A seahorse can weigh anywhere from less than 1 gram to up to 2 pounds. The big belly seahorse is the largest species of this aquatic animal and typically weighs close to 2 pounds.

There are more than 40 different species of seahorses, and 39 of them are listed as endangered. Seahorses live exclusively in the ocean, though some, such as the dwarf seahorse, can be kept as pets. In reproduction, the male is impregnated by the female and holds the fertilized eggs in his brood pouch for two to three weeks. After the seahorses hatch, they immediately become independent of the parent seahorses.

There is a great variety of seahorse species, and each species displays considerable variation within populations. This diversity makes it difficult to generalize about the physical characteristics of all seahorses. The situation is further complicated because seahorses have an exoskeleton that usually grows long fringes or tendrils that contribute to its camouflage but also add to each individual's weight.