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. Author manuscript; available in PMC: 2024 May 1.
Published in final edited form as: J Exp Zool B Mol Dev Evol. 2023 Dec 11;342(3):126–143. doi: 10.1002/jez.b.23233

FIGURE 3.

FIGURE 3

Examples of reproductive anatomies in different annelids. (a) Pristina leidyi (a clitellate naidid), is hermaphroditic, and gonads always appear in segments 6 and 7. Gonads, fission zones, and the posterior growth zone all express germline/multipotency markers. arrowheads indicate some of the piwi+ cells on the ventral nerve cord. Inset (a′) shows the piwi+ cells from the ventral view (adapted from Özpolat & Bely, 2015). (b) Platynereis dumerilii (an errant polychaete) is gonochoric, and does not have localized gonads. Instead gonial clusters are distributed along the body (shown by vasa expression). Adapted from Kuehn et al. (2021). (c) Cartoon of a frontal section of Criodrilus. Ovaries (yellow) and testes (blue) as well as secondary sexual structures such as seminal vesicles and ducts are shown (Janda, 1912a). This species has septae in between segments. (d) Schematics showing the normal distribution of gonads (bottom) and the supernumerary gonads that extend beyond gonadal segments in Criodrilus (top) (Janda, 1912a).