One word, from the Latin
/amˈplekəsəs/ · noun · pl. amplexus or amplexuses
He holds. She spawns. The eggs are fertilized outside both animals, in open water — so the grip is not a formality. The grip is the mechanism.
The mating hold in which a male climbs onto a female's back and grips her with his forelimbs, keeping their vents aligned while she releases her eggs and he releases sperm over them. He may hold on for minutes, or for weeks.
Any comparable clasp used in mating elsewhere in the animal kingdom. Most often said of horseshoe crabs, where the male hooks onto the rear of the female's shell with a modified pair of claws and is towed up the beach behind her.
An embrace. This is what the Latin actually says, and it is almost the only sense English never uses.
The Latin is a past participle doing a noun's job: an embracing, a thing that has been embraced. Two bodies wound around one another, which is the same image as a braid.
English borrowed it whole, handed it to zoologists, and left it there. Outside a herpetology paper you will almost never meet it — which is a pity, because it is a better word than any of its plain-English substitutes.
The grip is not one thing. Different lineages hold in different places, and the position is heritable enough to be a taxonomic character. Roughly eight forms have been named; two of them account for most frogs on earth. Below: seen from above, female outlined, male shaded, contact marked in gold.
Around the waist, in front of the hind legs. The oldest arrangement, kept by the oldest branches of the family.
Behind the forelimbs — the armpits. The commonest grip by a wide margin, and the one that lines the vents up best.
Hands over the top of her head. Used by small poison frogs that lay a handful of eggs on a leaf rather than a raft of them in a pond.
Hands reaching forward and meeting underneath her throat. Rare, and easy to mistake for the plate above until you look from the front.
He sits on her back and holds nothing at all. Described only in 2016, in a frog whose sperm simply runs down her back to the eggs.
He is too round and too short-armed to reach around her, so a skin secretion cements him in place until the eggs are laid.
Males of many species grow rough dark patches of hardened skin on their thumbs and forearms for the breeding season, then lose them again. They exist for one job: keeping hold of a wet animal that is trying to get away.
Minutes in some species, hours in most, days or longer in others. The male does not eat while he is holding on. Neither, in practice, does she.
A clasped female swims worse, walks worse, and feeds less than she otherwise would. The embrace is measurably expensive, and she pays most of it.
Where a whole population breeds in the same week, several males may pile onto one female at once and refuse to let go — a knot of animals that occasionally drowns the one at the bottom.
A male in the frenzy will clasp other males, other species, fish, floating debris and the occasional hand. A wrongly clasped male answers with a short chirp and a vibration of the flank that means, unambiguously, let go.
A few lineages have abandoned the clasp entirely — Madagascan frogs that never touch, others that only sit. Losing amplexus has happened more than once, in groups that are not closely related.
The pair remained in axillary amplexus for eleven days before the eggs were laid.Typical construction: in amplexus
Sense 2 is not a technicality. On the shores of Delaware Bay each spring, horseshoe crabs come out of the water in their tens of thousands on the high tides around the new and full moons — males already latched to the backs of females, sometimes several deep, and dragged up the sand to where the eggs go in.
They have been doing it since long before there were frogs to do it differently. It is the oldest embrace still being performed.