Inside a Bladderwort’s Belly

What am I looking at?

These images show the interior of the bladder (1) of a humped bladderwort plant. Inside the bladder, you can see some single-celled algae, known as desmids (2). The colors are the result of autofluorescence (colors generated when a laser shines on a sample, which is a key step in confocal microscopy), and of the cell walls (3) being stained with Calcofluor white dye, giving them a blue-green color. The quadrifid glands (4) are the small red X shapes that pump water out of the bladder to reset the trap, produce digestive enzymes, and absorb the resulting nutrients from digestion.

Biology in the background

This bladderwort’s bladder is only a few millimeters long and has outer walls that are only two cells thick. These plants prefer nutrient-poor environments and consume other organisms to obtain sufficient nutrients. Each bladder is a trap; when it opens, it sucks in small creatures swimming through the water. The walls of the trap are made of two layers of cells, the inner and outer epidermis. You can see the elongated, blue-green cells lining its inner walls; these are responsible for pumping water out of the bladder to set the trap. Then once prey is inside the bladder, it is slowly digested to give the plant the extra nitrogen it needs. Interestingly, algae will be digested if they’re caught in a young bladder but can survive if they’re trapped in an older, less metabolically active bladder.

These bladders are only about 1.5 to 2 millimeters long, or roughly 20 to 25 times the width of a human hair.

Technique

This image was created using confocal microscopy.