Article written by Vanessa McCole, B.S. Marine Biology
Scientific Study: Slingshot Feeding of The Goblin Shark Mitsukurina owstoni (Pisces: Lamniformes: Mitsukurinidae) by Kazuhiro Nakaya, Taketeru Tomita, Kenta Suda, Keiichi Sato, Keisuke Ogimoto, Anthony Chappell, Toshihiko Sato, Katsuhiko Takano & Yoshio Yuki
What Is A Goblin Shark?
The first Goblin shark was discovered in 1897 by a Japanese fisherman who was working in deep water when he captured a strange new shark. Based on this first specimen, Goblin sharks were placed under the order Lamniformes, commonly known as Mackerel sharks, but didn’t belong to any known Family, so an entire new Family was made. This new family was named Mitsukurinidae and Goblin sharks remain the only living members. They are also the only Mackerel shark to live in deep water.
Because Goblin sharks are a deep-ocean species, they are very difficult to study and are very rare to see. Most information about Goblin sharks has been gathered based on the few specimens that have been captured over the years and any information about their lifestyle has remained theoretical. As mentioned, Goblin sharks are a type of Mackerel shark, but the Goblin shark is very different anatomically than other Mackerel sharks, especially their jaws. Something that has captured the attention of scientists from the very beginning of their discovery was the Goblin shark’s strange jaws which protruded remarkably far from their head. This peculiar feature begged the question, how do they eat?
Divers Make A Discovery
The first videos of Goblin sharks feeding were taken in 2008, over 100 years after their discovery. In 2011, several more videos of their feeding behavior were captured. Based on these videos, scientists were finally able to study the feeding process of this elusive species. A group of scientists put together a study where they analyzed both the 2008 and 2011 videos – a total of 5 videos of two separate Goblin sharks feeding, – and then dissected a specimen in order to fully understand the process of a Goblin sharks feeding behavior, both physiologically, and evolutionarily. From this study, they were able to reveal a completely novel method of jaw protrusion and discovered unique evolutionary deviations of the species from the other Lamniformes.
Images from the videos taken in 2008 and 2011 showing the process of Slingshot feeding and the anatomy of the Goblin shark’s head.
Slingshot Jaws
This study showed that Goblin sharks have a totally unique form of jaw protrusion. First, their jaws protrude 2.1 to 9.5 times farther than the jaws of other sharks of the same order. They can also propel their jaws out incredibly fast. The jaw of a Goblin shark shoots out during prey capture at a maximum velocity of 1.6 m/s for the upper jaw and 3.14 m/s for the lower jaw. Other species known for their strike velocity and intense jaw protrusion include Narcine brasiliensis, an electric ray, and the sling-jaw wrasse Epibulus insidiator. The ray has a lower jaw velocity of only 0.28 m/s and an upper jaw velocity of only 0.87 m/s. The wrasse has a maximum strike velocity of 2.31 m/s. Neither of these compare to the extreme speed of the Goblin sharks jaw.
Striking velocities of upper jaw (a) and lower jaw (b) and gape angles (c) in one biting sequence of the 2008 shark.
A Novel Feeding Behavior
The prey capture of the Goblin shark has been divided into 4 separate phases: the resting phase, the expansive phase, the compression phase, and the recovery phase. The resting phase is the default state of the shark right before striking and the expansive phase is the when the jaws shoot out. The compression phase is separated into a shooting phase where the jaws are further projected, a grasping phase where the jaws enclose on the prey, and the holding phase where the jaws begin to retract. The way the jaw of the Goblin shark protrudes includes a novel behavior never before seen in any other shark species. When the jaws begin to retract after the holding phase, there is a re-opening and re-closing of the jaws that takes place; this is the recovery phase. Why does this occur? It’s a bit unclear why this happens. It could be because of the extreme protrusion and movement of the jaw. A better understanding of the complex mechanisms of the jaw movement is necessary to really understand if this is due to a physical complication or as a behavioral choice.
Evolution Is Weird
Why is this species so different from other Mackerel sharks? Why has it developed such a unique feeding method? The Goblin shark’s body is completely different from other Mackerel sharks. Its head is longer and flatter, its body is more slender, and its fins and musculature are weaker which has resulted in decreased swimming speed and stamina. The reason these changes occurred in this species was to adapt to living in the deep water. The slingshot feeding method was likely an adaptation meant to compensate for its slow swimming and poor stamina. The deep sea is a strange environment which demands many distinguishing adaptations from bioluminescence to slingshot jaws. Hopefully as we continue to explore this environment, we can continue to find exceptional species and strange adaptations.
References
- Nakaya, K., Tomita, T., Suda, K. Sato, K., Ogimoto, K., Chappell, A., Sato, T., Takano, K., Yuki, Y. (2016) Slingshot Feeding of The Goblin Shark Mitsukurina owstoni (Pisces: Lamniformes: Mitsukurinidae). Scientific Reports 6, 27786 https://doi.org/10.1038/srep27786
- Jordan, D. S. (1898). Description of a Species Of Fish (Mitsukurina owstoni) from Japan, The Type of a Distinct Family Lamnoid Sharks. Proc. Calif. Acad. Sci. 3rd ser. Zool 1, 199–201