ADW: Hippocampus Zosterae: INFORMATION - Animal Diversity Web

Physical Description

Seahorses have a head at a right angle to their body and swim upright, propelled by their dorsal fin. They steer with their pectoral fins, which are located on both sides behind the head (Indivigio, 2002). Seahorses also are distinctive in their possession of a prehensile tail that lacks a caudal fin and is used to anchor the animal to sea grass, coral, or any suitable holdfast (Randall, 1996). Instead of scales, seahorses have a thin layer of skin covering several bony plates that appear as rings around the trunk and tail. Seahorses can be distinguished by the number of trunks rings they possess and by the coronet on the top of the head, which is as unique as a human thumbprint (Vincent, 1997). The young, in comparison to their parents, have larger heads compared to their bodies, higher coronets, and more spines.

Seahorses are sexually dimorphic. Males have longer bodies and tails, whereas females have longer trunks. In addition, males possess a brood pouch, which is absent in the females (Lourie et al., 2004).

Hippocampus zosterae is one of the smallest of the many different seahorse species, ranging in size between 2 to 2.5 cm. The maximum reported size was a male of 5.0 cm (Jordan and Gilbert, 1882). This species of seahorse can be distinguished from other western Atlantic seahorse species by the presence of 10 to 13 dorsal and pectoral fin rays (Daswon and Vari, 1982). Also, dwarf seahorses possess 9 to 10 trunk rings, a high knob-like coronet that lacks spines or projections, knob-like spines on the body, a short snout that is one-third the length of the head, and skin covered in tiny warts (Lourie et al., 2004). Hippocampus zosterae also has a dorsal fin with a submarginal band (Dawson and Vari, 1982). Dwarf seahorses are found in colors of beige, yellow, green, and black, and may have white speckles or dark spots (Lourie et al., 2004).

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes shaped differently

Range length 2 to 5.0 cm 0.79 to 1.97 in Average length 2-2.5 cm in