ON FEEDING MECHANISMS AND CLEARANCE RATES OF MOLLUSCAN VELIGERS
| Autor: | Esther M. Leise, R. R. Strathmann |
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| Rok vydání: | 1979 |
| Předmět: | |
| Zdroj: | The Biological Bulletin. 157:524-535 |
| ISSN: | 1939-8697 0006-3185 |
| DOI: | 10.2307/1541035 |
| Popis: | The teeth of a mammal or the mouthparts of a copepod can tell a knowledgeable biologist much about that animal's feeding habits. Deductions based on the structure of ciliary bands can be at least as useful. This study is part of a larger effort to relate quantitative aspects of ciliary feeding to the morphology of ciliary feeders. Much more extensive biogeographic or taxonomic comparisons of developmental adaptations can be made when feeding capacities of larvae can be predicted from the length of cilia and the lengths of their ciliated bands. Molluscan veliger larvae possess a lobed veluni which produces both feeding and locomotory currents. Those veligers which feed on suspended particles con centrate these particles between two opposed bands of cilia which line the velar edge (Fretter, 1967 ; Strathmann, Jahn, and Fonseca, 1972 ; Thompson, 1959; Werner, 1955) . The preoral band consists of long compound cilia which produce the swimming and feeding currents. The postoral band consists of shorter cilia which beat towards the preoral band. The combination of the two bands captures and retains particles. Between these bands is a food groove with small cilia which transport particles towards the mouth. Veligers are tiny feeding machines which convert small eggs into larger juveniles. Parents which produce small eggs can produce large numbers of offspring, but there are costs that limit larval success as larval size is reduced. A reduced feeding capacity is one cost of a decreased larval size. This can take the form of a reduction in the clearance rate (volume of water cleared of particles per unit time) or restriction to a smaller range of particle sizes. In molluscan veliger larvae the clearance rate is likely to be limited by both the length of the velar edge and the length of the preoral cilia (Strathmann, et a!., 1972). The size of the particles captured is probably limited by the length of the preoral cilia. Here we are testing the hypothesis that longer preoral cilia contribute to higher clearance rates. The test consists of comparative observations with high speed microcinephotography of movements of the preoral cilia, the postoral cilia and particles captured at the velar edge. Clearance rates are calculated froni these measurements. We used three species whose veligers have different lengths of preoral cilia: the oyster Crassostrea gigas, the nudibranch Tritonia diomedea and the mud snail Nassarius obsoletus. Movements of cilia and particles, but no particle captures, were also observed for a veliger of an unidentified species of prosobranch gastropod. Our cinefilms of feeding larvae also have extended pre viotis interpretations of the veliger feeding mechanism. |
| Databáze: | OpenAIRE |
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