Diapause, Neurosecretion and Hormones in Copepoda

Carlisle, D. B.; Pitman, W J

doi:10.1038/190827b0

Cited by 42 publications

(23 citation statements)

References 2 publications

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“…Further exploration of cope-pod hormones in nature will be necessary to identify hormones that directly control diapause, perhaps by suppressing ecdysteroid secretion or by stimulating a hormone analogous to the molt-inhibiting hormone (MIH) in decapods. Neurosecretory cells in the head region, which have been observed to change during diapause in 2 copepod genera, may be implicated in diapause control (Carlisle & Pitman 1961, Watson & Smallman 1971. Insights and immunohistochemical tools from crustacean and insect endocrinology may greatly accelerate progress in understanding copepod endocrinology and in applying such understanding to ecological questions.…”

Section: Discussionmentioning

confidence: 99%

Ecdysteroids in the oceanic copepod Calanus pacificus: variation during molt cycle and change associated with diapause

Johnson¹

2003

Mar. Ecol. Prog. Ser.

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Development through the molt cycle in arthropods is characterized both by changes in exoskeleton morphology and by cyclical changes in ecdysteroids, i.e. molting hormones. This study describes for Calanus pacificus ecdysteroid variation during the molt cycle in the fifth copepodid (CV) stage and compares ecdysteroid content of diapausing and active field-collected CVs. In C. pacificus CVs, the pattern of ecdysteroid variation relative to the molt cycle phase is similar to that found in decapod crustacean larvae. Ecdysteroid levels are lowest in the postmolt, the first phase after molting, and then increase to a peak during early premolt. Ecdysteroid levels measured in fieldcollected diapausing C. pacificus CVs were lower than those in active CVs, as expected based on the predominance of the postmolt phase among diapausing CVs. Ecdysteroid analysis provides a faster, less labor-intensive alternative to jaw-phase analysis for identifying the molt phase of field-collected copepodids, and can provide valuable insights into their life-history status. Measurement of copepod hormonal status in situ may provide a direct means of determining the proximate cues for diapause induction and termination in oceanic copepods.

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Section: Discussionmentioning

confidence: 99%

Ecdysteroids in the oceanic copepod Calanus pacificus: variation during molt cycle and change associated with diapause

Johnson¹

2003

Mar. Ecol. Prog. Ser.

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“…Diapause was defined by Andrewartha (1952:99) as "as a stage in the development of certain animals during which morphological growth and development is suspended or greatly retarded. " The term has been applied to freshwater cyclopoid copepods that remain inactive, with or without encystment, in the sediment over winter or during other unsuitable periods (Elgmork, 1955) and to marine calanoids by Carlisle and Pitman (1961), who obtained some evidence for hormonal control of metabolism in Culunus finmarchicus and Euchuetu norvegicu. Evidence for some form of seasonally induced "resting" stage has been obtained for the arctic species Culunus hyperboreus (Conover and Corner, 1968;Head and Conover, 1983;Head and Harris, 1985) and C. glacialis (Arashkevich and Kosobokova, 1988), such as seeking deep water, regulating buoyancy, reducing activity and metabolism, changing the metabolic substrate oxidized during respiration, and lowering levels of digestive enzymes and gut peristalsis.…”

Section: Discussionmentioning

confidence: 99%

Dark-Season Survival Strategies of Coastal Zone Zooplankton in the Canadian Arctic

Conover¹,

Siferd²

1993

ARCTIC

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ABSTRACT. For herbivorous zooplankton, surviving the arctic winter requires that sufficient energy be stored in summer to enable ten months or more of possible starvation. Energy and materials for reproduction may also be totally derived from stored lipid and bodily protein. The predominant storage products are wax esters, often visible as translucent droplets or a fusiform inclusion in the tissues. Lipid may constitute more than 50% of dry weight at the end of summer. Reproduction is synchronized with season and environmental conditions to enable offspring to exploit the brief period of intense primary production. So far as we know, fertilization occurs only once in the copepods studied here, which make up more than 98% of the total zooplankton by numbers, and males are short lived, but in one species (Calanus hyperboreus) females may survive into a second productive season, thereby storing sufficient reserves to spawn a second time. Several planktonic species, including larval invertebrates, start growth early by utilizing algae that develop on the under-ice surface several months before the pelagic phytoplankton bloom. The minimum water temperature (-13°C) is constant and much warmer than the atmosphere, so overwintering should be less stressful for aquatic species than for terrestrial forms. Additional adaptations used by zooplankton in winter include seeking deeper water to escape predation, reducing swimming costs by regulating buoyancy, and further lowering metabolic rates by limiting synthesis of enzymes and increasing the fraction of lipid used in respiration. Key words: copepods, zooplankton, phytoplankton, ice-algae, fast ice, lipid, overwintering, survival strategies, growth, reproduction &SUMfi. Afin de survivre it l'hiver arctique, le zooplancton herbivore doit stocker suffisamment d'knergie en kt6 pour faire face it 10 mois ou plus de famine potentielle. Il se peut aussi que l'knergie et les mat6riaux servant it la reproduction soient tirks en totalit6 des lipides emmagasinks et des protkines du tissu corporel. Les produits stockks les plus importants sont les esters cireux, souvent visibles sous la forme de gouttelettes translucides ou d'une inclusion fusiforme dans les tissus. Les lipides peuvent constituer plus de 50 p. cent du poids sec ii la fin de l'ktk. La reproduction est synchroni& avec les saisons et les conditions environnementales de façon B pennettre it la progkniture de profiter de la courte pkriode de production primaire intense. Dans l'ktat de nos connaissances actuelles, la fertilisation a lieu une seule fois chez les copkpodes qui nous intkressent, et qui constituent plus de 98 p. cent du zooplancton total sur le plan numerique. Les &les ont une dur& de vie relativement courte, mais dans l'esp&ce Calanus hyperboreus, les femelles peuvent vivre assez longtemps pour entrer dans une deuxihme phase de reproduction, stockant ainsi suffisamment de &serves pour frayer une seconde fois. Plusieurs e s p h s planctoniques, y compris des invertkbrks larvaires, commencent it croître de bonne...

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“…It is likely that overwintering metabolism and moulting are under hormonal control, since Carlisle and Pitman (1961) have reported seasonal differences in the neurosecretory cells of Calanus finmarchicus. Endocrine processes could act as the 'biological clock', that controls termination of the overwintering stage, as has been suggested by Banse (1964), Conover (1965) and Gardner (1972).…”

Section: Laboratory Experimentsmentioning

confidence: 99%

Overwintering of Calanus finmarchicus and Calanus helgolandicus

Hirche¹

1983

Mar. Ecol. Prog. Ser.

189

122

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Overwintering of Calanus finmarchicus and C. helgolandicus was studied in the field and in laboratory experiments in a shallow (120 m) Swedish fjord and in a deep (650 m) Norwegian fjord. In the Norwegian fjord 2 populations were found in late summer and autumn: in the surface layer the copepods were smaller and more active with high respiratory and digestive enzyme activities. The deep population, consisting of Copepodid stage V (CV) and a few females, was torpid, had large oil sacs and empty guts. Their respiratory and digestive enzyme activities were very low. In the Swedish fjord CV in deep layers weighed much less than those in the Norwegian fjord. Weight-specific respiration was intermediate between deep and surface population in the Norwegian fjord. It is concluded that overwintering copepodids do not feed. Metabolic rates allowed successful overwintering only in the Norwegian fjord. Experiments performed on several occasions during overwintering witnessed -in contrast to the situation in field populations -increased rates of respiration and moulting. Mortality during moulting and time span between capture and onset of moulting decreased during autumn and winter. These observations suggest internal development during overwintering.

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Diapause, Neurosecretion and Hormones in Copepoda

Cited by 42 publications

References 2 publications

Ecdysteroids in the oceanic copepod Calanus pacificus: variation during molt cycle and change associated with diapause

Ecdysteroids in the oceanic copepod Calanus pacificus: variation during molt cycle and change associated with diapause

Dark-Season Survival Strategies of Coastal Zone Zooplankton in the Canadian Arctic

Overwintering of Calanus finmarchicus and Calanus helgolandicus

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