David Maitland - Academia.edu (original) (raw)
Papers by David Maitland
Journal of Experimental Biology, 1992
Soldier crabs, Mictyris longicarpus Latreille, inhabit intertidal sand-flats of Eastern Australia... more Soldier crabs, Mictyris longicarpus Latreille, inhabit intertidal sand-flats of Eastern Australia. Their gill chambers are modified for both water circulation and air-breathing. Water circulates through the lower gill compartments. The upper regions of the gill chambers are air-filled and function as lungs. The deep vascular parenchyma lining the upper gill chambers, or lungs, is penetrated by a regular series of fine branching airways. Scanning electron micrographs of lung architecture are shown. Measurements relating to lung structure were made on plastic casts. Because of the lung’s design, water circulating through the lower gill compartments does not interfere with lung function. The airways are blind-ended and nonanastomosing, acting in effect as air-filled capillary tubes sealed at one end. A mathematical model and explanation show how the air trapped within this lung structure substantially reduces water penetration, despite surface tension (capillary) processes. This same l...
Journal of the Marine Biological Association of the UK, 2001
The gastropod Littorina littorea shows increased mortality in the summer months when infected wit... more The gastropod Littorina littorea shows increased mortality in the summer months when infected with digenean parasites. One possible cause of this mortality is impaired respiration in infected hosts. Respiration rates of L. littorea infected with three species of digenea of varying pathogenicity were measured: Cryptocotyle lingua, Himasthla elongata and Renicola roscovita. No evidence of altered respiration rates in infected snails was found.
Comparative Biochemistry and Physiology Part A: Physiology, 1990
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1994
Direct manipulation of host behaviour by endoparasites is well known among animal eukaryotic para... more Direct manipulation of host behaviour by endoparasites is well known among animal eukaryotic parasitic taxa like nematodes, trematodes and acanthocephalans, but is poorly documented amongst other taxa like fungi. The insect-parasitic fungal complex Entomophthora muscae is a pathogen of adult Diptera. During the summer months in Europe and America, large numbers of housefly Musca domestica and yellow dungfly Scatophaga stercoraria succumb to the fungus. It has previously been demonstrated in house flies that Entomophthora muscae indirectly manipulates the sexual behaviour of uninfected flies to enhance transmissions to a susceptible host. The behaviour of the infected fly per se is not manipulated, however, but rather, susceptible male flies are attracted to fungus-killed cadavers by unknown fungus-related cues. In contrast, I show that, in yellow dungflies, E. muscae directly manipulates host perching behaviour causing infected dungflies to perch abnormally in a highly specific manner. This new perching position, which involves changes in perching site, body posture and orientation on the plant, appears to be designed to meet the fungus’s requirements for efficient spore dispersal and host infection. The fungus—animal interaction described here is a remarkable example of a parasitic organism which manipulates the behaviour of its host: an ‘enslaver’ parasite. Both animal (e. g. nematodes, acanthocephalans) and fungal (e. g. Entomophthora muscae, Puccinia monoica) enslaver parasites are known.
Naturwissenschaften, 1987
Table 1. Response of Ips typographus to traps baited with natural pheromone components and two cl... more Table 1. Response of Ips typographus to traps baited with natural pheromone components and two closely related components. Column means with the same letter are not significantly different (Duncan's multiple range test)
Nature, 1986
Sand-bubbler crabs, Scopimera and Dotilla (Crustacea, Brachyura, Ocypodidae, Scopimerinae), are s... more Sand-bubbler crabs, Scopimera and Dotilla (Crustacea, Brachyura, Ocypodidae, Scopimerinae), are small (carapace width 1 cm) round-bodied crabs which occur in vast numbers throughout the Indo-Pacific on suitable tropical and sub-tropical sheltered sandy beaches. At high tide they are found in burrows that contain a trapped pocket of air in which the crabs are able to breathe until low tide. During
Nature, 1992
IN contrast to terrestrial locomotion in animals with rigid internal or external skeletons (such ... more IN contrast to terrestrial locomotion in animals with rigid internal or external skeletons (such as insects or vertebrates), caterpillar crawling is slow and energetically costly1. Biomechanical constraints may be responsible for the high cost of crawling locomotion1, but the caterpillar body plan, which uses hydraulic-based skeletal and locomotory systems, does not necessarily preclude the possibility of high-#150;speed locomotion as has
Marine Biology, 1990
The mouthparts of the Australian semaphore crabHeloecius cordiformis (H. Milne-Edwards, 1837) are... more The mouthparts of the Australian semaphore crabHeloecius cordiformis (H. Milne-Edwards, 1837) are described. Male and female semaphore crabs were observed and collected from mangrove swamps around the south side of Botany Bay, Australia between 1983 and 1987. Semaphore crabs inhabit mangrove mud/sand flats between the midlittoral intertidal zone and the supralittoral fringe of bordering saltflats. Scanning electron micrographs provide detailed
Marine Biology, 1990
... For this reason, the edge of the cara-pace above Legs 1 and 2 is fringed with close-set plumo... more ... For this reason, the edge of the cara-pace above Legs 1 and 2 is fringed with close-set plumose setae (Figs. I and 4A). ... 4 C). Similarly, complex setae have also been found on gill-grooming appendages of pinnotherid crabs (Pohle 1989). Exhalant aperture Pterygostomium ...
Journal of Zoology, 2004
The claw geometry of birds can be used to predict their mode of life. Previous studies, however, ... more The claw geometry of birds can be used to predict their mode of life. Previous studies, however, have not considered how bird size might affect these predictions. Thus, in the present study, the geometric scaling relationships of bird claws are examined for a variety of extant birds with different modes of life: predatory, climbing, perching or ground‐dwelling. Measurements of hind‐limb claw radius (i.e. claw size) and claw angle (i.e. claw ‘hookedness’) of the third digit claw were made on 120 species of bird ranging from 0.0057 kg to 44 kg in body mass. Claw radius was found to be proportional to (body mass)0.34 across all species. Claw angle was found to increase with body mass for predatory and climbing birds (i.e. bigger birds have relatively more hooked claws), and decrease with body mass for ground‐dwelling birds (i.e. bigger birds have relatively less hooked or flatter claws). No significant relationship was found between claw angle and body mass for perching birds. Mode of ...
Journal of Crustacean Biology, 2008
The Manicou or mountain crab, Eudaniela garmani (Pseudothelphusidae), is a freshwater land crab f... more The Manicou or mountain crab, Eudaniela garmani (Pseudothelphusidae), is a freshwater land crab found at high elevations in the forests of Trinidad, Tobago, Margarita, and Eastern Venezuela. Anecdotal data suggest that the Manicou crab reaches sexual maturity at an unusually large size, and, by implication, at a relatively old age. Therefore, management and harvesting of this species need to be informed by accurate determination of the size and estimated age at maturity. Laboratory growth increment and intermoult period data were used to estimate the time for both sexes to mature. Breakpoint analyses and analyses of covariance (ANCOVA) of field-collected data were used to determine male and female morphometric or structural maturity while gross and histological examinations of ovaries were used to determine the size of onset of female sexual maturity. Morphometric maturity was initiated at about 42 and 47 mm carapace width (CW) in female and male crabs, respectively. Female morphometric or structural maturation ceased at about 67 mm CW, about the same size as the onset of female functional maturity (69 mm CW). It is estimated that female crabs attained functional maturity at about 3 years. A minimum capture size is thus recommended between 75 and 80 mm CW for female crabs. Patterns of allometric growth in the major propodus of males and the pleon width in females may be related to territorial and/or courtship behaviour in males and the use of the pleon as an incubation chamber in females.
Journal of Crustacean Biology, 2003
We recorded the incidence of predation on snakes by the amphibious freshwater land crab Eudaniela... more We recorded the incidence of predation on snakes by the amphibious freshwater land crab Eudaniela garmani (manicou crab) in the rainforests of the Caribbean island of Tobago during 168 days of field observation (spanning a 4-year period) conducted between the hours of 08.00 AM and 12.00 noon and 21.00 PM and 23.30 PM. Six instances of manicou crabs eating snakes were observed and photographed. Field notes are given for each predation event, and photographs are presented for three of these: clouded slug-eating snake, Sibon nebulata nebulata, three-lined snake, Atractus trilineatus, and vine snake, Oxybelis aeneus. We conclude that the potential predation pressure placed on local snake populations by manicou crabs merits investigation.
Journal of Crustacean Biology, 2002
The manicou crab, Eudaniela garmani (Rathbun, 1898), inhabits rainforest mountain streams on the ... more The manicou crab, Eudaniela garmani (Rathbun, 1898), inhabits rainforest mountain streams on the Caribbean islands of Trinidad and Tobago and small areas of northern Venezuela (
Journal of Crustacean Biology, 2002
Journal of Comparative Physiology B, 1992
While on land and recirculating branchial water the Australian semaphore crab Heloecius cordiform... more While on land and recirculating branchial water the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial airbreathing mangrove crab, sequentially depresses and elevates its carapace in a regular pump-like manner. The functional role of these carapace movements in aerial oxygen consumption is investigated. Carapace immobilisation (reversible and non-injurious) did not appear to affect branchial water circulation. In "dry" crabs (branchial water removed) carapace immobilisafion had no effect on the rate of oxygen consumption (1702) , heart rate or whole-body lactate (WBL) levels. In "wet" crabs (with branchial water) carapace immobilisation caused ~'O 2 to drop by 38% from 81 to 46~1 O2-g-1 .h-I, heart rate to decline by 32%, from 2.5 to 1.7 Hz, and WBL levels to increase over 2.5-fold, from 0.27 to 0.67 mg 9 g-1, after 3 h of carapace immobilisation. The I~O2 of carapace-immobilised crabs with branchial water was similar to lung-occluded crabs with branchial water. Severe hypoxia induced physiological responses similar to those of carapace-immobilised crabs with branchial water. After 3 h of severe hypoxia, heart rate had declined by 80%, from 2.2 to 0.43 Hz, and the incidence of carapace pumping slowed by 85%, from 2.4 to 0.37 cycles 9 min-1. It is concluded that in the absence of carapace movements branchial water in some way interferes with lung ventilation. Under normal circumstances water circulation and lung ventilation are mutually exclusive processes (due to their singular dependence on the scaphognathites), yet in Heloecius these processes must be carried out simultaneously. Carapace movements may alleviate this conflict.
Journal of Comparative Physiology B, 1992
Carapace movements in crabs are briefly reviewed. While on land and recirculating branchial water... more Carapace movements in crabs are briefly reviewed. While on land and recirculating branchial water, the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial air-breathing mangrove crab, sequentially depresses and elevates its carapace relative to its thorax (0.5-1 mm excursion) in a regular pump-like manner. In quiescent crabs each carapace-pumping cycle lasts about 4 s; carapace depression takes 3 s and elevation 1 s. Carapace movements are brought about by pressures generated within the branchial chambers by the scaphognathites, probably in combination with carapace muscles. Carapace movements are associated with bilaterally synchronised scaphognathite activity. Unilateral scaphognathite activity was not observed. During normal forward recirculation of branchial water the scaphognathites beat at about 1.5 Hz (slow-forward pumping) and the lungs (epibranchial chambers) are not ventilated. In Heloecius, the lungs are not physically separated from the gills below by an anatomical barrier. Lung ventilation is accomplished during the following sequence of events: the carapace is lowered and the scaphognathites pump in a fast-forward mode at about 2.8 Hz. This activity preferentially pumps air out of the lungs and generates suction within the branchial chambers (4-10 cm H20 below ambient) which draws water from external body surfaces into the hypobranchial space below and around the gills. At the end of the carapace's downward travel the scaphognathites switch from fast-forward to fastreverse beating at about 4 Hz. This pumps air into the lungs and the carapace elevates. As a result, during carapace elevation the water which had previously been drawn into the branchial chambers by fast-forward pumping activity is released and flows out between the legs and into the abdominosternal cavity.
Journal of Biological Education, 2002
Secondary and tertiary biology curricula typically use paper chromatography, and increasingly thi... more Secondary and tertiary biology curricula typically use paper chromatography, and increasingly thin layer chromatography (TLC), for the separation of plant photosynthetic pigments. The purpose of basic chromatography practical work is two fold. Firstly, plant pigment separation leads naturally into a consideration of the separateroles each pigment plays in photosynthesis. Secondly, chromatography techniques are fundamental analytical tools in industry, medicine and biology. Currently an estimated 60% of analyses worldwide are performed using chromatography and chromatography-derived methods. Correct understanding of the basic physico-chemical principles on which adsorption chromatography (paper chromatography and TLC) is based is essential in orderto understand and apply the many other different techniques of chromatography. We have found, however, that explanations for paper chromatography and TLC in a number of important textbooks are scant, non-existent,or incorrect. Errors have occurred due to the misuse of the term absorption instead of the correct term adsorption, and the improper emphasis placed on solubility. Here we offer corrective explanations.
Behavioural Processes, 1997
Unrestrained, naïve cats (Felis sil6estris catus) (n=48: 28 males and 20 females), living in a na... more Unrestrained, naïve cats (Felis sil6estris catus) (n=48: 28 males and 20 females), living in a natural domestic environment, were studied for paw preferences using a food reaching test. A total of 46% were right-preferent, 44% were left-preferent and 10% were ambilateral. 60% of the cats in our sample used one paw 100% of the time. This preference was stable over time (10 weeks), and was not influenced by the presence of food residue on the cats' non-preferred paw. There was no difference between male and female cats in the proportions of left and right paw-preferent individuals. We have reviewed the literature reporting paw preferences in cats and conclude that in static food-reaching tests, domestic cats show a marked paw preference with an equal distribution of left-and right-preferent individuals. They do not, however, show a group or population bias toward the use of any one paw. There are no significant sex differences. In contrast, there is previously published evidence which appears to suggest that moving-target reaching tests uncover a left-sided behavioural asymmetry.
Acta Ornithologica, 2009
A. G. 2009. Variation in the relationship between lay date and clutch size in three cavity-nestin... more A. G. 2009. Variation in the relationship between lay date and clutch size in three cavity-nesting woodland passerines. Acta Ornithol.
Journal of Experimental Biology, 1992
Soldier crabs, Mictyris longicarpus Latreille, inhabit intertidal sand-flats of Eastern Australia... more Soldier crabs, Mictyris longicarpus Latreille, inhabit intertidal sand-flats of Eastern Australia. Their gill chambers are modified for both water circulation and air-breathing. Water circulates through the lower gill compartments. The upper regions of the gill chambers are air-filled and function as lungs. The deep vascular parenchyma lining the upper gill chambers, or lungs, is penetrated by a regular series of fine branching airways. Scanning electron micrographs of lung architecture are shown. Measurements relating to lung structure were made on plastic casts. Because of the lung’s design, water circulating through the lower gill compartments does not interfere with lung function. The airways are blind-ended and nonanastomosing, acting in effect as air-filled capillary tubes sealed at one end. A mathematical model and explanation show how the air trapped within this lung structure substantially reduces water penetration, despite surface tension (capillary) processes. This same l...
Journal of the Marine Biological Association of the UK, 2001
The gastropod Littorina littorea shows increased mortality in the summer months when infected wit... more The gastropod Littorina littorea shows increased mortality in the summer months when infected with digenean parasites. One possible cause of this mortality is impaired respiration in infected hosts. Respiration rates of L. littorea infected with three species of digenea of varying pathogenicity were measured: Cryptocotyle lingua, Himasthla elongata and Renicola roscovita. No evidence of altered respiration rates in infected snails was found.
Comparative Biochemistry and Physiology Part A: Physiology, 1990
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1994
Direct manipulation of host behaviour by endoparasites is well known among animal eukaryotic para... more Direct manipulation of host behaviour by endoparasites is well known among animal eukaryotic parasitic taxa like nematodes, trematodes and acanthocephalans, but is poorly documented amongst other taxa like fungi. The insect-parasitic fungal complex Entomophthora muscae is a pathogen of adult Diptera. During the summer months in Europe and America, large numbers of housefly Musca domestica and yellow dungfly Scatophaga stercoraria succumb to the fungus. It has previously been demonstrated in house flies that Entomophthora muscae indirectly manipulates the sexual behaviour of uninfected flies to enhance transmissions to a susceptible host. The behaviour of the infected fly per se is not manipulated, however, but rather, susceptible male flies are attracted to fungus-killed cadavers by unknown fungus-related cues. In contrast, I show that, in yellow dungflies, E. muscae directly manipulates host perching behaviour causing infected dungflies to perch abnormally in a highly specific manner. This new perching position, which involves changes in perching site, body posture and orientation on the plant, appears to be designed to meet the fungus’s requirements for efficient spore dispersal and host infection. The fungus—animal interaction described here is a remarkable example of a parasitic organism which manipulates the behaviour of its host: an ‘enslaver’ parasite. Both animal (e. g. nematodes, acanthocephalans) and fungal (e. g. Entomophthora muscae, Puccinia monoica) enslaver parasites are known.
Naturwissenschaften, 1987
Table 1. Response of Ips typographus to traps baited with natural pheromone components and two cl... more Table 1. Response of Ips typographus to traps baited with natural pheromone components and two closely related components. Column means with the same letter are not significantly different (Duncan's multiple range test)
Nature, 1986
Sand-bubbler crabs, Scopimera and Dotilla (Crustacea, Brachyura, Ocypodidae, Scopimerinae), are s... more Sand-bubbler crabs, Scopimera and Dotilla (Crustacea, Brachyura, Ocypodidae, Scopimerinae), are small (carapace width 1 cm) round-bodied crabs which occur in vast numbers throughout the Indo-Pacific on suitable tropical and sub-tropical sheltered sandy beaches. At high tide they are found in burrows that contain a trapped pocket of air in which the crabs are able to breathe until low tide. During
Nature, 1992
IN contrast to terrestrial locomotion in animals with rigid internal or external skeletons (such ... more IN contrast to terrestrial locomotion in animals with rigid internal or external skeletons (such as insects or vertebrates), caterpillar crawling is slow and energetically costly1. Biomechanical constraints may be responsible for the high cost of crawling locomotion1, but the caterpillar body plan, which uses hydraulic-based skeletal and locomotory systems, does not necessarily preclude the possibility of high-#150;speed locomotion as has
Marine Biology, 1990
The mouthparts of the Australian semaphore crabHeloecius cordiformis (H. Milne-Edwards, 1837) are... more The mouthparts of the Australian semaphore crabHeloecius cordiformis (H. Milne-Edwards, 1837) are described. Male and female semaphore crabs were observed and collected from mangrove swamps around the south side of Botany Bay, Australia between 1983 and 1987. Semaphore crabs inhabit mangrove mud/sand flats between the midlittoral intertidal zone and the supralittoral fringe of bordering saltflats. Scanning electron micrographs provide detailed
Marine Biology, 1990
... For this reason, the edge of the cara-pace above Legs 1 and 2 is fringed with close-set plumo... more ... For this reason, the edge of the cara-pace above Legs 1 and 2 is fringed with close-set plumose setae (Figs. I and 4A). ... 4 C). Similarly, complex setae have also been found on gill-grooming appendages of pinnotherid crabs (Pohle 1989). Exhalant aperture Pterygostomium ...
Journal of Zoology, 2004
The claw geometry of birds can be used to predict their mode of life. Previous studies, however, ... more The claw geometry of birds can be used to predict their mode of life. Previous studies, however, have not considered how bird size might affect these predictions. Thus, in the present study, the geometric scaling relationships of bird claws are examined for a variety of extant birds with different modes of life: predatory, climbing, perching or ground‐dwelling. Measurements of hind‐limb claw radius (i.e. claw size) and claw angle (i.e. claw ‘hookedness’) of the third digit claw were made on 120 species of bird ranging from 0.0057 kg to 44 kg in body mass. Claw radius was found to be proportional to (body mass)0.34 across all species. Claw angle was found to increase with body mass for predatory and climbing birds (i.e. bigger birds have relatively more hooked claws), and decrease with body mass for ground‐dwelling birds (i.e. bigger birds have relatively less hooked or flatter claws). No significant relationship was found between claw angle and body mass for perching birds. Mode of ...
Journal of Crustacean Biology, 2008
The Manicou or mountain crab, Eudaniela garmani (Pseudothelphusidae), is a freshwater land crab f... more The Manicou or mountain crab, Eudaniela garmani (Pseudothelphusidae), is a freshwater land crab found at high elevations in the forests of Trinidad, Tobago, Margarita, and Eastern Venezuela. Anecdotal data suggest that the Manicou crab reaches sexual maturity at an unusually large size, and, by implication, at a relatively old age. Therefore, management and harvesting of this species need to be informed by accurate determination of the size and estimated age at maturity. Laboratory growth increment and intermoult period data were used to estimate the time for both sexes to mature. Breakpoint analyses and analyses of covariance (ANCOVA) of field-collected data were used to determine male and female morphometric or structural maturity while gross and histological examinations of ovaries were used to determine the size of onset of female sexual maturity. Morphometric maturity was initiated at about 42 and 47 mm carapace width (CW) in female and male crabs, respectively. Female morphometric or structural maturation ceased at about 67 mm CW, about the same size as the onset of female functional maturity (69 mm CW). It is estimated that female crabs attained functional maturity at about 3 years. A minimum capture size is thus recommended between 75 and 80 mm CW for female crabs. Patterns of allometric growth in the major propodus of males and the pleon width in females may be related to territorial and/or courtship behaviour in males and the use of the pleon as an incubation chamber in females.
Journal of Crustacean Biology, 2003
We recorded the incidence of predation on snakes by the amphibious freshwater land crab Eudaniela... more We recorded the incidence of predation on snakes by the amphibious freshwater land crab Eudaniela garmani (manicou crab) in the rainforests of the Caribbean island of Tobago during 168 days of field observation (spanning a 4-year period) conducted between the hours of 08.00 AM and 12.00 noon and 21.00 PM and 23.30 PM. Six instances of manicou crabs eating snakes were observed and photographed. Field notes are given for each predation event, and photographs are presented for three of these: clouded slug-eating snake, Sibon nebulata nebulata, three-lined snake, Atractus trilineatus, and vine snake, Oxybelis aeneus. We conclude that the potential predation pressure placed on local snake populations by manicou crabs merits investigation.
Journal of Crustacean Biology, 2002
The manicou crab, Eudaniela garmani (Rathbun, 1898), inhabits rainforest mountain streams on the ... more The manicou crab, Eudaniela garmani (Rathbun, 1898), inhabits rainforest mountain streams on the Caribbean islands of Trinidad and Tobago and small areas of northern Venezuela (
Journal of Crustacean Biology, 2002
Journal of Comparative Physiology B, 1992
While on land and recirculating branchial water the Australian semaphore crab Heloecius cordiform... more While on land and recirculating branchial water the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial airbreathing mangrove crab, sequentially depresses and elevates its carapace in a regular pump-like manner. The functional role of these carapace movements in aerial oxygen consumption is investigated. Carapace immobilisation (reversible and non-injurious) did not appear to affect branchial water circulation. In "dry" crabs (branchial water removed) carapace immobilisafion had no effect on the rate of oxygen consumption (1702) , heart rate or whole-body lactate (WBL) levels. In "wet" crabs (with branchial water) carapace immobilisation caused ~'O 2 to drop by 38% from 81 to 46~1 O2-g-1 .h-I, heart rate to decline by 32%, from 2.5 to 1.7 Hz, and WBL levels to increase over 2.5-fold, from 0.27 to 0.67 mg 9 g-1, after 3 h of carapace immobilisation. The I~O2 of carapace-immobilised crabs with branchial water was similar to lung-occluded crabs with branchial water. Severe hypoxia induced physiological responses similar to those of carapace-immobilised crabs with branchial water. After 3 h of severe hypoxia, heart rate had declined by 80%, from 2.2 to 0.43 Hz, and the incidence of carapace pumping slowed by 85%, from 2.4 to 0.37 cycles 9 min-1. It is concluded that in the absence of carapace movements branchial water in some way interferes with lung ventilation. Under normal circumstances water circulation and lung ventilation are mutually exclusive processes (due to their singular dependence on the scaphognathites), yet in Heloecius these processes must be carried out simultaneously. Carapace movements may alleviate this conflict.
Journal of Comparative Physiology B, 1992
Carapace movements in crabs are briefly reviewed. While on land and recirculating branchial water... more Carapace movements in crabs are briefly reviewed. While on land and recirculating branchial water, the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial air-breathing mangrove crab, sequentially depresses and elevates its carapace relative to its thorax (0.5-1 mm excursion) in a regular pump-like manner. In quiescent crabs each carapace-pumping cycle lasts about 4 s; carapace depression takes 3 s and elevation 1 s. Carapace movements are brought about by pressures generated within the branchial chambers by the scaphognathites, probably in combination with carapace muscles. Carapace movements are associated with bilaterally synchronised scaphognathite activity. Unilateral scaphognathite activity was not observed. During normal forward recirculation of branchial water the scaphognathites beat at about 1.5 Hz (slow-forward pumping) and the lungs (epibranchial chambers) are not ventilated. In Heloecius, the lungs are not physically separated from the gills below by an anatomical barrier. Lung ventilation is accomplished during the following sequence of events: the carapace is lowered and the scaphognathites pump in a fast-forward mode at about 2.8 Hz. This activity preferentially pumps air out of the lungs and generates suction within the branchial chambers (4-10 cm H20 below ambient) which draws water from external body surfaces into the hypobranchial space below and around the gills. At the end of the carapace's downward travel the scaphognathites switch from fast-forward to fastreverse beating at about 4 Hz. This pumps air into the lungs and the carapace elevates. As a result, during carapace elevation the water which had previously been drawn into the branchial chambers by fast-forward pumping activity is released and flows out between the legs and into the abdominosternal cavity.
Journal of Biological Education, 2002
Secondary and tertiary biology curricula typically use paper chromatography, and increasingly thi... more Secondary and tertiary biology curricula typically use paper chromatography, and increasingly thin layer chromatography (TLC), for the separation of plant photosynthetic pigments. The purpose of basic chromatography practical work is two fold. Firstly, plant pigment separation leads naturally into a consideration of the separateroles each pigment plays in photosynthesis. Secondly, chromatography techniques are fundamental analytical tools in industry, medicine and biology. Currently an estimated 60% of analyses worldwide are performed using chromatography and chromatography-derived methods. Correct understanding of the basic physico-chemical principles on which adsorption chromatography (paper chromatography and TLC) is based is essential in orderto understand and apply the many other different techniques of chromatography. We have found, however, that explanations for paper chromatography and TLC in a number of important textbooks are scant, non-existent,or incorrect. Errors have occurred due to the misuse of the term absorption instead of the correct term adsorption, and the improper emphasis placed on solubility. Here we offer corrective explanations.
Behavioural Processes, 1997
Unrestrained, naïve cats (Felis sil6estris catus) (n=48: 28 males and 20 females), living in a na... more Unrestrained, naïve cats (Felis sil6estris catus) (n=48: 28 males and 20 females), living in a natural domestic environment, were studied for paw preferences using a food reaching test. A total of 46% were right-preferent, 44% were left-preferent and 10% were ambilateral. 60% of the cats in our sample used one paw 100% of the time. This preference was stable over time (10 weeks), and was not influenced by the presence of food residue on the cats' non-preferred paw. There was no difference between male and female cats in the proportions of left and right paw-preferent individuals. We have reviewed the literature reporting paw preferences in cats and conclude that in static food-reaching tests, domestic cats show a marked paw preference with an equal distribution of left-and right-preferent individuals. They do not, however, show a group or population bias toward the use of any one paw. There are no significant sex differences. In contrast, there is previously published evidence which appears to suggest that moving-target reaching tests uncover a left-sided behavioural asymmetry.
Acta Ornithologica, 2009
A. G. 2009. Variation in the relationship between lay date and clutch size in three cavity-nestin... more A. G. 2009. Variation in the relationship between lay date and clutch size in three cavity-nesting woodland passerines. Acta Ornithol.