Anatomy and Physioloy

Seahorses are fishes of the genus Hippocampus belonging to the family of Syngnathidae , spite the very unfortunate classifications of the past which defined them as amphibia or even as insects !

Other members of the family are the well known and impressive sea dragon and the so called pipefishes , which are named after their peculiar shape, resembling a pipe. Seahorses size can variate among species from 16 mm (Hippocampus denise) to 35 cm (Hippocampus abdominalis).

Their body,wich is tambed on the sides, is covered by hard plates forming a thorax with parallel transverse on sided lines. It is furthermore distended in the front, at the point of the hypogastrium, and it then narrows towards the tail, which is thin and prehensile, so that they can grap on the underwater fauna, rock formations, corals et cetera. Their head is nearly perpendicular to the trunk and it eventually becomes a cannular like mouth (snout). The allocation of the upper body reseples that of a horse and hense the name Hippocampus in ancient greek [ ἱππόκαμπος/hippocampos> ἵππος /hippos (horse) + κάμπος /kampos(sea monster) >Hippocampus ] and Seahorse in English

Seahorses swim in the water by maintaining their body in standing position and by thrusting it forward with the very fast pulsatory movements of the dorsal fin, about 35 per second![1]. However due to their physiology and body shape they are very slow and thereby they have evolved other surviving strategies. Just like chameleons they can master camouflage and they change their colour according to their environment. However, most times they tend to adopt a more specific and "personal" coloration.

Generally their coloration can variate from white and black till red, yellow and even blue, moreover they can have small spots or strips and sometimes they can develop on their skin some beetling formations, called "cirri" [3] , so that they can blend even more successfully with their surroundings.

Furthermore their eyes can move independently from each other, meaning that it is not necessary for them to move around in order to have supervision of their surroundings and therefore they can both look for food and watch out for predators in the same time.

Seahorses do not have a jaw and consequently teeth, in addition to the fact that their digestive system is very primitive; therefore they have developed a special mechanism for the uptake of food. At the base of their snout, there is a specialized organ like a trigger that contracts abruptly (or more specifically it is like a foil that bends) and so food is sucked due to negative pressure, resembling the action of a syringe.

The seahorse is the only animal that the male undertakes the task of pregnancy. Seahorses have therefore developed certain characteristics. The male seahorse has in the level of his hypogastrium (front of his gut/underbelly), as in the figure, a small pouch, which serves as a specialized environment for the eggs to hatch. On the other hand the female seahorse has developed a canal in order to deposit her eggs in the pouch. Nonetheless the male seahorse during the pregnancy produces the female hormone prolactine[4].

More info in the The Life of Seahorses - Habits section

A.A.

Notes

Vincent 1996 and Whitley 1958 Stuart Westmoreland @ Corbis.com
Breder 1942
Clare Driscoll & Seahorse.org
Vincent 1994