Our Citizen Science Project at a Glance

Who are we?

The Bishop Laboratory at St. Francis-Xavier University

  • We conduct research into a symbiotic association between unicellular green algae and amphibian egg masses.

What are our goals?

  • Identify, map and observe breeding habitat of two amphibians: yellow spotted salamanders and wood frogs.
  • Cultivate interest of citizens in science and introduce ways in which they can participate.

Why are we doing this?

  • Identification of breeding habitat will help our research in numerous ways.
  • Amphibians populations are rapidly declining worldwide. Reproduction is where they are most vulnerable, so we wish to create a database of breeding sites, so we can track them over time.

The social and scientific objectives of our project

Welcome to our Yellow Spotted Salamander and Wood Frog breeding habitat-mapping project! Initiated by the Bishop Laboratory at St. Francis-Xavier University, this is a web-based interactive public outreach project in which we are encouraging people to observe aspects of amphibian breeding.

The first and most important task is to identify the location of breeding habitat around Nova Scotia, by simply observing the presence of egg masses deposited into ponds, seasonal melts pools and ditches and then uploading that information on to our site using a set of interactive of tools. These observations will then form a database of breeding sites. In addition to identification of breeding sites, citizen scientists can further contribute to this research by making a series of observations.

We have two main objectives. The social objective of this project is to foster community-based scientific research in the province, and more generally, to promote a cultural appreciation for the value of scientific research. We believe that science is too often seen as something done beyond the public view, or with little opportunity for the public to contribute beyond their tax dollars! A typical citizen science project (if there is such a thing) entails engaging non-scientists with the scientific process and introduction of simple methods of data collection that that can generate meaningful data that would otherwise be very time consuming or impossible for a small group of scientists to collect.

Think of it as “crowd-sourcing” data. When venturing through your local community we hope to introduce you to a deeper appreciation for Mother Nature, including some amazing biological interactions occurring in your area.

We study a fascinating symbiotic interaction between salamander and wood frog embryos and single celled algae. The scientific objective of this project is to gather information about amphibian breeding habitat, including shared habitat usage by wood frogs (Lithobates sylvatica) and yellow spotted salamanders (Ambystoma maculatum). Other observations that citizen scientists can make include the number of egg masses serviced by a particular body of water, the timing of arrival of these egg masses, hatching success and more. These data will form the basis of long term monitoring of amphibian breeding success, a critical aspect of the survival of amphibian populations.

Globally, amphibian populations are in serious decline so we need to be proactive about monitoring our local populations; the best way to do that is by observing their reproductive success.

Breeding habitat, behaviour and reproductive ecology of wood frogs and yellow spotted salamanders.

Many amphibians breed in temporary pools of water called vernal pools, or in spring-fed forest ponds. These bodies of water tend to be fish-free, thereby reducing predation (Whitford and Vinegar 1966). Salamanders will also breed in artificial ponds, floodplain wetlands, marches, and roadside ditches. During late winter to early spring (March-May), adult salamanders travel to breeding ponds, typically on warm rainy evenings.

Migration has been shown to correlate with heavy rainfall or snowmelt and increased temperatures. Homing behavior is generally exhibited regarding specific breeding locations where an animal inherited the ability to navigate to an original location (Whitford and Vinegar 1966). Males generally congregate in breeding ponds earlier than females. Reproduction is initiated by a nudging ritual referred to as a nuptial dance or “liebesspiel.” The male contacts a female, encircles her many times then deposits his spermatophores (little packets of sperm)

Salamander spermatophores

Salamander spermatophores (photo credit: Kieran Murphy)

on a substrate such as twigs, leaves or other submerged vegetation for the female to pick up with her cloaca. In 2-3 days once the females’ eggs are fertilized, egg masses containing 10-150 eggs are deposited on submerged vegetation or directly on the pond floor.

Newly laid egg mass (photo credit: C. Bishop)

Newly laid egg mass (photo credit: C. Bishop)

Eggs are coated with a thick jelly protecting the embryo from predation, physical disturbances and desiccation, but can deprive the embryo of much needed oxygen. Soon after the eggs are deposited, a symbiotic relationship begins between the eggs and unicellular algae.

Salamander egg mass with symbiotic algae (photo credit: C. Bishop)

Salamander egg mass with symbiotic algae (photo credit: C. Bishop)

The algae produce oxygen, which embryos need for healthy development. For their part, the embryos produce CO2 and fixed nitrogen, two things that all plants need to grow. The embryos develop for 4-7 weeks and then hatch into larvae, which feed for several weeks before undergoing metamorphosis to return to their terrestrial lives. All of this has to occur before the pond dries up!

Importance of mapping breeding habitat

Salamanders and wood frogs, like many amphibians, require access to aquatic habitat to breed. Since embryos are often the most sensitive and vulnerable stage in the life of many organisms, protecting the habitat in which they live and breed is critical. The space in between these two locations as well as the habitat quality is deteriorating due to human impact.

Deforestation, wetland destruction, rapid development of suburban areas and pesticides increase habitat fragmentation and decrease quality. Timber harvesting drastically changes a forest in regards to the forest floor’s makeup (decomposed woody debris) and the understory foliage in areas surrounding breeding sites. These changes affect whether the habitat is suitable for salamanders to live and breed. Roads impact salamanders by creating barriers between habitat and breeding grounds as well as pose a threat to salamanders trying to cross them at the risk of getting crushed. Run-off from roads poses a threat to the developmental stages of the life history of salamanders.

Salamander larvae are sensitive to lower pH levels in breeding pools. This sensitivity may be faced when acid deposition is increased due to the precipitation or road salting. These impacts could have very negative effects on embryo survival (Sadinski and Dunson 1992). Pesticides such as pyrethroid insecticides in breeding pools are not lethal to larvae, however they do cause alterations in behavior. Larvae in contact with pesticides responded abnormally to threats by twisting rather then a more efficient swimming motion. This observation demonstrates that a single occurrence of pesticide exposure was enough to affect behavior and render the salamanders more vulnerable to predation (Boone and James 2003). These pressures result in isolation of the local subpopulations and are problematic because isolation will lead to genuine concerns of gene flow and inbreeding. Conserving the connectivity and quality of breeding and living habitats of salamanders is essential for protection and preservation because a future decline in salamander numbers is possible.

Possible reasons for amphibian decline:

  • General habitat alteration and loss
  • Habitat modification from deforestation, or logging related activities
  • Urbanization
  • Habitat fragmentation
  • Local pesticides, fertilizers, and pollutants
  • Loss of genetic diversity from small population phenomena


Symbiosis is defined as a sustained intimate interaction between two or more distinct species, often for mutual benefit. The female yellow salamander deposits fertilized egg masses in a shallow body of water, where an endosymbiotic relationship arises between the single-celled alga Oophila amblystomatis and the spotted salamander embryos. The embryos and the alga form a symbiotic relationship in which the organisms benefit from one another.

As mentioned above, the algae may benefit from the embryonic release of nitrogenous waste and possibly CO2 (Small et al. 2014). On the embryos side of things, it is known that the alga assist with development of embryos by increasing oxygen supply (Pinder and Friet, 1994; Tattersall and Spiegelaar, 2008) and recent work suggest that algae transfer compounds to the embryo (Graham et al. 2013), the nature of which remain unknown.

In 2011 a group of scientists primarily from Dalhousie University discovered that algae invade embryonic cells. This was the first recorded instance of an algal cell invading a vertebrate in the world and was covered widely in the popular press, including on CBC’s [Quirks and Quarks.] This discovery has furthered our interest in this symbiosis and makes it more important than ever to investigate the evolution, physiology and ecology of this interaction.

Further Reading

  • Bishop CD, Miller AG (2014) Dynamics of growth, life history transformation and the photosynthetic capacity of Oophila amblystomatis (Chlorophyceae), a green algal symbiont associated with embryos of the northeastern yellow spotted salamander Ambystoma maculatum (Amphibia). Symbiosis 63: 2: 47-57 (CB2)
  • Boone, M. D., and James, S. M. (2003). ”Interactions of an insecticide, herbicide, and natural stressors in amphibian community mesocosms.” Ecological Applications, 13, 829-841.
  • Eunsoo Kim, Yuan Lin, Ryan Kerney, Lili Blumenberg, Cory Bishop (2014) Phylogenetic analysis of algal symbionts associated with four north American amphibian egg masses. PloS One 9: 11: e108915
  • Egan RS, Patron PWC (2004) Within-pond parameters affecting oviposition by wood frogs and spotted salamanders. Wetlands 24:1: 1-13 (Egan and Patron Graham, E. Fay, S.A. and Sanders, R.W. 2013. Intracapsular algae provide fixed carbon to developing embryos of the salamander Ambystoma maculatum. J. Exp. Biol. 216: 452-459.
  • Pinder, A., and Friet, S. 1994. Oxygen transport in egg masses of the amphibians Rana sylvatica and Ambystoma maculatum: convection, diffusion and oxygen production by algae. J. Exp. Biol.197: 17–30.
  • Kerney RK, Kim E, Hangarter RP, Heiss AA, Biship CD, Hall BK (2011) Intracellular invasion of green algae in the salamander host. PNAS 108: 6497-
  • Sadinski, W. J. and Dunson, W. A. (1992). ”A multilevel study of effects of low pH on amphibians of temporary ponds.” Journal of Herpetology, 26, 413-422.
  • Small DP, Bennett RS, Bishop CD (2014) The roles of oxygen and ammonia in the symbiotic relationship between the spotted salamander Ambystoma maculatum and the green alga Oophila amblystomatis during embryonic development. Symbiosis 63: 3.
  • Tattersall, G.J. and Spiegelaar, N. 2008. Embryonic motility and hatching success of Ambystoma maculatum are influenced by a symbiotic alga.
  • Whitford, W. G., and Vinegar, A. (1966). ”Homing, survivorship, and overwintering larvae in Spotted Salamanders, Ambystoma maculatum.” Copeia, 1966, 515-519.
  • http://www.amphibiaweb.org/cgi/amphib_query?where-genus=Ambystoma&where-species=maculatum&account=amphibiaweb
  • http://amphibiaweb.org/cgi/amphib_query?where-genus=Ambystoma&where-species=maculatum