Michael Berrill

Toxicity of glyphosate‐based pesticides to four North American frog species

Glyphosate-based herbicides are among the most widely used pesticides in the world. We compared the acute toxicity of the glyphosate end-use formulation Roundup Original to four North American amphibian species (Rana clamitans, R. pipiens, R. sylvatica, and Bufo americanus) and the toxicity of glyphosate technical, the polyethoxylated tallowamine surfactant (POEA) commonly used in glyphosate-based herbicides, and five newer glyphosate formulations to R. clamitans. For R. clamitans, acute toxicity values in order of decreasing toxicity were POEA > Roundup Original > Roundup Transorb > Glyfos AU; no significant acute toxicity was observed with glyphosate technical material or the glyphosate formulations Roundup Biactive, Touchdown, or Glyfos BIO. Comparisons between the four amphibian species showed that the toxicity of Roundup Original varied with species and developmental stage. Rana pipiens tadpoles chronically exposed to environmentally relevant concentrations of POEA or glyphosate formulations containing POEA showed decreased snout-vent length at metamorphosis and increased time to metamorphosis, tail damage, and gonadal abnormalities. These effects may be caused, in some part, by disruption of hormone signaling, because thyroid hormone receptor beta mRNA transcript levels were elevated by exposure to formulations containing glyphosate and POEA. Taken together, the data suggest that surfactant composition must be considered in the evaluation of toxicity of glyphosate-based herbicides.

THE LIFE CYCLE OF THE GREEN CRAB CARCINUS MAENAS AT THE NORTHERN END OF ITS RANGE

Along the central coast of Maine most female Carcinus maenas extruded their eggs in spring. The smallest ovigerous female was 34 mm in carapace width. Mating occurred from July to October, and in all mating pairs the male was larger than the female. Megalopae and Stage 1 crabs did not settle until late August, growing only to a mean of 5.5 mm carapace width (Stage 5) before winter. Renewed growth began the following June, and juveniles grew to 13-25 mm carapace width by their second winter. Most mature males molted by the end of July, whereas mature females molted from July to October, while guarded by males waiting to mate with them. On the central coast of Maine, therefore, C. maenas matures when 2-3 years old, breeds 2-3 times, and generation time is a minimum of 3 years. Compared with warmer water populations in southern Britain and Holland, the Maine coast population of C. maenas has later settlement of megalopae, slower growth, delayed maturity, longer generation time, and a longer life span. Such differences may account for the inability of populations to establish themselves in waters much colder than those of the central coast of Maine. The northern limits of the range of the green shore crab Carcinus maenas in the Gulf of Maine have reflected the periodic warming of the surface waters that occurred in the Gulf during the 1930s, 1950s and 1970s. During the warmer years the numbers of C. maenas increased in the northeastern part of the Gulf, but during the intervening colder years their numbers declined again and they then became uncommon north of the coast of central Maine (Welch, 1968, 1979). Do colder than average temperatures slow growth and delay larval recruitment to an extent sufficient to restrict the species from permanent or extensive colonization of the northern Gulf? The life cycle of C. maenas on the North American coast has not been examined in detail. Most accounts of its life cycle have described populations on the coasts of Britain and Holland (Broekhuysen, 1936; Crothers, 1967, 1968, 1970; Klein-Breteler, 1975a, b, c, 1976a, b) where water temperatures average 4-5?C warmer than on the coast of central Maine. The purpose of the present study is to compare the life cycle of C. maenas on the coast of central Maine with that of the populations from warmer waters as a way of assessing the ability of the species to penetrate cold-temperate regions.

Gonadal differentiation in frogs exposed to estrogenic and antiestrogenic compounds

Exposure of amphibians to endocrine disrupting compounds (EDCs) may alter differentiation of gonads, especially when exposures begin during early life stages. Gonadal differentiation was observed in leopard frogs (Rana pipiens) and wood frogs (Rana sylvatica) exposed as tadpoles to estrogenic (estradiol, ethinylestradiol, nonylphenol) and antiestrogenic compounds (an aromatase inhibitor, flavone, and an antiestrogen, ICI 182780). Exposure to all compounds at micrograms/L concentrations altered gonadal differentiation in some animals by inducing either complete feminization or an intersex condition, and altered testicular tubule morphology, increased germ cell maturation (vitellogenesis), and oocyte atresia. Comparisons between the two species indicate that R. pipiens are more susceptible to sex reversal and development of intersex gonads. However, R. sylvatica also showed alterations to testicular morphology, germ cell maturation, and ooctye atresia. These laboratory results indicate that amphibians could be susceptible to altered gonadal differentiation and development when exposed to estrogenic and antiestrogenic compounds in aquatic environments, such as those impacted by agricultural, industrial, and municipal runoff.

The breeding behaviour of a northern temperate orconectid crayfish, Orconectes rusticus

Abstract Observations of breeding activities of male and female crayfish ( Orconectes rusticus ) in a natural stream population during the explosive spring breeding period, and supplemental laboratory observations, indicate a promiscuous mating system characterized by intense intermale aggression. Males wandered extensively over the substrate, fought frequently with each other, and attempted to disrupt copulating pairs. Larger males (as distinguished by large chela size) more frequently initiated and won aggressive encounters and interrupted copulating pairs more successfully than smaller males, but were subjected to greater predation. Intense intermale aggression ceased when females sequestered themselves under rocks in the stream or were removed from the laboratory population. Brief resistance by females to approaching males, along with sequestering behaviour, suggests that female choice may also occur.

Spectral Irradiance in Pond Water: Influence of Water Chemistry

Knowing the depth of UV penetration in ponds and the chemical variables that control underwater spectral irradiance is a prerequisite to predicting the influence of UV on amphibians and other pond organisms. The present study found that over 99% of UVB (280–315 nm) radiation was attenuated in the top 10–20 cm of ponds sampled on the edge of the Canadian Shield near Peterborough, Ontario. While the principal attenuating substance was, as in lakes, dissolved organic carbon (DOC), neither DOC nor DOC fluorescence were useful predictors of the attenuation coefficients other than the observation that all values of DOC were high and all attenuation coefficients were also high. The lack of a reliable relationship between DOC and attenuation resulted from differences throughout the season in the fraction of the DOC capable of absorbing radiation (chromophores) and the fraction capable of fluorescing (fluorophores). Attenuation was higher than predicted from DOC during springtime when amphibians lay their eggs. Absorbance coefficients measured using a spectrophotometer proved to be reliable predictors of both UVB and UVA attenuation coefficients measured in the ponds with a spectro‐radiometer. While DOC provides an effective sun screen against the direct damage of UV radiation, the high attenuation means that the photochemical activity spread over at least 15 m in the ocean is confined to only a few centimeters in ponds.

Life cycles of the freshwater mysid shrimp Mysis relicta reared at two temperatures

Abstract To assess the role that temperature may play in determining the life cycle of Mysis relicta, we cultured newly hatched juveniles at 4 C and 8 C in the presence of a surfeit of food. Mysids first reached sexual maturity after 8 months at 8 C after molting 12–13 times. Mysids cultured at 4 C molted four to five fewer times in the same 8 months, yet grew the same amount per molt as the mysids cultured at 8 C. We predict that mysids that live in water of at least 8 C during the summer of their first year will complete their life cycle in 1 year, whereas mysids growing in water colder than 4 C during their first summer will require 2 years to complete their life cycle. Received July 12, 1982 Accepted April 9, 1983

Seasonal Activity of Spotted Turtles (Clemmys guttata) at the Northern Limit of Their Range

Seasonal activity of spotted turtles (Clemmys guttata) at the northern limit of their range in central Ontario was studied over two years using radio telemetry. Prior to this study, and a concurrent study in 1996 by J. D. Ltizgus on a northern population in Georgian Bay, most reports were based on spotted turtle populations from southerly populations. In the present study, six spotted turtles were tracked in 1994, and nine were tracked in 1995. Turtles emerged from hibernation early to mid-April and remained active until late October/early November, for 197 days in 1994 and 202 days in 1995. Average daily movement was greatest early in the season and generally declined as the year progressed. Spotted turtles were easier to observe earlier in the season compared to later in the year despite still being active. Droughtlike conditions in 1995 may have stimulated the turtles to aestivate. Results from the two northern studies are complemen- tary. Spotted turtles at the northern portion of their range are active longer than those in southerly popu- lations.

The effects of short-term laboratory pH depressions on molting, mortality and major ion concentrations in the mayflies Stenonema femoratum and Leptophlebia cupida

Field surveys of the distribution of mayfly nymphs suggest that Stenonema femoratum are more acid-sensitive than Leptophlebia cupida. To assess whether this apparent difference in sensitivity of nymphs is reflected in differences in the degree of whole-body loss of [Na], [Cl], [Ca] or [K] under laboratory conditions, we exposed nymphs of both species to low pH for 96–192 h in soft water ([Ca] = 0.1 mM). Although mortality and loss of whole-body [Na] and [Cl] occurred in both species at pH 3.5, unexpectedly they were considerably greater in L. cupida than in S. femoratum. Ion loss was not size related within the range of nymphal weights used (2–14 mg dry wt) for S. femoratum. Exposure to the environmentally more common pH 4.5 had no effect on whole-body [Na] and [Cl] or on mortality in either species. However, in L. cupida, molting by nymphs increased at both pH 3.5 and 4.5. A decrease in whole-body [Ca] occurred, and the loss of whole-body [Na] and [Ca] at pH 3.5 appeared to cease following the period of molting. In S. femoratum no molting or Ca loss occurred and whole-body [Na] and [Cl] decreased between 96 and 192 h exposures.

THE INFLUENCE OF SEASON AND pH ON MORTALITY, MOLTING AND WHOLE-BODY ION CONCENTRATIONS IN NYMPHS OF THE MAYFLY STENONEMA FEMORATUM

Abstract 1. 1. Using laboratory exposures (pH 3.5 and 6.5) and instrument neutron activation analysis, the seasonal variation in whole-body ion concentration, mortality and molting of Stenonema femoratum were investigated. 2. 2. Winter nymphs (dormant) had significantly lower Na and Cl than other times in the season (growth phase) at both pH levels. 3. 3. Na and Cl levels were consistently lower in nymphs exposed to pH 3.5 relative to pH 6.5. 4. 4. Mortality and molting were associated with ion loss during acid stress and were highest in growth phase nymphs. 5. 5. K levels did not vary with season or pH.

The aggressive behavior of Munida sarsi (Crustacea: Galatheidae)

Abstract Munida sarsi is a deep water, bottom-living galatheid. Its aggressive behavior was observed for several weeks in aquaria that could only partially mimic its natural habitat. It threatens by extending its chelipeds, snapping its pincers, and raising its abdomen off the mud. The cheliped extension appears to be the indispensible part of the display. Threatening individuals spar with each other, and though such bouts are unpredictable in occurrence, duration, and outcome, they are mutually stimulating, harmless, and involve a series of stereotyped movements. The aggressive behavior of M. sarsi seems primarily to ensure each its private space of mud on which to dig and feed.