Time for Another Time Lapse (time-lapse video)

Leopard Frog Eggs at the Homer Lake Wetland, 3/29/2021

As you can see in the photo above, leopard frogs lay their eggs in large masses. If you recall earlier posts in this blog, the spring peeper lays eggs singly and the boreal chorus frogs lay eggs in much smaller masses. These are probably northern leopard frog eggs as there was a pair of northern leopard frogs quite nearby, but it's beyond my expertise to differentiate the egg masses of different leopard frog species and as we know there are plains leopard frogs in the wetland as well.

As with the boreal chorus frog egg development time-lapse video, I borrowed the eggs in the video below from the wetland with permission from the Forest Preserve District and returned all tadpoles and remaining unhatched eggs to the wetland where they came from, not far from the egg mass pictured above. The eggs were collected on Wednesday March 31. The time-lapse began about 6:00pm the same day and ended a little after noon on Saturday April 3rd, so it ran for 66 hours and 18 minutes. One photo was taken every minute for a resulting time-lapse video length of 2 minutes and 13 seconds -- 1,800 x the actual speed.

Notes: 

  • You will see in the video that it appears to be taking place in a snow globe. The blizzard of little particles flying around the screen are actually very small crustaceans known as seed shrimp -- they were all over in the egg mass as you can see. As I've mentioned, you always get more than you bargain for when you take something out of the wetland!
  • 44 seconds into the video there is the brief appearance of a bright green creature in the lower-left portion of the egg mass. It is there only a few frames so if you want to see it, you'll probably need to stop the video and step through the frames. I believe that this is a very interesting flatworm species (or planaria) that actually has a symbiotic relationship with algae living inside its body. I hope to find another of these at some point and do a fuller coverage, but wanted to point this one out for those who might be interested enough to look for it.
  • At the point that the tadpoles begin hatching (also about 44 seconds into the video, or about 22 hours in real time after the time-lapse begins), they do not look much like tadpoles, unlike the chorus frog tadpoles when they hatched. These look more like little black commas consisting of two little round blobs joined together. They continue developing after hatching, however, and eventually look like tadpoles. I measured one of the tadpoles at the end of the time-lapse to be about 8mm long.
  • You will see the egg mass collapsing as more and more tadpoles emerge. You will also see that not all eggs develop or hatch. This is the same as we saw with the boreal chorus frog eggs. I do not know the reason for this but wonder again if the external fertilization relying on sperm meeting up with eggs in the water as the eggs are laid may simply not be entirely fool proof.
Nerd Note: Amazingly there is evidence from multiple studies (see https://www.jstor.org/stable/1448716 for example) indicating that the speed of development of amphibian eggs is impacted by the chemical cues of predators, such as crayfish or leeches that prey on frog eggs, in the water or by chemical cues released by others of their kind being attacked. It is possible that the hatching of the eggs in the time-lapse below may have been impacted by my having removed them from the pond. Certainly it is the case that development was faster due to warmer temperatures in the observation tank in my home vs. the pond itself in late March.


 Leopard Frog Egg Development

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