Talk:Sperm heteromorphism

Sperm also group for transport... This info may be helpful.

Sperm-grouping: Sperm groups have been found across several vertebrate and invertebrate taxa, ranging from sperm pairs to massive aggregates containing hundreds of sperm [7]. These social sperm are often highly adapted to the task. The charming great-diving beetle Dytiscus marginalis has sperm with a distinctive flat side that allows some sperm to pair up—stuck together by the head—and use both tails to propel themselves onward [8]. Meanwhile, sperm of gyrinid beetles are attached via a third-party rod-like object produced in the male epididymis, the spermatostyle. This appears to facilitate and synchronise sperm migration to the female sperm storage organs, where the spermatostyle disintegrates, releasing the sperm [8].

As might be expected, sperm grouping is sometimes found to drive more efficient migration towards the egg. Hundreds of sperm agglutinate by the head in the fishfly, Parachauliodes japonicus, and swim into the female spermatheca to the tune of a synchronised tail-beat, which propels them faster in large groups than in small [9]. More spectacularly social sperm are found in the humble Norway rat, Rattus norvegicus, and several other murid rodents, which have sperm with a distinctive hook-shaped head (Figure 2). Puzzling at first, this hook is now thought to help sperm to reversibly form groups of up to several hundred sperm (Figure 2A and 2B). And while no speed advantage in grouping was found in the house mouse, Mus musculus [10], sperm groups swim faster than single sperm in the Norway rat [10] and the wood mouse, Apodemus sylvaticus (discussed below) [3]. Sperm of the short-beaked echidna, Tachyglossus aculeatus, also form large groups of up to 100 in which coiled sperm heads are stacked tightly and cemented together, which again improves swimming speed [11]. Finally, in most species of American opossums, sperm rotate to align their head in pairs as they mature in the epididymis, leading to pairs of sperm conjugated by the head and propelled by the coordinated beat of both tails, which results in both a faster and straighter trajectory than solitary swimming sperm [12,13] (Figure 3).

http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0060130&ct=1

169.229.76.14 (talk) 17:13, 18 April 2009 (UTC)

kamikazi sperm not discredited in all animals, just humans.
parasperm (non-fertile sperm produced through a constant developmental process) occurs in several invertebrates (see Hayakawa, 2007). www.springer.com/life+sciences/evolutionary+%26+developmental+biology/book/978-0-387-28036-3 --Ryan W (talk) 07:48, 10 July 2012 (UTC)