IS THE GLUCOSE CONCENTRATION IN THE HAEMOLYMPH
A SUITABLE INDICATOR OF CIRCADIAN RHYTHMICITY IN
NEPHROPS NORVEGICUS (DECAPODA, NEPHROPIDAE)?
BY
J. AGUZZI
1
), J. B. COMPANY, F. SARDÁ, J. SÁNCHEZ-PARDO,J. A. GARCÍA
and G. ROTLLANT
Institut de Ciènces del Mar (ICM-CSIC), Passeig Marítim de la Barceloneta 37-49,
E-08003 Barcelona, Spain
ABSTRACT
The haemolymph glucose concentration shows marked fluctuations over a 24-hour cycle in
several decapods. In the present study, the influence of the diel light cycle as a modulator of
glucose concentration was evaluated in the haemolymph of Nephrops norvegicus in the northwestern
Mediterranean. Haemolymph samples were collected from animals caught by bottom trawls at two
depths, 100 m and 400 m, during two different seasons, October and June. A time series analysis
showed the absence of a rhythmic pattern in the glucose concentration at either depth and in
either season. Knowing that fishing stress increases haemolymph glucose concentration, laboratory
experiments were also planned under controlled conditions, under different photoperiod regimes
(day-night: 12-12, 18-6, 6-18). Again, no rhythmic fluctuations in glucose concentration were
detected. Field glucose concentrations were higher than those determined in laboratory experiments
(t -test, p 0.05), indicating a reference value of the stress for animals caught by trawling nets.
Therefore, the absence of rhythmicity in both field survey and laboratory experiments suggests that
this physiological variable is not a suitable indicator of the circadian rhythmicity in animals dwelling
at a depth greater than 100 m. We propose that rhythms in locomotor and emergence behaviour and
their influence on the underlying physiology may explain the glucose arrhythmicity in this species.
RESUMEN
La concentración de glucosa en hemolinfa muestra marcadas fluctuaciones diarias en varios
decápodos. En este estudio se evalúa la influencia del ciclo luminoso diario sobre la concentración
de glucosa en la hemolinfa de Nephrops norvegicus del Mediterráneo oeste. La hemolinfa fue
extraída de ejemplares capturados por artes de arrastre en profundidades de 100 y 400 m, durante
Octubre y Junio. El análisis de la serie temporal de datos no mostró ningún patrón rítmico en la
concentración de glucosa, ni por profundidad ni por época del año. Asumiendo que el efecto de estrés
de pesca incrementa la concentración de glucosa, se realizaron también extracciones en condiciones
1
) Present address: Neuroscience Institute, Morehouse School of Medicine, 720 Westview Drive
S.W., Atlanta, GA 30310-1495, U.S.A. Fax: +34.932217340; e-mail: jaguzzi@icm.csic.es
© Koninklijke Brill NV, Leiden, 2004 Crustaceana 77 (2): 213-229
Also available online: www.brill.nl