Range: Cosmopolitan Habitat: Lakes, ponds, streams, rivers, and more Size: 0.39-1.5 inches (1-4cm) thick Diet: Planktonic organisms Threats: Ducks, crayfish, midges, caddisflies, and more Life span: Unknown

Transcript:

Today on Animal Fact Files we’re discussing freshwater sponges. There are over 5,000 sponge alive today, however only about 200 of these are freshwater sponges. Freshwater sponges are found worldwide in lakes, ponds, streams, rivers, and other established water systems. By that we simply mean they aren’t found in, say, puddles. These sponges are also a good indicator of water quality as they require clean, clear water to survive.

Freshwater sponges have a preference for calmer water and are usually found no deeper than 6.5 feet (2m) below the surface, though some have been found at depths of 164 feet (50m). Freshwater sponges can appear yellow, brown, beige, even green - the green coloration comes from a symbiotic relationship with algae, not unlike how giant clams get their vibrant colors. The algae live inside the sponge for protection and in turn provide the sponge oxygen and food. Freshwater sponges are often mistaken for algae because of this green color, however, sponges are coarse and not slimy like algae - not usually anyway. The sponges can also obtain food through filter feeding and eat planktonic organisms.

Freshwater sponges are sessile as adults meaning they don’t move. They attach to hard surfaces like rocks or submerged objects or they may encrust on surfaces like sunken logs. Predators to freshwater sponges include ducks, crayfish, midges, caddisflies, and more. They vary greatly in size and shape. These sponges may form a thin, carpet-like layer over a surface or thicker branching stalks. These differences can even be seen in conspecific freshwater sponges - meaning individuals of the same species can look completely different! This is why freshwater sponges can only be identified on a microscopic level. In size, these sponges may be just a centimeter thick but cover an area more than three feet (91cm) across. Conversely, they may be more than 1.5 inches (4cm) thick but only covering a small area.

Freshwater sponges are able to produce both sexually and asexually. Some produce both eggs and sperm, others only produce one type of gamete, and others still may switch between producing sperm one year and eggs the next. From the fertilized eggs hatch larvae which are free swimming until they settle down on a spot and develop further. Once settled, the sponge is no longer able to move… sort of.

A piece of a freshwater sponge can break off from the original sponge and then settle and keep growing elsewhere. This can happen via water currents, animals, and even wind. Freshwater sponges go through periods of growth and dormancy, though some are active year round. Sponges living in areas that experience cold winters will go dormant during this time. Prior to this, the sponge will produce gemmules which are small, reproductive spheres that can withstand stressors the original sponge may not. So while the sponge may succumb to the extreme of winter, the gemmules will continue on, potentially for years, eventually creating a new sponge when conditions improve. These gemmules are used to identify freshwater sponge species under a microscope!

For more facts on freshwater sponges, check out the links in the description. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!