Santosh Mogali | Karnatak University, Dharwad (original) (raw)

Papers by Santosh Mogali

Phyllomedusa: Journal of Herpetology

Behavioral responses of tadpoles of Duttaphrynus melanostictus (Anura: Bufonidae) to cues of star... more Behavioral responses of tadpoles of Duttaphrynus melanostictus (Anura: Bufonidae) to cues of starved and fed dragonfly larvae. Tadpoles of Duttaphrynus melanostictus use chemoreception to detect kairomonal cues and excretory metabolites from predatory anuran tadpoles (Hoplobatrachus tigerinus) that consume them. We describe here the behavioral responses of tadpoles of D. melanostictus to predatory dragonfly larvae (Pantala flavescens). The predator’s kairomones (water conditioned by the starved predator) or its diet-derived metabolites released in excreta of predator after consumption of conspecific prey tadpoles were used to simulate predation risk. The tadpoles of D. melanostictus had no behavioral response to predator kairomones. However, the larvae reduced swimming movements and overall time spent in swimming, and had a higher burst speed/swimming velocity in response to water borne cues released from the excreta of predators fed conspecific prey. Thus, just the presence of drag...

Mechanisms of predator detection and the influence of the presence of nonlethal predators on anti... more Mechanisms of predator detection and the influence of the presence of nonlethal predators on antipredator defense behavior and metamorphic traits were studied in the Indian tree frog, Polypedates maculatus. Exposure of P. maculatus tadpoles to chemical cues of caged predator (crabs, Barytelphusa spp.) fed with either conspecific or heterogeneric tadpoles, or were starved elicited defense behavior (by avoiding predator zone) in them. Such a behavior was not evident when exposed to predators housed in a glass beaker (visual cues). Both early (Gosner stage 27-28) and later (Gosner stage 35-36) stage tadpoles when exposed to caged predators (fed with conspecific tadpoles), prey tadpoles spent less time swimming and remained motionless for longer periods. Yet, the time spent by prey in feeding was unaffected. Further, the predator avoidance behavior exhibited by them was of the same intensity regardless of whether the caged predators were fed or starved implying the influence of predator's kairomones. Tadpoles reared with caged predator reached the metamorphic climax stage (MC stage; Gosner stage 42) earlier than those reared without a predator. Size at emergence (Gosner stage 46) was comparable in both the groups. The findings suggest that P. maculatus tadpoles assess predation risk chiefly by sensing kairomones of the predator in eliciting antipredator defense behaviors. Accelerated development and early metamorphosis without any compromise

Phenotypic plasticity of metamorphic traits, in response to desiccation threat, was studied in Du... more Phenotypic plasticity of metamorphic traits, in response to desiccation threat, was studied in Duttaphrynus melanostictus under laboratory conditions. Newly hatched Gosner stage 19 tadpoles were exposed to decreasing water levels (gradually or rapidly) up to the beginning of metamorphic climax (MC, Gosner stage 42). The control group was reared in unchanging water levels. The tadpoles experiencing desiccation threat reached MC earlier than those reared in constant water levels and metamorphosed (Gosner stage 46) at smaller body sizes. Time to reach MC was comparable between the groups of tadpoles experiencing a gradual or rapid decrease in water levels but their size at the completion of metamorphosis varied. They emerged at a significantly smaller size under rapid desiccation threat compared to the gradual desiccation threat. Impact on size at emergence was in proportion to the level of desiccation threat and this accelerated development and led to an early metamorphosis. The study shows the ability of D. melanos-tictus for developmental plasticity under adverse ecological conditions like the desiccation threat.

We conducted an experiment to understand the influence of ecological factors (desiccation, predat... more We conducted an experiment to understand the influence of ecological factors (desiccation, predation threat and density) on two major metamorphic traits, larval period and size at metamorphosis, in the Indian bronze frog, Hylarana temporalis. Tadpoles were reared in groups of 15 (low), 30 (medium) and 60 (high) densities. We created the threat of desiccation by removing 0.5 l water at 10 days intervals until the water quantity reached 0.5 l. Caged dragonfly larvae (Pantala flavescens) provided the predation threat. Results show that each ecological factor independently influenced metamorphic traits but not in an interactive way. Under desiccation threat the tadpoles metamorphosed earlier and at smaller sizes compared to those reared in constant water (at corresponding densities) regardless of presence/absence of predator. In contrast, under predation threat, tadpoles metamorphosed early and at a bigger size than those reared without predator regardless of density of rearing, and desiccation threat. Alternatively, an increase in density of rearing delayed metamorphosis with smaller metamorphic size in constant water and also under threat of desiccation regardless of whether predation threat existed or not. Thus, our study revealed that H. temporalis tadpoles can modify their response to each ecological factor regardless of what other factors operate simultaneously; the threat of desiccation shortens larval period at the cost of growth. Whereas, predator pressure shortens larval period along with increased growth; while greater density increases larval period and slows down growth in H. temporalis.

Tadpoles of Sphaerotheca breviceps detect food and predators using waterborne chemical cues (odou... more Tadpoles of Sphaerotheca breviceps detect food and predators using waterborne chemical cues (odours), which evoke appropriate behaviour. The present study aimed to determine whether they are capable of resolving the conflict between foraging choice and predator avoidance on encountering both food and predatory chemical cues together. Experiments were designed using an association choice apparatus in which prey tadpoles were given a choice to move themselves close to or away from a given stimulus (food or a predator). Food odours were either strong or weak. Tadpoles of Hoplobatrachus tigerinus (n = 4) were placed in an open-ended mesh cage wrapped in a cheese cloth that provided predator cues. The time spent by the test tadpoles in the predator's zone or away from it and the time spent feeding were recorded for 10 min (n = 25 trials). When food odours were weak, the prey tadpoles avoided predators and spent significantly more time in the predator-free zone. In contrast, when food odours were strong, they foraged equally in the two zones of the test apparatus regardless of the presence or absence of predators. These findings confirm the inherent ability of S. breviceps tadpoles to distinguish between food and predators, and indicate that strong food odours mask pre-dation risk. We suggest that foraging theory and the pre-dation risk allocation hypothesis should include factors that mislead prey during predation risk assessment and the evocation of defence behaviours.

Predation threat-associated behavioral response was studied in Rana temporalis tadpoles to discov... more Predation threat-associated behavioral response was studied in Rana temporalis tadpoles to discover the importance of predators' visual and chemical cues (kairo-mones and diet-derived metabolites of consumed prey) in evoking antipredator behavior. The caged predators (dragonfly larvae) fed on prey tadpoles or insects (Noto-necta spp.) and water conditioned with the predators provided the threat stimuli to the tadpole prey. The predators' visual cues were ineffective in evoking antipredator behaviors in the tadpole prey. However, exposure to caged tadpole-fed predators or water conditioned with tadpole-fed predators elicited predator avoidance behavior in the tadpoles; they stayed away from the predators, significantly reduced swimming activity (swimming time and distance traveled), and increased burst speed. Interestingly, exposure to water conditioned with starved predators did not elicit any antipredator behavior in the prey. Further, the antipredator responses of predator-experienced tadpoles were significantly greater than those exhibited by predator-naı¨venaı¨ve tadpoles. The study shows that R. temporalis tadpoles assess predation threat based exclusively on chemical cues emanating from the predators' dietary metabolites and that the inclusion of conspecific prey items in the diet of the predators is perceived as a threat. The study also shows that antipredator behavior in these tadpoles is innate and is enhanced during subsequent encounters with the predators.

Gosner stage 19 tadpoles of Sphaerotheca breviceps were exposed to constant or progressively decr... more Gosner stage 19 tadpoles of Sphaerotheca breviceps
were exposed to constant or progressively decreasing
water levels until metamorphosis with abundant food
supply. The tadpoles experiencing constant water levels
(column height of 40 mm) reached metamorphic climax
(MC) in 35.07 ± 0.44 days and metamorphosed at
39.00 ± 0.43 days at a mean body mass of 409 ± 9.0 mg
and 14.64 ± 0.08 mm snout-vent length. In contrast,
the larvae experiencing decreasing water levels (from
40 to 12 mm column height) reached MC in 30.93 ±
0.35 days and metamorphosed at 34.73 ± 0.35 days at
a significantly smaller body mass and size compared
to those reared in constant water levels. In both the
treatments survival of tadpoles was 100%. The study
reveals that S. breviceps tadpoles are capable of developmental
plasticity and with progressive decrease in
water levels, the trade-off between growth and development
is in favour of development, resulting in early
metamorphosis at a small size.

The influence of the presence of nonlethal predators on antipredator defense behavior and metamor... more The influence of the presence of nonlethal predators on antipredator defense behavior and metamorphic traits was studied in the toad Bufo melanostictus. Tadpoles reared with caged predaceous tadpoles of Hoplobatrachus tigerinus delayed metamorphosis and also emerged at a smaller size compared to those in a predator-free environment. Different predaceous cues (kairomones, alarm cues and dietary cues, derived after feeding the predator with conspecific prey) induced increase in stationary phase and swimming speed and decrease in swimming spurts and time used for feeding. The intensity of defense behaviors varied with the cue. They were more intense in response to cues of predators fed on conspecific prey item. The response to alarm cues or kairomones or predators fed on heterogeneric tadpole species was similar but lower in magnitude compared to that elicited in response to predators fed on conspecific prey item. Most intense defense behavior in response to the odors of the predator that consumed conspecific members is possibly caused by a combined effect of kairomones, alarm, and dietary cues. The findings suggest that B. melanostictus tadpoles are capable of assessing levels of predation risk and modulating the intensity of their defense behavior in accordance with the perceived threat. Interestingly, despite longer larval period, size at metamorphosis of the toadlets was smaller in the presence of caged predator. An important component of anuran amphibian life-history strategy is successful completion of aquatic larval life and emergence on the land at the largest possible size. However, complex interactions and challenges are encountered in this phase of life because of biotic and abiotic factors that force the larvae to manipulate larval period and growth. Indeed, anuran larvae are known to exhibit plasticity in metamorphic traits in response to factors such as crowding, desiccation , and predator pressure (Wilbur and Collins, 1973; Travis, 1984; Hensley, 1993; Lepis and Trevis, 1994; Harris, 1999). Several studies have shown that, under predation pressure, the anuran larvae alter their foraging and swimming activities, morphology, and metamorphic traits, the larval period and size at metamorphosis

Phenotypic plasticity of metamorphic traits, in response to desiccation threat, was studied in Du... more Phenotypic plasticity of metamorphic traits, in response to desiccation threat, was studied in Duttaphrynus melanostictus under laboratory conditions. Newly hatched Gosner stage 19 tadpoles were exposed to decreasing water levels (gradually or rapidly) up to the beginning of metamorphic climax (MC, Gosner stage 42). The control group was reared in unchanging water levels. The tadpoles experiencing desiccation threat reached MC earlier than those reared in constant water levels and metamorphosed (Gosner stage 46) at smaller body sizes. Time to reach MC was comparable between the groups of tadpoles experiencing a gradual or rapid decrease in water levels but their size at the completion of metamorphosis varied. They emerged at a significantly smaller size under rapid desiccation threat compared to the gradual desiccation threat. Impact on size at emergence was in proportion to the level of desiccation threat and this accelerated development and led to an early metamorphosis. The study shows the ability of D. melanostictus for developmental plasticity under adverse ecological conditions like the desiccation threat.

Tadpoles of Sphaerotheca breviceps detect food and predators using waterborne chemical cues (odou... more Tadpoles of Sphaerotheca breviceps detect food and predators using waterborne chemical cues (odours), which evoke appropriate behaviour. The present study aimed to determine whether they are capable of resolving the conflict between foraging choice and predator avoidance on encountering both food and predatory chemical cues together. Experiments were designed using an association choice apparatus in which prey tadpoles were given a choice to move themselves close to or away from a given stimulus (food or a predator). Food odours were either strong or weak. Tadpoles of Hoplobatrachus tigerinus (n = 4) were placed in an open-ended mesh cage wrapped in a cheese cloth that provided predator cues. The time spent by the test tadpoles in the predator's zone or away from it and the time spent feeding were recorded for 10 min (n = 25 trials). When food odours were weak, the prey tadpoles avoided predators and spent significantly more time in the predator-free zone. In contrast, when food odours were strong, they foraged equally in the two zones of the test apparatus regardless of the presence or absence of predators. These findings confirm the inherent ability of S. breviceps tadpoles to distinguish between food and predators, and indicate that strong food odours mask predation risk. We suggest that foraging theory and the predation risk allocation hypothesis should include factors that mislead prey during predation risk assessment and the evocation of defence behaviours.

Predation threat-associated behavioral response was studied in Rana temporalis tadpoles to discov... more Predation threat-associated behavioral response was studied in Rana temporalis tadpoles to discover the importance of predators' visual and chemical cues (kairomones and diet-derived metabolites of consumed prey) in evoking antipredator behavior. The caged predators (dragonfly larvae) fed on prey tadpoles or insects (Notonecta spp.) and water conditioned with the predators provided the threat stimuli to the tadpole prey. The predators' visual cues were ineffective in evoking antipredator behaviors in the tadpole prey. However, exposure to caged tadpole-fed predators or water conditioned with tadpolefed predators elicited predator avoidance behavior in the tadpoles; they stayed away from the predators, significantly reduced swimming activity (swimming time and distance traveled), and increased burst speed. Interestingly, exposure to water conditioned with starved predators did not elicit any antipredator behavior in the prey. Further, the antipredator responses of predator-experienced tadpoles were significantly greater than those exhibited by predatornaïve tadpoles. The study shows that R. temporalis tadpoles assess predation threat based exclusively on chemical cues emanating from the predators' dietary metabolites and that the inclusion of conspecific prey items in the diet of the predators is perceived as a threat. The study also shows that antipredator behavior in these tadpoles is innate and is enhanced during subsequent encounters with the predators.

Phyllomedusa: Journal of Herpetology

Phenotypic plasticity of metamorphic traits, in response to desiccation threat, was studied in Du... more Phenotypic plasticity of metamorphic traits, in response to desiccation threat, was studied in Duttaphrynus melanostictus under laboratory conditions. Newly hatched Gosner stage 19 tadpoles were exposed to decreasing water levels (gradually or rapidly) up to the beginning of metamorphic climax (MC, Gosner stage 42). The control group was reared in unchanging water levels. The tadpoles experiencing desiccation threat reached MC earlier than those reared in constant water levels and metamorphosed (Gosner stage 46) at smaller body sizes. Time to reach MC was comparable between the groups of tadpoles experiencing a gradual or rapid decrease in water levels but their size at the completion of metamorphosis varied. They emerged at a significantly smaller size under rapid desiccation threat compared to the gradual desiccation threat. Impact on size at emergence was in proportion to the level of desiccation threat and this accelerated development and led to an early metamorphosis. The study shows the ability of D. melanostictus for developmental plasticity under adverse ecological conditions like the desiccation threat.

Tadpoles of Sphaerotheca breviceps detect food and predators using waterborne chemical cues (odou... more Tadpoles of Sphaerotheca breviceps detect food and predators using waterborne chemical cues (odours), which evoke appropriate behaviour. The present study aimed to determine whether they are capable of resolving the conflict between foraging choice and predator avoidance on encountering both food and predatory chemical cues together. Experiments were designed using an association choice apparatus in which prey tadpoles were given a choice to move themselves close to or away from a given stimulus (food or a predator). Food odours were either strong or weak. Tadpoles of Hoplobatrachus tigerinus (n = 4) were placed in an open-ended mesh cage wrapped in a cheese cloth that provided predator cues. The time spent by the test tadpoles in the predator's zone or away from it and the time spent feeding were recorded for 10 min (n = 25 trials). When food odours were weak, the prey tadpoles avoided predators and spent significantly more time in the predator-free zone. In contrast, when food odours were strong, they foraged equally in the two zones of the test apparatus regardless of the presence or absence of predators. These findings confirm the inherent ability of S. breviceps tadpoles to distinguish between food and predators, and indicate that strong food odours mask predation risk. We suggest that foraging theory and the predation risk allocation hypothesis should include factors that mislead prey during predation risk assessment and the evocation of defence behaviours.

Predation threat-associated behavioral response was studied in Rana temporalis tadpoles to discov... more Predation threat-associated behavioral response was studied in Rana temporalis tadpoles to discover the importance of predators' visual and chemical cues (kairomones and diet-derived metabolites of consumed prey) in evoking antipredator behavior. The caged predators (dragonfly larvae) fed on prey tadpoles or insects (Notonecta spp.) and water conditioned with the predators provided the threat stimuli to the tadpole prey. The predators' visual cues were ineffective in evoking antipredator behaviors in the tadpole prey. However, exposure to caged tadpole-fed predators or water conditioned with tadpolefed predators elicited predator avoidance behavior in the tadpoles; they stayed away from the predators, significantly reduced swimming activity (swimming time and distance traveled), and increased burst speed. Interestingly, exposure to water conditioned with starved predators did not elicit any antipredator behavior in the prey. Further, the antipredator responses of predator-experienced tadpoles were significantly greater than those exhibited by predatornaïve tadpoles. The study shows that R. temporalis tadpoles assess predation threat based exclusively on chemical cues emanating from the predators' dietary metabolites and that the inclusion of conspecific prey items in the diet of the predators is perceived as a threat. The study also shows that antipredator behavior in these tadpoles is innate and is enhanced during subsequent encounters with the predators.