. The Biological bulletin. Biology; Zoology; Marine biology. TAIL MELANOPHORES OF XENOPUS 5 dorsal fins. At this time, the formation of melanophores begins in the new ventral fin near the base of the somitic blastema. During the next 6 or 7 days, these melanophores increase in number and appear as a stream of cells stemming from the regeneration blastema (Figs. 5 and 6). These melanophores are present only in the ventral fin and remain excluded from the area anterior to the original cut. Thus, the proximal area retains its unpigmented state. During the course of tail regeneration, tail melanop
. The Biological bulletin. Biology; Zoology; Marine biology. TAIL MELANOPHORES OF XENOPUS 5 dorsal fins. At this time, the formation of melanophores begins in the new ventral fin near the base of the somitic blastema. During the next 6 or 7 days, these melanophores increase in number and appear as a stream of cells stemming from the regeneration blastema (Figs. 5 and 6). These melanophores are present only in the ventral fin and remain excluded from the area anterior to the original cut. Thus, the proximal area retains its unpigmented state. During the course of tail regeneration, tail melanophores gradually appear in the ventral fin, first making their appearance adjacent to the newly forming somites. After the tenth day of regeneration, the somitic core of the regenerating tail appears as a long spike to which is attached a generous ventral fin. Melanophores are abundant in the upper half of the fin near the developing somites, but are lacking in the lower half near the edge. After three weeks, tail regeneration is practically completed and the. Figure 9. Melanophores typical of the head of mature larvae under normal illumination. Magnification: X 100. new ventral fin is copiously supplied with melanophores. However, a clearly defined margin is present along the ventral edge of the fin (Figs. 7 and 8) which is permanently devoid of melanophores. Moreover, the melanophores at the edge of this margin are completely differentiated and there is no indication of any newly forming melanophores which might ultimately invade the clear margin. The unpigmented border extends along the complete length of the regenerated ventral fin except for the extreme proximal portion of the pigmented zone. This is the point at which the stream of melanophores was first seen in connection with the regeneration blastema. Apparently at the start of regeneration, a sufficient stim- ulus for melanization allows the complete reconstitution of pigmentation in this localized region. Presumably,
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectb, booksubjectzoology
