A comparative study of the buccal pumping mechanism of tadpoles

Abstract

To understand the ecological significance of diversity in the buccal pump morphology of anuran larvae we have developed a descriptive geometric model of the tadpole buccal pump. The model allows comparison ofthe buccal pumping mechanism ofdifferent species.The reliability of the model was established by comparing buccal volumes predicted by the model with buccal volumes reported in the literature for R a m sylvatica and Rana catesbeiana as well as those obtained from our own feeding experiments with Xenopus laevis larvae.The model was used to examine the following features for the larvae of 40 species from 1 1 anuran tainilies: ( 1 ) the amount of dellection in the buccal floor with each stroke of the buccal pump (angle of rotation of the ceratohyal); (2) the mechanical advantage of the pump (the relative length of the lever arm on the ceratohyal); and (3) buccal volume. We identify patterns in these three features that correlate with the feeding ecology of a variety of tadpoles. Macrophagous larvae tend to have a long lateral lever arm on the ceratohyal (high mechanical advantage), and produce a large buccal volume by deHecting a large buccal floor area through a shallow arc (i.e. a large bore, short stroke system). Midwater, niicrophagous larvae tend to have poor mechanical advantage, but nevertheless achieve a large buccal volume; in these forms the large buccal volume is obtained by deflecting a smaller buccal floor area through a larger arc (i.e. a small bore, long stroke system). Benthic larvae, such as stream forms with suctorial mouths, tend to have high mechanical advantage, but only modest buccal voluine.Larvae can regulate their feeding rate by varying either the pumpingrate (frequency modulation) or the buccal Hoor displacement (amplitude modulation). The anatomy of the buccal pump may determine not only the feeding ecology of a larva, but the predominant behavioral pattern it uses to regulate its feedingrate.Buccal volume has a negative allometric relationship to body length both intraspecifically and interspeci tically.KEY WORDS:-Anuratadpolesanuran larvaebuccal pumptadpole ecologytadpole morphologytadpole behaviorfeeding mechanismmorphological modellingallornetry.

Buccal pumping mechanics ofXenopus laevistadpoles: effects of biotic and abiotic factors

“…Our examination of the OH lever arm ratio confirmed values from previous research (0.18-0.22), similar to other microphagous suspension-feeding tadpoles (Wassersug and Hoff, 1979). The isometric IH lever arm ratio we measured has not been previously reported.…”

“…Evidence for X. laevis altering pumping frequency is prolific in the literature (Seale, 1982;Seale et al, 1982;Seale and Wassersug, 1979;Wassersug and Hoff, 1979). Our results from the viscosity manipulations indicate that while tadpoles are able to sense the amount of food in the water and regulate pumping frequency accordingly (Seale, 1982), changes in viscosity did not provoke a similar increase in pumping frequency.…”

“…Similarly, the ceratohyal lever arm ratio (i.e. the length of the in-lever divided by the length of the out-lever) was found to be correlated with feeding mode (Wassersug and Hoff, 1979). When the ratios were compared with the feeding mode of each taxon, the two pipids investigated lie at opposite extremes of the spectrum.…”

“…Lateral images were used to measure the dorsoventral thickness of the ceratohyal, which was taken as the in-lever length of the IH. Lever arm ratio of hyoid depression is calculated as the ratio of the in-lever to the out-lever (Wassersug and Hoff, 1979).…”

Functional morphology of feeding and gill irrigation in the anuran tadpole: electromyography and muscle function in larval rana catesbeiana

“…Studies of the functional morphology of feeding and respiration in larval anurans have provided data regarding the actions of the morphological structures involved in these behaviors (Schulze 1888(Schulze , 1892Kratochwill, 1933;Sedra, 1950;Savage, 1952;De Jongh, 1968;Gradwell, 1968Gradwell, , 1972aKenny, 1969;Severtzov, 1970;Wassersug and Hoff, 1979;Altig, 1991, 1992;Taylor and Altig, 1995;Taylor et al, 1996;Yamashita, 2000, 2001). However, studies of feeding and respiratory biomechanics (e.g., Wassersug and Hoff, 1979) and in vivo muscle function (e.g., Gradwell, 1968Gradwell, , 1972a are comparatively rare.…”