Polyorchis, or bell jellies, is a genus of hydrozoans in the family Corynidae. They are often found in harbors, marinas, and other calm waters close to shore. They feed on plankton and benthic crustaceans and are found near the sea floor. The bells can reach about 2.25 inches (5 cm).

General Morphology

Polyorchis are at least as tall as they are wide, reaching up to 60 millimeters in height and averaging 20 millimeters in width. They have a fragile, non-gelatinous bell membrane, and they have a whorl of around 100 - up to 160 - unbranched individual tentacles connected at the bell's margin.

They have a well-developed velum, which are common in Hydroid medusae for means of greater thrust when contracting their bell during movement. Running from top to bottom inside the bell are four simple radial canals with 15-25 pairs of lateral blind-sided channels called diverticula. Radial canals are part of the digestive system, aiding with nutrient distribution across the bell.

Polyorchis are transparent with red coloration in their internal organs and eye spots around the rim of their bell. The red pigmentation helps them camouflage. P. penicillatus is nicknamed "red-eyed jellyfish", because at the base of the tentacles are several eyes, called ocelli, which contain light-sensing cells and red pigments.

Extending the entire length of the bell cavity, the manubrium is a tubular stalk that starts from a short gastric peduncle at the top of the bell and ends at the mouth in the center of the underside of the bell. It is connected to the gastrovascular cavity and has four frilly lips, also called oral arms, that surround the mouth and help with food capture.

Geographical Range and Habitat