Functional response of suspension feeding anuran larvae to different particle sizes at low concentrations (Amphibia)

Abstract

The influence of particle size, initial particle concentration and larval stage on the ingestion rate, `retention efficiency', and filtering rate of anuran larvae with varying filter apparatus anatomy and different life histories was investigated for four species . Larvae of premetamorphic Stages 28 and 32 and prometamorphic Stage 40 were selected for filtering experiments on the basis of their different growth rates . Three different sizes of silica gel particles were offered as mock food . Particle concentration was measured photometrically. The Michaelis-Menten model was used to describe the dependency of ingestion rate, filtering rate, and `retention efficiency' upon initial particle concentration, and to calculate maximum ingestion rate, threshold concentration, and the half-saturation constant .(1) The highest ingestion rates, filtering rates and `retention efficiencies' were achieved byXenopus laevis larvae, followed by Bufo calamita larvae . Bufo bufo larvae lay at the opposite end of the scale . Rana temporaria larvae were placed between B . calamita and B . bufo larvae . This order is attributed to differences in life histories, especially the different breeding environments in which these larvae occur .(2) The larger the particle size and the older the stage, the greater the tendency toward saturation of the ingestion rate, filtering rate and `retention efficiency' . These filtration parameters are graded according to particle size . The ingestion rate (number of particles), filtration rate and `retention efficiency' are greatest for PS3 . Ingestion volume is greatest for PS 1 . The difference between PS3 and PS2 on the one hand, and PS1 on the other, is often great ; for Stage 28 X. laevis it is very great. This shows that larvae ingest large particles more effectively, and that the most effective ingestion takes place at Stages 28 and 32, owing to the growth function of these stages . The ability of larvae to ingest large particles effectively is possibly a very basic phylogenetic characteristic . (3) The threshold concentration is lowest when the particles are at their largest . In accordance with conclusions drawn by other authors, threshold feeding is attributed to regulation by buccal pumping and mucus production . Considerable importance is attributed to threshold feeding with respect to larval adaptation to oligotrophic environments . Introductioneffect on larval populations . A high nutrient supply, i .e . a high ingestion of exploitable food, leads Populations of anuran larvae are strongly conto large and rapid growth, rapid development and trolled by nutrient supply and predators . Envitherefore early metamorphosis (Collins, 1979 ; ronmental evaporation also has a catastrophic

Ontogeny, phylogeny, and morphology in anuran larvae: Morphometric analysis of cranial development and evolution inRana tadpoles (Anura: Ranidae)

“…Since both the distance between the upper jaw articulations (SRA; a measure of gape width) and the distance between the ceratohyal articulations (CAW; a measure of buccal cavity width) scale with negative allometry in all species, which together would seemingly diminish filter feeding capabilities through ontogeny, allometric or proportional enlargement of the jaw closing muscles suggests increasing importance of rasping feeding as these animals grow. This observation is supported by experimental data indicating decreasing efficiency of filter feeding at later stages during larval ontogeny in anurans (Viertel, 1990(Viertel, , 1992.…”

Acute Toxic Effects of the Herbicide Formulation and the Active Ingredient Used in Cycloxydim-Tolerant Maize Cultivation on Embryos and Larvae of the African Clawed Frog, Xenopus laevis

“…In contrary, the body surface of anuran larvae including their large tail fins play a role in gas exchange (Boutilier et al 1992;Ultsch et al 1999). Additionally high amounts of water are in close contact with the epithelia of the oral cavity, the filter apparatus and the gills during ventilation (Gradwell 1972a(Gradwell , b, c, 1975Hoff, 1979, 1982;Viertel 1990Viertel , 1992. It has to be suggested that anuran larvae are much more exposed to their aquatic environment and as Fig.…”

“…The larvae are obligate suspension feeders pumping high amounts of water through their buccopharynx with the suggested consequence of tremendously increased contact to the compounds (Viertel 1990(Viertel , 1992. Reproduction was initiated by injection of human chorionic gonadotropin into the dorsal lymph sac of X. laevis.…”

Chondrocranial development in larval Rana sylvatica (Anura: Ranidae): Morphometric analysis of cranial allometry and ontogenetic shape change

“…Hall and Larsen (1998), among other observations on the ontogeny of the chondrocranium of Spea intermontanus, indicated that the area of the muscular process of the palatoquadrate also scales with negative allometry. Since the muscular process serves as the insertion site for the orbitohyoideus muscle, which is the major depressor of the buccal pump, these observations taken together may provide some morphological evidence for the decreasing efficiency of filter feeding associated with ontogeny observed by other researchers (Gradwell, 1968(Gradwell, , 1972Wassersug, 1972;Viertel, 1990Viertel, , 1992. Unfortunately, most studies of larval anuran feeding mechanics and efficiency have focused on the buccal pump and comparable studies regarding scaling of components of the tadpole jaw apparatus are lacking.…”