Skip to main content

The effects of the cold winter of 1962/63 on the helgoland population ofBranchiostoma lanceolatum (Pallas)

Wie Wirkungen des kalten Winters 1962/63 auf die Helgoland-Population vonBranchiostoma lanceolatum (Pallas)

Kurzfassung

Über die Hälfte der HelgoländerBranchiostoma lanceolatum-Population starb, als die Wassertemperatur während des strengen Winters 1962/63 unter 0° C herabsank. Dies geht aus der Analyse von Fängen hervor, welche mit Van Veen und Hensen Dredgen gemacht worden waren. In der jüngsten Altersgruppe der Population stieg die Sterberate auf 100% an. Die Empfindlichkeit von Individuen verschiedener Größe gegenüber niedriger Temperatur wird diskutiert hinsichtlich ihres Verhaltens sowohl im Laboratorium als auch im Grobsand ihres Habitats. Untersuchungen über das Aktivitätsmuster von Vertretern der Helgoland- und der Neapel-Populationen in Abhängigkeit von verschiedenen Temperaturen machen wahrscheinlich, daßB. lanceolatum eine mediterrane Art ist, welche sich nordwärts in den Englischen Kanal und die Nordsee ausgebreiter hat. Die Tiere sind nicht in der Lage, sich bei Temperaturen unter 3° C — wie sie bei Helgoland im Winter normalerweise vorkommen — fortzubewegen.

Summary

1. Seawater temperatures at Helgoland were subnormal for six months during the winter of 1962/63 and fell to −1.3° C. Quantities of silt from the shores and estuaries of the mainland were released into the water when pack ice around the island melted in late February.

2. In a sample dredged from a ground near Helgoland in April, 1963, 40% of the lancelets consisted of isolated notochords. From comparison with a sample taken in November, 1962, it is estimated that at least 50% of the population died during the winter. The average number of animals per Van Veen grab fell from 6.9 before to 3.0 after the cold period.

3. None of the autumn settlement of newly metamorphosed animals survived, and there was a very high death rate estimated at 90% among the largest animals.

4. An analysis of activity in relation to temperature inBranchiostoma lanceolatum collected from Helgoland and Naples showed a temperature tolerance of 3° to 27° C in both populations with active swimming at temperatures of 10° to 20° C. There is no muscular movement below 3° C which is the lower limit of the normal winter temperature at Helgoland. It is suggested that the species is best adapted to Mediterranean conditions.

5. The pharyngeal mechanism cannot operate normally below 3° C and although it is considered unlikely that starvation was the primary cause of death, other effects of a reduced pharyngeal current may have proved lethal.

6. It is held that the depth to which lancelets of different sizes burrow into the substrate could account for differential mortality through cold.

Literature cited

  1. Dennell, R., 1950. Note on the feeding of Amphioxus(Branchiostoma bermudae).Proc. roy. Soc. Edinb. (B)64, 229–234.

    Google Scholar 

  2. Gruvel, A., 1933. Abondance duBranchiostoma lanceolatum (Pallas) dans le canal de Suez.C. R. Acad. Sci. Paris 197, 92–93.

    Google Scholar 

  3. Hagmeier, A. &Hinrichs, J., 1931. Bemerkungen über die Ökologie vonBranchiostoma lanceolatum (Pallas) und das Sediment seines Wohnortes.Senckenbergiana biol. 13, 255–267.

    Google Scholar 

  4. Webb, J. E., 1956. On the populations ofBranchiostoma lanceolatum and their relations with the West African lancelets.Proc. zool. Soc. Lond. 127, 125–140.

    Google Scholar 

  5. —— &Hill, M. B., 1958. The ecology of Lagos Lagoon. Part IV — On the reactions ofBranchiostoma nigeriense Webb to its environment.Phil. Trans. (B)241, 355–391.

    Google Scholar 

Download references

Author information

Affiliations

Authors

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Courtney, W.A.M., Webb, J.E. The effects of the cold winter of 1962/63 on the helgoland population ofBranchiostoma lanceolatum (Pallas). Helgolander Wiss. Meeresunters 10, 301–312 (1964). https://doi.org/10.1007/BF01626115

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1007/BF01626115

Keywords

  • Cold Period
  • Seawater Temperature
  • Temperature Tolerance
  • Active Swimming
  • High Death