Frog Blog – Week 3 – Little Black Commas

Our frog spawn in the office pond is approximately 2 weeks old and despite the very bad weather we have experienced in the last few days there are signs that things are beginning to happen.  The weather has been quite cold, although it is hard to say that it has been unseasonal, with the early Easter it is easy to forget that we are still in March and on the whole the winter has been relatively mild.

Only one warm sunny day over the last week, we have had heavy rain and blustery showers but fortunately not too many bonfires from the construction workers nearby polluting the water with ash drifting into the pond.  The water temperature remains cold but a close examination of the frog spawn shows that the little black dots we started with inside their protective jelly are beginning to change.  The majority of them are showing some definition, we have a lot of “little black commas”, the eggs are showing signs of development and we can see the start of a defined head end and a tail.

A Close up of the Frog Spawn

Picture credit: Everything Dinosaur

Despite the cold weather the spawn is beginning to change, the picture shows that the embryos are developing, becoming more elongated and showing signs of progress.  We suspect that the water temperature will still be determining the rate of development, perhaps the warmer weather forecast for next week will help the spawn to hatch in the next 10 days or so.

Only one adult frog has been observed in the pond during office hours.  Ironically, it has taken to sitting next to the frog spawn using the surround pond week (Elodea) to support its weight.  We were a little concerned about this frog, normally frogs confine themselves to the margins of the pond, where there is more cover.  However, this frog, (we think it is a male), seemed quite happy to sit amongst the pond week in the centre of the pond.

Some of us started to speculate that this was the father, checking on his family to be, but this was probably a bit too fanciful for the more rational members of the team.  Amphibians do adopt many strategies when it comes to looking after and raising their young.  It is not just the so called higher forms of life, the mammals and birds that adopt a benevolent attitude to their offspring.

Frog Blog Week 2 – Tiny Black Dots – no movement yet

We have been keeping a careful watch on the frog spawn in the office pond.  The frogs spawned for the first time in our pond last Sunday, so we have decided to keep an observational record of how the tadpoles get on.  Four frogs were in the pond, we suspect one female and three males.  Identifying males and female frogs is not our strong suit, but we estimated the ratio of boys to girls based on the fact that one frog was bigger than all the rest, so we speculated that this was the female.

During the breeding season, the male frogs develop pronounced dark pads on their first digits of the hand.  These pads are present all year round but swell up in the breeding season and help permit males to grip the usually larger females during mating.

Also, the smaller frogs croaked and we think that only the males do this.  The sound does not carry very far, it is certainly not the loudest frog croaking we have heard, many tropical frogs would easier drown out the noise made by these Common Frogs as these animals lack a vocal sac to help the sound resonate.

By Monday the pond was empty and the adult frogs had left, perhaps to hunt in the surrounding rockery, we did not expect to see all four of them together again, but surprisingly on Wednesday all four frogs (one big one and three smaller ones) returned to the pond and there was a lot of activity again but no further spawning.

Frog Blog – Week 2

Picture credit: Everything Dinosaur

The weather in the north-west of England has been particularly cold over the last few days.  We have experienced strong gales, hail storms and even some snow.  This is the earliest Easter for 95 years, we suspect that the development of the eggs will be dependent on the water temperature, so it may take a while for the embryos to start to develop.  The jelly surrounding the tiny black dots (each no more than about 2mm across), has swollen and this helps the spawn stay afloat and close to the surface of the pond.  In this way the spawn can be warmed by sunlight to the greatest extent (surface water of ponds tends to be warmest).

We have been concerned this week, as there has been a lot building work going on around us and the construction teams have lit several bonfires.  This has led to large deposits of ash and other debris getting blown into the pond.  The silvery “scum” surrounding some of the spawn that can be seen in the picture, is ash that has drifted into the pond, we are not sure what effect this pollution will have on the spawn’s development.

We will have to keep you posted on the spawn’s progress…

Science Bit

Amphibians were the first truly semi-terrestrial animals, evolving in the late Devonian and becoming more numerous and diverse during the Carboniferous and Permian periods before suffering in the Late Permian mass extinction.  At the end of the Permian there were about 35 known families of amphibians, many of them considerably larger than their modern counterparts.  After the mass extinction event, at the beginning of the Triassic (248 million years ago), there were about 10 families remaining.

About 70 percent of all the types of amphibians around at the time of the Late Permian went extinct.  Today, there are about 4,300 species of amphibians in the world (mostly frogs), but the amphibian class has never fully recovered from the Permian mass extinction.  Amphibians were at their most diverse (in terms of families) and spectacular something like 50 million years before our ancestors (the first mammals) evolved.