Storch, V.
and Jamieson, B.G.M. 1992c. Further
spermatological evidence for including the Pentastomida (Tongue worms)
in the Crustacea. International Journal for Parasitology
22:
95-108.
Phylogenetic relationships of
pentastomids with their putative maxillopodan and
remipedian
relatives have been deduced from sperm ultrastructure
intuitively and by
parsimony analysis using the PAUP program of Swofford
(1990, Version
3.01, Illinois Natural History Survey, Champaign, IL). A
remarkable degree
of homogeneity in the ultrastructure of the spermatozoa
of cephalobaenids
and porocephalids is demonstrated and a sister-group
relationship of
pentastomids and Branchiura, first proposed by Wingstrand (1972, Kongelige
Danske Videnskab Selskab Biologiske Skrifter 19: 1-72),
is confirmed.
Spermatozoal synapomorphies of the Pentastomida and the
branchiuran
Argulus include: absence of an acrosome vesicle and filament
in the mature
spermatozoon; presence of a pseudoacrosome, about 30mm long,
divisible
into a dorsal and a ventral component (the dorsal and
ventral rod), and
derived from pericentriolar structures; continuation of
the dorsal rod
with the dorsal ribbon of an axonemal sheath and with
material embedding
the centriolar doublets 1, 2 and 9; continuation of the
ventral rod with
material embedding the more ventrally situated doublets;
presence of the
axonemal sheath; presence of a connective from the dorsal
ribbon to axonemal
doublet 1; presence in the spermatid of nine dense
fibres peripheral
to the doublets; great elongation of the three
mitochondria
parallel to the nucleus; and total incorporation of the
axoneme in the
spermatozoon so that a free flagellum is absent. The sperm
of the
pentastome-branchiuran assemblage appear to be the most highly evolved of the
flagellate crustacean sperm.