Big-belly seahorse

The big-belly seahorse or pot-bellied seahorse, Hippocampus abdominalis, is one of the largest seahorse species in the world with a length of up to 35 cm (14 in), and is the largest in Australia. Seahorses are members of the family Syngnathidae, and are teleost fishes. They are found in southeast Australia and New Zealand, and are listed on Appendix II of CITES. The big-belly seahorse is found among algae, seagrasses, and rocky reefs in shallow water, and attached to sponges and colonial hydroids in deeper areas. They also attach to jetty piles and other manmade objects, and can be found in estuaries. They usually inhabit waters less than 50 m (160 ft) deep, but have been found as deep as 104 m (340 ft). Juveniles are pelagic or attached to drifting seaweed. The big-belly seahorse has a forward-tilted, a long-snouted head, a distended but narrow pot belly, and a long, coiled tail. It swims using its dorsal fin with a vertical stance; when not swimming, it coils its prehensile tail around any suitable growth, such as seaweed, waiting for planktonic animals to drift by, when they are sucked up by the small mouth set at the tip of the snout much like a vacuum cleaner. Seahorses are voracious feeders, eating mainly crustaceans, such as shrimp, and other small animals living among the seaweed, such as copepods and amphipods. They do not chew, so they can eat to excess because of their small gut tract. Each eye moves separately, making it easier for them to see food and predators. Distinguishing males from females is easy: The male has a smooth, soft, pouch-like area at the base of its abdomen where the stomach meets the tail on the front side. Males also have a fin there, but it is less obvious. The female has more of a pointed stomach with a very obvious fin at the base of it. In the wild, breeding can commence when the seahorses are about one year old, and this can be reduced to about eight months when in captivity. Breeding in big-belly seahorses year-round, with peaks in the warmer months. Courtship initiation involves a series of colour changes and postural displays. Dilating the opening of the brood pouch slightly, the male inflates the pouch to balloon-like proportions with water by swimming forwards, or by pushing his body forwards in a pumping action, then closing the pouch opening. At the same time, he lightens his pouch in colour to white or light yellow. The male also brightens his overall body colouration, typically intensifying the yellow. A male repeatedly approaches his selected female with his head tucked down, and dorsal and pectoral fins rapidly fluttering.