How much do we know about the parasites of great white sharks (Carcharodon carcharias) and why they matter?

There is growing recognition that excluding parasites from ecological and behavioural studies is a significant oversight, given their crucial roles in host health, energy allocation, and ecosystem function. Yet, the parasitic fauna of the great white shark (Carcharodon carcharias), a globally distributed apex predator, remains poorly understood. This review consolidates current knowledge of parasites infecting the great white shark and explores their potential ecological and physiological impacts. A synthesis of published literature and selected museum records revealed 116 parasite records, predominantly cestodes and copepods, with almost all studies being taxonomic in focus. Cestodes, known for their high reproductive output and metabolic demands, may influence growth, reproduction, and energy allocation, in their host, including great white sharks. Additionally, given that great white sharks acquire cestodes via prey infected with larval or infectious stages, parasite-induced changes in prey behaviour or vulnerability could bias dietary studies, an aspect largely overlooked in great white shark trophic ecology. Copepods, another frequently reported group, are known to cause tissue damage, respiratory inefficiency, and erratic swimming in fish, often requiring veterinary intervention in aquaculture. In sharks, behaviours such as breaching and tail-slapping have been speculatively linked to parasite removal, yet these assumptions overlook copepod biology and attachment mechanisms. Unsubstantiated interpretations risk perpetuating misconceptions and may hinder integration of parasitology into shark conservation strategies. This review also highlights critical knowledge gaps. For instance, several prey species consumed by great white sharks are known intermediate hosts of Toxoplasma gondii, a parasite capable of altering host behaviour and transmitting between intermediate hosts. Although unprovoked aggression has occasionally been reported in sharks, there are currently no data on the presence or potential effects of T. gondii in these apex predators as a potential intermediate/paratenic host. Clarifying such potential associations, alongside neglected areas such as embryonic infections (e.g., trebiid copepods), remains an important direction for future research. By identifying these critical knowledge gaps, we advocate for the integration of parasitological research into ecological and conservation frameworks to better understand apex predator health and ensure marine biodiversity protection.