Scanning and transmission electron micrographs of naked mole-rat spermatozoa. a) Scanning electron micrograph of a typical multi-lobed sperm head, b-h) Transmission electron micrographs of naked mole-rat spermatozoa sectioned in different planes: b) Longitudinal section almost similar to spermaozoon in (a) showing irregular arranged chromatin, small midpiece and thin tail; c) Two sperm heads showing severe fragmentation and small midpiece; d) Sperm head containing a simple acrosomal cap; d-e) Proximal centriole with capitulum and striations of cross banded structures; f) Transverse to oblique section of anterior part of midpiece showing mitochondria with tubular-like cristae, some cross banded structures and distal centriole; g) Axoneme (9+2 microtubules) surrounded by nine outer dense fibres in midpiece; h) Only axonome in tail principal piece without a fibrous sheath. ACR = acrosome, HEAD = sperm head, FRG = fragmented sperm head, CAP = capitulum, PC = proximal centriole, CBS = cross banded structures, DC = distal centriole, MIT = mitochondria, MP = midpiece. Scale bars: a, b, c = 1 μm; d, e, f = 0.5 μm; g, h = 0.25 μm.
van der Horst et al. BMC Evolutionary Biology 2011 11:351 doi:10.1186/1471-2148-11-351