The Angel shark is an interesting specimen and is an intriguing evolutionary cross between sharks and rays. At first glance, you might think it is a ray swimming in the water, but there are some subtle and important differences. Let’s look at this California local, the Pacific Angel Shark (Squatina californica).
Unlike and Angel Shark, the pectoral fins on the sides of a ray’s body are completely attached. Also if you take a close look at the tail (or to be scientific, the caudal fin) you will notice it doesn’t quite look like most rays or even other sharks. The lower part of the fin is longer than the upper part, unlike most other sharks species which possess the opposite. The mouth and gills are also formed differently than rays. The gills wrap around the sides of the head rather than under, and the mouth is located at the front of the face instead of on the underside of the shark.
All of these physical adaptations help this shark live in the benthos (which you will remember is the fancy scientific word for “bottom of the ocean”). They will strategically situate themselves at the bottom, cover their bodies in sand, and wait. As they wait, they are able to breathe without ingesting sand by passing water through an organ called the spiracles (http://www.arkive.org/pacific-angel-shark/squatina-californica/video-08a.html) and out through their gills. Camouflaged in the sand with barbels hanging near its nostrils, the Pacific Angel Shark waits until a small fish or mollusk passes by. At just the right moment, they ambush the unlucky entrée. Yum!
Come back next week to learn about another fascinating shark.
Edited by KC O’Shea
Photography from ARKive: Richard Hermann and Andy Murch
Cailliet, G.M. 2005. Squatina californica. The IUCN Red List of Threatened Species. Version 2015.1. <www.iucnredlist.org>. Downloaded on 18 June 2015.