Have you ever
heard of  ratfish?

The aquatic ecosystem is home to many mysteries and to all living and non-living things. As we dive deeper into the deep ocean, we can only imagine what lies ahead!

Subsequently, this article sheds light on the lives of ratfishes!


Spotted ratfish under the ocean

The spotted ratfish is a native to the northeastern Pacific Ocean. Spotted by divers at night in the Pacific Northwest regions, ratfishes get their name due to their physical appearance. They have a long and pointy tail that resembles that of a rat. 

Scientifically termed as Hydrolagus colliei, the ratfish lays eggs on the bottom of muddy or sandy surfaces. The names have a Greek origin. Apart from this, these species are not suitable for human consumption. They have no commercial value. 

Additionally, it has an attractive appearance. The females measure up to 97cm, and they are more abundant in comparison to males. 


Ratfishes belong to unrelated marine species. However, their skin is smooth and scaleless, with a silvery-bronze color. These species also come in sparkling shades like blue, gold, and green. The sparkling shades make them attractive and appealing. Spotted ratfishes are the most common species of ratfishes with circular spots all over their back. The outlines of dark edges are present in caudal and dorsal fins. Along with those, the pectoral fins are, however, transparent.

Appearance In Detail

The pectoral fins resemble the wings of an airplane. It is because they have enormous triangular pectoral fins. These fins extend out of the bodies of these ratfishes  

As a defense mechanism, the ratfish shark has a poisonous spine at the very tip of their dorsal fin.   

Hydrolagus colliei gets its native name due to its rat-like an elongated tail. This pointed rat-like tail covers half of its body. 

Besides, ratfishes lack bones: instead, they have cartilages that support the structure. Also, ratfishes have a face that resembles that of a rabbit. It also has a snout that resembles a duck.

The mouth of a ratfish is small. Although it has a pair of incisor shaped teeth in the lower jaw. They also have two pairs of incisor shaped teeth in the upper jaw. 

Sharks have temporary sharp teeth that help them to cut and tear their prey. Unlike them, ratfishes have plated, mineralized and permanent teeth. They mainly grind their prey. 

Apart from this, the jaw has a connection with the skull. But, don’t think any less of them! Ratfishes have soft jaws and a small mouth, but it also has the most significant biting force. This biting ability gives them a little leverage when it comes to consuming large prey. Their eyes resemble a cat. They have emerald eyes that light up in the dark, just like a cat. 

Also, the spotted ratfish grows about the size of 23.6 inches. Males, however, measure only 7.3 to 7.9 inches. 

the physical appearance


Owing to their peculiar abilities, here is the complete classification of a ratfish. 

  • They belong to the kingdom Animalia
  • They belong to the phylum Chordata
  • Ratfishes belong to the class Chondrichthyes
  • They also belong to the order Chimaeriformes
  • They belong to the family Chimaeridae
  • Belongs to the genus Hydrolagus
  • Part of the species H. colliei.


The spotted ratfish belongs to the family of Chimaeridae. Before we learn more about the spotted ratfish, let us dive deeper!

This family resembles other chimeras of different zoological classifications. They are always in comparison because of their general appearance and habits. However, they differ from them in some areas. They have short, round snouts, and some species like the spotted ratfish have elongated tails. They have defensive, poisonous spines on their back. 


The species of this family reside in temperate and tropical sea waters. Some species are below two hundred meters. Moreover, other species recede in shallow marine waters.

However, they measure depending upon the species. 

Where Do Spotted Ratfish Live?

They are common in Pacific zones. Precisely, we can find ratfishes in the eastern Pacific Ocean from Cape Spencer, Alaska, south to Vizcaíno, Baja California. 

Apart from this, ratfishes live in temperate portions of the sea. However, the spotted ratfish species reside near the end of the intertidal zones. Ranging to a depth of 2950 feet, they prefer muddy and sandy surfaces. This is one of the reasons why they are not in danger of being extinct. Aside from having no commercial value, they are far from environmental contaminants that can harm them.

Moreover, ratfishes have different anal and urogenital apertures. It is a belief that these ratfishes are an evolutionary descendant of sharks. Ratfishes are present on earth for four hundred million years ago. 


Ratfishes usually prey using their electroreceptive abilities and sense of smell. They are weak swimmers. They look for vulnerable marine animals to feed upon.

The spotted ratfishes swim close to the surface, looking for clams, crabs, etc. to feed.

They also feed on small fishes in the benthic regions. The spotted ratfishes also have a reputation for cannibalism.

To ensure their survival, they feed on their eggs. Apart from this, they also feed on younger species of ratfishes. They also migrate from deep to shallow sea waters in search of prey. The spotted ratfishes swim slowly and predominantly use the sense of smell. 

feeding habits and habitat


Reproduction mainly occurs in the spring and autumn seasons. The spotted ratfishes lay their eggs ( oviparous). 

The females release egg casings every ten to fourteen days. The eggs are spoon-shaped. It takes nearly eighteen to thirty hours to release the egg. The leathery egg sacks swing independently in the seawater. Attached to an elongated slender extension, which is the elastic capsular filament. 

Also, fertilization is internal. The mating ritual is elaborate. The mating ceremony usually includes color changes in male ratfishes. They also display several different movements that mark the beginning of the mating season. 

Moreover, these casings attach to the sea surface with the help of filamentous tendrils. The spotted ratfish has an incubation period of 12 months. The newborns measure about 14cm. However, they grow up to a length of thirty centimeters during their first year. 

Depending on age and sex, they often form groups and move together.


A female spotted ratfish lays an egg. The egg sack is leathery, measuring up to 12.7cm. The female spotted ratfish is protective of eggs. It swims around the new eggs to defend them from natural predators.

The males have different secondary sexual traits. They have a pair of pelvic claspers, a single frontal tentaculum, along with a couple of pelvic tentacula.

One can find these claspers on the ventral side of the fish. They project outwards from the pelvic fins. They are accountable for the locomotion of the sperm to the oviduct of a female spotted ratfish. However, the intrinsic part of the pelvic clasper has cartilages with two separate branchings. These branchings conclude enough fleshy lobe on the rear end.

The cephalic tentaculum of the male spotted ratfish is peculiar. It is a club like an organ that is unique as it is absent in other vertebrates. Their claspers are present on the top of the ratfish. It is a retractable organ. With small and sharp barbs, the tip is, however, fleshy, lined. Spotted ratfishes are sexually dimorphic. 


The spotted ratfish have several predators. The predators include six-gill sharks, seven-gill sharks, spiny dogfish, etc. When it comes to parasites, trematodes are some of the common parasites. 

However, other microorganisms inhabit this marine species.


Ratfishes are not fit for human consumption, they do not pose a severe threat. However, if you happen to cross paths with one, be sure to watch out!

Ratfishes have a poisonous dorsal spine that might inflict painful bruises. However, one must take care while handling the male species as they have clasping organs, which will inevitably cause a bad injury. 


Lay & Bennett (1839) were the first to coin the term Chimaera colliei. 

However, later on, Lay & Bennett changed its name into a more valid Hydrolagus colliei. Apart from this, the genus name, Hydrolagus, comes from the Greek word “hydra,” which means water. The term “Lagos” means hare. 


Spotted ratfishes are not likely under threat. Ratfishes have no commercial demand. We catch them as a part of trawl fishing or recreational fishing. People call them “trash fish”. People avoid them because their dorsal spines entangle in the fishing nets.  

However, they have issues to consider them as threatened species due to the growth of inshore trawl fishing. 


According to IUCN, it is present as the least concerned species. As a result, there are no conservation methods for these species. However, in Oregon, the authorities are taking steps.  


ratfish facts

Spotted ratfishes are not exactly sharks. However, it has a relation with sharks and is a cartilaginous fish. Moreover, it does not pass entirely as a shark. They are absent from the subclass Elasmobranchii.  

Apart from these, chimeras have a connection with sharks one way or the other. They have claspers for fertilization. The fertilization is internal, and the eggs in a leathery sack. They use the ability of electroreception and the sense of smell to prey. The point of dissimilarity lies where, unlike sharks, the male has retractable sexual parts. 


The discovery of the spotted ratfishes is revolutionary. Their development spurts the analysis of deep-sea creatures. Humans have always been curious about what lies in the deep regions of the sea. 

However, their discovery taught us that chimeras have fifty extant species in six genera. They also have four families. 


The spotted ratfish is always in comparison with the chimeras. They are cartilaginous fish and have a relationship with modern-day sharks and the closest relatives to sharks. It is a type of species with abundant and diverse groups. However, their last species that share common ancestry was present approximately four hundred million years ago. Concurrently, it inhabits the deep benthic regions. They have long, mushy bodies along with a massive head. They also have apertures present on their gills. Chimeras measure up to 150 cm. Similar to the spotted ratfish they also have cartilages. They have a black or brownish-grey appearance. As a defense mechanism, chimeras have a poisonous spine present at the tip of the dorsal fin. 


We do not know much of its origin. However, it has come to light that some are present from the Early Devonian period. For example, ratfishes. Due to the lack of abundant fossils, tracing their evolution was not easy. 

However, Chimaeras were present about 420 million years ago during the Silurian period. From this, 39 extant species fall into three specific families. These families are the Callorhinchids, The Rhinochimaerids, and the Chimaerids.

However, these families were not always present. These families came during the late Jurassic to early Cretaceous periods.


Similar to other fishes, chimeras also have various parasites. They are:

  • Chimaericola letogaster (Chimaericolidae): This monogenean parasite is present in the gills of Chimaera monstrosa.


The spotted ratfish is not dangerous but has a spine that is enough to give you the right bruise. it abundant and require no conservation. However, the spotted ratfish is a miracle of nature. This sexually dimorphic fish recedes near the benthic zones. 

Spotted ratfishes belong to the family of Chimaeridae. They have been present since the Early Devonian period. These fishes tell us more about the several mysteries of nature and what lies ahead!


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