Nebenkern

{{Short description|Covering of axoneme as a mitochondrial spiral}}

The nebenkern is a mitochondrial formation in the sperm of some insects such as Drosophila. After the completion of meiosis, spermatid mitochondria wrap around each other to form a spherical aggregate, adjacent to the nucleus.{{cite web |url=http://8e.devbio.com/article.php?ch=19&id=194 |title=Fuzzy Onions and the Nebenkern |publisher=Sinauer Associates, Inc |accessdate=February 29, 2012 |url-status=dead |archiveurl=https://web.archive.org/web/20070207233329/http://8e.devbio.com/article.php?ch=19&id=194 |archivedate=February 7, 2007 }} The nebenkern proceeds to elongate into a double-stranded helical structure.{{cite web |url=http://www.merriam-webster.com/medical/nebenkern |title=nebenkern|website=The Merriam-Webster Unabridged Dictionary |publisher=Merriam Webster, Inc. |accessdate=February 29, 2012}} During flagellum elongation the nebenkern unfolds and the two derivatives (major and minor mitochondrial derivatives) elongate down the bundle of microtubules that constitute the axoneme core of the flagellum.{{cite web|url=http://amigo.geneontology.org/cgi-bin/amigo/term_details?term=GO:0016006|date=May 27, 2013|title=Nebenkern (Gene Ontology term)|author=Michael Ashburner}}