Connecting bridges between axoneme and other components in the sperm tail of some insects

Spermatozoa from three insect groups were examined by electron microscopy and found to have bridges that connect some of the axonemal doublets with either the two mitochondrial derivatives or, in the phasmids, the so-called laminated bodies. Within Hemiptera Heteroptera the bridges extend from doublet Nos. 1 and 5, within chrysopid neuropterans from doublet Nos. 2 and 5, and in the phasmids from axonemal doublet Nos. 2 and 4. Bridges were looked for in spermatozoa from several other insect groups but not found. The bridges in the chrysopids are regularly curved rather than straight. While bridges in heteropterans and chrysopids were seen in spermatozoa fixed with “standard fixatives,” those in the phasmids were distinctly resolved only in spermatozoa that had been fixed with a tannic acidcontaining fixative. In spite of these differences, it is conceivable that the bridges in these three insect taxa are all derived from similar, faint, bridge-like connections that sometimes can be seen to extend from all or many doublets toward the axonemal sheath of the early insect spermatid. These bridges or bridge-like structures might have a morphogenic function in that they may specify the location of the mitochondria later to become mitochondrial derivatives or, in the phasmids, of the laminated bodies.