Jamieson, B.G.M. 1995e. Evolution of
spermatozoa with particular reference to amniotes. In Advances in
Spermatozoal Phylogeny and Taxonomy. Jamieson, B.G.M., Ausio, J.
and Justine, J.-L. eds. pp. 343-358. Mémoires du Muséum
national d'Histoire Naturelle, vol. 166, Paris.
Synapomorphies of tetrapod sperm appear to
be: nuclear 'shoulders'; elongation, relative to dipnoans, of two
elements (dense fibres) peripheral to the axoneme adjacent to doublets
3 and 8;
and, questionably, development of an annulus. A lissamphibian
relative to Neoceratodus may
have been loss of one undulating membrane,
a single undulating membrane adjacent to the fibre of doublet 3.
synapomorphies (retained in Chelonia and Sphenodontida) include:
the distal centriole through the entire length of the moderately
midpiece; subspheroidal mitochondria, with concentric cristae; a
sheath; nine peripheral axonemal fibres; inward projections
columns) of the fibrous sheath aligned with fibres 3 and 8; loss or
transformation of the retronuclear body, present in dipnoans and (as
structure) urodeles. A possible crocodilian synapomorphy is a thick
around the singlets of the axoneme or the distal centriole.
birds are loss of the subacrosomal cone and, less certainly derived,
of all nine dense fibres to their axonemal doublets (also in
conical acrosome, fibrous sheath, and elongate centriole of ratites are
symplesiomorphies not proving monophyly. Restriction of the endonuclear
to the anterior region of the nucleus in other non-passerines and
may be a synapomorphy of these, homoplasic with crocodiles and derived
(emu). Squamate synapomorphies are: loss of endonuclear canals with
of the perforatorial rod to a prenuclear location; intermitochondrial
forward extension of the fibrous sheath into the midpiece; a
subacrosomal cone; and, homoplasically, shortening of the centriole.
sperm are distinguished by loss of the perforatorium (and canal),
with some non-ratite birds, great reduction of the centrioles, and, in
therians, (apomorphic?) detachment of peripheral fibres, except
sometimes 3 and
8, from the doublets.