Giant Seahorse

Hippocampus ingens are one of the largest seahorses, with adult pacific seahorses ranging in size from 12 to 19 centimetres (4.7 to 7.5 in) in height, with a maximum known size of 30 centimetres (12 in). Offspring are approximately 9 mm after birth. While large compared to others of their kind, their size hinders them in the conservation world. Minimum size limits are a common and favored conservation tool, usually starting at 10 cm. Thus, it is crucial that Pacific seahorses are accurately measured when they reach sexual maturity, for it determines if they will be protected or not. Pacific seahorses can be a variety of colors, including green, brown, maroon, grey, and yellow. Males can be distinguished from females by their prominent keel. Pacific seahorses share the common traits of seahorses, including a prehensile tail used for anchoring, skin instead of scales, a digestive tract without a distinct stomach, no teeth, and the ability to move each eye independently. It is one of the six species listed as "under the greatest threat from unsustainable levels of harvest and international trade" by the Convention on International Trade in Endangered Species of Wild Fauna (CITES).

The pacific seahorse is distributed in the Pacific Ocean from Baja California to Chile, with an additional transient population off of San Diego.The only known oceanic island population occurs around the Galapagos Islands with some additional populations also located in Northern Peru. Pacific seahorses are nocturnal and known to inhabit a variety of sub-tidal habitats to a maximum depth of 60 metres (200 ft). Habitats include mangroves, seagrass meadows, rocky reefs, coral reefs and sponges. Other common habitats are sea kelp and eelgrass. They also camouflage around the branches of gorgonians and black corals. South America specifically is home to an abundance of aquatic ecosystems. As a result, this region is more susceptible to environmental crime and many species such as the Pacific seahorse are affected by this. Furthermore, Peru trades the most pacific seahorses and this environmental crime in this country regarding the species is very high. The first record of Hippocampus ingens in Guadalupe Island, Mexico, was in November 2015. This is a northern oceanic island, differing from its usual Eastern Pacific locations. …

Female pacific seahorses in captivity have been observed producing small broods at three months of age. Sexually mature females often develop a dark patch below the anal fin. Males reach sexual maturity at around 5.4 centimetres (2.1 in) in height. Unsuccessful reproductive activity in captivity has been noted at around three months of age, with successful pregnancies as early as six months of age. Like all seahorses, females deposit their eggs in the brood pouch of the male, where they are subsequently fertilized by the male and sealed into the pouch. As the embryos develop, the fluid inside the pouch changes in salinity to acclimate the embryos to the salinity of the surrounding sea water. Research suggests that pacific seahorse males can brood up to 2000 eggs at once, and may brood multiple times in a breeding season. At the end of the fourteen day gestation period, the male goes into labor and must force the young out of the pouch one at a time, which sometimes takes hours.

Hippocampus ingens have low genetic diversity, which is one of the reasons they are a vulnerable species, and thus it is difficult identify a geographic origin for this species. Researchers are looking into possibly sequencing loci of the species or microsatellite markers to gain more information about the geographic origin of the species and how they are relocating to new locations. However, it is known that the lineage of seahorses leading to modern pacific seahorses diverged from slender seahorses after the rise of the Isthmus of Panama, between 4 and 5 mya. Pacific seahorses and Fisher's seahorses split from this lineage 2.5 to 3 mya. Although little research has been conducted regarding the origins of the Hippocampus ingens, one study looked at the histological structure of the species' digestive tract as well as their digestive enzymes and found informative data. The histological structure of their intestine is similar to that of seahorse species that also lack a stomach (agastric teleosts) such as the H. abdomnialis and the H. guttulatus. Thus, these species may have split from each other from a common ancestor, but more than just morphological data would be needed to confirm this observation.