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Pentylphenols 1 and 2, cyclopropane fatty acid 3, and cyclopentenones 4 and 5, were isolated from an ascidian, Diplosoma sp. The structures of 1-5 were determined by spectroscopic analysis and/or synthesis. Compound 1 inhibited the division of fertilized sea urchin eggs and compound 4 showed mild cytotoxity against HCT116 cells (human colorectal cancer cell).

We have found a novel embryonic cell population in the keyhole sand dollar Astriclypeus manni, which we refer to as lucent fluorescent cells (LFCs). Live LFCs are transparent, but emit autofluorescence after formaldehyde fixation. LFCs become noticeable in the vegetal plate of early gastrulae immediately after the appearance of pigment cells. As development progresses, LFCs increase in number and migrate from the vegetal plate toward the animal pole in a manner similar to pigment cells. Notably, LFCs also migrate into the oral ectoderm, while pigment cells do not. In addition, we determined that there were nearly 300 LFCs per embryo, which greatly exceeds the number of pigment cells. Treatment with the Notch signaling inhibitor N-[(3,5-Difluorophenyl)acetyl]-l-alanyl-2-phenyl]glycine-1,1-dimethylethyl ester (DAPT) resulted in a marked decrease in pigment cell number, but only a modest decrease in LFCs. In DAPT-treated embryos, LFCs had a distribution pattern similar to pigment cells and were excluded from the oral ectoderm. Unlike other sea urchins, Nodal signaling was not involved in the specification of pigment cells and LFCs in these embryos. Pulse treatment and measurement of cell diameters revealed that LFCs underwent 13-15 cycles of cell division and were specified during the 11th cleavage, one cell cycle later than observed for pigment cells. At the pluteus stage, a cluster of LFCs was observed in the animal plate in addition to two rows of LFCs running along the ciliary band. In addition, dozens of LFCs aligned at the uppermost level of the stomodaeum. Therefore, though the two cell populations share some features, LFCs are considerably different from pigment cells., (© 2011 The Authors. Development, Growth & Differentiation © 2011 Japanese Society of Developmental Biologists.)

Interspecific and intraspecific morphological and fertilization variations were studied in three sibling species of Echinometra (known as sp. B, C and D) found off the coast of Okinawa, Japan. Eggs from C and D were readily fertilized by sperm from all three color morphs of B when the sperm concentrations were high, but no fertilization was observed when sperm of the former were mixed with eggs from the latter. Under limiting sperm concentrations, however, both C and D were incapable to fertilize reciprocally with B. In contrast, crossing between C and D produced fertilization membrane at high and limiting sperm concentrations in both directions. Interspecific crosses between B vs. C and B vs. D clearly showed that these combinations were reproductively isolated in contrast to that observed for crossing between C and D. Interestingly, intraspecific fertilization of B showed considerable morphological variation in addition to variability in fertilization success. Intraspecific fertilization and morphological variations may occur due to a number of genetic and/or non-genetic factors. While the underlying cause(s) remain to be elucidated, the results of the present study suggest that B is now speciating very slowly.