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Posts tagged “Lithobates clamitans

Green Frogs’ Coloring

7-13-16  turquoise green frog 030Despite their name, Green Frogs are not always green.  They can be brown or tan, as well as many shades of green.  Usually Green Frogs in the Northeast are a combination of these colors, but occasionally one sees greenish-blue coloring on a Green Frog.  An understanding of what causes a frog’s green color sheds light on why sometimes all or part of a Green Frog may be close to turquoise than green.

Basically there are three types of pigment cells (chromatophores) which stack up on top of each other in a frog’s skin.  The bottom layer (melanophores) of pigment cells contain melanin, a pigment that appears dark brown or black.  On top of these cells are iridopores, which reflect light off the surface of crystals inside the cells.  When light hits these cells, they produce a silvery iridescent reflection in frogs, as well as other amphibians, fish and invertebrates. In most green frogs, sunlight penetrates through the skin to the little mirrors in the iridophores. The light that reflects back is blue. The blue light travels up to the top layer of cells called xanthophores, which often contain yellowish pigments. The light that filters through the top cells appears green to the human eye.

The pictured turquoise-headed Green Frog most likely lacks some xanthophores in the skin on its head, and thus we see reflected blue light there.

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Young Green Frogs Absorbing Tails

6-30-16  green frog metamorphosing 183Generally speaking, green frog tadpoles that hatch early in the season will transform into frogs by mid-to late summer.  Tadpoles that hatch late are likely to overwinter in their ponds and metamorphose late the following spring or early in the summer. Thus, the Green Frogs you see now with both legs and a tail spent the winter as tadpoles and are maturing now.

A specific process called “apoptosis” occurs as the tail is absorbed by the frog.  It involves programmed cell death, and occurs in various forms in multicellular organisms.   Humans experience apoptosis throughout their lives.  It is responsible for the separation of fingers and toes in a developing embryo, as the cells between the digits undergo apoptosis and it is responsible for the death of between 50 and billion cells each day in the average human adult.  Once it has begun, apoptosis cannot stop, and thus is a highly regulated process.

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Green Frogs Mating & Laying Eggs

6-14-16  green frogs 008The loose banjo string call of the Green Frog is a familiar sound near wetlands this time of year.  Males (to the right in photo, with bright yellow throat) have been busy serenading females (to the left in photo, with white throat), in an attempt to breed with one.  Female Green Frogs select their mate, a choice which is based partially on the suitability of the male’s territory (underwater plants are a plus).  After inspecting several males’ territories at night, the female chooses one and slowly approaches him, turning to face away from him as their bodies come in contact.  External fertilization takes place as he clasps her while she lays her eggs (known as “amplexus”).

Unlike Wood Frog eggs that are laid in clumps, or Spring Peepers’ individually-laid eggs, Green Frog eggs are laid in a loose cluster that often floats on the water’s surface (see photo) or is draped on underwater plants.  Each cluster usually consists of 1,000 to 5,000 eggs that hatch in three to five days.  Females sometimes return to breed a second time with a different mate, in which case the second egg clutch is usually smaller, consisting of about 1,000 to 1,500 eggs.

The larval, or tadpole, stage of a Green Frog lasts from 3 to 22 months, which explains why you might have already seen large Green Frog tadpoles this summer.

(Outstanding theories were submitted on yesterday’s mystery. Be sure to read comments!)

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Aquatic Frogs Hibernating in Ponds

1-9-15  green frog IMG_0181Most aquatic frogs such as this Green Frog have been deep in hibernation for several months. A common misconception is that frogs spend the winter the way aquatic turtles do, dug into the mud at the bottom of a pond or stream. In fact, hibernating frogs would suffocate if they dug into the mud for an extended period of time. A hibernating turtle’s metabolism slows down so drastically that it can get by on the mud’s meager oxygen supply. Hibernating aquatic frogs, however, must be near oxygen-rich water and spend a good portion of the winter just lying on top of the mud or only partially buried. They may even slowly swim around from time to time.

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