Quistadrilus multisetosus (Smith, 1900) 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 rings of large, finger-like papillae especially along the chaetal line, scattered smaller papillae, and possibly some foreign material. The dorsal bundles contain 3–14 thin hairs with bifid tips (hard to see at 40x) and 1–5 lyre-shaped pectinate chaetae. Anterior ventral bundles contain 2–3 bifid chaetae with the upper tooth longer than the lower. The posterior chaetae, usually single, have two forms: ones where the upper tooth is much longer than the lower throughout (Q. m. longidentus), and those that change to very thick, hooked chaetae with a large, curved lower tooth and a very short upper tooth. There are no cuticular penis sheaths and the clitellum is inconspicuous.
Q. multisetosus is identified by having a papillate body wall with finger-like papillae in rings, hair chaetae, and lyre-shaped pectinate chaetae. It either has ventral chaetae with the upper tooth much longer than the lower or a single chaeta with a strongly recurved lower tooth with a very short, thin upper tooth. There are no penis sheaths. It usually has many hair chaetae (up to 14 per bundle), but even if the hairs have been shed, the finger-like papillae and ventral chaetae (whether hooked or with a long upper tooth) are distinctive.
Q. multisetosus occurs in a wide range of habitats but is most abundant in those with organic enrichment.
Lakes Erie, Huron, Michigan, and Ontario.
Unlike many other tubificids, Quistadrilus multisetosus does not need to be mature to be identified because it is one of only a few species that are covered in papillae. There might be some confusion because of the two forms of Q. multisetosus. It is most often confused with Spirosperma ferox, which also has the body wall covered in papillae. 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 S. ferox are retractile and may be sunken into the body, but Q. multisetosus does not have a retractile prostomium and I. 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. 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 Q. multisetosus, 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 the ventral chaetae, some large, finger-like 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 strongly recurved chaetae like Q. multisetosus, although they are not typically found in the Great Lakes region. Varichaetidrilus 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 Q. multisetosus.
Q. multisetosus is a large freshwater oligochaete.
No, this species does not yet 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 scope photograph of a whole Q. multisetosus. The arrow is pointing out the finger-like papillae. Long hair chaetae are also visible.
Kathman, R.D., and R.O. Brinkhurst. 1998. Guide to Freshwater Oligochaetes of North America. pp. 182–183, 108, 178–179, 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. 13–15, 49–50, 21, 32, 45, 51.
