Copepods are very ancient arthropods. They poorly fossilize, and thus it is
rare to find such
traces of their remains in sediments which could have facilitated the study of their morphological,
physiological, and ecological evolution (Frey, 1964; Walossek & Müller, 1997).
Only some recent remains have been identified, mainly spermatophores (Frey, 1964;
Warner, 1990) and also, diaptomid egg-sacs found from Denmark and West Greenland
in Late Quaternary lake sediments (12 000 to 10 000 and 5 000 to 500 14 C years BP
respectively) (Bennike, 1998).
Zoogeographical data suggest that the copepod fauna of continental waters was already
rich and diversified in the Tertiary (Palmer, 1960, 1969; Cressey & Patterson, 1973), such that
different species have had ample time to adapt to the conditions of their environment.
While numerous species are freeliving, utilizing various preys, others are stenophagous,
and some have become parasites or semiparasites at different stages of their development.
Copepods are associated with the aquatic environment, although some can permanently
tolerate low humidity. In oceans and lakes, they proliferate in pelagic waters as well as on,
and even within the sediments (psammic fauna of coarse sand). In freshwaters too, they
are present in many different biotopes, as well as in the humid litter of deciduous forests,
in decaying leaf-mould of hollow trees, inside ant nests, etc.
This book is primarily a practical guide, intended to provide the reader with a general
idea of what a freshwater copepod is. It will also serve as a basis for further study, and
as an introduction to the literature. The bibliography is not exhaustive, but has been
constructed to pave the way for further research. A natural approach is adopted, in which
copepods are viewed as active players in the complex network of interactions within
communities of organisms.
The complexity of copepods is not limited to their morphology. They provide ideal
subjects for the study of numerous problems in general biology and cytogenetics as well as
physiological processes associated with their feeding behaviour, reproduction, and ecology.
All these subjects will be briefly touched upon.
Although highly diversified at the species level, the copepods of inland waters,
they are free-living or parasites, present a unity in their anatomical organization.
Jurine, in 1820, was considering the free-living copepods that he studied in the area
of Geneva as belonging to the genus Monoculus. Later, this genus has been divided.
Thus, the Monoculus castor of Jurine, now named Diaptomus castor, corresponds to the
Order Calanoida; Monoculus quadricornis to the Cyclopoida, and Monoculus staphylinus
to the Harpacticoida (Fig. B1). In freshwaters, some copepods are parasitic of fish.
In temperate regions, they are distributed now in three families corresponding to three
orders: Lernaeidae (Cyclopoida) exclusive of freshwaters, Ergasilidae (Poecilostomatoida)
and Lernaeopodidae (Siphonostomatoida).
Whether free-living or parasitic, copepods have adapted themselves to both aquatic and
simply humid ecosystems, irrespective of altitude, area or continent. Their distribution is
still imperfectly known in many cases. In spite of the constant increase of knowledge of
this group, and the continuous discovery of new species, genera and even families, their
relationships are still under discussion.
In inland waters, copepods are relatively well known, at least at the family level,
but numerous species remain to be discovered, particularly in deep interstitial waters,
and in tropical regions.
If a systematist determines the species of an animal, he looks at some features in
morphology, the color, pattern, etc., and last, but not least, at the place and time of
the catch. Observed differences in morphology between species could be functional,
thus involved in the separation of niches, or could be a side product through multiple
alleles (Strickler, 1975a).
It is undeniable that copepods play an important role in ecosystems, by virtue of their
place in food webs as well as by their potential to be used by man in different ways.
At the end of the last century, they were already used as a source of food by shipwrecked
persons, who needed to feed themselves in situ (Albert de Monaco, 1888). Richard (1900)
also underlined their edibility, as tested by Herdman (1897).
C The copepods of inland waters Methodology
a - Generalities
b - Sampling techniques, culture and preservation
c - Observation techniques
d - Biochemical methods
a - The body
b - The appendages
c - Other structures
d - Morphological anomalies
a - Integument
b - Muscular system
c - Digestive system
d - Nervous system
e - Sensory organs
f - Vascular system
g - Respiratory system
h - Excretory system
i - Reproductive system
a - Development
aa - Embryonic development
ab - Postembryonic development
b - Growth rate
c - Feeding
d - Diapause and dormancy
e - Behaviour
f - Locomotion
g - Grooming
a - Sex ratio
b - Sexual behaviour
c - Parthenogenesis
d - Chromosomes and genome size
a - Response to abiotic environmental factors
aa - Geomorphology and climatic factors
ab - Light
ac - Temperature
ad - pH effect
ae - Salinity
af - Sensitivity to chemicals
afa - Sensitivity to organic products
afb - Sensitivity to pesticides
afc - Sensitivity to heavy metals
afd - Sensitivity to chlorinated compounds
ag - Migrations
b - Response to biotic environmental factors
ba - Prey-predator relationships
baa - Copepods as prey
bab - Copepods as predators
bb - Fecal pellets
c - Biological indicators
d - Parasites and pathology in copepods
e - Use of copepods in biological control
f - Copepods and drinking water
g - Other uses of copepods
h - Endangered copepods
I Dispersal factors
K Keys to orders, families and genera
a - Natural classification: orders and families
b - Practical classification
c - Practical methods for identification
d - Other methods
e - Keys to genera 103
L Brief diagnoses of genera
a - Calaniformes
b - Cyclopiformes
c - Gelyelliformes
B.H. Dussart and D. Defaye
(2nd revised and enlarged edition)
2001, 352pp., 155 figs., 4 tables, paper (GIM 16)