. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LARVAE ACROSS EAST PACIFIC BARRIER 147 160 140 120 100. Figure I. Distribution of sampling locations in relation to generalized surface and near surface currents of the eastern tropical Pacific Ocean. Open circles indicate the positions where oblique plankton samples were taken. Arrows illustrate generalized patterns of major surface circulation. Currents from wesl to east: Equatorial Undercurrent (EUC) shown by dashed line occurs between 50 and approximately 300 meters depth; the Equatorial Countercurrent (ECC) lies between
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LARVAE ACROSS EAST PACIFIC BARRIER 147 160 140 120 100. Figure I. Distribution of sampling locations in relation to generalized surface and near surface currents of the eastern tropical Pacific Ocean. Open circles indicate the positions where oblique plankton samples were taken. Arrows illustrate generalized patterns of major surface circulation. Currents from wesl to east: Equatorial Undercurrent (EUC) shown by dashed line occurs between 50 and approximately 300 meters depth; the Equatorial Countercurrent (ECC) lies between the surface and approximately 50 meters depth. The Countercurrent is well developed between August and December and absent during February to April. Currents front east to west: North Equatorial Current (NEC); South Equatorial Current (SEC). Details of the strength and direction of currents are very much more complex than shown and are subject to seasonal variations (see Wyrtki 1965. 1966 for a detailed discussion). equal areas of the east than in the central tropical Pacific (compare column 2 and 4. Table I). On the other hand, the Semper*s. cerianthula. and planula larvae of coelen- terates evidently are not significantly impeded by the â 'east Pacific ; There are data indicating a greater incidence of echinoderm larvae in the east (47%) than in the central tropical Pacific (16%) (not shown in Table I). This is misleading, since larval skeletons in the older central Pacific samplesâsome preserved over twenty yearsâwill have deteriorated with time resulting in an underestimate of pluteus abundance (see Scheltema. 1986a: p. 243 for source of central Pacific samples). The table shows that overall the east Pacific may act as a sub- stantial barrier to many forms. The data further suggest that the east Pacific does act as a filter and that it is a significant but incomplete barrier to larval dispersal. Discussion Three kinds of evidence can be used to support the
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
