Pollen as food: effects of consumption on tadpole growth, development, and mobility

Abstract

The structure of many aquatic food webs is influenced by tadpole survivorship and duration of seasonal occupancy, which depend on tadpole diet. Pollen has been occasionally reported to occur in tadpole diets, and the available studies show that tadpoles have a strong preference for this supposedly
nutritive resource. Thus, we aimed to test whether a diet composed of pollen from varied plant species
would boost tadpole growth, development, and agility/mobility, compared to a regular artificial balanced
and nutritive diet. Tadpoles in initial developmental stages 25 and 30 grew more when fed with
pollen, compared to artificial food and a mixture of both diets. Those initially in stage 30 advanced more
developmental stages during one month when fed exclusively with pollen. Tadpoles fed with pollen
moved longer distances in response to an aversive stimulus simulating a predatory attack than tadpoles
fed with artificial food or a mixed diet. Our results corroborate the hypotheses of pollen being a very
important food source to aquatic consumers such as tadpoles, being likely to influence the structure of
aquatic food webs through tadpole nutrition and modulation of growth/development speed, as well as tadpole ability to escape predators.
Keywords: Tadpole diet · Growth · Development · Pollen · Mobility

Introduction

Amphibian larvae are key to many aquatic food webs (e.g., O’Neil & Thorp, 2014; Schmidt et al., 2017)
and their patterns of food consumption, growth, and development influence other trophic levels (Costa &
Vonesh, 2013; Hite et al., 2018). Predation on anurans in all life stages can trigger a trophic cascade
effect leading to increase in populations of their prey (Hite et al., 2018), whereas their seasonal role as
aquatic consumers can increase complexity of food webs (Schmidt et al., 2017).
The larval phase is key for growth and development of most amphibians (Heyer, 1979; Wells,
2007) and its duration is affected by many factors such as nutrition, temperature, species interactions,
and environmental features (Montaña et al., 2019). Diet composition can be considered a key factor, as rates of food consumption directly influence size and time to metamorphosis (Kupferberg, 1997).
Anuran larvae usually adjust their growth to environmental conditions such as resource levels. They
can grow until they reach a minimum size to metamorphose and leave an unfavorable aquatic habitat
or grow to a maximum size if the aquatic habitat is favorable (Wilbur & Collins, 1973).

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