Spirosperma nikolskyi

Spirosperma nikolskyi (Lastochkin and Sokolskaya, 1935) is a freshwater oligochaete worm that is uncommon in the Great Lakes. It is a tubificid worm with dorsal bundles with hairs and lyre-shaped pectinate chaetae and bifid ventral chaetae beginning in II. The body wall is opaque with small, close papillae covering it, and possibly some foreign material. The prostomium and I are retractile and may be withdrawn into the body. The dorsal bundles contain 2–4 hairs and 2–4 hair-like chaetae with minutely bifid or pectinate tips, although these chaetae are usually difficult to see. Ventral bundles of II–IV contain 1–3 simple pointed chaetae, bifid chaetae, or both. The rest of the anterior ventral chaetae have the upper tooth longer and thinner than the lower and occasionally with a small additional spine; posterior ventral chaetae are single with a thin upper tooth and a broad lower tooth. When mature, there is a long, thin, hollow spermathecal chaetae on X, and thin penis sheaths that are hard to see. The close, dense papillae may obscure the dorsal and anterior ventral chaetae, making it difficult to tell if the first few segments have simple-pointed ventral chaetae. This species is synonymous with S. variegatus and S. oregonensis, which used to be Peloscolex variegatus and Peloscolex oregonensis.

S. nikolskyi is identified by having a densely papillate body wall with small papillae, hair chaetae, and hair-like chaetae with minutely bifid or pectinate tips. The ventral chaetae of II–IV are either simple-pointed, bifid, or a mixture of both, while the rest of the anterior ventral chaetae have the upper tooth longer and thinner than the lower, and posteriorly the chaetae are single with a broad lower tooth and short upper tooth. The prostomium and I are retractile. There are spermathecal chaetae in X and thin penis sheaths. The body wall is often very opaque and the features are sometimes obscured, so I have sometimes turned the slide to the opposite side to see the other side of the worm and have had some success at finding features, although it is limited because there is less room for focal adjustments on the microscope in that orientation.

Most often found in the profundal area of cold, oligotrophic habitats.

Lakes Huron, Michigan, Ontario, and Superior.

Unlike many other tubificids, Spirosperma nikolskyi does not need to be mature in order to be identified because it is one of only a few species that are covered in papillae. S. nikolskyi is most likely to be confused with other species of Spirosperma or Quistadrilus multisetosus, which also has papillae.

S. ferox is usually larger than S. nikolskyi with less opaque papillae and body wall, variable few to dense coverage with small papillae and foreign matter. S. ferox has lyre-shaped pectinate chaetae instead of hair-like dorsal chaetae with minutely bifid to pectinate tips. All of S. ferox’s ventral chaetae are bifid, so there are no simple-pointed chaetae in the anterior ventral chaetae; instead, S. ferox has anterior ventrals with the upper tooth longer than the lower becoming subequal, and the posterior ventrals have a short, thin upper tooth with a broad, curved lower tooth. The prostomium and I are also retractile. S. ferox has more chaetae in each bundle than S. nikolskyi. When mature, S. ferox has a conspicuous clitellum and barrel-shaped penis sheaths, instead of no obvious clitellum, spermathecal chaetae on X, and thin, hard-to-see penis sheaths in S. nikolsklyi. Generally, if the body wall is that opaque, it is often S. nikolskyi instead of S. ferox. S. ferox is found in Lake Erie, unlike S. nikolskyi, so all Spirosperma in Lake Erie can be separated during sorting instead of being mounted for identification. The other two species of Spirosperma are endemic to very small ranges in the Carolinas and Lake Tahoe, California, so it is unlikely to find S. carolinensis or S. beetoni. They both have simple pointed ventrals beyond IV and needles with bifid, pectinate, or webbed tips, instead of hair-like chaetae.

S. nikolskyi can also be confused with Q. multisetosus, which also has the body wall covered in papillae and hairs. The papillae of Q. multisetosus include small papillae but also large, finger-like papillae that tend to form in rings around the chaetal line. S. nikolskyi is densely covered in small papillae, but not large, finger-like papillae in rings. The prostomium and I of Q. multisetosus are not retractile. Q. multisetosus is usually hairier than S. nikolskyi because it can have up to 14 hairs instead of up to 4 hairs. Q. multisetosus has hairs that have bifid tips, but they are hard to see at 40X. The dorsal chaetae are lyre-shaped instead of hair-like. There are two types of ventral chaetae for Q. multisetosus: one where all of the ventral chaetae have the upper tooth much longer than the lower tooth, and one where the anterior chaetae have the upper tooth longer than the lower but the posterior chaetae are strongly recurved with a short, thin upper tooth over a broad lower tooth. Q. multisetosus does not have any simple-pointed chaetae in II–IV. The posterior ventral chaetae of S. nikolskyi are not as hooked as Q. multisetosus. Another big difference is that S. nikolskyi has spermathecal chaetae and thin penis sheaths, both of which Q. multisetosus lacks. It is easier to distinguish S. nikolskyi and Q. multisetosus than S. ferox and Q. multisetosus.

S. nikolskyi is a medium or large freshwater oligochaete.

Yes, this species does have a barcode reference from the Great Lakes.

Spirosperma nikolskyi entry in BOLD database

Kathman, R.D., and R.O. Brinkhurst. 1998. Guide to Freshwater Oligochaetes of North America. pp. 178–183, 108.

Stimpson, K.S., D.J. Klemm, and J.K. Hiltunen. 1982. A Guide to the Freshwater Tubificidae (Annelida: Clitellata: Oligochaeta) of North America. pp. 13–16, 49–51.