The Soldierfish and the Parasite

A large Isopod living on an unfortunate Soldierfish (Holocentridae: Myripristinae). Grand Cayman.

Image supplied by Steven Kovacs Nature Photography, you can find him on Facebook and Instagram

They are nocturnal fish that hide in dark areas during the day, emerging at night to feed upon large zooplankton and small fish. They have large serrated scales and sharp venomous fin and head spines capable of delivering painful wounds if handled.

There are many species of soldierfish, some named after physical characteristics, such as the blackbar soldierfish, whitetip soldierfish, and the bigscalesoldierfish. Under stress, blackbar soldierfish make clicking and grunting noises with their swim bladder, an internal sac that fishes use to control their position in the water. Blackbar soldierfish often swim upside down. These fish use external fertilization on the days that follow a full moon.

The high biodiversity of coral reefs increases the complexity of the interactions between parasites and their various and numerous hosts. Numerical estimates of parasite biodiversity have shown that certain coral fish species have up to 30 species of parasites.

Usually parasites need to avoid killing their hosts, since extinct hosts can mean extinct parasites but there are exceptions. The tapeworm Schistocephalus solidus turns infected threespine stickleback white, and then make them more buoyant so that they splash along at the surface of the water, becoming easy to see and easy to catch for a passing bird, this bird is then the next host to the parasite.

Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration.

Other infamous aquatic parasites that we've seen before are the Cymothoa exigua, or the tongue-eating louse, this is a parasitic isopod of the family Cymothoidae. This parasite enters fish through the gills. C. exigua is thought to extract blood through the claws on its front,[clarification needed] causing the tongue to atrophy from lack of blood. The parasite then replaces the fish's tongue by attaching its own body to the muscles of the tongue stub

Family Holocentridae Squirrelfishes Soldierfishes; https://www.marinelifephotography.com/fishes/squirrelfishes/squirrelfishes.htm

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