The first comparison of the sperm ultrastructure of Lymexyloidea with Mordelloidea and Tenebrionoidea (Coleoptera)

The work has considered the sperm structure of Lymexyloidea to test the relationship of this group with Tenebrionoidea and the recently proposed "Mordelloid clade", consisting of the families Mordellidae and Ripiphoridae. The sperm structure of the Hylecoetidae Elateroides dermestoides partially supports the above mentioned relationship as it has a short sperm provided with a peculiar acrosome characterized by an electron-dense ring at half-length and a dot at the apex. The Mordellidae species examined, Curtimorda maculosa and Conalia baudii share the unique organization of the posterior flagellar region provided with only the 9 axonemal accessory tubules. Moreover, due to the sperm length, sperm looping is evident. The Ripiphoridae Pelecotoma fennica exhibits notably differences from Mordellidae species lacking the unusual structure of the flagellar posterior region. The sperm looping is, however, still evident. • The sperm structure of Lymexyloidea partially supports its relationship with Mordelloidea. • The sperm of Mordellidae has a posterior flagellar region containing only the axonemal accessory tubules. • The sperm of Ripiphoridae shows a conventional flagella axoneme structure.