Chronobiology: Implications for Marine Resource Exploitation and Management
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sm69s1157nay1 30/5/05 20:08 Página 157 SCI. MAR., 69 (Suppl. 1): 157-167 SCIENTIA MARINA 2005 PROMOTING MARINE SCIENCE: CONTRIBUTIONS TO CELEBRATE THE 50TH ANNIVERSARY OF SCIENTIA MARINA. C. MARRASÉ and P. ABELLÓ (eds.) Chronobiology: implications for marine resource exploitation and management ERNEST NAYLOR School of Ocean Sciences, University of Wales-Bangor, Marine Science Laboratories, Menai Bridge, Anglesey LL59 5AB, UK. E-mail: [email protected] SUMMARY: Chronobiology began as a curiosity-driven science and now impacts significantly on the science of medicine through medical rhythm research and chronotherapeutics. However, whilst it has long been evident that rational exploita- tion and management of living organisms and their environments require detailed biological understanding, incorporation of the time-base of living systems into such activities has been slow. Evidence suggests that marine management and con- servation strategies, whether directed towards the environment or fisheries, are only slowly taking account of the time-scales of endogenously controlled rhythmic animal behaviour as a basis from which to achieve their objectives. Similarly, in com- mercial aquaculture practices, there is a need for greater evaluation of the role of photoperiod manipulation and optimiza- tion of feeding regimes against the background of the endogenous rhythmicity of the organisms concerned. Correct syn- chronization of an organism’s endogenous biological oscillators, of tidal and/or daily to annual periodicities, is fundamen- tal to its optimal physiological performance and survival. Keywords: chronobiology, marine exploitation, management, rhythms, rhythmic behaviour. RESUMEN: CRONOBIOLOGÍA: IMPLICACIONES PARA LA EXPLOTACIÓN Y GESTIÓN DE RECURSOS MARINOS. – La cronobiología se inició como una ciencia dirigida por la curiosidad y hoy día impacta significativamente en la ciencia de la medicina a tra- vés de investigación médica sobre ritmos y cronoterapéutica. No obstante, mientras que ha sido evidente por mucho tiem- po que la explotación y gestión racional de los organismos vivos y de su ambiente requiere una detallada comprensión bio- lógica, la incorporación de la base temporal de los sistemas vivos en tales actividades ha sido lenta. La evidencia sugiere que las estrategias de gestión y conservación marinas, ya sea dirigidas hacia el ambiente o a las pesquerías, están tomando en cuenta únicamente de una manera lenta las escalas temporales del comportamiento animal rítmico controlado endógena- mente como una de las bases con las que conseguir sus objetivos. De manera similar, en prácticas de acuicultura comercial, existe una gran necesidad para una mayor evaluación del papel de la manipulación del fotoperíodo y de la optimización de los regímenes de alimentación respecto a la ritmicidad endógena de los organismos. Una correcta sincronización de los osci- ladores biológicos endógenos de un organismo, con periodicidades mareal y/o diaria a anual, es fundamental para el fun- cionamiento fisiológico óptimo así como para la supervivencia. Palabras clave: cronobiología, explotación marina, gestión, ritmos, comportamiento rítmico. INTRODUCTION more. In the early eighteenth century, for example, the French astronomer de Mairan observed that the Chronobiology, the study of biological rhythmic- daily leaf movements of Mimosa continued in plants ity in living organisms, began as a curiosity-driven placed in continuous darkness in a cellar (Daan, science. Daily patterns of behaviour in animals and 1982). Yet a reluctance to accept control of such plants, in some cases persisting in constant condi- behaviour by internal biological clocks persisted tions, have been recognized for two centuries or until the second half of the twentieth century. Semon CHRONOBIOLOGY 157 sm69s1157nay1 30/5/05 20:08 Página 158 (1905) defended the idea that animals and plants that adaptation to lunar variables. Early reluctance to expressed daily rhythms of behaviour in constant accept the possibility of direct control of animal conditions did so by learning during their lifetime to behaviour by moonlight (Korringa, 1957) was respond rhythmically to cyclical changes in their understandable. However, experimental approach- environment. Subsequently, as late as the latter half es in recent decades have demonstrated lunar of the twentieth century, Brown and others (see influences on animal behaviour both indirectly Brown, 1960, 1972) continued to reject the notion through the influence of ocean tides and directly of internal biological clocks, insisting that biolog- through moonlight itself (Naylor, 2001). ical rhythms in constant conditions were driven by There are differences in the characteristics of residual variables that pervaded the environment circadian and circatidal rhythms as expressed by and which were not controlled in so-called con- animals in constant conditions in the laboratory. stant conditions in the laboratory. Such interpreta- Circadian rhythms, which free-run at approxi- tions persisted despite crucial observations such as mately 24 h periodicity, often do so for many days those of Kleinhoonte (1928, see Daan, 1982) con- or weeks in the laboratory, with little change in the cerning the behaviour of another plant, Canavalia. characteristics of the peaks of the rhythm. In con- The periodicities of the “daily” rhythms of leaf trast, circatidal rhythms of behaviour in marine movement of this plant in constant light were animals usually free-run for only a few days in the shown to deviate from 24 h at circadian, that is, laboratory and, in many cases, “activity” peaks approximately daily periods quite different from relatively quickly become diffuse. The differences any known residual geophysical variable that may be due to the predictability of 24 h light/dark might drive such rhythms in otherwise “constant changes in the environment compared with the rel- conditions” in the laboratory. This prescient find- ative variability of tidal time-cues. Tide times and ing and numerous later examples in plants and ani- amplitudes vary considerably over short geo- mals now confirm that many biological rhythms graphical distances and in response to local weath- are endogenous, free-running at periods approxi- er conditions. Matching this contrast between cir- mating to environmental cycles when deprived of cadian and circatidal rhythms are the relative exposure to such cycles in the laboratory. states of knowledge concerning the nature of the Today the concept of the circadian body clock biological clockwork controlling such rhythms. is well accepted, based on a wealth of curiosity- Hormonal and neural physiological mechanisms driven science, and it now forms the basis of sev- driven by clock-genes are well understood to con- eral aspects of human medicine. Apart from its trol circadian rhythms (Helfrich-Foster, 1995 ). In implications for the understanding of sleep and contrast, whilst hormonal and neural mechanisms wakefulness, circadian patterns are apparent in have been shown to be involved in some circatidal various physiological processes and in human sus- rhythmic processes (Naylor, 1988; Aréchiga and ceptibility to medicinal drugs. Scientific journals Rodríguez-Sosa, 1997), little is known about the and conferences commonly combine papers on genetic basis of such rhythms (Palmer, 1995a). chronobiology with others, for example, on med- Indeed there is even debate as to whether or not ical rhythm research and chronotherapeutics. true circatidal rhythmicity exists at the physiolog- When jet-lagged chronobiologists meet at interna- ical level in coastal animals. Conflicting hypothe- tional conferences, discussion of the merits and ses that postulate control by truly circatidal clock- demerits of ingesting melatonin, a mediator of the work (Naylor, 1996, 1997) or by paired circaluni- circadian clock system, becomes of more than aca- dian clocks coupled in antiphase (Palmer, 1995b, demic significance. At such conferences one also 1997) remain to be resolved. Nevertheless there is meets the occasional chronobiologist interested considerable evidence that coastal marine animals not only in circadian rhythms but also in circatidal do exhibit endogenously controlled rhythms of rhythms. Such biologists are rare because the physiology and behaviour that match the rhythms study of biological rhythms in marine animals and of ocean tides (Palmer, 1995a; Naylor, 2002) and plants subjected to ocean tides is a Cinderella-sub- even lunar phase (Naylor, 2001). These aspects of ject compared with the study of biorhythms in ter- chronobiology have considerable implication for a restrial animals and man (Palmer, 1995a). The range of applied marine sciences from fisheries process of adaptation to solar variables in the envi- and aquaculture to conservation and management ronment has been more readily accepted than of coastal environments. 158 E. NAYLOR sm69s1157nay1 30/5/05 20:08 Página 159 BIORHYTHMS AND COASTAL ZONE phasing of surface foraging activity between adult MANAGEMENT and juvenile members of the same species of sand hopper (see Naylor and Kennedy, 2003). Indeed, in In a major evaluation of the world’s seas at the a study of the sand hopper Orchestoidea tubercula- turn of the millennium (Sheppard, 2000) environ- ta on a tourist beach at Mehuin, Chile (39° 25’ S, mental quality and resource exploitation issues were 73° 13’ W), Kennedy et al. (2000) found that during discussed in the context of coastal resource manage- daytime low tides adults typically