. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HATCHING PERIOD (d) Figure 10. Effects of cultunng separated embryos in the presence of: (A) seawater only (n = 10 cultures): (B) seawater plus Chaetomorpha limirn (n = 10): and (C) seawater plus egg mass jelly pieces (n = 10). Values plotted are means plus standard error bars for each day ot the hatching period. rate of metamorphosis could be enhanced by substrata collected from the adult habitat. Three substrata were tested, all of which were frequently observed in associa- tion with small juveniles in Spencer's Spit: Chae
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HATCHING PERIOD (d) Figure 10. Effects of cultunng separated embryos in the presence of: (A) seawater only (n = 10 cultures): (B) seawater plus Chaetomorpha limirn (n = 10): and (C) seawater plus egg mass jelly pieces (n = 10). Values plotted are means plus standard error bars for each day ot the hatching period. rate of metamorphosis could be enhanced by substrata collected from the adult habitat. Three substrata were tested, all of which were frequently observed in associa- tion with small juveniles in Spencer's Spit: Chaetomor- pha, silt, and egg mass jelly. Metamorphosis occurred under all of these conditions (Fig. 11). The presence of Chaetomorpha and egg mass jelly enhanced the rate of metamorphosis such that it took 9 days for all veligers to successfully metamorphose ( and mortality, respectively), rather than 20 days as in the control condi- tions ( mortality). Veligers provided with silt as a substratum showed mortality. Discussion The development of Haminoea callitlegenita is mor- phologically similar to that described for Haloa japonica (Usuki, 1966), another cephalaspidean species, and to lecithotrophic opisthobranchs in general (Thompson, 1967). However, the timing of metamorphosis in H. cal- lidegenita is variable: veligers can metamorphose within the egg capsule or after hatching. This unusual pattern has the adaptive advantage of allowing immediate re- cruitment within a population while simultaneously al- lowing larval dispersal. However, the prominence of pe- lagic veligers of this species in its natural habitat has not yet been determined (Gibson and Chia, in progress). The percent of total hatchlings that emerged as veligers was variable among masses cultured simultaneously un- der identical conditions. Although mass size (ranging from 155 to 591 hatchlings/mass) and duration of the hatching period (from 3 to 11 days) may have influenced the percentage of
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
