Monday, December 26, 2005
Star fruit: great taste, looks to kill and a cinch to prepare, this fruit really is a star
Looking for something sweet, juicy and different in the fruit department? Star fruit--or carambola as it's also known--is just the ticket. This tropical treat has been cultivated for hundreds of years throughout Southeast Asia. Now flourishing in the warm climates of Florida and Hawaii, it's enjoying a growing audience in even the United States' not-so-balmy locales.
The golden yellow fruit gets its name from the perfect five-pointed star shape that appears when it's cut crosswise. The edible skin is shiny, thin and waxy to the touch. Choose one that is firm, golden yellow and emits a fragrant aroma.
There are two main types of star fruit: sweet (think orange meets pineapple) and tart (think lemon). Tart varieties have thinner ribs and may be a paler shade of yellow. (The two can be hard to tell apart, so ask your grocer just to be sure,) You may also find some less common white varieties that are sweet.
Even though this fruit is exotic, that doesn't mean it's complicated lust wash, cut and eat. And when it comes to cooking, star fruit is surprisingly versatile. Slice and saute it as an easy side dish, or add star fruit to a standard stir-fry. While tart varieties work best for cooking, the sweeter ones are great mixed into fruit salads or used in preserves or desserts. Finally, the fruit's unique shape makes it a ready-made garnish. So put down the pastry bag, and throw a slice or two of star fruit on top of that cake. This star of the produce department is a wish come true.
Nutrition Facts
Serving: 1 cup, cubed (137g)
Calories: 45
Fat Calories: less than 1g
Carbohydrates: 11g
Fiber: 3.4g
AKA: Carambola, Chinese star fruit and five-angled fruit
Availability: Late fall to early winter
Bonus: Vitamin C (29mg and 40% RDA)
What You Won't Miss: Sodium, cholesterol and saturated fat
Storage: Place any green-tinged fruit in a paper bag at room temperature until ripened; once golden, star fruit will keep up to two weeks in the refrigerator.
COPYRIGHT 2005 PRIMEDIA Intertec, a PRIMEDIA Company. All Rights Reserved.COPYRIGHT 2005 Gale Group
Looking for something sweet, juicy and different in the fruit department? Star fruit--or carambola as it's also known--is just the ticket. This tropical treat has been cultivated for hundreds of years throughout Southeast Asia. Now flourishing in the warm climates of Florida and Hawaii, it's enjoying a growing audience in even the United States' not-so-balmy locales.
The golden yellow fruit gets its name from the perfect five-pointed star shape that appears when it's cut crosswise. The edible skin is shiny, thin and waxy to the touch. Choose one that is firm, golden yellow and emits a fragrant aroma.
There are two main types of star fruit: sweet (think orange meets pineapple) and tart (think lemon). Tart varieties have thinner ribs and may be a paler shade of yellow. (The two can be hard to tell apart, so ask your grocer just to be sure,) You may also find some less common white varieties that are sweet.
Even though this fruit is exotic, that doesn't mean it's complicated lust wash, cut and eat. And when it comes to cooking, star fruit is surprisingly versatile. Slice and saute it as an easy side dish, or add star fruit to a standard stir-fry. While tart varieties work best for cooking, the sweeter ones are great mixed into fruit salads or used in preserves or desserts. Finally, the fruit's unique shape makes it a ready-made garnish. So put down the pastry bag, and throw a slice or two of star fruit on top of that cake. This star of the produce department is a wish come true.
Nutrition Facts
Serving: 1 cup, cubed (137g)
Calories: 45
Fat Calories: less than 1g
Carbohydrates: 11g
Fiber: 3.4g
AKA: Carambola, Chinese star fruit and five-angled fruit
Availability: Late fall to early winter
Bonus: Vitamin C (29mg and 40% RDA)
What You Won't Miss: Sodium, cholesterol and saturated fat
Storage: Place any green-tinged fruit in a paper bag at room temperature until ripened; once golden, star fruit will keep up to two weeks in the refrigerator.
COPYRIGHT 2005 PRIMEDIA Intertec, a PRIMEDIA Company. All Rights Reserved.COPYRIGHT 2005 Gale Group
Miso for breast cancer? - goodnews - findinds of study by National Cancer Center Research Institute, Tokyo, Japan - Brief ArticleBetter Nutrition, Sept, 2003
Women of the West, it may be time to follow the example of your Asian sisters: Eat more miso soup with its soy isoflavones if you want to reduce your breast-cancer risk. In Japan, where women on average consume 700 times more isoflavones than you do, thanks in part to miso soup, their breast cancer risk is just a fraction of yours.
This suggestion is based on a study by the National Cancer Center Research Institute in Tokyo, released last June. Of 21,000 middle-aged Japanese women studied across 10 years, only 179 developed breast cancer. Women who ate the most miso soup--2-3 cups daily-along with other isoflavone-filled foods such as soybeans and tofu were least likely to suffer the disease.
But Japanese researchers would only say the study shows a "probable" link between soy/isoflavones and reduced breast cancer risk.
COPYRIGHT 2003 PRIMEDIA Intertec, a PRIMEDIA Company. All Rights Reserved.COPYRIGHT 2003 Gale Group
Women of the West, it may be time to follow the example of your Asian sisters: Eat more miso soup with its soy isoflavones if you want to reduce your breast-cancer risk. In Japan, where women on average consume 700 times more isoflavones than you do, thanks in part to miso soup, their breast cancer risk is just a fraction of yours.
This suggestion is based on a study by the National Cancer Center Research Institute in Tokyo, released last June. Of 21,000 middle-aged Japanese women studied across 10 years, only 179 developed breast cancer. Women who ate the most miso soup--2-3 cups daily-along with other isoflavone-filled foods such as soybeans and tofu were least likely to suffer the disease.
But Japanese researchers would only say the study shows a "probable" link between soy/isoflavones and reduced breast cancer risk.
COPYRIGHT 2003 PRIMEDIA Intertec, a PRIMEDIA Company. All Rights Reserved.COPYRIGHT 2003 Gale Group
Shadhrah 6 and the earth quakes
Geologists have a convincing explanation: major earthquakes occur when tectonic plates beneath large mountains shift and snap. A great deal of seismic activity takes place beneath the mountains but remains unnoticed by everyone except a handful of experts, until the earth quakes. And when it quakes, it takes its toll, devastating millions of lives. This explanation is self-sufficient, objective, scientific; none of this has anything to do with the One Who created the mountains, the earth, and those affected by the event. Scientific explanations have removed God from the equation.
Despite their pervasive presence, these are relatively new explanations. They have emerged only in the wake of the Scientific Revolution of the seventeenth century, and have since been adopted as the official religion of the scientific community, rendering all other explanations "unscientific" and thus somehow flawed. Until their appearance, humanity believed in a Creator Who was actively present in earthly affairs. Modern science calls this belief superstition. This reigning scientific orthodoxy has not only removed the hand of God from human and natural affairs, it has also led humanity to a state of despair--for, if earthquakes can be explained away in terms of the movement of tectonic plates, and all that happens on earth in terms of randomly occurring processes, then life on this ravaged planet itself becomes a terminus ad quem, without any hope of a future life.
Millions of intelligent human beings now believe in this "scientific religion". Caught in their daily routines, they live out their lives in a universe whose incredibly vast and complex systems are present in their consciousness only to the extent allowed by a pervasive scientism which conceives the beginning of the universe as a remote, nebulous, and indeed unascertainable affair. Once formed, this original matter somehow starts to cool and eventually this primal matter gives birth to simple forms of organic life which, in time, become complex through innumerable random chance processes, leading to the evolution of Homo sapiens. This explanation, in the sense that it provides at least some semblance of a rational account for existence, is deemed to be a satisfactory account--at least until the earth quakes, shattering the belief-system based on the pseudo-religion of science. And when the earth quakes, many of those who gaze into the void left by the scientistic account realize a hidden spiritual anguish, perhaps as reaction to physical carnage or an immediate recognition of fundamental mortality, which calls out for a more substantive explanation to the basic questions.
This realization, transcending the mundane realm and opening another plane of consciousness, then directs our attention to the presence of a spirit within the ephemeral bodies, a spirit capable of feeling pain and anguish at the departure of loved ones, reflective remorse, despair, and fear of the unknown. Once realized, this consciousness leads to an awareness of something higher than physical needs, emotional desires, and survival demands dictated by hormones or organs. At such times, human beings know with certainty that they have a spiritual life which originates in their innate nature. And those who are receptive to this higher truth also realize that inherent in their innate nature is an awareness of the Creator Who fashioned us out of clay and infused us with Spirit (r), giving life to earthly creatures.
This consciousness also opens a small window through which we can revisit the vast and complex processes of the universe that not only cause the earth to quake and hurricanes to arise, but also provide compelling evidence for the presence of a Wise, Powerful, Majestic, and Merciful Creator Who designed the universe and all that it contains for a purpose and for a fixed duration. The teleological argument of the ancients, then, appears with a new meaning, a meaning that is reinforced and supplemented with copious new data that our ever-more sophisticated instruments have generated, but data that was never before looked at by hearts yearning for solace in the wake of an earthquake or hurricane. Now the calamities which are visiting humanity with increasing frequency do not seem to be the work of nature, for in such a state of receptivity human beings understand that nature has no independent authority to cause anything. Likewise, they now realize that what they had previously called "laws of nature" are, in fact, laws created by the One Who created nature.
This realization not only shatters the house of cards that scientism has been unceasingly building for the last three hundred years, it also inspires us to seek afresh the real nature of earthquakes, tsunamis, hurricanes, and tornados by refocusing our attention to something beyond the secondary causes which ascribe these processes to the movement of tectonic plates, or to warm and cold currents of water and winds. Now we come face to face with primary questions beginning with a "why", and leave aside the "how".
Suffering softens hearts, an ancient proverb tells us, and softened hearts not only yearn for kindness and solace but also become receptive to an understanding of the universe and life that provides real answers about the nature of this universe and, indeed, about the nature of life itself. These questions can no longer be confined to the cold realm of reason, but now arise from the deep recesses of the heart: why? Why was this calamity sent to us? Why did the earth quake? Why did the hurricane rage with such ferocity? Why do we suffer?
Of course, each one of us has to find our own answers to these primary questions, for no man can carry the burden of another and no amount of rational persuasion can lead to that gnosis which yields certainty in the heart, but at such moments of truth we can at least be sure of one thing: the reductive explanations of scientism are no longer adequate to deal with the most fundamental questions about the universe and the human condition.
Wuddistan Shawwal 5, 1426/November 07, 2005
COPYRIGHT 2005 Center for Islam & ScienceCOPYRIGHT 2005 Gale Group
Geologists have a convincing explanation: major earthquakes occur when tectonic plates beneath large mountains shift and snap. A great deal of seismic activity takes place beneath the mountains but remains unnoticed by everyone except a handful of experts, until the earth quakes. And when it quakes, it takes its toll, devastating millions of lives. This explanation is self-sufficient, objective, scientific; none of this has anything to do with the One Who created the mountains, the earth, and those affected by the event. Scientific explanations have removed God from the equation.
Despite their pervasive presence, these are relatively new explanations. They have emerged only in the wake of the Scientific Revolution of the seventeenth century, and have since been adopted as the official religion of the scientific community, rendering all other explanations "unscientific" and thus somehow flawed. Until their appearance, humanity believed in a Creator Who was actively present in earthly affairs. Modern science calls this belief superstition. This reigning scientific orthodoxy has not only removed the hand of God from human and natural affairs, it has also led humanity to a state of despair--for, if earthquakes can be explained away in terms of the movement of tectonic plates, and all that happens on earth in terms of randomly occurring processes, then life on this ravaged planet itself becomes a terminus ad quem, without any hope of a future life.
Millions of intelligent human beings now believe in this "scientific religion". Caught in their daily routines, they live out their lives in a universe whose incredibly vast and complex systems are present in their consciousness only to the extent allowed by a pervasive scientism which conceives the beginning of the universe as a remote, nebulous, and indeed unascertainable affair. Once formed, this original matter somehow starts to cool and eventually this primal matter gives birth to simple forms of organic life which, in time, become complex through innumerable random chance processes, leading to the evolution of Homo sapiens. This explanation, in the sense that it provides at least some semblance of a rational account for existence, is deemed to be a satisfactory account--at least until the earth quakes, shattering the belief-system based on the pseudo-religion of science. And when the earth quakes, many of those who gaze into the void left by the scientistic account realize a hidden spiritual anguish, perhaps as reaction to physical carnage or an immediate recognition of fundamental mortality, which calls out for a more substantive explanation to the basic questions.
This realization, transcending the mundane realm and opening another plane of consciousness, then directs our attention to the presence of a spirit within the ephemeral bodies, a spirit capable of feeling pain and anguish at the departure of loved ones, reflective remorse, despair, and fear of the unknown. Once realized, this consciousness leads to an awareness of something higher than physical needs, emotional desires, and survival demands dictated by hormones or organs. At such times, human beings know with certainty that they have a spiritual life which originates in their innate nature. And those who are receptive to this higher truth also realize that inherent in their innate nature is an awareness of the Creator Who fashioned us out of clay and infused us with Spirit (r), giving life to earthly creatures.
This consciousness also opens a small window through which we can revisit the vast and complex processes of the universe that not only cause the earth to quake and hurricanes to arise, but also provide compelling evidence for the presence of a Wise, Powerful, Majestic, and Merciful Creator Who designed the universe and all that it contains for a purpose and for a fixed duration. The teleological argument of the ancients, then, appears with a new meaning, a meaning that is reinforced and supplemented with copious new data that our ever-more sophisticated instruments have generated, but data that was never before looked at by hearts yearning for solace in the wake of an earthquake or hurricane. Now the calamities which are visiting humanity with increasing frequency do not seem to be the work of nature, for in such a state of receptivity human beings understand that nature has no independent authority to cause anything. Likewise, they now realize that what they had previously called "laws of nature" are, in fact, laws created by the One Who created nature.
This realization not only shatters the house of cards that scientism has been unceasingly building for the last three hundred years, it also inspires us to seek afresh the real nature of earthquakes, tsunamis, hurricanes, and tornados by refocusing our attention to something beyond the secondary causes which ascribe these processes to the movement of tectonic plates, or to warm and cold currents of water and winds. Now we come face to face with primary questions beginning with a "why", and leave aside the "how".
Suffering softens hearts, an ancient proverb tells us, and softened hearts not only yearn for kindness and solace but also become receptive to an understanding of the universe and life that provides real answers about the nature of this universe and, indeed, about the nature of life itself. These questions can no longer be confined to the cold realm of reason, but now arise from the deep recesses of the heart: why? Why was this calamity sent to us? Why did the earth quake? Why did the hurricane rage with such ferocity? Why do we suffer?
Of course, each one of us has to find our own answers to these primary questions, for no man can carry the burden of another and no amount of rational persuasion can lead to that gnosis which yields certainty in the heart, but at such moments of truth we can at least be sure of one thing: the reductive explanations of scientism are no longer adequate to deal with the most fundamental questions about the universe and the human condition.
Wuddistan Shawwal 5, 1426/November 07, 2005
COPYRIGHT 2005 Center for Islam & ScienceCOPYRIGHT 2005 Gale Group
evolution of the motor control of feeding in amphibians, The
SYNOPSIS. Based on studies of a few model taxa, amphibians have been considered stereotyped in their feeding movements relative to other vertebrates. However, recent studies on a wide variety of amphibian species have revealed great diversity in feeding mechanics and kinematics, and illustrate that stereotypy is the exception rather than the rule in amphibian feeding. Apparent stereotypy in some taxa may be an artifact of unnatural laboratory conditions. The common ancestor of lissamphibians was probably capable of some modulation of feeding movements, and descendants have evolved along two trajectories with regard to motor control: (1) an increase in modulation via feedback or feed-forward mechanisms, as exemplified by ballistic-tongued plethodontid salamanders and hydrostatic-tongued frogs, and (2) a decrease in variation dictated by biomechanics that require tight coordination between different body parts, such as the tongue and jaws in toads and other frogs with ballistic tongue projection. Multi-joint coordination of rapid movements may hamper accurate tongue placement in ballistic-tongued frogs as compared to both short-tongued frogs and ballistic tongued-salamanders that face simpler motor control tasks. Decoupling of tongue and jaw movements is associated with increased accuracy in both hydrostatic-tongued frogs and ballistic-tongued salamanders.
INTRODUCTION
Until recently, study of the motor control of amphibian feeding was limited to a few model taxa, for example the genera Bufo and Rana representing the Anura, and salamanders of the genus Ambystoma representing the Caudata. Kinematic studies of these taxa gave the impression that amphibian feeding in general is highly stereotyped, that is, it is performed in much the same way every time, with little variation in the timing or extent of movements. However, kinematic studies of a great diversity of salamanders, frogs and caecilians have revealed, in the last 15 yr or so, that these taxa are probably exceptions among amphibians, and were unfortunate models on which to base generalizations about feeding in amphibians. Indeed, Bufo is now known to be among the most stereotyped of frogs in its feeding movements (Nishikawa et al., 1992; Nishikawa and Gans, 1996), and Ambystoma lies at the low end of variation for salamanders (Larsen and Guthrie, 1975; Reilly and Lauder, 1989, 1990, 1992; Beneski et al., 1995). The perspective gained over this time, and the rapid growth of understanding in the field have motivated the current survey of motor control in amphibians. Now is a good time to reassess some early conclusions that were drawn, particularly that of stereotypy of movement, and to highlight some instructive examples and general evolutionary patterns to present a more balanced view of amphibian feeding.
A major conclusion that can be drawn from a survey across living amphibians is that feeding mechanisms are extremely varied, and that kinematics of feeding are accordingly diverse. Part of this diversity stems from the biphasic life cycle that is ancestral for amphibians and which characterizes most living taxa. Most amphibians make a transition from an aquatic larval stage in which suction-based feeding mechanics and lateral line and chemosensory cues dominate (Himstedt et al., 1982; Bartels et al., 1990), to a more terrestrial adult stage in which feeding is accomplished with the tongue and jaws, and visual stimuli become more important in guiding feeding movements (Ewert, 1987; Roth, 1987). There are clear exceptions to this ancestral developmental pattern, such as direct development and viviparity in which the larval stage is skipped, as well as paedomorphosis in which the ancestral larval characteristics are retained in the adult stage. Direct development and viviparity have evolved in all three groups of Lissamphibia: frogs, salamanders and caecilians. Perennibranchiation (a form of paedomorphosis in which external gills persist in adults) has evolved repeatedly only in salamanders, and the perennibranchiate adults use larval biomechanics and sensorimotor control of feeding movements. Feeding movements can be extremely rapid (i.e., five msec for tongue projection in bolitoglossine salamanders; Thexton et al., 1977; Larsen et al., 1989) and controlled by feed-forward mechanisms in which sensory feedback plays no role, or movements can be relatively slow and deliberate (i.e., about 150 msec for tongue protraction in the frog Hemisus, which has a hydrostatic tongue; Ritter and Nishikawa, 1995), relying heavily on feedback to adjust movements as they are performed. Movements can be triggered and guided by visual stimuli alone, as in many frogs and salamanders (Ewert, 1987; Roth, 1987), or by a combination of mechanical and chemical cues as in most caecilians and some frogs (Himstedt and Simon, 1995; Lettvin et al., 1959; Comer and Grobstein, 1981).
Secondarily aquatic adult amphibians provide another source of diversity. Although the common ancestor of amphibians most likely had a terrestrial adult stage, many adult amphibians are now either facultative or obligate aquatic feeders. Adult frogs that feed in water generally use modifications of terrestrial mechanisms, such as tongue protraction and jaw prehension, and only one taxon (Hymenochirus) has reevolved suction feeding (O'Reilly et al., 2002). All caecilians and many salamanders that feed in water as adults use jaw prehension, although the retention of suction feeding in adult salamanders is widespread and probably related to their generalized morphology as compared to frogs and caecilians. Those salamanders that lose all ability to suction feed are specialized for tongue projection.
Biomechanical diversity has been accompanied by diversity of motor control strategies. For example, the fundamentally different biomechanics of ballistic tongue projection in frogs and salamanders call for different characteristics of motor planning. Frogs use a mechanism that requires tight coordination between jaw and tongue movements via feedback, while salamanders have decoupled the tongue from the jaws and project the tongue using feed-forward mechanisms in which feedback is not used to coordinate movements.
Because motor control mechanisms (i.e., feedback vs. feed-forward control) have only been examined directly in a few taxa of frogs and salamanders, we must infer mechanisms for most taxa based on behavioral and kinematic evidence. The lack of direct evidence for many taxa and behavioral data on only a fraction of the extant species makes reconstruction of the evolution of motor control in a phylogenetic context difficult and tenuous. Although a formal phylogenetic analysis of characters should be conducted when more data become available, such an analysis using current data would include many unknown character states. Therefore, instead of a formal phylogenetic analysis, we discuss the trends observed in each of the three groups of extant amphibians with examples of representative taxa, as well as the patterns observed in the Lissamphibia as a whole.
Definitions
For the purposes of this discussion, it is necessary to lay down some operational definitions of terms that appear in the literature that relate to amphibian feeding and the neural control of movement.
Amphibians capture prey using a variety of behaviors that can involve movements of the jaws, hyobranchial apparatus, tongue, limbs, and the entire body. Several modes of prey capture have been discussed in the literature; we describe our understanding of these terms here. Jaw prehension is the grasping of prey between the jaws, and is performed both in water and on land; this is also called biting. Tongue prehension is the grasping of prey with the tongue, and involves tongue protraction or projection followed by tongue retraction. Suction feeding is drawing a single, relatively large prey item into the mouth by a single expansion of the buccal cavity, and is performed only in water. Filter feeding is removing multiple small food particles from the water either by rhythmically repeated buccal expansions that draw water into the mouth, or by moving forward over the particles. Lunging is forward movement of the entire body and can be combined with the other behaviors.
SYNOPSIS. Based on studies of a few model taxa, amphibians have been considered stereotyped in their feeding movements relative to other vertebrates. However, recent studies on a wide variety of amphibian species have revealed great diversity in feeding mechanics and kinematics, and illustrate that stereotypy is the exception rather than the rule in amphibian feeding. Apparent stereotypy in some taxa may be an artifact of unnatural laboratory conditions. The common ancestor of lissamphibians was probably capable of some modulation of feeding movements, and descendants have evolved along two trajectories with regard to motor control: (1) an increase in modulation via feedback or feed-forward mechanisms, as exemplified by ballistic-tongued plethodontid salamanders and hydrostatic-tongued frogs, and (2) a decrease in variation dictated by biomechanics that require tight coordination between different body parts, such as the tongue and jaws in toads and other frogs with ballistic tongue projection. Multi-joint coordination of rapid movements may hamper accurate tongue placement in ballistic-tongued frogs as compared to both short-tongued frogs and ballistic tongued-salamanders that face simpler motor control tasks. Decoupling of tongue and jaw movements is associated with increased accuracy in both hydrostatic-tongued frogs and ballistic-tongued salamanders.
INTRODUCTION
Until recently, study of the motor control of amphibian feeding was limited to a few model taxa, for example the genera Bufo and Rana representing the Anura, and salamanders of the genus Ambystoma representing the Caudata. Kinematic studies of these taxa gave the impression that amphibian feeding in general is highly stereotyped, that is, it is performed in much the same way every time, with little variation in the timing or extent of movements. However, kinematic studies of a great diversity of salamanders, frogs and caecilians have revealed, in the last 15 yr or so, that these taxa are probably exceptions among amphibians, and were unfortunate models on which to base generalizations about feeding in amphibians. Indeed, Bufo is now known to be among the most stereotyped of frogs in its feeding movements (Nishikawa et al., 1992; Nishikawa and Gans, 1996), and Ambystoma lies at the low end of variation for salamanders (Larsen and Guthrie, 1975; Reilly and Lauder, 1989, 1990, 1992; Beneski et al., 1995). The perspective gained over this time, and the rapid growth of understanding in the field have motivated the current survey of motor control in amphibians. Now is a good time to reassess some early conclusions that were drawn, particularly that of stereotypy of movement, and to highlight some instructive examples and general evolutionary patterns to present a more balanced view of amphibian feeding.
A major conclusion that can be drawn from a survey across living amphibians is that feeding mechanisms are extremely varied, and that kinematics of feeding are accordingly diverse. Part of this diversity stems from the biphasic life cycle that is ancestral for amphibians and which characterizes most living taxa. Most amphibians make a transition from an aquatic larval stage in which suction-based feeding mechanics and lateral line and chemosensory cues dominate (Himstedt et al., 1982; Bartels et al., 1990), to a more terrestrial adult stage in which feeding is accomplished with the tongue and jaws, and visual stimuli become more important in guiding feeding movements (Ewert, 1987; Roth, 1987). There are clear exceptions to this ancestral developmental pattern, such as direct development and viviparity in which the larval stage is skipped, as well as paedomorphosis in which the ancestral larval characteristics are retained in the adult stage. Direct development and viviparity have evolved in all three groups of Lissamphibia: frogs, salamanders and caecilians. Perennibranchiation (a form of paedomorphosis in which external gills persist in adults) has evolved repeatedly only in salamanders, and the perennibranchiate adults use larval biomechanics and sensorimotor control of feeding movements. Feeding movements can be extremely rapid (i.e., five msec for tongue projection in bolitoglossine salamanders; Thexton et al., 1977; Larsen et al., 1989) and controlled by feed-forward mechanisms in which sensory feedback plays no role, or movements can be relatively slow and deliberate (i.e., about 150 msec for tongue protraction in the frog Hemisus, which has a hydrostatic tongue; Ritter and Nishikawa, 1995), relying heavily on feedback to adjust movements as they are performed. Movements can be triggered and guided by visual stimuli alone, as in many frogs and salamanders (Ewert, 1987; Roth, 1987), or by a combination of mechanical and chemical cues as in most caecilians and some frogs (Himstedt and Simon, 1995; Lettvin et al., 1959; Comer and Grobstein, 1981).
Secondarily aquatic adult amphibians provide another source of diversity. Although the common ancestor of amphibians most likely had a terrestrial adult stage, many adult amphibians are now either facultative or obligate aquatic feeders. Adult frogs that feed in water generally use modifications of terrestrial mechanisms, such as tongue protraction and jaw prehension, and only one taxon (Hymenochirus) has reevolved suction feeding (O'Reilly et al., 2002). All caecilians and many salamanders that feed in water as adults use jaw prehension, although the retention of suction feeding in adult salamanders is widespread and probably related to their generalized morphology as compared to frogs and caecilians. Those salamanders that lose all ability to suction feed are specialized for tongue projection.
Biomechanical diversity has been accompanied by diversity of motor control strategies. For example, the fundamentally different biomechanics of ballistic tongue projection in frogs and salamanders call for different characteristics of motor planning. Frogs use a mechanism that requires tight coordination between jaw and tongue movements via feedback, while salamanders have decoupled the tongue from the jaws and project the tongue using feed-forward mechanisms in which feedback is not used to coordinate movements.
Because motor control mechanisms (i.e., feedback vs. feed-forward control) have only been examined directly in a few taxa of frogs and salamanders, we must infer mechanisms for most taxa based on behavioral and kinematic evidence. The lack of direct evidence for many taxa and behavioral data on only a fraction of the extant species makes reconstruction of the evolution of motor control in a phylogenetic context difficult and tenuous. Although a formal phylogenetic analysis of characters should be conducted when more data become available, such an analysis using current data would include many unknown character states. Therefore, instead of a formal phylogenetic analysis, we discuss the trends observed in each of the three groups of extant amphibians with examples of representative taxa, as well as the patterns observed in the Lissamphibia as a whole.
Definitions
For the purposes of this discussion, it is necessary to lay down some operational definitions of terms that appear in the literature that relate to amphibian feeding and the neural control of movement.
Amphibians capture prey using a variety of behaviors that can involve movements of the jaws, hyobranchial apparatus, tongue, limbs, and the entire body. Several modes of prey capture have been discussed in the literature; we describe our understanding of these terms here. Jaw prehension is the grasping of prey between the jaws, and is performed both in water and on land; this is also called biting. Tongue prehension is the grasping of prey with the tongue, and involves tongue protraction or projection followed by tongue retraction. Suction feeding is drawing a single, relatively large prey item into the mouth by a single expansion of the buccal cavity, and is performed only in water. Filter feeding is removing multiple small food particles from the water either by rhythmically repeated buccal expansions that draw water into the mouth, or by moving forward over the particles. Lunging is forward movement of the entire body and can be combined with the other behaviors.
