Form and Function

     The Stenella clymene is very closely related to and frequently misidentified with the spinner dolphin (Stenella longirostris). Compared to the spinner dolphin, the Stenella clymene has a more stocky body shape and shorter length (Perrin et al. 1981). Once an adult, the dolphin will measure 183-196 cm in length (Perrin et al. 1981) and weigh 150-190 pounds (Jefferson and Curry 2003). The pectoral flippers, beak and dorsal fin are typically noticeably shorter than those of the spinner dolphin (Perrin et al. 1981).The Stenella clymene will have anywhere from 38-49 small teeth per row and have a beak measuring 9-11 cm long (Perrin et al. 1981).

Figure 5: This figure shows the size of a Clymene dolphin compared to a human.

     As a member of the Delphinidae family, the Stenella clymene has many of the same general physical characteristics as other dolphins such as the spotted dolphin (Stenella frontalis) and whales including the killer whale (Orcinius Orca). They have a hydro-dynamic body shape with two pectoral flippers, a single blowhole, and a tail comprised of two flukes (Sea World: Adaptations 2002). The tail is composed of two lobes which help the organism to move in an aquatic environment. The back muscles move the tail in an up and down motion to propel the dolphin forward (Sea World: Physical 2002). The pectoral flippers are what help the organism steer. All dolphins possess a bone structure in the flippers closely resembling the forelimbs of land mammals. This suggests that species of the Delphinidae family are derived from a terrestrial ancestor (Sea World: Physical 2002). The dorsal fin is located at the center of the Stenella clymene’s back just like most other dolphins. This is what helps the organism balance and stay stabilized while swimming (Sea World: Physical 2002).
Figure 6. This diagram shows the anatomy of a dolphin. It displays the dorsal fin, flippers, flukes and blowhole.

    The blowhole at the top of the head allows the organism to breathe at the surface via a muscle at the opening that contracts to open and relaxes to close (Sea World: Adaptations 2002). The Stenella cylemene and other dolphin species have developed the ability to hold their breath for extended periods of time to allow for prolonged submerges. With each breath, a dolphin is able to exchange oxygen from more than 80% of the air in its lungs while humans exchange about 17% (Sea World: Adaptations 2002). This efficiency of oxygen exchange helps the Clymene dolphin in particular to dive to deep pelagic depths.

    Echolocation is an ability that the Stenella clymene is able to utilize in order to familiarize itself with its surroundings and efficiently locate prey. This process works by sending high-frequency sound waves through its melon, or head, and interpret the echo waves that are deflected back at the dolphin into a mental picture of its surroundings (Sea World: Communication 2002). Collecting the echo waves in the fat-filled cavities inside the lower jawbone, the information is able to be sent to the brain to be interpreted. Proximity, shape, speed and size are able to be determined and allows the dolphin to hone in on prey or avoid a predator (Sea World: Communication 2002).



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