Onychophoran-euclitellate relationships: evidence from spermatozoa ultrastructure

Jamieson B.G.M. (1986) Onychophoran-euclitellate relationships: evidence from spermatozoa ultrastructure. Zoologica Scripta, 15 2: 141-155. doi:10.1111/j.1463-6409.1986.tb00217.x


Author Jamieson B.G.M.
Title Onychophoran-euclitellate relationships: evidence from spermatozoa ultrastructure
Journal name Zoologica Scripta   Check publisher's open access policy
ISSN 0300-3256
Publication date 1986-01-01
Sub-type Article (original research)
DOI 10.1111/j.1463-6409.1986.tb00217.x
Open Access Status Not yet assessed
Volume 15
Issue 2
Start page 141
End page 155
Total pages 15
Subject 1103 Clinical Sciences
Abstract Onychophoran sperm share striking apomorphies with sperm of oligochaetes: the elongate, cylindrical, strongly condensed nucleus with (enchytraeid oligochaetes only) spiral keel(s); interpolation of mitochondria, which are spiral as in some microdriles, between nucleus and axoneme (autapomorphy); presence of postmitochondrial annulus; occurrence of a basal cylinder at the anterior end of the two central singlets (autapomorphy). Onychophoran sperm differ notably from oligochaete sperm: in possessing periacrosomal material; in the helical coiling, reduction, or absence of the acrosome vesicle (though acrosomal coiling occurs in leeches); in the conical subacrosomal structure contrasting with the characteristic acrosome tube of euclitellates; in the absence of a perforatorium (though these two features could be consequent on the reduction of the acrosome); in lacking a distinct padlike thickening of the anterior nuclear envelope; in possessing (external to the mutual 9 + 2 axoneme) 9 peripheral singlets and a subplasmalemmal microtubular manchette (also present in questid annelids); and in the scattered, rather than regularly arranged, peripheral glycogen of the axoneme; they also lack two additional fibres which give the characteristic tetragon of the oligochaete axoneme; and, although the centriolar triplets are disrupted, having a more complete distal centriole than in euclitellates. The remarkable similarities to euclitellate sperm, coupled with embryological similarities between Onychophora and Euclitellata, suggest that the onychophoran-euclitellate assemblage is a monophyletic group and the sister-group of the myriapod-hexapod assemblage. Wider phylogenetic implications of these findings are discussed.
Q-Index Code C1
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: Scopus Import - Archived
 
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