Euphausiacea
Identification and taxonomy

The more obvious characters used in the indentification of adult euphausiids can be readily observed with the aid of a low power stereo-micrscope, and light (incident and transmitted) or dark field illumination. In separating some species (e.g. members of the Euphausia gibba group) it may be necessary to examine the arrangement of the various processes on the petasma of males, or the thelycum of females. Not only are such examinations difficult, time-consumming and frustrating to do successfully, but as these organs develop (in an often unknown manner) with age, their observation should be confined to mature specimens. More detailed methods for the examination of petasmae and thelyca can be found in Baker et al. (1990, and references therein), from which the following brief account is taken. The petasma of preserved material is usually rolled up and necessitates spreading before observation. If material is abundant, or specimens are small, we recommend the petasma be detached, mounted on a slide and gently spread out, before examination at high magnification under a compound microscope. In order to view the surface morphology of the thelycum it is first necessary to remove obscuring limbs, gills and spermatophores prior to either staining with methylene blue or gentian violet, or coating with silver particles in a photographic process developed by James (1977).

—Adults
See Eu. 11 Adults and Eu. 12 Euphausiid morphology for morphological characters important in the identifiction of adult euphausiids. Keys to (adult) genera and to species start at Page 17: Euphausiacea.

—Larval stages
See pages Eu. 15 Morphology of larval development, Eu. 16 Identification of larvae and Eu. 17 Characters used in identification of larvae for morphological characters importand for the identification of larval stages of euphausiids. There is no key available.