Stickleback

Sticklebacks are small fishes in the family Gasterosteidae, distinguished by sharp dorsal spines and found in marine, brackish, and freshwater habitats.

Gasterosteidae: Gasterosteidae is a family of small fishes commonly known as sticklebacks. This family contains sticklebacks and defines their taxonomic placement.
Predator defense: Predator defense comprises traits and behaviors that reduce an animal's risk of being eaten. Stickleback spines can make them harder for predators to swallow.
Evolutionary biology: Evolutionary biology studies how populations and species change across generations. Stickleback populations provide direct examples of adaptation and repeated evolution.
Paxton Lake sticklebacks: Paxton Lake sticklebacks are freshwater populations in British Columbia, including distinct benthic and limnetic forms. Their contrasting body shapes and feeding niches became a classic study of ecological divergence.
Three-spined stickleback: Gasterosteus aculeatus is a widespread stickleback species with three dorsal spines. It is the best-studied species and a frequent example of the family.
Parental care: Parental care is behavior by an animal that increases offspring survival after fertilization. Male sticklebacks build nests, guard eggs, and fan them with oxygenated water.
Adaptive radiation: Adaptive radiation is the diversification of a lineage into forms adapted to different ecological niches. Postglacial stickleback populations diversified into distinct freshwater forms.
Lake Washington stickleback: Lake Washington sticklebacks are a freshwater population of threespine sticklebacks in Washington State. Their rapid armor reduction after colonizing freshwater became a case study in evolution.
Dorsal fin: A dorsal fin is a fin along the midline of a fish's back. Stickleback spines are modified fin rays positioned ahead of the dorsal fin.
Osmoregulation: Osmoregulation is the control of water and dissolved-ion balance in an organism. It enables sticklebacks to function across marine, brackish, and freshwater conditions.

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GasterosteoideiBroader topic: This family forms the familiar core of the group.