Harford’s Isopod, Cirolana harfordi

Harford’s Isopod, Cirolana harfordi. Length: 2.5 cm (1.0 inch). Identification courtesy of Dr. Julianne Passarelli, Cabrillo Marine Aquarium, San Pedro, California.

Phylogeny: Harford’s Isopod, Cirolana harfordi (Lockington, 1877), is a member of the Cirolanidae Family of Cirolanid Isopods. This is a large Family containing fourty-eight genera. The Genus Cirolana is very large, consisting of one hundred and thirty-four species. Some of the frustration experienced by taxonomists with this Family may be sensed from the species named Cirolana namelessensis. In Mexico this species is called isópodo de harford. There are two subspecies of Harford’s Isopod that are geographically separated- Cirolana harfordi japonica and Cirolana harfordi spongicola.

Morphology:  Harford’s Isopods have an oval profile and are about 2.5 times longer than they are wide. They are white in color with very fine brown spots that gives the animal a blotch tan or brown overall color. Their simple, compound eyes are the only obvious feature on the body. Harford’s Isopod reach a maximum of 2.0 cm (0.8 inches) in length.

Habitat and Distribution:  Harford’s Isopods are common under rocks on sand, on marine plants, and in mussel beds. They are found along exposed coastline, lagoons, and mangrove forests;  from the intertidal zone to depths up to 135 m (450 feet).  They have a discontinuous range around the North Pacific, that includes Japan and Russia. In the Eastern Pacific, they range from British Columbia to San José del Cabo, Baja California Sur. They extend north into the Gulf of California to at least La Paz. Harford’s Isopods are one of the most common littoral isopod species in California. Harford’s Isopods have been introduced to Australian waters, where they are considered invasive.

Diet:  Harford’s Isopods are an active predator and scavenger that feeds on crustaceans, detritus, and polychaete worms. They are also thought to filter suspended food particles from the water. They use their antennules to detect the odor of food. They do feed on the flesh of living. dying, and dead fish and mammals, including humans. It is believed that Harford’s Isopods have the ability to sense injured and sick fish and parasitize them.

Predators: Harford’s Isopods are preyed upon by shore birds, crustaceans, and fish.

Reproduction: Harford’s Isopods are gonochoric (either male or female for life) and viviparous (live-bearing). Mating can occur anytime of the year, but usually slows during the fall. Females mate shortly after molting. She carries the fertilized eggs inside her thorax for three to four months, before giving birth to twenty to sixty-eight live offspring. She will give birth one or two times during her two year lifespan.

Ecosystem Interaction:  Harford’s Isopods are know to host many species of smaller organisms, however there is very little documented about the nature of those relationships. Similarly, while this species will parasitize sick and dying animals the exact relationships are not well understood.

Human Interactions:  In locations where Harford’s Isopods have been introduced and they lack predators to keep their populations in check, they are known to scavenge and parasitize fish in nets or traps. This does have a negative economic impact on some fisheries. This species will attack humans, leaving pinpoint bites, usually on the feet of waders. In large dense swarms they can cause minor bleeding and risk of infection.

Synonyms:  Aega harfordi and Cirolana toyamaensis.