Marionina Michaelsen 1890
MARIONINA MICHAELSEN, 1890 Type species: Pachydrilus georgianus Michaelsen, 1888. In addition to the Lumbricillus specimens described above, we received six other enchytraeid specimens from the recent southern expeditions. Two of them were small, semi-mature and unpigmented individuals from Snow Isl...
| Main Authors: | , , , , |
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| Format: | Other/Unknown Material |
| Language: | unknown |
| Published: |
2021
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| Subjects: | |
| Online Access: | https://zenodo.org/record/6461127 https://doi.org/10.5281/zenodo.6461127 |
| Summary: | MARIONINA MICHAELSEN, 1890 Type species: Pachydrilus georgianus Michaelsen, 1888. In addition to the Lumbricillus specimens described above, we received six other enchytraeid specimens from the recent southern expeditions. Two of them were small, semi-mature and unpigmented individuals from Snow Island, and four were large, mature worms with dark pigmentation from South Georgia. Although the six specimens differed greatly in appearance, the molecular data strongly supported them as a monophyletic group of three species. The two unpigmented specimens belonged to the same, but yet unidentified, species, whereas the four pigmented specimens (constituting two additional species) were all highly reminiscent of M. aestuum, a taxon placed in Lumbricillus by Nielsen & Christensen (1959), but here regarded as a member of Marionina s.s. As mentioned in the Introduction, Marionina s.l. has grown to become a large genus, with a wide definition allowing for the inclusion of many unrelated taxa. A formal revision of this genus is beyond the scope of our study, but we aim here to provide enough information to allow for such a revision in the near future. The definition of Marionina s.s. can only originate from the type species M. georgiana, which fortunately has been given two extensive redescriptions (Rota et al., 2008; Schmelz & Collado, 2008). Marionina georgiana is marine and has the following characters: epidermis densely glandular; sigmoid chaetae, with upper bundles dorsolateral (closer to lateral line than the ventral bundles); ventral nerve cord with continuous, scattered occurrence of perikarya (and not concentrated in separate ganglia like that of Achaetinae; Rota et al., 2008); brain with posterior incision; three pairs of pharyngeal glands; gradual transition between oesophagus and intestine; oesophageal appendages absent; dorsal vessel arising in XIII and bifurcating anteriorly at front of peristomium (= lumbricilline pattern); nephridia with anteseptale consisting of funnel only and nucleated ... |
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