What are facts about the stickleback fish?

Three-spined sticklebacks (_Gasterosteus aculeatus_) are small fish found in both fresh and saltwater habitats in Europe, North America, and Asia. They are small, with adults typically reaching a length of 2-3 inches. Sticklebacks have a distinctive body shape, with a slender body and a deep caudal peduncle (the area of the body just before the tail). Their bodies are covered in bony plates, and their dorsal spines are used to deter predators. Sticklebacks are carnivorous, feeding on small invertebrates like zooplankton and insects. They are also territorial, and males build nests to attract females during breeding season.

Here are some additional facts about sticklebacks:

* Sticklebacks are one of the most studied fish species in the world due to their importance as a model organism in evolutionary biology.

* Sticklebacks are sexually dimorphic, meaning that males and females have different body shapes and coloration.

* Males are typically larger than females and have brighter coloration, especially during breeding season.

* Females lay their eggs in the males' nests, and the males guard the eggs until they hatch.

* Sticklebacks are important prey for larger fish and birds, and their populations can be used as an indicator of overall ecosystem health.

Overall, sticklebacks are fascinating creatures that are important to both the scientific community and the ecosystem as a whole.