Burrowing barnacle (dwarf male)
Cryptophialus minutus
1.3 mm
Length of the dissected penis 'when not stretched', from one dwarf male 0.30 mm long. Darwin's figure, converted to millimetres: 1.27 mm
Relative champion, Microscopic
Darwin dissected a 1.27 mm penis out of a male barnacle only 0.30 mm long, about four times the male's length. He guessed it might extend to eight or nine times, and that guess is where the popular 'eight times its body length' barnacle figure comes from.
Margin note: Darwin ended that sentence with an exclamation mark, which seems fair.
Sources
- Darwin C. (1854) A Monograph on the Sub-class Cirripedia, with Figures of All the Species. The Balanidae (or Sessile Cirripedes); the Verrucidae, etc. London: Ray Society. pp. 566–586 (Cryptophialus minutus), Pl. 23–24 link
- Neufeld C.J., Palmer A.R. (2008) Precisely proportioned: intertidal barnacles alter penis form to suit coastal wave action. Proceedings of the Royal Society B 275(1638):1081–1087 doi:10.1098/rspb.2007.1760
Drawn from
- Darwin 1854, Pl. 24, fig. 19 (Cryptophialus minutus, mature male): The dwarf male: rounded, slightly bilobed sac, pointed upper lobe with the orifice (d), pupal antennae (a) at the attachment. Penis not shown (it is coiled inside)
- Darwin 1854, Pl. 23, fig. 19 (Alcippe lampas, mature male, penis exserted): Closest figured relative: the dwarf male of Alcippe with its 'probosciformed penis, shown exserted' (m): a very long, thin, gently curved tube tapering to a fine tip. Darwin says the two males are 'truly surprising' in their resemblance
- Darwin 1854, pp. 585–586 (page scans): The measurement text, for the verifier
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