Table 1. Summary of experimental evidence on the main calcium channels proposed in the pathway activated by SAPs.

^aIt is worthwhile to mention that out of the pharmacological blockers listed, none of them are 100% specific to the associated channels. ^bAntibody raised against a polypeptide of the α subunit in rat, which also recognises the homologous version in mouse and human sperm. ^cAntibody raised against pore-forming subunit polypeptides of A. punctulata [12] and S. purpuratus [18]. ^d It is of note that direct electrophysiological recordings for this ion channel have not been achieved in mature sea urchin spermatozoa compared with the homologous complex in mouse, human and macaque spermatozoa [19].

Ca2+ channel	Experimental evidence on sea urchin sperm
	Molecular biology	Pharmacologya
LVA (T type)	mRNA in testis tissue [10]	Nickel [13]
		Nimodipine [14, 15]
HVA (L type)	mRNA in testis tissue, immunolocalisationb [16]	Nimodipine [16]
		Nifedipine [16]
		Verapamil [17]
CatSperd	mRNA in testis tissue, immunolocalisationc, mass spectrometry [12, 18]	Mibefradil [12]
		MDL12330A [12]
		NNC 55–0396 [18]