Ocular lesions associated with attachment of the parasitic copepod Ommatokoita elongata (Grant) to corneas of Greenland sharks, Somniosus microcephalus (Bloch & Schneider)

Abstract

The eyes from six Greenland sharks, Somniosus microcephalus (Bloch & Schneider), infected with the parasitic copepod Ommatokoita elongata (Grant) were collected in the Arctic waters of Victor Bay, North‐west Territories, Canada, for study. Transformed adult female copepods, one per eye, were firmly attached to the corneas by an anchoring structure (i.e. the bulla) and each bulla was associated with an opaque area on the cornea. Two eyes additionally had one O. elongata copepodid attached to the cornea via frontal filaments with bullas which were each associated with a small corneal opacity. In addition to opacities associated with copepods at the time of collection, there were several randomly distributed, small, round‐to‐irregular, full‐thickness corneal opacities which were not associated with copepods. Two unfixed eye lenses grossly examined in the field were normal in appearance. Histologically, corneal epithelial ulceration and heterophilic keratitis, disruption, mineralization, and detachment of Bowman's membrane, thinning, disorganization, mineralization and fibrosis of the corneal substantia propria, and focal thinning and mineralization of Descement's membrane were observed. Mild heterophilic and mononuclear anterior uveitis was also present. Based on the present observations, it is concluded that parasitism by O. elongata could lead to severe vision impairment (possibly including blindness) in Greenland sharks. However, the otherwise healthy appearance of the infected sharks studied and the information contained in the literature suggests that O. elongata infections do not significantly debilitate the hosts.

Ocular Lesions Associated with Attachment of the Copepod Ommatokoita elongata (Lernaeopodidae: Siphonostomatoida) to Corneas of Pacific Sleeper Sharks Somniosus pacificus Captured off Alaska in Prince William Sound

“…The high prevalence and low intensity of infection observed for 0. elongata on the eyes of Pacific sleeper sharks is similar to observations reported concerning infections of this parasite on the eyes of Greenland sharks (see Berland, 1961;Borucinska et al, 1998). How the typical attachment pattern of 1 adult female per eye is achieved remains a mystery; however, results of this study as well as those of Borucinska et al (1998) indicate that it is not unusual for individual sleeper shark eyes to be concomitantly infected by 1 adult female and 1 to several larvae of O. elongata.…”

“…Benz et al (1998) reported the eyes of some Pacific sleeper sharks in the eastern Pacific to be infected with the parasitic copepod Ommatokoita elongata (Grant, 1827) (Lernaeopodidae: Siphonostomatoida) and noted gross eye lesions associated with infections. Borucinska et al (1998) examined lesions associated with O. elongata infections in Greenland sharks and concluded that these parasites can cause eye damage resulting in vision impairment including partial blindness. However, these same authors also concluded that 0. elongata infections do not significantly debilitate Greenland sharks and that this may be because this host species does not rely on keen vision.…”

George William Benz (1 January 1954–9 February 2015)

“…George's gateway interest to sleeper sharks was, naturally, in its parasitic copepods. The lernaeopodid Ommatokoita elongata embeds its bulla (attachment structure) in the cornea of the Greenland shark, and the resulting lesion causes corneal opacity or near blindness in chronic infections, with the prevalence of infection being typically high and each shark typically having a single female O. elgonata attached to each eye (Borucinska et al 1998, Borucinska and. George also was captivated by the fact that despite the shark being regarded as a sort of toothed manatee, slow moving, oafi sh, and visually-impaired if infected with O. elongata, it was known to harbor seal parts plus swiftswimming fi shes in its stomach.…”

Meet the Greenland shark, a seemingly sleepy Arctic predator

“…Will this cause impaired vision, and will the shark suffer from it? Several studies have investigated how O. elongata affects the corneas of Somniosus spp., and how vision could be affected (Benz et al 2002;Borucinska, Whiteley, and Benz 1998). Although these sharks may go partially blind, this does not affect their ability to survive.…”