Predatory Sea Squirt

The predatory tunicate (Megalodicopia hians) is a unique sea squirt that is defined because of its aggressive feeding style! Whereas other tunicates nourish themselves by filter-feeding on planktonic particles, the predatory tunicate consumes live prey that are unfortunate enough to enter its hood-shaped mouth. Despite its simple appearance, the hermaphroditic, five-inch-wide predatory tunicate is something to fear if you're small enough to get too close!

Tunicates are members of the Tunicata, a subphylum of the phylum Chordata and are almost all exclusively marine filter feeders with a sac-like body structure. They are commonly known as 'sea squirts', and in order to respire and feed, they take in water through an incurrent (or inhalant) siphon and expel the filtered water through an excurrent (or exhalant) siphon. Most adult tunicates are sessile (permanently fixed to a surface) and are attached to rocks or similar surfaces on the ocean floor, being either solitary or colonial in their habitat. A few, such as salps, doliolids and pyrosomes swim in the pelagic zone of the oceans (neither close to the bottom nor near the shore) as adults. The Tunicata are known to have evolved around 550 million years ago, and despite their simple appearance and very different adult form, are a sister subphylum to the Vertebrata. In other words, each and every tunicate is one of your long-lost distant family members, as both humans and tunicates belong the phylum Chordata!

There are thought to be about 2,000 species of tunicate in the world's oceans, with fewer than 100 being found at depths greater than 200 metres. They appear in a huge range of solid or translucent colours and sizes. In fact, one of the largest is Pyura pachydermatina, a sea tulip, which can be over a metre tall. In contrast, some of the smallest, the 23 species of doliolids, are under 2 cm.

The hood-and-stalk physiology of the predatory tunicate may appear squishy but don't be fooled as this yawning mouth strikes repeatedly and without warning. They are found in the Monterey Canyon, off of the coast of Northern California, at depths of 180-1000 metres anchored along the deep sea canyon walls and seafloor. Looking something like a cross between a Venus Flytrap and a jellyfish, its mouthlike hood is quick to close when a small animal drifts inside. Once the predatory tunicate catches a meal (mostly zooplankton and small marine animals), it keeps its trap shut until it is ready to eat again. 

Predatory tunicates are simultaneous hermaphrodites, meaning each animal can produce both eggs and sperm. Therefore, if conditions are poor or there are no other tunicates nearby, each tunicate can reproduce by itself and ensure the survival of this fascinating species.