A study of certain aspects of ammocoete biology

MacDonald, T. H (1960) A study of certain aspects of ammocoete biology. PhD thesis, University of Glasgow.

Abstract

Three species of lamprey are found in Britain; the Sea Lamprey (Petromyzon marinus), the River Lamprey (Lampetra fluviatilis) and the Brook Lamprey (Lampetra planeri). Although the adult stages of these species can readily be distinguished because of their great differences in size, colour and dentition, the larvae, or ammocoetes, of all three species look superficially alike. The first part of the thesis, therefore, concerns itself with the selective identification of the ammocoetes of the three species concerned. Close examination of more than 11,000 ammocoetes collected from streams in England, Scotland and Wales, indicated that the following are useful taxonomic characteristics: (a) Pigmentation and shape of the precursor of the tongue. (b) Pigmentation and shape of the caudal fin. (c) Pigmentation of the branchial region. (d) Number of trunk myomeres. The pigmentation of ammocoetes is subject to some variation in intensity within the same species. For instance, ammocoetes of L. planeri tend to be darker in the winter than they are in the summer within any given small area. Likewise, during the summer months, ammocoetes taken from streams in the north of Scotland are considerably darker than ammocoetes of the same species from streams in southern England. As a suitable prelude to experimental and field studies made on the rates of growth in ammocoetes, the spawning requirements and embryological development of all three species is discussed. This leads into, and forms a foundation for, the third part of the thesis, i.e. growth in ammocoetes. Samples of ammocoetes were taken from various streams, and the number of year classes making up the larval life of each species were estimated. Ten ammocoetes of each size-class of each species were then reared for one year in the laboratory in order to verify the field data. The conclusions arrived at in the field were thus upheld in the laboratory and were as follows: (a) L. planeri has a larval life of about five years. Metamorphosis begins in August or September, and is completed in about seven months. (b) L. fluviatilis has a larval life of approximately six years. Metamorphosis begins in August or September, and is completed in about seven months. (c) P. marinus larvae complete metamorphosis in approximately five years and eight months. As in the other two species, metamorphosis commences in late summer but is completed in only four months or so. A series of laboratory experiments in which ammocoetes were reared under artificially high and low temperatures, indicated that the rate of increase in weight and lengthy is closely correlated with the water temperature. The data make it apparent that ammocoetes do not feed during the winter months (the critical water temperature being about 11

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Robertson
• Keywords: Zoology
• Date of Award: 1960
• Depositing User: Enlighten Team
• Unique ID: glathesis:1960-73665
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 14 Jun 2019 08:56
• URI: https://theses.gla.ac.uk/id/eprint/73665