that it subsists in part on tropical frogs. These amphibians frequently possess highly toxic integument. We examined the salivary glands of this bat to determine if these glands could be the source of protective factors that permit consumption of seemingly unsavory prey. The parotid and principal salivary glands of this bat are similar to homologous glands in other phyllostomids, but the accessory submandibular gland is unique. METHODS: The accessory submandibular glands of live-trapped T. cirrhosus were fixed and processed for transmission electron microscopy by conventional means. RESULTS: The accessory submandibular gland consists of follicles and ducts. The principal cells of the follicular walls have an abundance of rough endoplasmic reticulum (RER), free ribosomes, and extensive Golgi apparatuses. Typically, these cells have relatively few serous secretory granules. The ells contain collections of peculiar lipid droplets, and some of their mitochondria have dense crystalloids within expanded cristae. A layer of irregular, moderately dense bodies lies immediately subjacent to the luminal plasmalemma; it is not clear if these structures are endocytotic or exocytotic. Clusters of mucous cells, some of which have a single, hugely distended RER cisterna, are ensconced in the follicular walls; mucus from these cells reaches the lumen via intercellular canaliculi. Ducts progress from simple cuboidal to simple columnar epithelium. They lack basal striations, and their constituent cells contain relatively few mitochondria. Follicles and ducts have numerous myoepithelial cells at their periphery, and both are heavily innervated by hypolemmal nerve terminals. CONCLUSIONS: The unusual accessory submandibular gland in T. cirrhosus documents the extreme modifications in gland histology and in cell ultrastructure that have occurred in mammalian families. The cells composing the follicle walls and ducts bear little similarity to typical acinar or duct cells. Duplication of the submandibular gland in some bat lineages might be the key innovation underlying such plasticity. The heavy innervation of both follicles and ducts also implies that these structures are sensitive to and capable of responding to various inputs, perhaps including dietary factors.
Animals↗
Ultrastructure of the parotid salivary glands in seven species of fruit bats in the genus Artibeus.
BACKGROUND: In previous studies, we determined that the submandibular glands of five species of Neotropical fruit bats in the genus Artibeus had seromucous granules in their demilune cells with substructures that varied interspecifically in accordance with systematic relationships. Moreover, the striated ducts in these frugivores exhibited structural modifications that apparently are related to the consumption of a diet rich in potassium, but deficient in sodium. We now turn our attention to the parotid gland in a large number of species in this genus to determine if it follows the same structural pattern as does the submandibular gland. METHODS: Members of seven different species of Artibeus were live-trapped in various Neotropical locations. The parotid glands were extirpated from euthanized bats, fixed in the field, and prepared for electron microscopic examination by conventional means. The parotid glands in all seven species were virtually identical in morphology. The acinar cells (determined to be seromucous on the basis of ultrastructural criteria) contain large numbers of what appear to be vacuoles, but which are a type of secretory granule. These granules have an electron-lucent matrix and may contain one or several circular membranous profiles arranged either concentrically or in a random array. These granules appear to form by progressive dilatation of the termini of Golgi saccules, with the nascent granules finally severing their connection with the Golgi apparatus. Many of the internal membranous profiles are formed simply by invaginations of the limiting membrane of the granule; others may result from indentation of the limiting membrane by protrusions from adjacent granules; the source of multiple internal membranes in certain granules is unclear. The exocytosis of these granules results in the acinar and intercalated duct lumina being filled with an abundance of membranous material. Such extruded membranes are present in some striated ducts, but not in others, suggesting that they are degraded during passage through the duct system. The striated ducts are of conventional appearance, lacking the frondose processes that are prominent in the submandibular glands of Artibeus. CONCLUSIONS: The parotid gland in Artibeus shows none of the interspecific ultrastructural variability that characterizes the submandibular gland in bats of this genus. The seromucous acinar cells secrete granules that release phospholipids as well as glycoconjugates into the saliva. Based on the lack of frondose processes with their sodium-transporting portasomes, the striated ducts of the parotid gland are less concerned with electrolyte homeostasis than are those in the submandibular gland.
Animals↗
Ultrastructure of the salivary glands in the midtongue of the common vampire bat, Desmodus rotundus.
BACKGROUND: All examined mammals have at least two sets of lingual salivary glands: von Ebner's glands and Weber's glands. A third set, the glands of Blandin and Nuhn, is present in the tongues of some but not all mammals. Vampire bats, Desmodus rotundus, are unusual in that they possess another set of lingual glands, these being in the midtongue region. METHODS: The anterior half of the tongue was extirpated from several adult vampire bats, dissected, and tissue blocks derived from the midregions of the body of the tongue prepared for transmission electron microscopy by conventional means. RESULTS: The midlingual glands are in the form of long, tubular secretory endpieces that are succeeded by ducts of simple morphology. In general, the secretory portions consist of two cell types, which may be intermingled in the same tubule or may form tubules that consist wholly of one cell type or the other. Seromucous cells usually have one or several rough endoplasmic reticulum cisternae that are hugely distended by a homogeneously dense material. Their granules have a bizonal substructure: one or several dense bands are embedded in a lighter matrix. Mucous cells are rather typical in structure, but their secretory product is different from run-of-the-mill mucous droplets. These droplets vary in density from cell to cell. In some cells, these droplets have a relatively light matrix; in other cells, the droplet is unusually dense, consisting mainly of a dark, structureless matrix with marginal lenticular lacunae of low density in which some short, irregular filaments are scattered. A rare finding is the presence of ciliated cells intermingled with secretory endpiece cells. The cilia are of conventional morphology. Secretory tubules are succeeded by ducts that resemble intercalated ducts; the epithelium of these ducts gradually increases in height to form a kind of excretory duct, without the intervention of striated ducts. As the ducts approach the lingual surface, the epithelium changes to stratified squamous. CONCLUSIONS: Saliva produced by the midlingual glands may be an aid in the reciprocal grooming behavior of vampire bats. Based on their morphology, the excurrent ducts may not modify the initial saliva elaborated by these glands and might act simply as pipelines by which the saliva reaches the mouth.
Animals↗
A unique parotid gland in Hart's little fruit bat, Enchisthenes hartii.
BACKGROUND: Hart's little fruit bat, Enchisthenes hartii, is uncommon and, although it has been the subject of recent molecular genetic studies, is little known biologically. Because chiropteran salivary glands vary interspecifically in ways that reflect evolutionary history and ecology, we examined the parotid gland in E. hartii to ascertain the extent to which it resembles homologous glands in species to which this bat presumably is related. METHODS: The parotid glands were prepared for electron microscopic examination by conventional means. RESULTS: The parotid gland of E. hartii is structurally unique among all previously studied species of bats (> 230 species examined) and other mammals. In contrast to the same gland in other mammals, the parotid gland in E. hartii lacks secretory endpieces. In their place, there is a type of striated duct. Thus, in this species single secretory elements consist of (proceeding in the direction of salivary flow): striated duct--intercalated duct--and a conventionally located striated duct. The proximal ducts possess microvillus-lined intercellular canaliculi, whereas the walls of the distal ducts include occasional dark cells. Some small serous-like granules may be present in the intercalated duct cells. CONCLUSIONS: The function(s) and biological role of the unique parotid gland in E. hartii are unknown. Nevertheless, the presence of two sets of striated ducts provides two separate glandular components seemingly capable of electrolyte transport. This might be of adaptive significance in enabling this species to make use of tropical nutrient resources that otherwise would be unavailable. The uniqueness of its parotid glands lends support to the current hypothesis that E. hartii should be classified as a monotypic genus rather than as a species of Artibeus, whose members it resembles morphometrically.
Animals↗
Equating the perceived intensity of coloured lights to hens.
1. Previous investigations of the effects of light colour on the productivity or behaviour of chickens have not equated the intensity of the different coloured lights. 2. Ten pullets (Warren Studler 128) were used to determine the perceived intensity of two colours at opposite ends of the visible spectrum (blue, peak wavelength 415 nm and red, peak wavelength 635 nm). 3. Initially half of the birds were trained with food rewards to detect the brighter of two white lights and half the dimmer one. 4. Two discrimination tests then investigated the generalisation of this learnt ability (to distinguish white lights of different intensity) to coloured lights. They were rewarded for distinguishing the brightness of red and blue filtered lights when blue intensity was initially high and gradually reduced, and when red intensity was initially low and gradually increased. The birds identified the lights as being of equal intensity when the blue light was 3.6 times as bright as the red. 5. A second test examined the situation in reverse. A bright red light that was reduced was compared to a dim blue light that was increased in intensity. The birds were again successful and identified the lights as of equal intensity when the blue was 3.1 times as bright as the red. A final test confirmed that there was no difference in the perceived intensity of blue and red lights in the ratios 3.6 or 3.1 : 1. 6. The difference in perceived red and blue light intensities was less than predicted from the spectral sensitivity curve for chickens. It was expected that the blue light would be perceived as dimmer than the red because the red filter transmitted more light than the blue and the tungsten filament light illuminating the filter emitted more long than short wavelength light. The observed discrepancy emphasises that perceived intensity is difficult to predict from spectroscopic measurements. 7. The birds then underwent a simple visual test, to discriminate the length of two lines, equally well in red or blue filtered lights that were equiluminescent as determined previously. 8. It is concluded that coloured lights can be equated for intensity by psychophysical testing, and that there was no difference in visual acuity under equiluminescent blue and red filtered lights.
Animal Husbandry↗