. The Biological bulletin. Biology; Zoology; Marine biology. DEVELOPMENT IN A MARINE SNAIL 459 (Fig. 4f). Ingestion and feeding activity may continue in some capsules up to the veliger stage illustrated in Figure 4e. The next stages of the intracapsular veliger (Figs. 4g, h) show a gradual and extensive increase in size, especially of the shell, foot and tentacles. The yolk gradually disappears in the visceral hump with accompanying differentiation of the viscera. A columella muscle faintly visible on the left side of the visceral hump is able to effect withdrawal of both head and foot into th
. The Biological bulletin. Biology; Zoology; Marine biology. DEVELOPMENT IN A MARINE SNAIL 459 (Fig. 4f). Ingestion and feeding activity may continue in some capsules up to the veliger stage illustrated in Figure 4e. The next stages of the intracapsular veliger (Figs. 4g, h) show a gradual and extensive increase in size, especially of the shell, foot and tentacles. The yolk gradually disappears in the visceral hump with accompanying differentiation of the viscera. A columella muscle faintly visible on the left side of the visceral hump is able to effect withdrawal of both head and foot into the shell. By the end of intra- capsular development, the lateral lobes of the velum have been resorbed and this pre-hatching juvenile shows an active crawling foot and large tentacles. Embryonic feeding and rate of development During intracapsular development, some embryos acquire more nurse eggs than their capsulemates and this is reflected in the size distribution of embryos and hatchlings. Embryos in trochophore phase as small as 450 (im were found together with others as large as 775 /xm after all nurse eggs had been eaten. By this time, the number of eggs eaten by each larva varies from 3 to 20 as shown in Figure 5 (left side) for three capsules with different numbers of capsulemates. This figure also shows the frequency at which embryos ingest different numbers. X= '_ J Ti = 24 ; m. Jb NURSE EGGS INGESTED X=1230>im n=20 V.' b,! I I 1^1 I I fl=r HATCHIN6 SIZE (jjm) Figure 5. TV. crassilabrum. Left, frequencies of embryos ingesting different of nurse-eggs in three different capsules. Right, hatching size frequencies between of three different capsules, = nurse-eggs. numbers embryos. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lillie, Frank Rattray, 1870-1947; Moore, Carl Ric
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectb, booksubjectzoology
