#sperm attraction

Regeneration -ll

Egg jelly in sea urchins primarily functions in:

Egg jelly is thick layer of sulfated fucan polysaccharides and glycoproteins surrounding vitelline envelope, deposited during oocyte growth and containing embedded chemotactic peptides resact and speract. Its primary adaptive functions are attracting sperm from distance via diffusion gradients ensuring fertilization in dilute seawater and inducing acrosome reaction through fucose-sulfate ligands that raise sperm calcium and pH. Jelly also contributes to species-specific agglutination of sperm. Polyspermy block is achieved by fertilization envelope elevation and hardening after cortical reaction, nutrient supply comes from yolk platelets, and embryonic genome activation depends on calcium and pH changes inside egg not jelly components.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Egg jelly functions - chemotaxis and acrosome induction.

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Regeneration -ll

Sea urchin eggs attract sperm via:

Sea urchin reproduction involves broadcast spawning where eggs and sperm meet in seawater at low concentrations, requiring efficient guidance mechanisms. Eggs achieve this via diffusible small peptides that establish steep chemical gradients attracting sperm by chemotaxis. Peptides bind flagellar receptors triggering guanylate cyclase, cGMP rise, potassium efflux, intracellular alkalization, and CatSper-mediated calcium pulses causing transient flagellar asymmetry and turning up-gradient. Repeated sampling creates biased random walk toward egg source. Electrical signals, temperature gradients, or phototaxis play negligible roles in this marine invertebrate, where chemotaxis optimizes fertilization efficiency and species-specificity via peptide-receptor matching.

Ref: Nature Review, Kaupp et al., Chemotaxis in sea urchin sperm - resact-guided navigation via Ca2+ signaling.

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Sea urchin -l

Egg jelly in sea urchins primarily functions in:

Egg jelly is thick gelatinous extracellular mucoid coat outside vitelline envelope composed of sulfated fucan polysaccharides intermingled with small peptides such as resact and speract. Its principal biological functions include long-range sperm chemoattraction and preparation for fusion. Diffusible peptides establish chemotactic gradient guiding motile sperm toward egg, while polysaccharides interact with sperm receptors inducing Ca2+-dependent acrosomal reaction ensuring membrane fusogen bindin becomes exposed precisely before reaching vitelline membrane. Although it contributes to species filtering, core specificity arises later at bindin-receptor binding step. It does not block polyspermy nor supply metabolic nutrition; polyspermy prevented by electrical shift and fertilization envelope.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Egg jelly role - sperm attraction and acrosome induction.

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Sea urchin -l

Sea urchin eggs attract sperm via:

Broadcast spawning sea urchins release gametes freely into seawater where sperm must locate relatively immobile eggs efficiently to ensure reproductive success. Egg jelly coat surrounding oocyte releases species-specific peptides that diffuse forming stable chemical gradient extending millimeters. Spermatozoa sense gradient concentration via receptor guanylate cyclase and CatSper Ca2+ channels, adjusting flagellar waveform asymmetry to bias swimming up gradient, classic chemotaxis analogous to bacterial navigation. Electrical signals, temperature gradients or light cues are not directional guides for marine gametes. This peptide-based chemoattraction substantially increases fertilization probability. Resact and speract peptides exemplify chemical attractants guiding sperm propulsion in open ocean.

Ref: Kaupp et al., Annu Rev Physiol, Chemotaxis in sea urchin sperm; Gilbert Chapter 7: Egg jelly chemotaxis.

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Sea urchin -lll

Sperm attraction peptides released from sea urchin egg jelly are:

Sea urchin egg jelly contains diffusible peptides that attract sperm via chemotaxis. Purified factors Resact from Arbacia punctulata and Speract from Strongylocentrotus purpuratus are small 10-14 amino acid sulfated peptides. They bind receptors on sperm flagellum activating membrane guanylate cyclase, increasing cGMP, calcium influx, and altering flagellar beating to orient toward gradient source. This chemotaxis enhances encounter rates in seawater where dilution is extreme. Bindin and Hyalin are structural adhesion proteins, acrosin is acrosomal protease, not chemoattractants, leaving Resact and Speract as established sperm attraction peptides guiding fertilization.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Resact Speract chemotaxis peptides sea urchin fertilization.

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