Obtaining gametes and embryos of ascidians.

Ascidians are basal chordates that have become increasingly important for understanding chordate evolution. They comprise three orders. In the orders Phlebobranchia and Stolidobranchia, most species freely spawn eggs and sperm, whereas members of the order Aplousobranchia form colonies that brood their eggs and broadcast sperm.

Signaling pathways in ascidian oocyte maturation: the roles of cAMP/Epac, intracellular calcium levels, and calmodulin kinase in regulating GVBD.

Most mature ascidian oocytes undergo germinal vesicle breakdown (GVBD) when released by the ovary into sea water (SW). Acidic SW blocks this but they can be stimulated by raising the pH, increasing intracellular cAMP levels by cell permeant forms, inhibiting its breakdown or causing synthesis. Boltenia villosa oocytes undergo GVBD in response to these drugs.

Ascidian follicle cells: Multifunctional adjuncts to maturation and development.

Ascidians are primitive chordates, subphylum Tunicata, that are sessile filter-feeding hermaphrodites as adults. Released oocytes are enclosed within a monolayer of follicle cells, a non-cellular vitelline coat and a monolayer of test cells that cover the egg membrane. Follicle cell structure is distinctive in different groups.

Signaling pathways in ascidian oocyte maturation: the role of cyclic AMP and follicle cells in germinal vesicle breakdown.

Many ascidian oocytes undergo 'spontaneous' germinal vesicle breakdown (GVBD) when transferred from the ovary to normal pH 8.2 sea water (SW); however, low pH inhibits GVBD, which can then be stimulated while remaining in the low pH SW. Oocytes of Boltenia villosa blocked from GVBD by pH 4 SW undergo GVBD in response to permeant cyclic AMP (8-bromo-cyclic AMP), phosphodiesterase inhibitors (isobutylmethylxanthine and theophylline) or the adenylyl cyclase activator forskolin.

Signaling pathways in ascidian oocyte maturation: effects of various inhibitors and activators on germinal vesicle breakdown.

The Ascidiacea, the invertebrate chordates, includes three orders; the Stolidobranchia is the most complex. Until the present study, the onset of oocyte maturation (germinal vesicle breakdown) had been investigated in only a single pyurid (Halocynthia roretzi), in which germinal vesicle breakdown (GVBD) begins when the oocyte contacts seawater (SW); nothing was known about internal events. This study strongly suggests the importance of protein phosphorylation in this process.

Sperm surface proteases in ascidian fertilization.

Ascidian eggs are surrounded by a noncellular layer and two cellular layers, which are penetrated by sperm. Three sperm surface proteases are essential for fertilization of eggs from the stolidobranch ascidian Halocynthia: spermosin, acrosin, and the proteasome. In the phlebobranch Ciona, a chymotrypsin-like protease and the proteasome are essential in fertilization.

Independent Initiation of Calcium Dependent Glycosidase Release and Cortical Contractions during the Activation of Ascidian Eggs: (Ascidian, Ryanodine, Thimerosal, Thapsigargin, N-acetylglucosaminidase).

During fertilization or ionophore induced activation, ascidian eggs rapidly release cell surface N-acetylglucosaminidase activity used in the block against polyspermy and undergo cortical contractions before they re-initiate meiosis. To better understand the activation process, we probed the relationship between these two processes in Ascidia ceratodes eggs by activating with different agents that increase intracellular Ca levels and under different ionic conditions. Glycosidase activity release was followed by the use of a fluorogenic substrate, and cortical contractions were followed by examining changes in cell shape with light microscopy.

Spicule formation in the solitary ascidian, herdmania momus.

Two types of calcareous spicules occur abundantly in Herdmania momus, a solitary pyurid ascidian with a worldwide warm water distribution. The large spindle-shaped body spicules are 1.5-2.

THE EFFECT OF LIGHT ON THE SPAWNING OF CIONA INTESTINALIS.

1. The spawning of Ciona intestinalis with respect to light was studied, using both white light and monochromatic light. 2.