Spermatophore in the context of Pyrrolizidine alkaloid

Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. Male animals inseminate females in order to internally fertilize their egg cells.

Most taxa that reproduce by internal fertilization are gonochoric. Male mammals, reptiles, and certain other vertebrates transfer sperm into the female's vagina or cloaca through an intromittent organ during copulation. Most birds use the "cloacal kiss," pressing cloacas together to transfer sperm. Salamanders, spiders, some insects and some molluscs undertake internal fertilization by transferring a spermatophore, a bundle of sperm, from the male to the female. After fertilization, embryos develop in eggs in oviparous species or inside the mother’s reproductive tract in viviparous ones.

A hectocotylus (pl.: hectocotyli) is one of the arms of male cephalopods that is specialized to store and transfer spermatophores to the female. Structurally, hectocotyli are muscular hydrostats. Depending on the species, the male may use it merely as a conduit to the female, analogously to a penis in other animals, or he may wrench it off and present it to the female.

The hectocotyl arm was first described in Aristotle's biological works. Although Aristotle knew of its use in mating, he was doubtful that a tentacle could deliver sperm. The name hectocotylus was devised by Georges Cuvier, who first found one embedded in the mantle of a female argonaut. Thinking it to be a parasitic worm, in 1829 Cuvier gave it a generic name (Hectocotyle),which is a New Latin term combining the Greek words for "hundred" (hec(a)to(n)) and for "hollow thing, cup" (cotyle).

The Salamandroidea are a suborder of salamanders, referred to as advanced salamanders. The members of the suborder are found worldwide except for Antarctica, sub-Saharan Africa, and Oceania. They differ from suborder Cryptobranchoidea as the angular and prearticular bones in their lower jaws are fused, their trunk ribs are bicapitate, and all members use internal fertilization. The female is fertilized by means of a spermatophore, a sperm-containing cap placed by the male in her cloaca. The sperm is stored in spermathecae on the roof of the cloaca until it is needed at the time of oviposition.

The earliest known salamandroid fossils remain contested. Some studies suggest that the earliest salamandroids are represented by specimens of the species Beiyanerpeton jianpingensis and Qinglongtriton gangouensis from the Tiaojishan Formation of Inner Mongolia, China, dated to the Late Jurassic about 157 million years ago. Alternative analyses suggest that Beiyanerpeton jianpingensis and Qinglongtriton gangouensis are stem salamanders and that the oldest known certain salamandroid is Valdotriton gracilis from the Early Cretaceous of Spain, about 127 Ma.