Category Archives: Invertebrates

Northern Widows at QUBS

Posted by Mark Conboy

Photo is by Philina English.

Eastern Ontario has its fair share of interesting and charismatic spiders. There are the argiopes (Argiope spp.), whose webs are decorated with an ultraviolet-reflective stabilimentum, presumably to attract insect prey; there are the enormous and parentally-minded pisaurids (Dolomedes and Pisaurina spp.) which carry their eggs with them in a bundle of silk to keep them safe from predators and parasitoids; there are also the beautifully marked jumping spiders (Salticidae) whose leaps propel them many times their own body length, and for safety sake always tether themselves with a string of silk. But among the most exciting spiders in our region is the highly venous and exceeding beautiful northern widow (Latrodectus variolus). I’ve found not one, but two northern widows at Queen’s University Biological Station this year; perhaps the first year this species has ever been documented there.

The northern widow is a close relative of the better known and often maligned black widow (L. mactans). Black widows are typically confined to the southern United States and their distribution does not normally include Canada. Occasionally black widows (and other charismatic subtropical invertebrates) arrive in Canada on shipments of produce from the southern states but probably do not survive long outside of buildings. Northern widows however are native, though they seem to be fairly rare throughout most of Eastern Ontario. In southwestern Ontario they are a little more common, with several large localized populations. Throughout much of their range though they are patchily distributed and not often encountered. Many people are not even aware of their existence in the province.

The first of the two females at QUBS was found below a black light at Ironwood Cottage on QUBS Point. She had constructed a nest and egg sac under a cinder block. She preyed on a mixture of insects attracted to the black light including June beetles (Phyllophaga spp.) and medium-sized moths. The second female was underneath a flat rock on a rock barren at the Elbow Lake Environmental Education Centre. The only prey item found in this female’s web were parts of a Pennsylvania woodroach (Parcoblatta pennsylvanica). This female also had an egg sac.

According to most sources northern widows can produce painful and potentially dangerous bites, but apparently no fatalities have been reported from the bite of this species, at least in Ontario. Widows in general are retiring spiders that typically only bite humans during accidental interactions. Their neurotoxic venom can cause pain and breathing difficulties and in the case of the black widow, can be fatal to young children or the infirmed. Northern widow bites should be taken seriously and a physician should be seen if you are unlucky enough to be bitten by one.

Next summer year I’ll be on the lookout for more northern widows across the rock barrens and inside the various abandoned buildings at QUBS. It’s impossible to say if we’ve always had a small and cryptic population of this species that’s just gone unnoticed, or if northern widows have only recently arrived here. The presence of eggs sacs clearly shows that whatever the history of widows at QUBS was, there is currently a reproductive population.

Crayfish in the back lakes.

Posted by Sarah M. Larocque and Mark A. Conboy

Figure 1. A) Dorsal and B) ventral view of a calico crayfish (Orconectes immunis) found in Lindsey Lake.

In a recent blog post (November 11), we reported our results of the small fish community survey undertaken in the QUBS back lakes and wetlands this summer. In addition to gathering information on fish, we took advantage of our time on the water to sample crayfish diversity at each water body. We captured crayfish using baited minnow traps and seine nets as outlined in the fish post. In this post we also included crayfish data from Lake Opinicon (which we did not sample in the fish survey). Specimens from Lake Opinicon were caught using minnow traps, seine nets and by hand. Crayfish are yet another group of organisms that have received virtually no attention at QUBS; we present the first (preliminary) summary of crayfish diversity and distribution for the station.

Understanding the diversity and distribution of crayfish at QUBS is important for three reasons. First, we would like to provide distributional information to future crayfish researchers who may be looking for study populations. Second, we want to compare contemporary species distribution to future sampling results in order to understand the changes that take place in lake and wetland ecology over time. Finally, crayfish, though often abundant in healthy ecosystems can quickly become imperiled through pollution and the introduction of invasive species. Crayfish are the largest mobile invertebrates in Ontario, and play an important role as scavengers, predators and prey in our aquatic ecosystems. We want to be able to monitor the health of QUBS’s crayfish populations to ensure their continued vitality and the vitality of our aquatic ecosystems at large.

Worldwide there are more than 540 species of crayfish (also called crawfish or crawdads). Crayfish diversity in Canada is low with only 11 species, all of which, except for the Signal Crayfish (Pacifastacus leniusculus), are found in Ontario. The centre of crayfish diversity in the province is southwestern Ontario, but at least five native and two introduced species of crayfish may be found at or near QUBS. Our sampling turned up four species:

  • Virile Crayfish (Orconectes virilis) –  Very common in Lake Opinicon and Warner Lake
  • Calico Crayfish (O. immunis) – Fairly common in Lake Opinicon, Warner Lake, Round Lake, Lindsey Lake, Cold Springs Pond and Lower Poole Pond. Abundant in the Dowsley Ponds.
  • Northern Clearwater Crayfish (O. propinquus) – Appears to be fairly common at Chaffey’s Lock and other locations in Lake Opinicon. Found in some wetlands along Cataraqui Trail. Not yet recorded in the back lakes.
  • Common Crayfish (Cambarus bartonii) – One collected at Warner Lake; first record for this species at QUBS. Could also be found in streams but has not been to date.

An additional native species reaches eastern Ontario but it prefers large rivers, a habitat type which is lacking at QUBS, so it is unlikely to be found at the station. Fortunately, no invasive crayfish species have been found at QUBS. There are two invasive species of concern in eastern Ontario Rusty Crayfish (O. rusticus) and Allegheny Crayfish (O. obscurus). The spread of these invasive crayfish is due in large part to transportation from their native ranges to other watersheds by anglers who use them as bait. The introduction of the Rusty Crayfish in Ontario took place in 1960’s when it was brought here for use as bait by a non-resident angler. To help stop the spread of invasive crayfish it is currently illegal in Ontario to transport crayfish (dead or alive) to water bodies other than where it was caught. Also, if you think you caught an invasive crayfish, you are supposed to kill it and report the observation to the Ministry of Natural Resources. However, it is important to identify crayfish correctly before killing them. An excellent visual guide to all of Ontario’s crayfishes can be found here.

Some native crayfish (e.g., Northern Clearwater) are in decline due to competition for food and shelter from the dominant and more aggressive Rusty Crayfish. Recently an article published in Fisheries (Lieb et al. 2011) explores various management strategies to prevent the spread of invasive crayfish spread and conserve threatened native crayfishes in North America. Restrictions on transport of bait and education can be effective tools to prevent the further spread of invasive species but once non-native crayfish become established it can be almost impossible to remove them. As we expand our sampling of lakes and wetlands at QUBS this coming summer we’ll continue to document the native and non-native crayfish and work towards monitoring our local water bodies for the first signs of invasion by invasive species so that we can act quickly to ensure the integrity of our native crayfish diversity.

Lieb DA, Bouchard RW, Carline RF, Nuttall TR, Wallace JR, Burkholder CL. 2011. Conservation and management of crayfishes: Lessons from Pennsylvania. Fisheries 36: 489-507

Figure 1. A) Dorsal and B) ventral view of a calico crayfish (Orconectes immunis) found in Lindsey Lake.

Observations; Below the Surface, Round Lake, QUBS lands

Posted by: Shirley French

Daphnia pulicaria

For August and September, 2010, I helped a student, Amy McMullin, conduct experiments in the ‘field’ at Round Lake.  We measured the physical parameters (i.e. temperature, oxygen, light), sampled the zooplankton and ran experiments with live critters (Daphnia) in bottles at different depths.  Our study species was D. pulicaria (a water flea, left figure), a key component in many lake food webs where they consume tiny plants, the phytoplankton, and in turn, Daphnia are food for insect larvae (such as the Phantom midge) and for larval or juvenile fish.  The top predator at Round Lake seemed to be a pair of loons residing at the lake over the summer and their single offspring (young with their mother, below right).

Loon mother with baby.

Round Lake is appropriately named for its circular shape. The steep sides plunge down to a maximum depth of 30 meters.  The more gradual shore on the SE side is where we launch the boat.  One of the interesting features of this lake is the low oxygen in the bottom waters (i.e. 0.26 -0.10 mg/L from 15 m & below, Aug. 31/10).  As we were setting out and retrieving the Daphnia from jars in the water at 15 and 20 meters, I kept finding lovely dark pinkish-red clusters of cells in the water from the 20 m depth (Amy worked on the 15 m samples).  At first I wondered why there were red algae at a depth of 20 meters since we had measured the amount of light and it was extremely low!  I realized that it was not an algae after seeing an article on ‘Bahamas Blue Holes’ in National Geographic (August, 2010).   The articles’ description of diving through a zone of pink stained water (a layer of purple sulfur bacteria), made a strong impression.  As it turned out, the purple sulfur bacteria are inhabitants of freshwater environments as well as saltwater.  After examining some of the pinkish-red stuff under the microscope, the cells were easily identified as the purple sulfur bacteria, Amoebobacter (Pfennig and Trüper, 1989).  Even though the individual round cells are only 2-3 microns across, the colony is held together by wispy strands of mucus and so the bacteria are very easy to see with your eye.

What do the purple sulfur bacteria need to persist?  Like plants, they photosynthesize, but they use bacteriochlorophyll and carotenoids to capture light energy at wavelengths quite different from the ones used by algae (Pfennig and Trüper, 1989).  In addition, the purple sulfurs can photosynthesize at light levels 500 times lower than that available in the water’s surface layers on a sunny summer’s day. They are not as efficient at photosynthesis as the phytoplankton but they also grow in darkness and can adjust their buoyancy depending on their needs (Overmann and Pfennig, 1992).   In summary, the purple sulfur bacteria need sulfide compounds, have species specific ranges in temperature, need low oxygen or no oxygen for growth, and, have a wide range of salinity tolerances.  As mentioned, purple sulfurs grow in high salinity as in the Bahamas, salty lakes (Mahoney Lake, B.C.), or, in fresher water such as Round Lake.  Not surprisingly, the purple sulfur bacteria are thought to have arisen a long time ago (1.6 billion years before present; see Brocks and Schaeffer, 2008) when there was not a lot of oxygen in the oceans and the cyanobacteria were just getting started. Daphnia, on the other hand, have been around since “at least the Permian” (299 – 251 million years ago; Taylor et al., 1999).

Daphnia pulicaria. Actual size is ~2 mm (for adult females). Click on image for larger version.

In Round Lake Daphnia pulicaria are found throughout the water column. Some individuals are found in the low oxygen water, why are they there at all?  We noticed that some live specimens have an obvious red coloration that has been noted by other researchers and studied in Daphnia.   Like their predator found in Round Lake, the phantom midge Chaoborus flavicans, Daphnia produces hemoglobin in their bodies when they have been under low oxygen stress. It is their interesting adaptative plasticity and their suitability for lab experiments, which make Daphnia a good organism for studying energy budgets in Bill Nelson’s lab at Queen’s.

There are many unanswered questions about the plankton community and the physical features of Round Lake.  I had hoped to determine whether the lake had ‘turned over’ in the fall (i.e. early December), as is characteristic of many lakes, so it was necessary to sample the lake in the winter.  The weather was finally favorable Feb. 24th , the depth of the snow had shrunk and the air temperature was close to 0◦C.  The ATV didn’t make it very far on the trail and so I want to mention that my son, Linden’s, effort in dragging most of the sampling equipment to the lake and back was greatly appreciated.  Mark Conboy (Operations Manager at the Biological Station) had loaned us an ice auger and axe to cut a hole in the ice which was ~18 inches thick as Mark had said to expect.  Much to my excitement the temperature of the water in Round Lake was warmest in the bottom 20 to 29 meters.  The oxygen also abruptly changed from >3 mg/L in the upper 19 meters; to a low range of 0.56 – 0.43 mg/L in the bottom 9 meters.  The temperature profile indicated that the ‘densest’ (4◦C ) cool water in the upper layers, did not mix with the bottom waters (max. 4.7◦C); maintaining the low oxygen environment for the bacterial community.   It also suggests that the nutrients at the deep depths are not completely brought back into the water column with a fall or spring ‘turn over’ depriving the phytoplankton of a high nutrient supply.  The zooplankton appeared healthy, plump and many were red with hemoglobin in the February samples.


  1. Brocks, J.J., and Schaeffer, P., 2008.  Okenane, a biomarker for purple sulfur bacteria (Chromatiacea) and other new carotenoid derivatives from the 1640 Ma Barney Creek Formation. Geochima et Cosmochimica Acta 72:  1396-1414.
  2. Overmann, J. and Pfennig, N. 1992. Buoyancy regulation and aggregate formation in Amoebobacter purpureus from Mahoney Lake. Microbiology Ecology 101:  67-79.
  3. Pfennig,N.  and Trüper,H.G.  1989.  Anoxygenic phototrophic bacteria.  In: Bergey’s manual of systematic bacteriology, Vol 3 (Staley, J.T., Bryant, M.P., Pfennig,N. and Holt, J.G. Eds.) pp.1635-1709. Williams and Wilkins, Baltimore,M.D.
  4. Taylor, D.J., Crease,T.J. and Brown, W.M.  1999.  Phylogenetic evidence for a single long-lived clade of crustacean cyclic parthenogens and its implications for the evolution of sex. Proc. R. Soc. London B, 266:  791-797.

Slug expert Ulrich Schneppat visits QUBS

On Thursday September 25 slug expert Ulrich Schneppat visited QUBS to help document our terrestrial gastropods and search for the charismatic

Adam Zieleman (left), Ulrich Schneppat (centre) and Vanya Rohwer (right) looking for slugs on the Bonwill Tract. Photo: Mark Andrew Conboy.
Adam Zieleman (left), Ulrich Schneppat (centre) and Vanya Rohwer (right) looking for slugs on the Bonwill Tract. Photo: Mark Andrew Conboy.

introduced Giant Garden Slug (Limax maximus). This is apparently the first survey of slugs ever done at QUBS.

Despite rather dry weather we did manage to find and collect 11 specimens from two genera. We began our search before dark by flipping logs which produced all sorts of other invertebrates but only a single Arion slug. After sunset things changed and we found numerous large specimens of both Arion and Philomycus. We did not find any Limax maximus but slime trails high up some tree trunks made Ulrich suspicious that L. maximus or another introduced species from the family Limacidae may be present at QUBS.

Identifying Arion and Philomycus slugs beyond genus requires dissection. Ulrich and the staff of the Bishops Mills Natural History Centre will diagnose our specimens and report the species to us at a later date.

The genus Philomycus is endemic North America. We found most of our Philomycus specimens on fallen Ironwoods (Ostrya virginiana) with very loose bark which provides shelter during the day when slugs are at risk of desiccating. This slug is sharing a meal of young Phellinus fungus with julid millipede. Photo: Mark Andrew Conboy.
The genus Philomycus is endemic North America. We found most of our Philomycus specimens on fallen Ironwoods (Ostrya virginiana) with very loose bark which provides shelter during the day when slugs are at risk of desiccating. This slug is sharing a meal of young Phellinus fungus with julid millipede. Photo: Mark Andrew Conboy.
Arion sp. are among the most commonly encountered slugs at QUBS but are not native; all are introduced from Europe. They can be found on almost any substrate close to the ground or under moist logs. Photo: M.A. Conboy.
Arion sp. are among the most commonly encountered slugs at QUBS but are not native; all are introduced from Europe. They can be found on almost any substrate close to the ground or under moist logs. Photo: M.A. Conboy.

Mark Andrew Conboy