Sharp-point Fish Clinger, Nerocila acuminata

Sharp-point Fish Clinger, Nerocila acuminata, Aster. Isopod provided by the commercial fishermen of the greater Los Cabos area, January 2012. Size 2.6 cm (1.0 inch). Identification courtesy of Dr. Julianne Passarelli, Cabrillo Marine Aquarium, San Pedro, California.

Phylogeny:  The Sharp-Point Fish Clinger, Nerocila acuminata (Schioedte & Meinert, 1881), is a common ectoparasite that is a member of the Cymothoidae Family of Ectoparasite Isopods. The Shape-point Fish Clinger is known in Mexico as puntiagudo adherito. They have two distinct forms, acuminate and aster. The forms can be easily separated by the length of the coxae and pereonites which are large in the aster form (giving it a star-like appearance) and smaller in the acuminate form.

Morphology: The Sharp-Point Fish Clinger is dark brown dorsally and cream colored ventrally with symmetrical ovate flattened bodies. The abdomen tapers smoothly from the thorax.  The telson is broad and extends out further than the rest of the abdomen. The head is fused with the first of seven thoracic segments, followed by a a six-segment abdomen. One pair of thoracic appendages is modified into mouth parts. The eyes vary in size from very small to moderately large. They have long legs with pointed tips that are utilized for attachment to the skin of their host fish. The Sharp-Point Fish Clinger reach a maximum of 3.0 cm (1.2 inches) in length.

Diet: This species feeds on the blood and tissues of their hosts causing tissue damage, blood loss, and secondary bacterial infections. The Sharp-Point Fish Clinger is not host specific and is commonly found attached to various commercial fishes such as anchovies, flounder, groupers, jacks and perch. Juveniles are free swimming until they find a host.

Reproduction:  The species is a protandrous hermaphrodite containing both types of sex organs with males transitioning to females at mid-life. The male form undergoes 2 or 3 molds before transitioning to female, which then undergoes 3 or 4 molts as a female. The females are capable of releasing a pheromone that prevents the males in the vicinity from changing to females.

Habitat & Distribution:  The Sharp-pointed Fish Clinger resides in all Mexican waters of the Pacific Ocean. As the common name suggests, this species attaches itself to the base of the fin of schooling and bottom fish, including anchovy, flounder, leather jack and surfperch. The effect of isopods on humans if consumed is unknown. The behavioral study of this species is difficult as the majority are captured via bottom trawls and these isopods commonly abandon their hosts before they reach the surface.

Synonym:  Pterisopodus bartschii