Diet

• Pennaria disticha is a carnivorous hydroid that feeds primarily on zooplankton and small epibenthic organisms.

• Its feeding polyps use stinging cells (nematocysts) to capture and immobilize small organisms that come into contact with the tentacles.

• The longer, thread-like tentacles help intercept prey, while the shorter capitate tentacles around the upper part of the hydranth assist in handling and transporting food towards the mouth.

Range

• In the eastern Pacific it occurs along the Pacific coast of Mexico and Central America. It has been documented on the Pacific coast of Oaxaca, where it was reported as a new record for the Mexican Pacific.

• It occurs in the tropical Pacific waters of Mexico and is likely present in the broader Zihua region.

Habitat

• It is a shallow-water hydroid that attaches to hard substrates, including rocks, reef surfaces, artificial structures and other submerged objects.

• It is commonly associated with areas having some water movement and can occur in protected reef areas, cracks, crevices, harbour structures and other sheltered locations.

• It has been recorded from the intertidal zone to approximately 29 m depth, with most records from relatively shallow coastal habitats.

• Colonies can also grow on mangrove roots, dead coral, gorgonians and artificial reef structures.

Description

• Pennaria disticha forms erect, branching colonies arising from a creeping, branched base.

• The colonies can reach approximately 30 cm in height and have a dark brown to blackish protective perisarc surrounding the main stem and branches.

• Branching is generally alternate, producing a distinctive feather-like or Christmas-tree appearance.

• The feeding polyps are pale white to reddish and have two types of tentacles: a basal circle of approximately 10–18 long, thread-like tentacles and up to 12 shorter, knobbed (capitate) tentacles around the upper part of the hydranth.

• Annulations, or ring-like constrictions, occur on the main stem and branches and are particularly noticeable on younger portions of the colony.

• The dark perisarc is frequently covered by microscopic algae and other growth, which can make colonies appear muddy brown or darker than the underlying hydroid structure.