Involvement of thyroid hormones in the control of larval metamorphosis
in Sicyopterus lagocephalus (Teleostei: Gobioidei) at the time of river recruitment
L. Taillebois
a,
⇑
, P. Keith
a
, P. Valade
b
, P. Torres
a
, S. Baloche
a
, S. Dufour
a
, K. Rousseau
a,
⇑
a
Muséum National d’Histoire Naturelle, DPMA, UMR BOREA CNRS 7208, IRD 207, UPMC, 57 rue Cuvier, 75231 Paris Cedex 05, France
b
ARDA, Route forestière de l’étang du Gol, 97427 Etang Salé, La Réunion, France
article info
Article history:
Received 30 September 2010
Revised 1 June 2011
Accepted 4 June 2011
Available online 14 June 2011
Keywords:
Metamorphosis
Thyroid hormone
Teleost
Goby
Reunion Island
abstract
After oceanic migration, post-larvae of the amphidromous Sicyopterus lagocephalus recruit to rivers in
Reunion Island. As they enter the river mouth, post-larvae undergo many morphological, physiological
and behavioural changes. These drastic changes, which allow them to change feeding regime and to
colonise the juvenile and adult freshwater habitat, are defined as metamorphosis. The endocrine control
of these changes has never been investigated in Gobioid fish. Here, we investigated whether thyroid hor-
mones (TH) influence metamorphosis in recruiting S. lagocephalus. An analytical study was first per-
formed on a cohort of 2400 fish caught at post-larval stage 1 and maintained for 37 days after capture
in a flume tank (fluvarium), which replicates as closely as possible the natural conditions. Biometrical
parameters (total and standard lengths, corner of mouth angle, body mass and condition factor) and
whole-body thyroxine (T
4
) and triiodothyronine (T
3
) contents were measured on fish, sampled at regular
intervals during these 37 days (192 fish). TH levels, measured by radioimmunoassays, were highest when
morphological changes, such as the change in the position of the mouth, were most important. An exper-
imental approach was then used to test the effect of the hormonal treatment (T
4
or thiourea, TU, a TH
inhibitor) on biometrical parameters of 576 post-larvae. The change in the position of the mouth was sig-
nificantly accelerated in the T
4
-treated post-larvae, while it was significantly delayed in the TU-treated
post-larvae, compared to controls. Our study suggests that S. lagocephalus post-larva undergoes a true
metamorphic event under the control of thyroid hormones at the time of its recruitment into the river.
Ó 2011 Elsevier Inc. All rights reserved.
1. Introduction
In the Indo-Pacific areas, river systems are colonised by freshwa-
ter gobies (Teleostei: Gobioidei) with a life cycle adapted to the
conditions in these distinctive habitats, which are, particularly in is-
lands, young oligotrophic rivers subject to extreme climatic and
hydrological seasonal variation. These species spawn in freshwater,
the free embryos drift downstream to the sea where the larvae un-
dergo a planktonic phase, before returning to rivers to grow and
reproduce [13], hence they are called amphidromous. Amphidromy
is a strategy involving migration of post-larvae from the sea to fresh
water, which is the main feeding, growing and reproductive biome
[22]. Sicyopterus lagocephalus (Pallas, 1770) is one of the most com-
mon amphidromous species inhabiting island freshwaters from the
Indian Ocean to the Pacific. Its larvae hatch in freshwater and are
rapidly carried by river currents to the sea where they begin a
planktonic life phase [40]. After 130–300 days spent in the ocean
for their larval growth [19], they return to the river mouth as post-
larvae; this is the recruitment phase. Soon after entering fresh water,
they undergo several morphological changes in body, mouth posi-
tion, fin shape and colour, related to the planktonic to benthic envi-
ronment switch and the feeding mode modification [16,40].
According to Keith et al. [16], they undergo a metamorphosis. Then,
juveniles migrate upstream using their sucker, resulting from the fu-
sion of the pelvic fins, in order to colonise the juvenile and adult hab-
itat [15,19].
Metamorphosis in teleosts occurs when species experience an
abrupt transition from larval form to juvenile form, consisting of
morphological, physiological and behavioural modifications asso-
ciated with the colonisation of a new habitat (for review, see
[44]). In pleuronectiforms such as flounders or halibuts, a symmet-
rical pelagic larva metamorphosises into an asymmetrical benthic
juvenile, with among other changes, a spectacular eye migration
[29,33]. In elopomorphs such as congers, tarpons or eels, oceanic
leptocephalus larvae migrate from the ocean and metamorphose
into glass eels off the continental shelf [31]. During this
0016-6480/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.ygcen.2011.06.008
⇑
Corresponding authors.
E-mail addresses: taillebois@mnhn.fr (L. Taillebois), rousse@mnhn.fr
(K. Rousseau).
General and Comparative Endocrinology 173 (2011) 281–288
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