Obese Sea Pen

Cavernularia obesa

The Obese Sea Pen, known scientifically as Cavernularia obesa, is a colonial marine cnidarian found in the class Octocorallia. It is part of the order Pennatulacea, commonly referred to as sea pens. This species is distinctive due to its elongated ellipsoidal body shape and eightfold radial symmetry, featuring eight tentacles. Unlike other octocorals, sea pens, including the Obese Sea Pen, have a basal peduncle that anchors them into the substrate, allowing them to remain partially buried in sediments. This species is distributed across the northeastern Pacific Ocean and the coast of southern Japan, inhabiting sandy shores, mudflats, silty bottoms, and rocky outcrops. They are typically found from shallow intertidal regions to depths of 6,100 meters, although they are most commonly recorded between 5 and 20 meters. The Obese Sea Pen primarily feeds on small plankton, and its behavior is significantly influenced by environmental factors such as light and temperature, rather than its diet. Reproduction in the Obese Sea Pen involves external fertilization, with both males and females releasing sperm and eggs into the water. This process is synchronized with environmental cues like light, rather than direct communication between individuals. The species exhibits bioluminescence, emitting green and blue light, likely as a defense mechanism to deter predators. Despite this capability, the luciferase activity in C. obesa is relatively weak. Currently, the conservation status of the Obese Sea Pen has not been evaluated by the IUCN.