Aulodrilus pigueti
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Figure 1. The anterior dorsal bundles of Aulodrilus pigueti have 2–5 short hair chaetae with 4–5 (or up to 10) bifid chaetae with short, thin upper teeth. It may be missing some or all chaetae or at least hair chaetae in II–IV or VII.
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Figure 2. Starting in about VII, the dorsal chaetae become a flattened spoon shape. It can be hard to distinguish because there is low contrast to the edges of the specialized chaetae, and if they are facing the edge, they will appear as a very thin chaetae.
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Figure 3. The anterior ventrals are slightly curved, with the upper tooth a little shorter and thinner than the lower tooth.
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Figure 4. The posterior ventral chaetae have the upper tooth much shorter and thinner than the lower tooth.
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Figure 5. Like most of the species in genus Aulodrilus, A. pigueti may be covered in a sediment tube, which can make it difficult to see the chaetae or even the head to tell if it is a fragment or not.
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Figure 6. It is not necessary for A. pigueti to be mature in order to identify it, but it may have a thickened clitellum if it is mature.
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Figure 7. When mature, A. pigueti has true penes that lack a cuticle and penial chaetae in VIII that resemble spermathecal chaetae.
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Aulodrilus pigueti
Taxa description
Aulodrilus pigueti Kowalewski, 1914 is a freshwater oligochaete worm that is uncommon in the Great Lakes. It is a tubificid worm with dorsal hairs beginning in II and both dorsal and ventral chaetae are bifid or specialized. This genus is known for having distinctive somatic chaetae, which vary from species to species. They have true penes, but often reproduce asexually. They are often found in sediment tubes, which can obscure the features when mounted if not removed. The anterior dorsal bundles of A. pigueti have 2–5 short hair chaetae with 4–5 (or up to 10) bifid chaetae with short, thin upper teeth. There are 4–11 ventral chaetae which resemble the dorsal needles. Starting in VII, all dorsal needle chaetae are oar-shaped when viewed facially, appearing simple-pointed or compressed to a point from the lateral aspect. Many bundles may need to be looked at to find chaetae in the correct orientation. When mature, there are penial chaetae that are spoon-shaped and resemble spermathecal chaetae, often in VIII, 1-2 per side. Unlike other Aulodrilus species, A. pigueti may be missing some or all chaetae or at least hair chaetae in II–IV or VII.
Distinguishing features
A. pigueti is identified mainly by the distinct somatic chaetae. This species has hair chaetae, anterior dorsal needle chaetae are bifid with a short, thin upper tooth, oar-shaped dorsal chaetae starting in VII, and ventral chaetae with a short, thin upper tooth. There may be chaetae missing anteriorly and penial chaetae in VIII in mature specimens. It may be found in sediment tubes like other Aulodrilus species.
Habitat
Aulodrilus spp. are found in mesotrophic habitats or locations with weeds. A. pigueti is found in mesotrophic habitats with a silty substrate and can be found in the drift of rivers. It is often found with A. limnobius or other Aulodrilus species.
Lake occurrence
Lakes Erie, Huron, and Ontario.
Similar species
Unlike many other tubificids, A. pigueti does not need to be mature in order to be identified. This species is quite distinctive, but it could be confused with other species from Aulodrilus. If there is a sediment tube on the mounted worm, it may be possible to see the short, thin upper teeth of the anterior chaetae but be unable to see the specialized chaetae posteriorly through the sediment tube. It should also be possible to see hair chaetae through the sediment tube. The anterior chaetae of A. pigueti are closer to either Aulodrilus pluriseta or A. limnobius than A. americanus because the former three have upper teeth shorter and thinner than the lower, but not simple-pointed or minutely bifid. However, A. pluriseta and A. pigueti both have hair chaetae, while A. limnobius and A. americanus do not. The dorsal chaetae of A. pluriseta do not change posteriorly, but A. pigueti has oar-shaped chaetae starting in VII. It is most likely that A. pigueti could be confused with A. limnobius because they are often found together and their anterior and posterior chaetae are similar, and the main difference lies in whether there are hair chaetae or not. The chaetae of A. limnobius also form a spatulate shape, but they have an upper tooth like a dot at the top of the spatulate chaetae and appear bifid with a thin upper tooth in profile; A. limnobius also lacks hair chaetae. In addition, A. pigueti may be missing some chaetae or all in II–IV or VII, unlike other Aulodrilus species. Lastly, A. paucichaeta also has bifid chaetae with short upper teeth but it lacks hair chaetae and posterior chaetae become solitary and very thick with large recurved lower teeth. A. paucichaeta is not usually found in the Great Lakes region.
Similar to A. pigueti, Branchiura sowerbyi also has chaetae with short, thin upper teeth. B. sowerbyi is quite large and has gill filaments on each segment posteriorly, but it readily fragments and the anterior end bears some resemblance to A. pigueti. The dorsal bundles contain several hairs and several bifid chaetae with a short, thin upper tooth with replications on the lower tooth when examined under an oil immersion lens; posterior chaetae do not change shape. A. pigueti does not have replications and posterior chaetae are spatulate. The ventral chaetae of B. sowerbyi have short, thin upper teeth, but the anterior ventral chaetae may be simple-pointed in II–IV. A. pigueti does not have simple-pointed ventral chaetae. B. sowerbyi has eversible pseudopenes, not true penes and penial chaetae, and it does not have sediment tubes.
Relative size
A. pigueti is a medium-sized oligochaete that is often smaller than many other tubificid worms and may be closer in size to naidid worms.
Does it have a barcode reference from the Great Lakes?
No, this species does not yet have a barcode reference from the Great Lakes.
References
Kathman, R.D., and R.O. Brinkhurst. 1998. Guide to Freshwater Oligochaetes of North America. pp. 184–187, 122, 200–201, 198–199, 192–193, 166–169.
Stimpson, K.S., D.J. Klemm, and J.K. Hiltunen. 1982. A Guide to the Freshwater Tubificidae (Annelida: Clitellata: Oligochaeta) of North America. pp. 17, 44.