The Impact of Variation in Labial Tooth Number on the Feeding Kinematics of Tadpoles of Southern Leopard Frog

ABSTRACT: The keratinized mouthparts of tadpoles are complex structures that play a significant role in feeding. Recent evidence has shown that the keratinized labial teeth function in two ways: to anchor the oral disc to a substrate and to rake material from it.

Reports of tadpoles with missing or deformed keratinized oral structures have increased. Yet, the impact missing teeth has on feeding remains unexplored. Here we use high speed videography (500 frames per second) of tadpoles of Southern Leopard Frog (Lithobates sphenocephalus [=Rana sphenocephala]) to study how missing teeth affect feeding. Specifically, we test the hypothesis that the number of teeth present correlates with two metrics of the effectiveness of a tadpole to rake material from a substrate. Those are the duration of the full gape cycle (opening and closing of the jaws) and of the closing phase (closing of the jaws once attached to a substrate).

We found a significant positive relationship between duration of time of the closing phase of the gape cycle and the number of labial teeth present. Thus, tadpoles with fewer teeth were in contact with a planar algal-covered substrate for a shorter duration than tadpoles with more teeth. Given the reports of tadpole mouthpart abnormalities, data relating feeding kinematics of tadpoles with missing labial teeth are relevant in assessing the impact these abnormalities have on larval performance. Our data indicate that tadpoles missing labial teeth forage less effectively than tadpoles with undamaged dentition.

This may help explain the pattern of reduced growth and developmental rates commonly observed in tadpoles raised in polluted environments or infected with pathogens that attack keratinized oral structures.

Source: Copeia 2010(3):481-486

Kirtland Peterson

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