Basking Shark

Basking sharks are aquatic animals that are categorized as sharks. The etymology of the term basking shark is attributed to the slow-moving nature of the shark. The basking shark is generally seen floating or swimming very slowly beneath the water, due to this behaviour they are commonly known as the basking shark. It is important to note that although the term is very popular it is not a scientific term and is not used in any form of taxonomic classification. Another common term used to describe this animal is the sea serpent. 

The scientific name of the basking shark according to the binomial nomenclature is Cetorhinus maximus. They belong to the genus Cetorhinus. The name itself signifies the large structure of the body, the species is considered the second largest species of sharks. Although it might seem that sharks are dangerous predators, they are considered harmless species of shark. Basking sharks like the other large aquatic mammals, the great whales are filter feeders. The term is used to define the food habits of animals that capture zooplankton and small phytoplankton by swimming. 

The body size of basking sharks can grow up to 46 feet, they are generally grey or black. The skin of these animals are spotted and have various small planktons attached to it. An important question that comes to mind while discussing the topic is what makes these species of shark important to be studied? The reason for this enormous fascination is the heavy build of the shark, another reason is the economical importance of the sharks. Basking sharks have high body fat due to this they are hunted to extract liver oil. The dead carcass of the shark body is often seen on the beach and are referred to as sea serpents. 

The article focuses on the general description of the sharks, the article also discusses the taxonomic classification, feeding habits, reproduction and life span of the shark. Behavioural traits are among one of the most important aspects of the study of an animal, the article also briefly discusses such behavioural aspects of the shark.

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General Description

An important question is what is basking and why the shark is named so? This can be answered by understanding the basic nature of these animals. They have developed fins present in the body, these fins are mainly responsible for swimming. They are generally found swimming just below the surface and thus are said to have a basking or floating nature. This is also the reason they are named basking sharks.

Basking sharks are the member of the Cetorhinidae family. They are classified under the genus Cetorhinus under this family. One of the most intriguing features of the shark is the basking shark size, they are one of the largest organisms of the marine ecosystem. The basking shark size can range up to 46 feet, they are almost as large as the great whales. Apart from their large size, they are known for their strong caudal fins.

They are considered a cosmopolitan species. Animals that live in various, vestigial geographical areas are termed cosmopolitan species. The basking sharks are found in the temperate waters across the world. 

As discussed earlier the basking shark is considered a filter feeder, since they are primarily dependent on the planktons as a food source they are subjected to anatomical modification adaptation that helps them in the sustenance of their life. One such anatomical modification that is found in this species is the largemouth. Apart from the Modification of the mouth, the second most important anatomical modification is the presence of the gill ranker. These are the appendages that project from the branchial arch. Gill rankers are involved in the predation.

When discussing the general anatomical modification, the anatomy of the basking shark teeth is very important. The teeth are also among the most distinctive features that these species have, there are approximately 100 teeth in a row in the buccal cavity of the shark. The basking shark teeth are also known for their small shape of the teeth.

Lastly, many marine scientists have concluded that these sharks have a very passive lifestyle. This observation was made by correlating the size of the brain with the activity. The C. maximus is known to have a very small brain, they have the smallest weight-for-weight brain size of any shark. 

They are hunted for their liver oil and because of this continuous hunting. They are now classified as endangered species.

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Taxonomical Classification

Taxonomical classification is the process of categorizing animals on the basis of their similarity. The main purpose of this classification system is to develop a better understanding of the species. The taxonomic classification helps us to understand the interspecies relationship, phylogenetic relationships between species. The classification system is also used to study the evolution pattern and the adaptation that was made during the course of evolution. The question of what is basking shark can be answered by taxonomic classification. The taxonomic classification of the basking shark, Cetorhinus maximus is mentioned below.

The shark is categorized into the Animalia kingdom, the basic feature of this kingdom is that all members of the kingdom are multicellular in nature, they are also of eukaryotic cell type. The kingdom is the highest level of classification which is followed by the phylum. The phylum in which the basking shark is categorized is termed Chordata. There are five main requirements that are necessary to be classified as a chordate, they are as follows: the presence of a notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. These synapomorphies must be present during any stage of the life cycle. All the above-mentioned features are present in the basking shark.

The phylum is further classified into classes, basking sharks belonging to the class Chondrichthyes. The characteristic feature of this class is the presence of the jawed vertebrates with paired fins, paired nares, scales, and a heart with its chambers in series. Another important feature is the absence of bone marrow. Since the bone marrow is absent in the members of this class, the red blood cells are produced by the spleen. The class is further classified into two subclasses called  Elasmobranchii and  Holocephali. The subclass Elasmobranchii consist of all the sharks, rays, skate and sawfish.

The subclass is further classified into orders, basking sharks belongs to the order called Lamniformes. This order is more commonly known as the order of mackerel sharks. Some of the most common members of this order apart from the basking shark is the great white shark, goblin shark and megamouth shark. The characteristic feature of this order is the possession of possessing two dorsal fins, an anal fin, five-gill slits, eyes without nictitating membranes, and a mouth extending behind the eyes. All these features are prominent in the basking shark apart from these they also possess a pair of lateral fins called caudal fins that assist in floating.

They belong to the genus called Cetorhinus, the genus consists of the basking shark species. The scientific name for the basking shark according to the binomial nomenclature is Cetorhinus maximus.

Morphological Features

A common question that arises during the study of this species of shark is what is basking and its relevance. As discussed earlier the etymology of the name has little to do with the morphological description. When discussing the morphological features of the shark the most obvious and important feature is basking shark size. The average size of the shark ranges from 23 to 28 feet but there are some cases where the size of these sharks are recorded up to 47 feet. Apart from their huge size, the second most important feature is the presence of the teeth. The teeth of the basking sharks are very small. The teeth of the shark are in the single conical cusp, are curved backwards. A unique feature about the basking shark teeth is the number of teeth, there are about 100 teeth in a row in both the upper and lower jaw. 

These animals are generally found in grey or whitish-grey colour. The skin of a basking shark is easily distinguishable because of the presence of moulting on the upper surface of the body. The body also has prominent gill slits around the head, and there are about 5 to 7-gill slits in the body. They also possess very strong gill rankers. Gill rankers are defined as the bony or cartilaginous processes that project from the branchial arch or gill arch. The sole purpose of these appendages is to catch tiny planktons. These are the main modifications that help the shark in filter-feeding.

These sharks are known to possess highly developed fin structures. They possess two dorsal fins, an anal fin, and caudal fins. All these fins assist in swimming, they are also known to have a very pointy snout.

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Habitat

Basking sharks are pelagic aquatic animals, they prefer living in warm waters. The optimal temperature range of these sharks is  8 to 14.5 °C alternatively calculated as 46.4 to 58.1 °F. One of the important points to notice is that they are migratory in nature during cold seasons they tend to move to warmer water near the equator. They primarily prefer living on the continental shelf but they are also sometimes seen in the brackish waters. They are recorded to live at a depth of 910 meters which when converted into feet is about  2,990 ft.

The most common geographic location of these sharks includes countries like southwest England, Wales and the west coast of Scotland. They are also found in the Republic of Ireland and along the coast of northern France, Norway, southern Brazil, Argentina, and Iceland.

Diet

The basking sharks are considered filter-feeding animals. Filter-feeders are those animals that feed by straining suspended matter and food particles from water. The filtration is done by special appendages. The basking shark has such a straining appendage as called gill ranker. They are the appendage that projects from the gill arch. The diet primarily includes small zooplankton that floats in the water, they also eat the phytoplankton. Apart from the planktons, their diet might include very small fish and invertebrates.

The food is ingested by swimming towards the organic material by opening their mouth. It is estimated that they can filter up to 450 tons of water per hour.

Reproduction

Basking sharks are sexually reproducing organism, the fertilization process in these organisms are internal. A very interesting fact about these sharks is that they are categorized as ovoviviparous. The term can be defined as the animal that lay an egg but the egg develops inside the body of the female. The development of this organism is based on the nutrient present in the yolk sac. There is no placental connection between the body as seen in mammals.  Basking shark teeth play an important role in the developmental stages, the teeth help in the ingestion of nutrients from the unfertilized eggs of the female shark. An intriguing fact about the female reproductive system is that only a single ovary usually the right ovary is functional. The reason for this is not completely understood. 

The gestation period of the animal is about a year. The litter size of these animals is unknown. The basking shark size for the young members at birth is about 1.5 to 2 meters. Some of the young ones of the basking shark are about 4 to 7 feet long. 

Behavioural Traits

The behavioural trait discussed in the article discusses the migration pattern and social behaviour. Basking sharks are considered solitary animals, the only time they are seen in a group is during the mating season. The groups contain about 3 to 4 members. After mating the group dissolves. It is believed that pregnant females stay away from the population of the basking shark, the reason for this behaviour is still unknown. 

These animals are migratory in nature, they move to warmer waters near the equator during the winter. Many marine scientists associate migration with the reproductive cycle of sharks. The basking sharks during this migratory period are seen at depths of 200 and 1,000 metres which are about 660 and 3,280 feet.

Predators 

There are only a few predators of this species, examples of the predators of the shark include the following, White sharks, killer whales and Lampreys. Apart from the natural predators the largest threat to the basking shark population. The animal is hunted for their flesh oil and skin. The flesh used as a food product, while the fat of the body is used to extract the liver oil. The continuous hunting has led to a severe decline in the population.

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Conservation Status

The main reason for the decline in the population of these aquatic animals is human exploitation. They are listed as Endangered species in the IUCN red list of threatened species. Many countries have banned the trade of this species under the CITES. The countries that have fully protected these species include the United Kingdom and the Atlantic and Mexican Gulf regions of the United State. They are partially protected in Norway and New Zealand.

Summary: At a Glance

• The scientific name of the species is Cetorhinus maximus.

• They are known for their large size, the basking shark size can range up to 46 feet.

• The teeth of the basking shark are vestigial.

• They are considered ovoviviparous animals.

• They are found in temperate water and prefer living in warm water

• They are migratory animals.

• They are considered solitary animals.

• The only few natural predators include killer whales and white sharks.

• They are listed as endangered species by IUCN.