Table 2 Eukaryotic organisms that lack a synaptonemal complex and the supporting lines of evidence.

Ciliates

Loidl and Scherthan⁷⁸ observed no SC for Tetrahymena thermophila, but Chi et al.⁴⁰ observed fragmented SCs in Stylonychia mytilus, a close relative of Oxytricha trifallax.

Tetrahymena thermophila, Paramecium tetraurelia, Ichthyophthirius multifiliis, and Oxytricha trifallax⁴⁰

Dinoflagellates

Gymnodinium pseudopalustre, Amphidinium cryophilum, Alexandrium tamarense, Alexandrium minutum, and several species of Tovelliaceae^3,20,21,22

In unspecified taxa²³

Diatoms

Unconfirmed. Frustule and dense chromatin obstruct view of potential SCs^79,80. Manton et al.⁸¹ observed SC-like ribbons in Lithodesmium undulatum.

Pseudo-nitzschia multistriata, Seminavis robusta, Fragilariopsis cylindrus, Thalassiosira pseudonana, and Phaeodactylum tricornutum⁴⁸

Corn smut fungus Ustilago maydis

⁴⁹

^50,82

Fission yeast Schizosaccharomyces pombe

^45,83

⁴⁵

Filamentous fungus Aspergillus nidulans

⁸⁴

Putative genes encoding Hop1, Red1, and Mer3 (GenBank: CBF81757.1, EAA61648.1, CBF81763.1) are present. Genes encoding Pch2, Zip1, Zip2, Zip3, and Zip4 are absent.

Male fruit fly Drosophila melanogaster

⁸⁵

Gilboa and Lehmann⁸⁶ showed molecular pathways taken during spermatogenesis versus oogenesis.