Longhorn cowfish: Characteristics, types, reproduction and more….

One of the most striking and unusual looking fish is the Longhorn cowfish or  Lactoria cornuta in scientific terms. We invite you to learn in this post everything about this very exotic fish whose popularity has increased in recent times


Kingdom: Animalia  Phylum: Chordata Class: Actinopterygii Order: Tetraodontiformes  Family: Ostraciidae Subfamily: Ostraciinae  Gender: Lactoria  Species: Lactoria



The Longhorn cowfish is a horned marine species  that has a square figure similar to a cow, bull, or toad. In this horned fish we find a wide range of colors distributed in the 25 existing species.

Ostraciidae Family

This fish belongs to the  Ostraciidae family.  Members of this family come in a variety of different colors, and are notable due to the hexagonal patterns (known as honeycombs) on their skin.

Their plate-shaped hexagonal scales merge together into a solid, triangular or

 box-shaped shell, from which the fins, tail, eyes and mouth protrude.

Because of these heavy armored scales, the Ostraciidae are limited to slow movements, although few other fish are able to eat the adult specimens of this family.

Although adults are generally quite square in shape, the young Ostraciidae have a slightly rounded silhouette and a brighter color than adult specimens.

One highlight to know about this family, is that its different members are able to secrete an active cationic substance through their skin when they are tense.  Such a substance acts as a mechanism of chemical defense.

An example of this is pahutoxine, a water-soluble crystalline chemical toxin that is contained in the skin-segregated mucus of Ostracion lentiginosus and other family members when they are under stress.

Pahutoxin is a choline chloride ester of 3-acetoxypalmitic acid that behaves similarly to steroid saponins found in echinoderms. When this toxic mucus is released from the fish, it dissolves rapidly in the environment and negatively affects any fish in the surrounding area.

Let’s meet them

The Longhorn Cowfish’ Main Characteristics

In their natural habitat the Longhorn cowfish can reach about 50 centimeters, but in the aquarium they rarely exceed 30 centimeters.

They have a box-shaped angled body, characterized by the presence of a bony shell, which completely covers their body. From this shell, the anal, dorsal and pectoral fins stick out as well as the tail. Their fins are too far back which makes them lousy swimmers.

Yet, the most highlighting trait about these creatures, are their horn-shaped protuberances that come from the forehead, barely visible in the youngest specimens, but that grow with age.

It is not uncommon for them to lose their horns from time to time, but they come out again. They also have other horns under the caudal fin.

Body Color

The Longhorn Cowfish’s color is yellowish, with a very light green bottom, although there are specimens in other less attractive colors such as brown or gray. In addition, it’s worth mentioning that their body has dots whose color can be white, blue, brown or green.In this species there is no sexual dimorphism

Other interesting facts

    • Their body has a powerful toxin (Ostracitoxin), which is released and dissipated into the water, in order to poison their potential predators.
    • Males Longhorn Cowfish tend to extremely mark their territory.

When Longhorn cowfish become adults, they are usually solitary animals. On the other hand, they prefer to be accompanied by a group in their youth.

Their teeth are conical but moderate.

They have enough poison to kill everything around them

Their mouth is located on the underside of their head

    • Their eyes look like a galaxy
    • It can ‘hover’ in the water
    • They can make a grunting sound
    • They lack gills.

We invite you to read our article the anatomy of fish to learn more about such a topic…

Let’s learn about boxfish in general

The Longhorn Cowfish ’ Habitat and Distribution

Longhorn cowfish thrives on lagoon reefs and offshore protected reefs, where it is easy for them to find a cavity or hole to hide if they are in need of doing so.

Normally the place inhabited by them is at depths ranging from 1 to 280 meters deep.

Their geographical  distribution occurs in the following regions: Atlantic coast of Africa, the United States, southeast of Brazil, northern Gulf of Mexico,  Canada, northern Japan, Peru, Hawaii,  Chile, Red Sea, , northern Australia, New Zealand and Atlantic Ocean, between Central America and South America.

Longhorn Cowfish’ Common Behavior

Longhorn cowfish have a unique swimming method called “ostraciform swimming”. This technique makes them look as if they were floating looking up.

Additionally it’s worth mentioning that they are very slow swimmers and easy to capture with hands. People who have achieved it indicate that Longhorn cowfish make a grunt-like noise.

Juveniles of this species reproduce mainly in brackish water, and then migrate to salt water during adulthood. .

If severely stressed, this species may be able to exude a lethal toxin called ostracytoxin, considered unique among the known poisonous fish. Oystocytoxin, resembles red tide and sea cucumber toxins in their general properties. We invite you to read our article puffer fish to learn about other poisonous fish.

Let’s watch and learn


How do Longhorn Cowfish Reproduce?

This is an oviparous fish that breeds at the time that the ocean waters raise their temperatures in spring. Their mating occurs when the male courts one of the females of his harem, showing his bright colors and climbing with her to the surface.Longhorn cowfish: Longhorn cowfish in an aquarium

This is carried out in order that the male can make a very loud buzz and the female can spawn the eggs.

The Longhorn cowfish’ Feeding Pattern

Their diet is based on seaweed, although they sometimes add microorganisms and invertebrates, such as mollusks, tunicates, , worms, and smaller fish to their menu.

Threats and Predators

The Population numbers of longhorn cowfish in their natural habitat are unknown. The IUCN Red List for conservation lists them as not assessed.

Their horns make  longhorn cowfish  difficult to eat, however, they do not have many predators. Larger fish such as albacore and bigeye tuna are their main predators, even humans in some occasions.

Longhorn Cowfish in Captivity

This species has become quite popular given its funny appearance and its ability to adapt well to the aquarium environment.

Yet, Longhorn cowfish need special care and aren’t that easy to maintain. Therefore, they are recommended only for people who have deep aquarium knowledges or scientific research facilities.

Keep in mind that horned boxfish (as they are also called) are also dangerous because Ostracitoxin can cause severe damages to other fish.

Therefore it is highly recommended to join them with peaceful tank mates who don’t stress them if they are going to be housed in a community aquarium.


Longhorn cowfish should be housed in a 150-gallon aquarium, provided with plenty of live rock and live sand for shelter and food. They love to eat and this fact along with the large size they reach in adulthood, can add a considerable biological load to your aquarium.

For this reason a good filtration system is recommended since in nature they prefer calm waters, and are not exposed to turbulent water movements. Thus, a slow to moderate water movement is recommended.

Sudden movement, sound or bright lights tend to easily stress Longhorn cowfish these little creatures, causing them to secrete their dangerous toxin.

It has been reported that Ostracitoxin doesn’t affect invertebrates so easily.

On the other hand, if you have a horned boxfish that is stressed or has died in your aquarium, it’s advisable  to make a series of substantial water changes and place a fresh bag of activated carbon somewhere in the filtration system near the pump return in your sump.  Change the carbon every 24 hours.

Although they may be compatible with reef aquariums similar to those used for mandarin fish, a FOWLR (fish only with live rock) system is recommended, since Longhorn cowfish do not usually damage corals and anemones.

Be careful when placing this fish in a reef tank, as it can bite tubular worms. When properly housed, horned boxfish are long-lived.

They are generally peaceful and as we mentioned earlier, they must be housed with other peaceful tank mates that will not cause them stress in community aquariums.

However, they can become aggressive with fish of their own species which entail employing a much larger aquarium to ensure a lot of separate territory.

When possible, horned boxfish should be the first fish introduced into the aquarium to become established.

Choose tank mates wisely and remember horned boxfish have the ability to release ostracitoxin into the water column and their horns can be accidentally caught by the aquarium ornaments.

So, it’s  necessary to be careful with these objects to ensure the safety of this particul

Ar fish.

Water parameters

dKH:  8 – 12,

 pH:  8.1 – 8.4

, sg 1.020 – 1.025

Temperature: 72 – 78 ℉ (22 – 25.5 ℃).

Longhorn cowfish need excellent water quality upkeep to prevent them from succumbing to illnesses they may be susceptible to.  In addition, the water quality should be checked weekly.

Finally, remember that they aren’t very tolerant of others of their kind and when adapting them never introduce the water from their bag into your aquarium, since it may contain their poison if they have found the journey to their new home stressful.

Let us learn

Other Boxfish

Let’s learn about other species of this family

Thornback Cowfish (Lactioria fornasini)

This species has the box fish’s characteristic horns and toxins. It is distributed throughout the Indo-Pacific East Africa to Rapa Island.

It lives in tropical and some temperate waters in Australia from the south to the northwest of Western Australia and from the north coast of Queensland to the south coast of New South Wales.

Their body is covered with hard bone armor, and has a pair of large spines that project forward to the eyes.

It also has another pair of spines that project below the caudal fin from the back of the ventral-lateral ridges.

Similarly, a single spine is observed that is dorsally positioned.

The coloring of Lactioria fornasini varies from green to brown with blue spots and short stripes around its body.

It is worth mentioning that their horns are not as long and prominent as those of the Longhorn cowfish, but it does have the same toxic capacity as the previous one. However, reportedly, they are less likely than other boxfish.

Other Traits

    • The Thornback Cowfish grows to approximately twenty centimeters. 
    • Their diet is varied and consists of large pieces of fleshy foods, such as krill, raw table shrimp, squid, clams and mussels. Sometimes they also supplement their diet with some kind of herbivorous diet that contains seaweed.
    • These fish live between three and fifty meters deep.

Camel cowfish-Humpback turretfish (Tetrosomus gibbosus)

This species has a triangular section body. Camel cowfish can reach up to 30 cm in length although its average size is 20 cm.

Like all boxfish, it has a shell made up by hexagonal plates with holes corresponding to the eyes, mouth and fins, also useful for gills and anus.

It should be noted that they lack ventral fin and locomotion consists of the characteristic undulating movements of the dorsal and anal fins.

The pectorals caudal serve, mainly as rudders and for precise maneuvers.

Tetrosomus gibbosus present two small horns over their eyes and, above all, a pyramidal stinger on the back that has earned them the Humpback appellative. Its lateral edges have defensive spiny bumps.

The color ranges from yellow sand to blue, in adult specimens.

Like the other species in this family they have the ability to secrete ostracitoxin which can be lethal to other fish if they are repeatedly bothered or if they die.


Swim between 40 and 110 m deep, and also in deep waters near coral reefs and in the seagrass beds on sandy, detritic and muddy bottoms in which, since it is not a great swimmer, they merit that the waters be calm and can calmly look for food.

Let’s watch them

Yellow Boxfish, (Cubicus Oyster)

This species has an angular body covered with foil-shaped scales. Ostracion cubicus grows to a maximum length of 47 centimeters, although 20 centimeters is the standard size of this species.

Its body is enclosed in a bony-shell that when seen from a frontal view, has a triangular shape with a narrow top and a wide base.

The fish has a pointed snout with protruding lips surrounding a small mouth. In turn, the tail is brush-shaped, the body color is usually dark with a pattern of small white spots, often in hexagonal groups giving a honeycomb-like appearance in the middle area of the body.

The tip of the snout and the area around the pectoral fins are dark with few spots and the eyes are black. The fins usually have a yellowish tone with a dark base and tips and only soft spokes without spines.

Young individuals have dark-colored bodies covered with large yellow spots, but as they grow, a pale area develops where the honeycomb marks will appear later.

It is located up to a depth of about 50 meters on coral reefs and on the sandy seabed in the Caribbean Sea, the Gulf of Mexico and the western Atlantic Ocean.

This fish is usually solitary, although sometimes it moves in small groups. Yellow Boxfish usually uses its bulging lips to expel a jet of water that stirs the sandy seabed, exposing any benthic invertebrates that are not heavily buried.

They feed on small molluscs, polychaete worms, small crustaceans and sponges just like any other box fish.

In some regions, this species is captured for human consumption, and is also frequently used in reef aquariums. However it should be used with caution, because like any member of this family has the ability to release ostracitoxin in stressful situations.

Let’s keep learning

Honeycomb Cowfish (Acanthostracion polygonius)

This species has armor with hexagonal scales that cover most of its body. Like Longhorn cowfish its name comes from the unique pattern in the form of a honeycomb and the horns it possesses.

This pattern helps fish mingle with coral reefs. Most fish of this species tend to be blue, but there are also yellow, grey or green specimens.

Juveniles, on the other hand, are generally more colorful than adults, have no pelvic fins, and the caudal fin is rounded.

This fish has several modified bone scales and horns, which serve as a protection mean. Honeycomb Cowfish can be distinguished from similar fish by the two thorns above its eyes and hexagonal pattern.

Compared to other boxed fish, Honeycomb Cowfish has a smaller, protruding mouth and fleshy lips. The maximum length of the body is 50 centimeters, but the average length is 25 centimeters.

This species is distributed throughout the western Atlantic, the Caribbean Sea and waters near Brazil.

They are absent in most of the Gulf of Mexico, but there are populations around Florida. Honeycomb Cowfish lives in warm, clear waters near coral reefs, seagrass and estuaries, it is a rare and cautious species.

They are usually solitary, although they can be seen in groups of three individuals consisting of one male and two females.

Little is known about their reproduction, but they are known to mate in open water.

They have been observed swimming rapidly to the surface in pairs; releasing their gametes and swimming quickly back down.

They have the ability to change color in order to protect themselves from predation, once camouflaged, fish can remain stationary for long periods of time. Juveniles have better swimming skills than adults because of their more rounded bodies.

The diet develops during the day, consisting of small marine invertebrates including shrimp, sponges, algae and tunicates.

This is considered a valuable fish as food, is marketed fresh, and is appreciated in the Caribbean where it is very abundant.

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Scrawled Cowfish

Its scientific name is Acanthostracion quadricornis, is a cowfish of the family Ostraciidae, whose size varies from 8 to 15 inches. Scrawled cowfish can be found at depths between 6 and 80 feet. It’s a common fish in Florida and the Bahamas, but rare in the Caribbean,

It has distinctive features such as a scribbled model of bluish markings covering its body. In addition, Acanthostracion quadricornis has a blue line that goes from the snout to the anal fin and has a pair of sharp spines above each eye.

In general, it is green blue to faded yellow, although they can change hue significantly. Scrawled cowfish

Have two sharp spines in front of the anal fin, but lack pelvic fins and a spiny dorsal. They almost always have dark spots spotted along their body; and three to four horizontal lines on the cheek usually have fewer than fifteen teeth in each jaw.

The Scrawled cowfish breeds during January and February, and from July to September.

They release the eggs into pelagic waters and eventually settle as juveniles out of the water column. It is a species of shallow waters, mostly always found in and along water beds.

It feeds on small invertebrates such as crabs  and tunicates, and also eats some species of marine vegetation. It can be very tasty as food if cooked properly according to many consumers. It’s  locally abundant in the Caribbean region and sold often fresh, and although they are very good to eat, in many places around the world they are used as an aquarium fish due to its beautiful coloration.

here they are


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