Hard Bubble Seaweed, Dictyosphaeria versluysii

Hard Bubble Seaweed, Dictyosphaeria versluysii. Underwater photographs taken in Bahía de La Ventana, El Sargento, Baja California Sur, March 2025. Photographs courtesy of Aaron Woodrow, Juneau, Alaska. Identifications courtesy of Greg Timms, youtube.com/@CoralmasterdivesPuerto-Vallarta/videos.

Phylogeny: The Hard Bubble Seaweed, Dictyosphaeria versluysii (Weber-van Bosse 1905), is a green algae in the Siphonocladaceae Family. The Dictyosphaeria Genus is one of six genera in the Siphonocladaceae Family, and there are eleven species in the Dicthophaeria Genus. The genus name Dictyosphaeria comes from the Greek words meaning “network sphere” and refers to the spherical or hemi-spherical structure of tightly interlocking cells that comprise these algae. This species was first described by the Dutch phycologist Anna Weber-van Bosse, who named it in honor of the Dutch zoologist and anatomist Jan Versluys. The Hard Bubble Seaweed is also known as the Pimply Green Seaweed and the Button Weed.

Morphology: Hard Bubble Seaweeds may be mistaken for green plants but, in actuality, are protists. Unlike common bubble algae from the Ventricaria Genus, Hard Bubble Seaweeds form dense, solid, flattened cushions. The textured surface consists of many smaller, tightly interlocking bubble-shaped cells that give it a distinctive “pimpled” or honeycomb look. These primary cells may be angular or polyhedral in surface view, and measure 0.5 mm to 1.0 mm in diameter. Daughter segments from these cells, maturing in many planes, form pseudoparenchymatous (false plant-like material) tissue of intertwined filaments. Younger specimens are more spherical than the somewhat flattened mature specimens. They are firm and tough in texture. Their rhizoids are short and generally unbranched. Hard Bubble Seaweeds range in color from bright green to iridescent bluish-grey. The thallus (main body) can reach a maxium of 5.0 cm (2.0 inches) in diameter. This species over laps range and habitat with the similar looking Green Bubble Algae or Green Bubble Seaweed, Dictyosphaeria cavernosa (larger and forms hollow sacks, which are often ruptured and convoluted).

Habitat and Distribution: Hard Bubble Seaweeds are found attached to rocks and coral rubble, often surrounded by sand. They live in shallow calm reef flats, tide pools, and wave and current swept areas. They are found at depths up to 76 m (250 feet), though most grow in shallower, sun-lit waters. Hard Bubble Seaweeds are thought to be indigenous to the Indo-Pacific and Central Pacific though they now have a global distribution in tropical and subtropical seas. In Mexican waters they are found the Gulf of Mexico and Caribbean in the Atlantic Ocean and have not been formally documented as residents of the Pacific Ocean.

Predation:  Hard Bubble Seaweeds are firm and tough, which deters most herbivorous consumers. However they are preyed upon by some species of fishes, gastropods and sea urchins These predators vary throughout the wide geographic range of Hard Bubble Seaweeds.

Reproduction: Hard Bubble Seaweeds reproduce vegetatively and sexually. They propagate vegetatively by producing daughter segments that start inside parent segments but grow outwards in the form of a bubble. They reproduce sexually by releasing reproductive cells through pores in the walls of the vegetative cells of the thallus.

Ecosystem Interactions: Hard Bubble Seaweeds contain chlorophyl and utilize photosynthesis for energy. They absorb other nutrients from the surrounding water. They provide structural habitat for small invertebrates such as crabs, mollusks and shrimp. They also host marine fungi internally in what appears to be a commensal relationship. Hard Bubble Seaweeds are not as aggressively invasive as other species in the Dictyosphaeria Genus, but if introduced they can thrive and produce algal mats that smother and displace corals and other organisms in some envirnoments.

Human Interactions: Hard Bubble Seaweeds are occasionally used a low quality animal feet, as fertilizer and as fish bait. They contain unique chemical compounds that are of interest to the scientific and medical communities. The fungi they host are in the Penicillium Genus that produce novel metabolites. From a conservation perspective, Hard Bubble Seaweeds have not been formally evaluated, but they are widespread, common, with stable populations and should be considered to be of Least Concern.

Synonyms: Dictyosphaeria bokotensis and Dictyosphaeria vanbosseae