Acclimation of intertidally reproducing sea-snails protects embryos from lethal effects of transient hyperthermia.

Embryos of Ilyanassa obsoleta (from Massachusetts and Florida) and Phrontis vibex (from Florida) were exposed to temperatures from 33 to 37°C. In both species, very young embryos are especially sensitive to thermal stress. Brief early heat shock did not disturb spiral cleavage geometry but led to variable, typically severe defects in larval morphogenesis and tissue differentiation.

Embryonic organizer specification in the mud snail Ilyanassa obsoleta depends on intercellular signaling.

In early embryos of the caenogastropod snail Ilyanassa obsoleta, cytoplasmic segregation of a polar lobe is required for establishment of the D quadrant founder cell, empowering its great-granddaughter macromere 3D to act as a single-celled organizer that induces ectodermal pattern along the secondary body axis of the embryo. We present evidence that polar lobe inheritance is not sufficient to specify 3D potential, but rather makes the D macromere lineage responsive to some intercellular signal(s) required for normal expression of 3D-specific phenotypes. Experimental removal of multiple micromeres resulted in loss of organizer-linked MAPK activation, complete and specific defects of organizer-dependent larval organs, and progressive cell cycle retardation, leading to equalization of the normally accelerated division schedule of 3D (relative to the third-order macromeres of the A, B and C quadrants).

Mollusc models I. The snail Ilyanassa.

Ilyanassa obsoleta has been a model system for experimental embryology for over a century. Here we highlight new insight into early cell lineage specification in Ilyanassa. As in all molluscs and other spiralians, stereotyped cleavage patterns establish a homunculus of regional founder cells.

Two Rab2 interactors regulate dense-core vesicle maturation.

Peptide neuromodulators are released from a unique organelle: the dense-core vesicle. Dense-core vesicles are generated at the trans-Golgi and then sort cargo during maturation before being secreted. To identify proteins that act in this pathway, we performed a genetic screen in Caenorhabditis elegans for mutants defective in dense-core vesicle function.

Cell lineage of the Ilyanassa embryo: evolutionary acceleration of regional differentiation during early development.

Cell lineage studies in mollusk embryos have documented numerous variations on the lophotrochozoan theme of spiral cleavage. In the experimentally tractable embryo of the mud snail Ilyanassa, cell lineage has previously been described only up to the 29-cell stage. Here I provide a chronology of cell divisions in Ilyanassa to the stage of 84 cells (about 16 hours after first cleavage at 23 degrees C), and show spatial arrangements of identified nuclei at stages ranging from 27 to 84 cells.