Ultrastructure of the integument of a pelagic Crustacean: moult cycle related studies on the Antarctic krill, Euphausia superba

Buchholz, Cornelia; Búchholz, Friedrich

doi:10.1007/bf00428132

Cited by 47 publications

(33 citation statements)

References 27 publications

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“…Intermoult individuals beat their pleopods at a slower rate and with larger amplitudes than moulting, post-moult or pre-moult individuals. The thickness and rigidity of the exoskeleton changes throughout the moult cycle and reaches its peak during the intermoult period (Buchholz & Buchholz 1989). As an individual enters premoult, the cuticle will gradually become resorbed and the new cuticle developed underneath.…”

Section: Effect Of Moultingmentioning

confidence: 99%

Influence of individual state on swimming capacity and behaviour of Antarctic krill Euphausia superba

Johnson¹,

Tarling²

2008

Mar. Ecol. Prog. Ser.

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Swarms of Antarctic krill are frequently biased towards certain body sizes, sexes, maturities and physiological states. However, the mechanisms causing such biases remain unclear, with some speculating on differential responses to chemical or visual cues. This study examines the influence of individual state on swimming behaviour and performance, which, in turn, may cause biases in swarm composition. The frequency and strength of pleopod beats as well as the overall swimming capacity of Antarctic krill Euphausia superba were measured using a tethering technique. Individual state was considered in terms of body size, sex, maturity, moult stage and stomach fullness. Significant differences in the rate and strength of pleopod strokes as well as in the overall swimming capacity were found between individuals in different states. Body size had one of the strongest influences, with beat rate decreasing and beat strength increasing with increasing size. The sex and maturity of an individual altered this pattern, with adult females having faster but weaker pleopod beats than males of equivalent size. The difference in swimming style of females may impose a different lifestyle to that of males. Moult stage also had a significant influence on swimming, with moulting/post-moult individuals having significantly lower swimming capacities, making them unlikely to keep pace with intermoult counterparts. Both the rate and the strength of the pleopod beat were significantly lower in satiated compared to unsatiated individuals, which may contribute to the dispersion of swarms during feeding.KEY WORDS: Sex-dependent · Moult · Maturity · Swarm · Satiation · Pleopods · Antarctic · Southern Ocean Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 366: [99][100][101][102][103][104][105][106][107][108][109][110] 2008 organise themselves in a similar fashion to fish schools with respect to orientation matching and collective response to stimuli (Hamner & Hamner 2000).A number of studies have found that the composition of individuals within krill swarms is biased towards certain types or physiological states. Marr (1962), for instance, determined that many swarms have similarly sized individuals, which he believed resulted from cohorts remaining as integral units over their entire lifespans. Other studies, such as those of Watkins et al. (1992) and Nicol (1984), have shown biases with regards to sex and maturity, which were attributed to mating and reproductive activity. Buchholz et al. (1996) found that the distribution of moult stages in numerous swarms were non-random and posited the existence of a hormonal synchrony between individuals.Although state-based biases in the composition of swarms are well established, the mechanisms by which krill sort themselves between swarms remain unclear. Fregin & Wiese (2002) demonstrated that krill are capable of signalling through photophores. proposed that krill use rheotactic cues to maintain swarm integrity. The use of sex pheromones to...

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Section: Effect Of Moultingmentioning

confidence: 99%

Influence of individual state on swimming capacity and behaviour of Antarctic krill Euphausia superba

Johnson¹,

Tarling²

2008

Mar. Ecol. Prog. Ser.

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“…There rnay b e a number of possible explanations for this phenomenon. Firstly, although krill continue to be able to swim during ecdysis through maintaining muscle attachments to both the old and the new cuticle (Buchholz & Buchholz 1989), it is unlikely that they are able to achieve a high performance potential. This is because the changes in water balance and structure of the cuticle are likely to increase basal metabolism (Buchholz 1991).…”

Section: Percentage (%)mentioning

confidence: 99%

Vertical migration behaviour in the northern krill Meganyctiphanes norvegica is influenced by moult and reproductive processes

Tarling¹,

Cuzin-Roudy²,

Búchholz³

1999

Mar. Ecol. Prog. Ser.

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A population of the northern knll Meganyctiphanes norvegica was sampled between 24 July and 3 August 1998 in the Alkor Deep, Kattegat, in order to investigate the influence of sexual and developmental factors on the vertical distribution of adult krill. Depth-discrete samples of knll were taken with a 1 m' hlOCNESS net at the cardinal tirnes of day (midnight, midday, sunnse and sunset). Specimens were immediately measured and categorised for moulting and spawning Status. Further samples were preserved for detailed analysis in the home laboratory. Results showed that the population concentrated in the deep (80 to 100 m) during day-time but segregated vertically during nighttime. Moulting occurred in the deep during night-time, away from the main part of the non-moulting population, which was located between 80 and 50 m. Spawning females were most evident in the uppermost depth interval (30 to 5 m). Yloulting at night in the deepest layers may b e viewed a s a mechanism to avoid cannibalism whilst in a vulnerable condition. Spawning in the warm upper layers accelerates reproductive processes and may also reduce the depth to which the eggs sink before hatching into nauplii.

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“…Firstly, they show high activity associated with the moult cycle and are responsible for reabsorption of the old cuticle prior to ecdysis. It is interesting to note that the capacity for the moult-related turnover of chitin corresponds to that of tropical insects (Buchholz 1989;Buchholz and Buchholz 1989) and thus highlights the physiological performance in the Antarctic krill. Secondly, they function as true digestive enzymes and occur at high activities (Buchholz and Saborowski 1996;Saborowski and Buchholz 1999) in the midgut gland and stomach in krill.…”

Section: Digestive Enzymesmentioning

confidence: 97%

Metabolic and enzymatic adaptations in northern krill,Meganyctiphanes norvegica, and Antarctic krill,Euphausia superba

Búchholz¹,

Saborowski²

2000

Can. J. Fish. Aquat. Sci.

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Abstract:The Antarctic krill, Euphausia superba, is restricted to the Antarctic Ocean. The northern krill, Meganyctiphanes norvegica, is extremely widely distributed from the arctic North Atlantic to the warm Mediterranean. Respiration measurements showed no seasonal differences in rates determined in krill from the thermally stable Clyde Sea (Scotland) and the cooler but variable Danish Kattegat. In the warm Ligurian Sea, where temperatures are stable, krill showed higher rates in April than in September, indicating reactions to the short but intensive productive season. Krill can passively benefit from enhancements of overall metabolism when ascending into upper, warmer water strata during their pronounced diel vertical migration. Michaelis-Menten constants (K m ) of citrate synthase (CS) were compared. In terms of respiration and enzyme regulation, krill from the Ligurian Sea stand apart: temperature and nutrition appear to be of different influence, relatable to genetic differentiation in the species. In contrast, K m of CS in E. superba is temperature independent, highlighting the species' stenothermal physiology. A basal level of activity of digestive enzymes ensures immediate utilization of patchy food sources. Specific induction, including that of chitinases, indicating omnivory in both species, underlines krill's exceptional capacity to adapt to highly variable trophic environments. Processes of moult, growth, and reproduction are locally and seasonally adjusted.Résumé : Le krill antarctique, Euphausia superba, n'habite que l'Océan antarctique, alors que le krill nordique, Meganyctiphanes norvegica, possède une répartition géographique très étendue qui va de la région arctique de l'Atlantique Nord aux eaux chaudes de la Méditerranée. Les taux respiratoires n'accusent pas de variation saisonnière chez le krill de la mer de Clyde en Écosse, un milieu à forte stabilité thermique, ni chez celui du Cattégat danois, une mer plus froide et plus changeante. Dans la mer Ligurienne, où les températures sont chaudes et stables, le krill a des taux respiratoires plus élevés en avril qu'en septembre, en réaction à la courte mais intense saison de production. Le krill peut bénéficier passivement d'un accroissement général de son métabolisme lorsqu'il se déplace vers les couches d'eau supérieures plus chaudes durant sa migration verticale quotidienne marquée. Nous avons comparé les constantes de Michaelis-Menten (K m ) de la citrate synthase (CS). En ce qui a trait à la respiration et la régulation enzymatique, le krill de la mer Ligurienne fait bande à part: la température et la nutrition semblent y avoir une influence particulière, à cause d'une différentiation génétique chez l'espèce. En revanche, la K m de la citrate synthase est indépendante de la température chez E. superba, une caractéristique physiologique d'une espèce sténotherme. Le maintien d'un niveau d'activité de base chez les enzymes digestives permet l'utilisation immédiate de ressources alimentaires à répartition contagieuse. L'induction spécifique, e...

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Ultrastructure of the integument of a pelagic Crustacean: moult cycle related studies on the Antarctic krill, Euphausia superba

Cited by 47 publications

References 27 publications

Influence of individual state on swimming capacity and behaviour of Antarctic krill Euphausia superba

Influence of individual state on swimming capacity and behaviour of Antarctic krill Euphausia superba

Vertical migration behaviour in the northern krill Meganyctiphanes norvegica is influenced by moult and reproductive processes

Metabolic and enzymatic adaptations in northern krill,Meganyctiphanes norvegica, and Antarctic krill,Euphausia superba

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