Conceptual and terminological consistency is an important component of science, promoting clarity and preventing confusion. Scientists should therefore always try to avoid giving different meanings to the same term. Apart from this general aspect, multiple definitions of a single term also give rise to practical problems, particularly in connection with literature search. In this note, I will bring attention to a term, cryptobiosis, that has relatively recently appeared in the field of fish disease research, but which has a much longer history and use in a completely different area.

The concept of cryptobiosis was introduced by Keilin (1959) and defined as ‘the state of an organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill’ (Keilin 1959, p. 166). Cryptobiosis replaced the earlier term anabiosis, and is today generally accepted as the common term for different ametabolic life forms (e.g. Clegg 2001; Wright 2001). Cryptobiosis means ‘hidden life’, an appropriate name for a state in which all traditional attributes of life (metabolism, reproduction, DNA replication) are absent. Cryptobiotic life forms have been documented in a variety of organisms, including both plants and animals, but in the latter category mainly among invertebrates (Wright, Westh & Ramløv 1992). Cryptobiosis is commonly induced by desiccation (so-called anhydrobiosis; e.g. Keilin 1959; Jönsson 2001), and aquatic invertebrates such as rotifers, nematodes and tardigrades living in microhabitats exposed to rapid desiccation frequently enter a cryptobiotic state. The research field dealing with cryptobiotic, sensu ametabolic, life forms has expanded considerably during the last 30 years, to a large extent fuelled by the detection of the ability of the disaccharide trehalose to protect dry and frozen biological cells (Crowe 2002).

More recently, a completely different use of the term cryptobiosis has appeared in the literature on fish disease. In this literature, the term refers to infections of fish by biflagellated protozoa of the genus Cryptobia. Because of the economic importance of salmonid fish, much of the Cryptobia research has focused on Cryptobia salmositica (Katz) that infects salmonids (Woo 2001). The origin of the term cryptobiosis within fish pathology and studies of Cryptobia is unclear, but the earliest record of the term that I have found is Obradovic & Fijan (1979) who used it in a paper on chemotherapeutic treatment against Cryptobia in carp. From 1987 onwards, Woo et al. have used the term frequently (e.g. Woo, Leatherland & Lee 1987; Woo 1987, 1998, 2001), but apparently without any comments on the original proposal of the term. Curiously, few other researchers on Cryptobia seem to have adopted the cryptobiosis terminology, at least as judged from an examination of published titles. Other authors have instead used the expression ‘infections by Cryptobia’. Although using cryptobiosis as a term for infections by Cryptobia is consistent with the rule of creating names for infectious diseases by putting -osis as a post-fix to the name of the infecting organism, in the current case it creates terminological confusion.

The problems of using the term cryptobiosis in several unrelated fields are obvious. A title such as ‘The biology of cryptobiosis’ would attract the attention of many students interested in ametabolic life forms. They would be disappointed, however, if the paper turned out to be about Cryptobia infection biology. Similarly, fish biologists would find the publication irrelevant to their research if it were properly confined to ametabolic life forms.

Because ‘cryptobiosis’ as a term for ametabolic life forms is well established and has been used for more than 40 years, it should have priority over the more recent and limited use within fish pathology. I therefore hope that fish pathologists will avoid using the term cryptobiosis and instead use ‘infections by Cryptobia’, ‘cryptobiasis’ or some other term that does not interfere with already established terminology.