Fused Jaws and Male Pregnancy: The fascinating world of horses and dragons of the sea

Guest Author: Paul Anderson, PhD, Research Scientist, Mystic Aquarium
Artist: Hannah Dean
Editor: Patrick Cooney

It is an honor to be invited to share my passion for a very unique group of fish here with you on The Fisheries Blog!

In ancient Greek, syn = together, gnathos = jaws, and formes = of similar form.

All fish in the Order Syngnathiformes are united by the physical feature that gives rise to their name: A fused jaw.  At the front end of their long, narrow, bony ring-covered bodies is a long tubular snout formed from fused jaws, designed specifically to vacuum unsuspecting prey from their surroundings.

Pipeworks by The Fisheries Blog artist, Hannah Dean
Syngnathiformes by The Fisheries Blog artist, Hannah Dean

I owe my career in marine biology to probably the most well-known taxon of the order, the seahorses (genus Hippocampus).  The very first fish I kept as a kid was the dwarf seahorse (Hippocampus zosterae).  Right away, this species got me hooked on ocean science.  I later came back to study the dwarf seahorse’s cousin, the lined seahorse (Hippocampus erectus, described below), for my PhD Dissertation.  I quickly learned that the seahorse is only one of many fascinating fishes in the order!

Order Syngnathiformes

Family Aulostomidae

Trumpetfish (Aulostomus maculatus)


Mastery of camouflage is a common theme among the Syngnathiformes, and the trumpetfish is a prime example of this, floating head down among coral, able to change color rapidly to blend in with surrounding sea fans, pipe sponges, and sea whips.  The trumpet-like mouth, or “flute mouth,” as its genus name implies, can open to the diameter of its body to ambush and rapidly suck in reef fishes finding cover among gorgonians and, unknowingly, trumpetfish mouths.  This species is found among reefs of the western Atlantic Ocean, from southern Florida and Bermuda to the northern coast of South America.  This species has also been discovered among the isolated St. Peter and Paul’s Rocks, an archipelago of islets and rocks in the central equatorial Atlantic.

Family Centriscidae

Razorfish (Aeoliscus strigatus)


Like the trumpetfish, the razorfish also lives head-down to camouflage, which also provides this fish with the opportunity to ambush its prey and hide from predators.  Unlike the trumpetfish, this much smaller species camouflages head-down among sea urchin spines and sea grass blades, preying on small invertebrates.  This species also schools head-down, and to see this is quite a sight!  Its other protective feature is its row of protective bony plates, which cover the dorsal surface and end at a sharp spine over the caudal fin.  This species is found in two ranges among the world’s oceans; off the coasts of Tanzania and the Seychelles in the Indian Ocean, and from southern Japan to New South Wales eastward to Vanuatu in the Pacific.

Family Fistularidae

Cornetfish (Fistularia tabacaria)


Another eccentric of the Syngnathiformes, the cornetfish is characterized by an extremely elongate, eel-like body, but with a very long snout (about a third the length of the fish) and forked caudal fins whose center rays form a lengthy, wiry filament that extends far backward.  Interestingly, this fish has a well-developed lateral line which extends all the way back to the filaments, suggesting that they play an important role in sensing vibrations in the fish’s vicinity.  Much like the trumpetfish, they are ambush predators, and have been known to hide in fish schools (perhaps a good reason for the extended and well-developed lateral line).  They are ambush predators, much like the trumpetfish, and can be found in the eastern and western Atlantic, including the Gulf of Mexico.

Family Solenostomidae

Harlequin Ghost Pipefish (Solenostomus paradoxus)


This ornate Syngnathiform displays variable coloration to camouflage among crinoids, gorgonians, and black corals in its environment.  Like other Syngnathiforms, the Harlequin ghost pipefish is also an ambush predator, targeting small crustaceans which they also suck in through their long snouts.  Unlike the Syngnathids, though, who rely on the dutiful care of fathers to bring larvae into the world; in this family, it’s the mothers who incubate eggs within their larger pelvic fins which unite to form a ventral brood pouch, or marsupium.  This species is widespread in tropical and warm-temperate regions of the Indo-West Pacific.

Family Syngnathidae

Lined Seahorse (Hippocampus erectus)


The lined seahorse serves as a good mascot and representative of the seahorses, being one of the largest seahorse species.  Ironically, it is found in the western Atlantic Ocean along with two other species, including its cousin, the dwarf seahorse (Hippocampus zosterae), one of the smallest.  With some exceptions, most seahorses are known for their monogamous pair bonds; with the timing of female egg production closely matching the timing of gestation of eggs in the male’s specialized brood pouch, or marsupium.  This and some other species display ornate cirri, filaments resembling seaweed, as juveniles; which disappear as the individual enters adulthood.  I couldn’t help but choose this fish as one of the representative seahorses, as it was the subject of my PhD dissertation.  As a popular marine aquarium fish species that can be aquacultured to provide a sustainable source for the industry; I studied the impact of noise on its health/welfare in aquarium/aquaculture environments.  I found that though it has relatively limited hearing ability (like many marine fishes), chronic loud noise from pumps, etc. in aquarium/aquaculture environments can still impact their health; and soundproofing retrofits are easy to make to improve aquarium environments and aquaculture operations for these and other fish species.  Aquaculture presents a needed solution as an alternative to wild collection for the marine aquarium industry; as this species is listed as vulnerable on the IUCN Red List.  Fortunately, it (along with other Hippocampus spp.) has been listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which regulates international trade of the genus.

Bargibant’s Pygmy Seahorse (Hippocampus bargibanti)


The pygmy seahorses are relatively new to science.  Bargibant’s pygmy seahorse was the first to be described in 1970; the remaining six described to date weren’t named until the 2000’s.  The pygmys are unique among the seahorses in that they only have a single gill opening on the back of the head (other seahorses have a pair of gill openings on either side of the head).  The Bargibant’s pygmy seahorse lives exclusively in association with one genus of gorgonians (Muricella spp.), with which it has evolved masterful camouflage.  This species has become a celebrity because of its photogenic nature, and made another splash in the media when highly-skilled aquarists from the California Academy of Sciences learned to successfully keep the species’ host gorgonian, and subsequently collected, mated, and reared larvae of the species in 2014.  Still, though, this species is considered a “husbandry challenge,” and is best left to thrive in its natural habitat.  Bargibant’s pygmy can be found throughout the Coral Triangle and eastward to tropical Japan, Vanuatu and the Great Barrier Reef.

Yellow-banded Pipefish (Doryrhamphus pessuliferus)


This colorful pipefish can be found swimming in pairs around large remote coral heads on mud slopes.  Like other syngnathids, the male carries eggs in a brood pouch found under the tail.  This species serves a valuable ecological role as a cleaner fish, picking parasites off of other fishes for food.  While attractive to the aquarium industry; in Australia, one of its native countries, the species is protected under the Environment Protection and Biodiversity Conservation Act.  It is found more broadly throughout the Western Central Pacific, from Australia up into the Philippines.

Leafy Seadragon (Phycodurus eques)


This Syngnathiform species represents the pinnacle of mastery in camouflage among the order, with its ornate lobes rendering it indistinguishable from floating seaweed also found in its kelp forest environment.  Like other syngnathids, the father also gestates eggs, but unlike seahorses, which gestate eggs within a specialized brood pouch, the seadragon gestates them on a brood patch under the tail which is otherwise open to the environment.  This species is highly prized in the marine aquarium trade and in traditional Chinese medicine.  It is also vulnerable to population depletion from pollution and habitat loss, given its low dispersal ability.  Given these threats, and with data partially obtained from “Dragon Search,” a citizen-science based monitoring program that tracked the species’ population dynamics; it is listed as near threatened on the IUCN Red List, and is totally protected throughout its range across the southern coast of Australia.  The regal appearance of the leafy seadragon has landed it the auspicious designation as the marine emblem of the state of South Australia, the mascot for marine conservation and the object of adoration for the biennial Leafy Sea Dragon festival in the region.  To Pokémon fans out there:  Has anybody captured a Dragalge?  Notice the resemblance?

About the Guest Author:

Credit: Abigail Pheiffer, Mystic Aquarium
Credit: Abigail Pheiffer, Mystic Aquarium

Dr. Paul Anderson has been a marine biologist ever since he set-up his first seahorse aquarium as a kid many moons ago.  Today, he is a Research Scientist with Mystic Aquarium (Mystic, CT) where he conducts conservation-based research to provide data about the role that aquaculture plays in the sustainable development of the marine aquarium industry, while developing cost- and labor-effective methods for commercial aquaculture.

Paul’s connection to The Fisheries Blog: He and Patrick Cooney, Co-Founder of The Fisheries Blog, had adjoining office walls while attending graduate school at University of Florida in the early 2000s.  Patrick enjoyed typing his research results to the rythym of Paul’s upbeat music.

For Further Reading

Anderson, P.A. 2013. Acoustic characterization of seahorse tank environments in public aquaria: A citizen science project. Aquacultural Engineering 54: 72-77.

Anderson, P., Berzins, I., Fogarty, F., Hamlin, H., Guillette, L.J. 2011. Sound, stress, & seahorses: The consequences of a noisy environment to animal health. Aquaculture 311: 129-138.

Anderson, P., Mann, D.A. 2011. Evoked potential audiogram of the lined seahorse, Hippocampus erectus (Perry), in terms of sound pressure & particle acceleration.  Environmental Biology of Fishes 91: 251-259.

Australian Government, Department of the Environment and Energy.  2016.  About the Environment Protection and Biodiversity Conservation Act.  www.environment.gov.au/epbc/about

Bulbapedia.  2016.  Bulbapedia, the community driven Pokémon encyclopedia.  bulbapedia.bulbagarden.net/

Conservation Council SA.  2016.  Dragon Search.  www.conservationsa.org.au/dragon_search

Convention on International Trade in Endangered Species.  2016.  CITES.  www.cites.org

Encyclopedia of Life. 2016.  www.eol.org.

Festival Fleurieu.  2016.  Festival Fleurieu.  www.festivalfleurieu.org.au/

Florida Museum of Natural History.  2016.  Fishes & Sharks Species Profiles.   www.flmnh.ufl.edu/fish/discover/species-profiles/

Froese, R., Pauly, D. (eds.).  FishBase, v. 06/2016.  www.fishbase.org

International Union for the Conservation of Nature.  2016.  The IUCN Red List of Threatened Species.  www.iucnredlist.org

Kuiter, R.  2009.  Seahorses and Their Relatives.  Aquatic Photographics.

Marine Education Society of Australasia.  2016.  Marine emblems – Victoria, NSW, and South Australia.  www.mesa.edu.au/resources/marine_emblems.asp

Mills, D., Young, J.  1993.  Aquarium Fish.  Dorling Kindersley Limited.

OzFishNet.  1996.  Fishes of Australia.  Fishesofaustralia.net.au

Paxton JR, Eschmeyer WN. 1994.  Encyclopedia of Fishes. University of New South Wales Press.

Pedersen, M.  2014.  Steinhart Team Breeds Rare Bargibanti Pygmy Seahorse For The First Time.  Reef To Rainforest Media.  www.reef2rainforest.com/2014/06/17/steinhart-team-breeds-rare-bargibanti-pygmy-seahorse-for-the-first-time/

Smith, R.  2011.  Pygmy seahorse facts and images.  Ocean Realm Images. oceanrealmimages.com/blog/10/04/11/pygmy-seahorse-facts-images

Yankalilla Visitor Information Centre.  2016.  The Leafy Sea Dragon (pdf).  www.yankalilla.sa.gov.au/webdata/resources/files/Leafy_Sea_Dragon_Information.pdf

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