Martinidrilus, Fend, Steven V. & Lenat, David R., 2007

Fend, Steven V. & Lenat, David R., 2007, Two new genera of Lumbriculidae (Annelida, Clitellata) from North Carolina, USA, Zootaxa 1666, pp. 1-22 : 10

Martinidrilus n. gen.

Diagnosis. Small to medium sized worms. Chaetae simple-pointed, sigmoid. Short, blind blood vessels numerous on dorsal vessel in posterior segments. First nephridia paired in VII; nephridial ducts terminate in narrow vesicles. Two pairs of testes in IX and X, one pair of ovaries in XI. Male pores in X, near 10/11, paired on ventral chaetal lines. Penes are very short papillae at most. Atria short, slightly petiolate, pyriform, with multicellular prostate glands. Two pairs of simple male funnels. Posterior vasa deferentia penetrate posterior septum (10/11), forming a short loop in XI. Vasa deferentia join a short, narrow common duct, which approaches the atrial ampulla from the posterior-median side, joining it apically or subapically. One or two pairs of spermathecae originate more than two segments anterior to male pores; spermathecal pores midlateral near middle of VI, or dorsolateral in VII and VIII. Spermathecae with a thick duct, and an elongate-sacciform ampulla with undifferentiated epithelium and unordered sperm.

Remarks. Currently, the genus includes two species from southeastern USA, Martinidrilus carolinensis n. sp. and Martinidrilus arenosus n. sp. Unique apomorphies include the anterior position of spermathecae, beginning three or four segments anterior to the atria; the vasa deferentia uniting to join a single duct to the atrial ampulla; and the unusual pattern of posterior blood vessels. The lateral to dorsolateral position of the spermathecal pores is also unusual, but common to other lumbriculid genera (e.g., Lumbriculus , some Trichodrilus ). Although the spermathecal position varies between the two described species, the other listed synapomorphies, plus general body form and morphology of the vasa deferentia, atria, nephridia and spermathecae all argue for placement in the same genus. The semiprosoporous male ducts and rather simple atria and penes suggest a relationship to either Stylodrilus or Trichodrilus ; of these two existing genera, the anteriorly placed spermathecal pores of Martinidrilus are closer to the arrangement seen in Stylodrilus , which has spermathecae in the first preatrial segment. However, the abovementioned apomorphies easily distinguish Martinidrilus from all described Stylodrilus species. Characters and possible phylogenetic relationships are discussed below, in the Discussion.