Potamothrix vejdovskyi

  • Photomicrograph of a slide mounted worm with evenly spaced bundles of chaetae. Dorsal bundles have short hairs and rounded bifid chaetae, while ventral bundles have just rounded bifid chaetae.

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    Figure 1. Potamothrix vejdovskyi has short hairs with bifid chaetae dorsally and bifid chaetae ventrally.

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  • Photomicrograph of part of a worm showing a bundle of somatic hairs (chaetae). There are several bifid chatae with rounded teeth, and one short sigmoid hair. scale bar 100 µm.

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    Figure 2. The bifid chaetae are rounded to varying degrees and the hairs are short. This can be even seen on young worms. These chaetae are very rounded.

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  • Photomicrograph of part of a worm showing several bundles of somatic hairs (chaetae). The bundles mostly have bifid chaetae with two divergent, slightly rounded teeth at the end (one labeled v), while one also has short, thin hairs (d). Scale bar 100 µm.

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    Figure 3. The dorsal (d) and ventral (v) bifid chaetae are similar. These ones are divergent and slightly rounded but more pointed than the previous image.

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  • Photomicrograph of part of a worm showing a few bundles. II and III are mostly broken bifid chaetae, but III is unbroken bifid chaetae with rounded teeth and a hair chaetae.

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    Figure 4. The first few anterior dorsal bundles may be broken or missing hairs, but hairs should be visible by IV or V.

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  • Photomicrograph of part of a worm showing a modified reproductive chaetae with a long spear-shaped trough that comes to a sharp point. Labeled X. Scale bar 100 µm.

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    Figure 5. There are 1–2 large spermathecal chaetae per bundle, spear-shaped with a hollow trough, and coming to a sharp point. They sometimes stick out very visibly from the body. Reproductive structures are not needed to identify P. vejdovskyi since the chaetae are unique, but it can be a very easy means to confirm the identity if mature.

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  • Photomicrograph of part of a worm showing two modified reproductive chaetae. One is a long spear-shaped trough that comes to a sharp point. The other is a bifid chaetae with a large rounded lower tooth and a very thin upper tooth. Scale bar 100 µm.

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    Figure 6. There is some variability in the development of the spermathecal chaetae. Here we see a slightly modified bifid chaetae with a fully developed spermathecal chaetae coming in to replace it.

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  • Photomicrograph of a worm showing part of the body that is thickened with a granular texture. There are two needle-like chaetae just next to this section, and other bundles of chaetae.

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    Figure 7. The spermathecal chaetae are often associated with a thickened clitellum, although the clitellum is not always developed.

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  • Photomicrograph of a worm with a redeveloping head evident from a smaller, thinner body lacking chaetae coming from a much thicker body. The first chaetal bundles are labeled IX and the second, labeled X, have two needle-like chaetae.

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    Figure 8. This mature individual is regrowing its head from IX. The spermathecal chaetae can be used as a point of reference for regrowing or fragmented individuals and can be useful for deciding whether to count a fragmented worm if it is only missing a few segments that are not found in other size categories. It is not best practice to count fragmented worms lacking heads, especially since P. vejdovskyi can be identified by chaetae alone and a head with only a few segments may be easily identified.

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Potamothrix vejdovskyi

Taxa description

Potamothrix vejdovskyi (Hrabě, 1941) is a freshwater oligochaete worm that is common and sometimes abundant in the Great Lakes. It is a tubificid worm that has dorsal hairs and bifid chaetae and bifid ventral chaetae beginning in II. When mature, it has spermathecal chaetae on X. The dorsal bundles have 2–4 short, bent hair chaetae with 4–6 bifid chaetae with rounded subequal teeth. The hair chaetae may be missing from the first few segments. There are up to 10 chaetae in ventral bundles that are similar to the dorsals. The spermathecal chaetae are large and long, with elongate teeth that form a trough-shaped distal end that is hollow, although the shape may vary with the degree of maturity. P. vejdovskyi is the only species of Potamothrix with bifid chaetae and hairs anteriorly, and the only tubificid in the region with rounded bifid teeth.

Distinguishing features

P. vejdovskyi is identified by bifid dorsal chaetae with rounded teeth, short bent hair chaetae, and spermathecal chaetae on X when mature.

Habitat

It is often found in mesotrophic habitats with Potamothrix moldaviensis.

Lake occurrence

Lakes Erie, Huron, Michigan, and Ontario.

Similar species

Unlike many other tubificids, P. vejdovskyi does not need to be mature in order to be identified because the bifid chaetae with rounded teeth are distinct and can often be found even in younger immature worms. If the chaetae do not appear very rounded, it may be confused with an immature tubificid with hair. The other Potamothrix species either lack hair chaetae or have hair chaetae with pectinate chaetae anteriorly.

Relative size

P. vejdovskyi is a large freshwater oligochaete.

Does it have a barcode reference from the Great Lakes?

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

Potamothrix vejdovskyi entry in BOLD database

References

Kathman, R.D., and R.O. Brinkhurst. 1998. Guide to Freshwater Oligochaetes of North America. pp. 150–153, 122.

Stimpson, K.S., D.J. Klemm, and J.K. Hiltunen. 1982. A Guide to the Freshwater Tubificidae (Annelida: Clitellata: Oligochaeta) of North America. pp. 18, 49.