Hall of Fame - Arthur Humes (1)

[Adapted from Huys, R. & G.A. Boxshall (2001). An appreciation of the contribution of Arthur Humes to copepod systematics. Journal of Crustacean Biology, 21(1): 13-27. Published with permission.]

Introduction

Arthur Humes had a long and distinguished career in biology. His first publication was in 1938 and his first paper on copepods was in 1941. Since then he has produced an incredible 252 publications on copepods. Arthur is best known to the members of the Crustacean Society as the founding editor of the Journal of Crustacean Biology but, in the copepod research community, he is recognized as being responsible for opening up one of the four main fields of copepod systematics: the taxonomy and biodiversity of copepods associated with, and parasitic on, marine invertebrates. Starting virtually from scratch, building a new field has required an immense volume of descriptive taxonomy. By providing this he has established the basic framework of knowledge on these groups - the knowledge base, which has, in recent years, provided phylogeneticists with an incredibly rich source of data.

Arthur Humes' success in opening up the field of invertebrate associates depended initially on his recognition that virtually any marine macro-invertebrate was a potential host to copepods. In 1993, in the Maxilliped lecture given when he was president of the World Association of Copepodologists, Humes calculated that associated copepods are known from only 1.14% of the 151,400 species of potential marine invertebrate hosts worldwide (Humes, 1994). On these calculations, the amount of descriptive taxonomy remaining to be done is enormous.

His Methods

During his career, Humes himself surveyed a huge range of invertebrate host taxa and developed an extraction technique, which was to prove suitable for coaxing the copepods out from many hosts. This method, as applied to the extraction of xarifiid copepods from hard corals (Humes and Dojiri, 1982) is repeated here: immediately on collection in the field each colony or fragment of coral is isolated in a plastic bag. In the laboratory the coral and sea water are placed in a bucket to which sufficient 95% ethanol is added to make an approximately 5% solution. The coral is left in this solution at ambient temperature for several hours or over night. Then the coral is thoroughly rinsed by shaking well and the wash water is poured through a fine net (120 holes per 2.5cm, each hole approximately 100 m square). The copepods are then picked from the sediment retained in the net. It appears that the dilute alcohol, together with the accumulating products of decomposition, stimulates the copepods to leave the polyps of the coral host, and they fall to the bottom of the container. In comparison, rapid washing of the freshly collected corals usually yielded very few xarifiids (Humes and Dojiri, 1982). This method can be applied equally to many other host groups, such as soft corals, echinoderms, sponges etc.

In addition to his extraction method, Humes also pioneered various improvements in methods for the microscopic study of copepods. A much cited methods paper is Humes and Gooding (1964) in which the hanging-drop slide method is described in detail. In this short paper Humes and his brilliant student, Richard Gooding, recommended the use of lactic acid as the best clearing agent for the preparation of temporary mounts for whole or dissected copepods. They also recommended that dissections be carried out in a drop of lactic acid on a 22mm coverslip cemented to a wooden slide with a bored central hole 15mm in diameter. The preparation is then ready for examination under the compound microscope by inverting the slide. One of the major advances of this method is that a single specimen can usually provide a full set of observations of all appendages. Humes and Gooding explicitly stated another major advantage of this technique in that it causes little or no compression of the copepods or their dissected parts - a problem that plagued the taxonomic studies of many copepod researchers before 1964 (and still does). They also noted that staining is usually undesirable in this kind of mount and that phase-contrast microscopy may be used. In all these respects Humes and Gooding pioneered the best modern practice, except that the development of differential interference contrast microscopy has essentially replaced phase contract microscopy.

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