Possible causal relation between the acrosome reaction and cross-fertilization in the sea urchins hemicentrotus pulcherrimus and pseudocentrotus depressus

1979 ◽  
Vol 2 (1) ◽  
pp. 15-23 ◽  
Author(s):  
Kenji Aketa ◽  
Tadayuki Ohta
Keyword(s):  
Acrosome Reaction ◽  
Sea Urchins ◽  
Causal Relation ◽  
Cross Fertilization ◽  
Hemicentrotus Pulcherrimus

Cellular analyses of sea urchin metamorphosis

Zygote ◽  
1999 ◽  
Vol 8 (S1) ◽  
pp. S77-S78
Author(s):  
Yukiko Sato ◽  
Ikuko Yazaki
Keyword(s):  
Electron Microscopy ◽  
Fatty Acids ◽  
Squamous Epithelium ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Chromatin Condensation ◽  
Environmental Cues ◽  
Nuclear Chromatin ◽  
Intracellular Changes ◽  
Hemicentrotus Pulcherrimus

Larvae of marine invertebrates undergo metamorphosis in response to environmental cues (Chia & Burke, 1978). In sea urchins, free fatty acids (Kitamura et al., 1993), dibromomethane (Taniguchi et al., 1994), pheromonal peptides (Burke, 1984) and L-glutamine (Yazaki & Harashima, 1994; Yazaki, 1995) have been known as metamorphosis-inducing substances. The mechanisms by which cells respond to these cues and how the larval tissues are absorbed have not been clear, however. In the present study, we used L-glutamine (Gln) and a natural cue, green algae (Ulvella sp.), to induce metamorphosis of Hemicentrotus pulcherrimus and Anthocidaris crassispina, and investigated the intracellular changes during metamorphosis.After being subjected to 10−5–10−3 M Gln for 10–24 h, larvae cease swimming, settle, begin to retract their larval arms, extrude the primary podia and finally evert their echinus rudiment (ER). In H. pulcherrimus, larvae retracted their arms from 6 h to 24 h after the start of Gln treatment and then everted the ER. A. crassispina larvae underwent similar processes to those of H. pulcherrimus. The larval surface is composed of squamous epithelium and columnar epithelium. The epithelium of the ciliary bands or epaulets is columnar.In the squamous epithelium, the nuclear chromatin in the larval arms and body, and in the oesophagus, markedly condensed after treatment with Gln for 24 h. Electron microscopy revealed swelling of both nuclei and mitochondria, while their membranes seemed to be intact. In the cytoplasm, lipid-like structures and electron-dense substances appeared. A further 24 h after Gln treatment, the chromatin condensation had progressed. Most nuclei in which chromatin had condensed were positive to the TUNEL assay, which detects DNA fragmentation. These results suggest that cell death in the squamous epithelium is apoptotic rather than necrotic.

scholarly journals Ligands and receptors mediating signal transduction in sea urchin spermatozoa

Reproduction ◽  
2004 ◽  
Vol 127 (2) ◽  
pp. 141-149 ◽  
Author(s):  
Anna T Neill ◽  
Victor D Vacquier
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Signaling Pathways ◽  
Sea Urchin ◽  
Acrosome Reaction ◽  
Sea Urchins ◽  
Model System ◽  
Surrounding Seawater ◽  
Sea Urchin Sperm

Sea urchins have long been a model system for the study of fertilization. Much has been learned about how sea urchin sperm locate and fertilize the egg. Sperm and eggs are spawned simultaneously into the surrounding seawater. Sperm signaling pathways lead to downstream events that ensure fertilization. Upon spawning, sperm must acquire motility and then they must swim towards or respond to the egg in some way. Finally, they must undergo a terminal exocytotic event known as the acrosome reaction that allows the sperm to bind to the vitelline layer of the egg and then to fuse with the egg plasma membrane. Motility is stimulated by exposure to seawater, while later events are orchestrated by factors from the egg. The sperm signaling pathways are exquisitely tuned to bring the sperm to the egg, bind, and fuse the two cells as quickly as possible.

Peptide-induced hyperactivation-like vigorous flagellar movement in starfish sperm

Zygote ◽  
2006 ◽  
Vol 14 (1) ◽  
pp. 23-32 ◽  
Author(s):  
Kogiku Shiba ◽  
Tomoko Tagata ◽  
Junko Ohmuro ◽  
Yoshihiro Mogami ◽  
Midori Matsumoto ◽  
...  
Keyword(s):  
Acrosome Reaction ◽  
Sea Urchins ◽  
Beat Frequency ◽  
Swimming Velocity ◽  
Jelly Coat ◽  
Cgmp Signalling ◽  
Flagellar Beat ◽  
Aphelasterias Japonica ◽  
Significant Difference ◽  
Egg Jelly

Asterosap, a sperm-activating peptide (SAP) from the starfish egg jelly coat, is diffusible and controls a cGMP-signalling pathway in starfish sperm in the same manner as resact, a potent chemoattracting SAP in sea urchins. This fact suggests that asterosap may serve as a chemoattractant like resact at concentrations with appropriate gradients. Since asterosap is one of three egg jelly components, which in concert induce the acrosome reaction, it is still worthwhile to evaluate how asterosap modulates sperm motility prior to this reaction. We analysed the flagellar movement of sperm of the starfish Aphelasterias japonica in artificial seawater (ASW) containing the asterosap isoform P15 at 1 μmol l−1. We found that sperm swim straighter with more symmetrical flagellar movement in P15 than in ASW, but without any significant difference in the flagellar beat frequency and the swimming velocity. The flagellar movement is, however, dramatically different between sperm firmly attached to the solid surface by the head in P15 and those attached in ASW: in P15 the flagellum bends to a greater extent, with higher curvature and with higher shear angle up to a right angle to the flagellar wave axis, and beats at an increased frequency. The vigorous flagellar movement of sperm, which can be activated when sperm are placed in high-load circumstances just as entering into a jelly layer, may increase propulsive forces and hydrodynamic resistances, allowing sperm to undergo the acrosome reaction as effectively as possible.

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