. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ONTOGENIC CHANGES IN TRANSPORT 165 70 60- 50- 40- ~ 30- ^i ? 20- 0 Veliger (48-h-old) Trochophore (24-h-old) CO 70 n <D 15 rr 50- 40- 30 20- 10- 0 20 40 60 80 [Alaninel/jM 100. 1 2 3 Transport rate/tSubstratel Figure -4. Upper graph (A): a comparison of the effect of increasing substrate concentration on the transport rate of alanine by two larval stages of Haliotis rufescens. Each point represents the rate determined from a time course experiment at that particular substrate concentra- tion (all values for r were >
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ONTOGENIC CHANGES IN TRANSPORT 165 70 60- 50- 40- ~ 30- ^i ? 20- 0 Veliger (48-h-old) Trochophore (24-h-old) CO 70 n <D 15 rr 50- 40- 30 20- 10- 0 20 40 60 80 [Alaninel/jM 100. 1 2 3 Transport rate/tSubstratel Figure -4. Upper graph (A): a comparison of the effect of increasing substrate concentration on the transport rate of alanine by two larval stages of Haliotis rufescens. Each point represents the rate determined from a time course experiment at that particular substrate concentra- tion (all values for r were >). Lower graph (B): Eadie-Hofstee plots of the raw data from the upper graph. Trochophores (210 larvae ml ') had a K, of nM and a Jmax of pmol larva V; veligers (274 ml ') had a K, of and a Jmjv of pmol larva' 'rr'. fore, further experiments to investigate ontogenic changes in transport rate as a function of size were car- ried out with feeding larvae of the bivalve Crassostrea gigas. Veligers of this species undergo substantial in- crease in size during growth when fed with cultures of phytoplankton (Helm and Millican, 1977). Preliminary experiments showed that the rate of ala- nine transport by veliger larvae of Crassostrea gigas could be saturated at concentrations of 200 nM. This was the substrate concentration chosen for further experi- ments with bivalve larvae. Larvae representing seven different sizes, ranging from 80 j/m to 300 ^m in shell length, were chosen and their transport rates for alanine measured at 200 pM. Their respective rates of transport are shown in Figure 5 (upper graph), where each data point represents the rate obtained from a separate time course experiment (all r values >). The upper graph (Fig. 5) shows that there is a continuous increase in the value for Jmax during larval development from an 80 /urn larva to a 300 ^m larva. The least-squares regression of the increase in the log-rate of alanine transport, as a func-
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
