Scud

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See how they move!

SCIENTIFIC NAME: Amphipoda

Number Of Species/Distribution

There are approximately 6,000 described species of amphipods worldwide. 

  • Roughly 1,200 species live in freshwater.

Diet/Feeding

Amphipods have a diverse range of feeding strategies and can be any one of the below;

  • Herbivores (vegetarians) and eat only plants.

  • Carnivores (meat eaters) and eat other small organisms.

  • Scavengers and eat dead and decaying organic material.

  • Parasites which live on and feed off another animal such as a fish, which causes harm to the fish.

  • Suspension feeders or filter feeders- using tiny hairs on their antennae or legs to strain the water and catch any detritus that is floating by in the water.

Habitat

Freshwater amphipods can live in a range of conditions;

  • They can survive in shallow water areas and be found on vegetation, such as decaying leaves and aquatic plants, under rocks, on the sand, or burrowing deep into the sediment along the bottom.

  • They may also thrive at the bottoms of lakes which have less vegetation.

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SCUD: INTERESTING FACTS

  • Scuds shed their exoskeleton up to nine times throughout their lifetime (once every 3-40 days) and grow bigger with each molt.

  • If you find an orange or pink scud, it is likely dieing. This is not to be confused with when a female is pregnant and only her egg sack is orange in colour. 

  • Scuds contain the pigment carotene and when ingested by trout the pigment is transferred to the tissue of the fish displaying a pinkish-red colour. 

  • Contrary to popular belief, scuds are omnivores and will often group together to take down water boatmen, midges and smaller insect nymphs.

Life Cycle

The lifespan of amphipods is usually about one year, but some species may live for over two years. Amphipods use sexual reproduction methods, but mating habits vary broadly depending on species.

  • When mating, the male wraps part of his body around the female and releases sperm into a brood pouch, called a marsupium, where fertilization occurs.

  • Depending on the species, the eggs may hatch in anywhere from one to three weeks, and the newly hatched amphipods look like little adults 

  • They leave the pouch during the following one to eight days.

  • The number of eggs in each clutch depends upon the species, but can range anywhere from two to 750 eggs.

  • The breeding season can be extended with multiple broods produced, or it can be short with only a result of a single brood.

Role in Food Chain

Amphipods are eaten by many species of fish, making them an important species in the food chain.

  • They also play a significant role in recycling nutrients (by eating and then defecating) that can then be used by other members of the food chain.

Sources

  • Absolute Astronomy (2010). Amphipoda. Available here.

  • Animal Life Resource (2010). Amphipods. Available here.

  • Brusca, R. C, and Brusca, G. J., 2003. Invertebrates, 2nd ed. Sinauer Associates, Inc., Publishers, Massachusetts. Page 540.

  • Canada's Aquatic Environments (2002). Amphipoda. Available here.

  • University of Florida (2009). Amphipods. Available here