Spirosperma ferox Eisen, 1879 is a freshwater oligochaete worm that is common 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 slightly opaque with small, close papillae covering it, and possibly some foreign material; if the cuticle has recently shed, there may be few papillae. The prostomium and I are retractile and may be withdrawn into the body. The dorsal bundles contain up to 7 hairs with bifid tips (easily seen at 40x) and 1–5 lyre-shaped pectinate chaetae. Anterior ventral bundles contain up to 5 bifid chaetae with the upper tooth much longer than the lower and occasionally with a small additional spine; the length changes to subequal before the clitellum. Posteriorly, the upper teeth are shorter than the broad, recurved lower teeth. When mature, the clitellum is conspicuous and clear of papillae, and there are barrel-shaped, thick-walled penis sheaths, although they may be difficult to see.
S. ferox is identified by having a papillate body wall with small papillae, hair chaetae, and lyre-shaped pectinate chaetae. It has ventral chaetae with the upper tooth much longer than the lower anteriorly becoming shorter than the broad lower tooth posteriorly. The prostomium and I are retractile. There is a conspicuous clitellum with penis sheaths when mature. It sometimes sheds the cuticle and may be missing some or most of the papillae, but conspicuously bifid hairs and the lyre-shaped pectinate chaetae can help identify it.
S. ferox is common and often abundant in habitats that are moderately enriched, but uncommon in either oligotrophic or heavily polluted habitats.
This species occurs in all five Great Lakes.
Unlike many other tubificids, Spirosperma ferox does not need to be mature to be identified because it is one of only a few species that are covered in papillae. S. ferox is most likely to be confused with other species of Spirosperma or Quistadrilus multisetosus, which also has papillae, lyre-shaped pectinates, and minutely bifid hairs.
Spirosperma nikolskyi is also found in the Great Lakes except for Lake Erie. It is usually smaller than S. ferox with even more opaque papillae and body wall which can obscure some of the features that need to be observed for identification. S. nikolskyi has hair-like dorsal chaetae with minutely bifid to pectinate tips instead of lyre-shaped pectinate needles, and ventral bundles of II–IV contain some simple-pointed chaetae along with bifid chaetae. The prostomium and I are also retractile. S. nikolskyi has fewer chaetae than S. ferox. When mature, there are spermathecal chaetae on X and thin, hard-to-see penis sheaths. Because the features are sometimes obscured, 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. 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 anteriorly and needles with bifid, pectinate, or webbed tips.
S. ferox can also be confused with Q. multisetosus, which also has the body wall covered in papillae, hairs, and lyre-shaped pectinate chaetae. 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. ferox varies from having a sparse covering of papillae to being 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. ferox because it can have up to 14 hairs instead of up to 7 hairs. Both species have hairs that have bifid or pectinate tips, but they are much easier to see at 40X for S. ferox; hairs in Q. multisetosus are generally thinner, so the bifid or pectinate tips may require higher magnification. The dorsal chaetae are lyre-shaped in both species. 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. The ventral chaetae of S. ferox may be slightly longer than the lower anteriorly, but posteriorly always have broad lower teeth with short, thin upper teeth; they are not as hooked as Q. multisetosus. There are also up to 7 chaetae anteriorly in S. ferox, while Q. multisetosus will only have 2–3. Another big difference is that S. ferox has a conspicuous clitellum when mature, as well as barrel-shaped penis sheaths with thick walls, both of which Q. multisetosus lacks. They can be hard to distinguish when immature, but several of the above methods combined may help differentiate them.
The hardest specimens to distinguish are those which have some features of S. ferox, such as lyre-shaped pectinate chaetae, without very many papillae on the body wall. S. ferox sometimes sheds its cuticle and may therefore be lacking most of its papillae. These specimens must be carefully examined to look for other distinguishing features like recurved ventral chaetae, papillae, or bifid hairs. If none of these features can be distinguished, it may need to be considered an immature tubificid without hair.
There are a few tubificid species that lack papillae but have recurved chaetae like S. ferox, although they are not typically found in the Great Lakes region. Varichaetadrilus harmani has strongly recurved, sigmoid chaetae in both dorsal and ventral posterior segments, and spermathecal chaetae in X. Teneridrilus columbiensis has only bifid chaetae, but posterior dorsal and ventrals have a recurved lower tooth and short upper tooth; it is only found in the Columbia River, Oregon. Aulodrilus paucichaeta has no hair chaetae, but a variety of strange chaetae shapes with the upper tooth much smaller than the lower. Isochaetides curvisetosus is found in the Great Lakes, but not our samples. It has no pectinate chaetae and no hairs, but from XXV onward has solitary recurved chaetae with even shorter upper teeth than S. ferox.
S. ferox is a large freshwater oligochaete.
Yes, this species does have a barcode reference from the Great Lakes.
This work is licensed by Susan Daniel under a Creative Commons Attribution-NonCommercial 2.0 Generic License.
Figure 1. A dissecting microscope photo of a whole S. ferox, showing the opaque body wall and clitellum. In Lake Erie, S. ferox is the only Spirosperma species present, so it may be possible to identify while sorting instead of mounting.
Figure 2. This picture shows several features, including the retracted prostomium (P), the small papillae completely covering the body wall, and the ventral chaetae of II through V.
Kathman, R.D., and R.O. Brinkhurst. 1998. Guide to Freshwater Oligochaetes of North America. pp. 178–181, 108, 182–183, 144–147, 166–167, 186–187.
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, 51, 49–50, 21, 32, 45.
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