Impairments of Endocrine Functions: Causes and Consequences - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 201

assessment. The second focuses on the study of the impact of compounds designed to
modulate the regulation of juvenile hormones found in insects (pesticides), in order to
evaluate their effect on nontarget species, because of the similarity of endocrine systems
within arthropods, and to improve knowledge on the endocrine regulation of crustaceans.
For known vertebrate endocrine disruptors, most studies have focused on the impact
assessment of these compounds on growth, reproduction, and molt in many species of
crustaceans, many of which have standardized or chronic bioassays available. In a context
of risk assessment, although these studies have been shown to be relevant by taking into
account the toxicity of these compounds to a large number of living species in aquatic
systems, they do not provide (1) the potential of these compounds as EDCs in crustaceans,
(2) knowledge on modulation of hormone regulation in relation to the effects observed,
and (3) the role played by steroid hormones in endocrine regulation in crustaceans. In
the copepod Eurytemora affinis, , Forget-Leray et al. (2005) showed the adverse effects on
the development and sex ratio of several vertebrate EDCs. Mortality and reduced fertil-
ity, reproduction, and growth may result from a disturbance of hormone regulation, but
these responses may also result from other mechanisms such as modulation of energy
allocation, disturbance of the nervous system, and/or transfer of genetic abnormalities
after exposure to genotoxic compounds. Indeed, several studies on marine crustaceans
( Tisbe battagliai , Nicotra spinipes , and Palaemon elegans ) have shown that compounds such as
17α-ethinyl estradiol, 17β-ethinyl estradiol, estrone, and 4-nonylphenol have few adverse
effects on survival, development, reproduction, and sex ratio (Lye et al. 2008). Similarly,
Hannas et al. (2011) clearly show that the measurement of VTG mRNA levels in Daphnia
magna can be used in biomonitoring exposure of daphnids to some environmental chemi-
cals but is not useful as an indicator of exposure to estrogenic chemicals.
To a lesser extent, a more specific exploration of endocrine disruption has been con-
ducted for the major insect and crustacean hormones (ecdysteroids and terpenoids) and
analog chemicals such as insect growth regulators (IGRs), which are pesticides specif-
ically developed to mimic, interfere with, and/or block the action pathway of ecdyste-
roids and juvenile hormone in insects. IGRs are by definition arthropod-specific EDCs.
Thus, pesticides designed as juvenile hormone mimics such as fenoxycarb, pyriproxyfen,
or methoprene, showed deleterious effects on the embryo-larval development and molt
cycle in decapods (e.g., McKenney et al. 2004; Tuberty and McKenney 2005) as well as in
mysidaceans (e.g., McKenney and Matthews 1990; Ghekiere et al. 2006a) and cladocerans
(Olmstead and LeBlanc 2001), for exposure concentrations much lower than lethal con-
centrations. These insecticides also caused alterations of reproductive functions such as
inhibition of oogenesis and vitellogenesis (e.g., Tokishita et al. 2006; Ghekiere et al. 2006b),
delays in sexual maturity, and/or decreased fertility (e.g., Olmstead and LeBlanc 2001;
McKenney 2005). More recently, several studies have shown that juvenile hormone and
analog chemicals induced male neonate production in parthenogenetic cladoceran species
(for a review, see Tatarazako and Oda 2007).
8.5.3 Tools for Monitoring Crustacean Exposure to EDCs
The in vitro measurement of the (ant)agonist potential of chemicals toward a specific hor-
monal receptor is a relevant approach for screening the endocrine-disrupting potential of
a compound and/or extracts of a natural matrix. Clément et al. (1993) proposed a rapid in
vitro bioassay for the detection of ecdysteroid agonistic and antagonistic activities based
on the ecdysteroid receptor-specific responses of a tumorous blood cell line of Drosophila
melanogaster . To our knowledge, this is the only in vitro bioassay available using a specific