. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 24 S. AMEMIYA AND R. B. EMLET. Figure 8. Later stages of larval development of Asthenoxoma ijimai. For all specimens, the anterior end is to the right of figure, a. Ventral side of live specimen nine days after fertilization. Scale bar, mm. b. Ventral side of live specimen 14 days after fertilization. The larval para-arms and anterior yolky mass have been contorted toward the juvenile aboral surface. P, podia; Sp, spines. Same scale as a. c. Fourteen-day post fertilization, approximate frontal section at the level of the
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 24 S. AMEMIYA AND R. B. EMLET. Figure 8. Later stages of larval development of Asthenoxoma ijimai. For all specimens, the anterior end is to the right of figure, a. Ventral side of live specimen nine days after fertilization. Scale bar, mm. b. Ventral side of live specimen 14 days after fertilization. The larval para-arms and anterior yolky mass have been contorted toward the juvenile aboral surface. P, podia; Sp, spines. Same scale as a. c. Fourteen-day post fertilization, approximate frontal section at the level of the hydropore and hydroporic canal (He). Same scale as a. d. Close-up of juvenile oral region showing epineural sinuses (Es), gut (G), water vascular system (W), radial canal (R), and podia (P). Compare with e. Scale bar. 200 ^m. e. SEM of partially sectioned specimen showing similar structures as seen in d. He, hydroporic canal; Rs, right somatocoel (aboral part of body cavity); Ls, left somatocoel (oral part of body cavity). Scale bar, 200 pm. were associated with plates in the para-arms and not with other ossicles. In one larva, each of the spine buds con- tained a growing spicule. In this same larva, the two os- sicles of the left para-arms and three additional ossicles formed a circle beneath the juvenile oral surface that rep- resented the five ocular plates of the adult skeleton. Discussion Larval structure o/'Asthenosoma ijimai Our re-examination of the larval development of As- thenosoma ijimai has demonstrated several morphological features that were not reported in the initial study of this species. Amemiya and Tsuchiya (1979) reported that the early post-gastrula of .1. ijimai resembled an early bi- pinnaria and not a prism larva. That study also reported the appearance of para-arms later in development and distinguished these projections from pluteus larval arms, because the former apparently lacked larval spicules and apparently arose from different regions of the la
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
