Physiological adaptations of the living agnathans

  title={Physiological adaptations of the living agnathans},
  author={M. W. Hardisty and Ian C. Potter and R. W. Hilliard},
  journal={Earth and Environmental Science Transactions of the Royal Society of Edinburgh},
  pages={241 - 254}
ABSTRACT The modes of life and environments of the extant agnathans (cyclostomes) are discussed in relation to their adaptations to temperature, light, oxygen and salinity. As their antitropical distribution indicates, both hagfishes and lampreys are cold water groups. Since hagfishes live in deeper waters than lampreys, they are not exposed to the marked seasonal changes in temperature and light which influence major events in the lamprey life cycle. Both groups tend to be nocturnally active… 

Cellular composition and ultrastructure of the gill epithelium of larval and adult lampreys

Proposals are made regarding the ways in which lampreys use their gill epithelial cells for osmoregulating in hypo- and hypertonic environments.

The taxonomy, phylogeny and distribution of lampreys

The phylogenetic relationships of the lampreys were similar in most respects to those obtained by subjecting molecular data for those species to Bayesian analyses, however, in contrast to the results of morphological analyses, the genera Eudontomyzon and Lampetra were not monophyletic when using molecular analyses.

The Agnathan Enteropancreatic Endocrine System: Phylogenetic and Ontogenetic Histories, Structure, and Function1

It is concluded that due to the ancient lineage and successful habitation of lampreys and hagfishes, and the importance of the EP system to their survival, that their EP systems should be a research focus well into the next century.

Life History Evolution in Lampreys: Alternative Migratory and Feeding Types

  • M. DockerI. Potter
  • Environmental Science, Biology
    Lampreys: Biology, Conservation and Control
  • 2019
The existence of three closely related freshwater parasitic species suggests that Pacific lamprey successfully colonized fresh water in the past, and the “invasion-by-canal” hypothesis appears to be the most convincing, but definitive resolution should be possible with genome-level analyses.

Categorization of the mitochondria-rich cells in the gill epithelium of the freshwater phases in the life cycle of lampreys

It is proposed that the subtype A of the branchial intercalated MR cell of lampreys provides the driving force for the Na+ uptake by active H+ secretion.

Electrical Excitation of the Heart in a Basal Vertebrate, the European River Lamprey (Lampetra fluviatilis)

Electrical excitability of the lamprey heart seems to possess both primitive and advanced characteristics, while relatively low AP upstroke velocities enable only relatively slow propagation of contraction over the heart.

Claudins of sea lamprey (Petromyzon marinus) - organ-specific expression and transcriptional responses to water of varying ion content.

The idea that claudin (Cldn) TJ proteins play an important role in the osmoregulatory physiology of pre- and post-metamorphic sea lamprey is supported and that Cldn participation can occur across organs, in an organ-specific manner as well as differ spatially within organs that contribute to the regulation of salt and water balance in these fishes.

Parathyroid hormone-related protein production in the lamprey Geotria australis: developmental and evolutionary perspectives

The presence of PTHrP in the lamprey, a representative of a group of vertebrates, which apparently evolved over 540 million years ago, strongly suggests that it is a protein of ancient origin and provides evidence that the PTHRP molecule may have been conserved from lampreys through to humans.

Structural changes in the zonulae occludentes of the chloride cells of young adult lampreys following acclimation to seawater

The zonulae occludentes between the chloride cells of lampreys acclimated to seawater are similar to those in the gills of teleosts in seawater, and are considered to be leaky and to provide a low-resistance paracellular pathway for the passive transepithelial movement of Na+.



Respiration of Lampreys

In lampreys, though the gross morphology of the branchial chamber and the method of ventilating the gills are radically different from that found in gnathostomes, the total gill area of larval and adult Lampetra fluviatilis and the thickness of the water–blood barrier are similar to active teleosts.

Osmoregulation in Juvenile and Adult Lampreys

Nonparasitic lampreys are well adapted for a freshwater existence but are less tolerant of salt water than representatives of the parasitic species and changes in serum osmolality are primarily the result of corresponding shifts in sodium and chloride ions.


Standard oxygen consumption and ventilatory frequency were influenced greatly by temperature, e.g. values for stage 6 of L. fluviatilis rose from 24.3 μl g−1 h−1 and 33.0 beats min−1 at 5 °C to 103.8 μlG −1 h −1 and 98.2 beats min −1 at 15 °C.

The Mechanism of Marine Osmoregulation in the Lampern (Lampetra Fluviatilis L.) and the Causes of its Breakdown During the Spawning Migration

An analysis of the mechanism of osmoregulation in fresh-run lamperns shows that it is similar in many respects to that employed by marine teleosts, and it is calculated that chloride is excreted by an extra-renal route, presumably by means of chloride excretory cells which have been discovered in the gills.

On the Feeding of the Hagfish Myxine Glutinosa in the North Sea

  • R. Shelton
  • Environmental Science
    Journal of the Marine Biological Association of the United Kingdom
  • 1978
The myxinoid cyclostomes, of which the hagfish Myxine glutinosa L. is one of the best known examples, are of unique biological interest as representatives of a group of jawless vertebrates which

Studies on an Isolated Spawning Population of the Brook Lamprey (Lampetra planeri)

In the course of physiological work on the brook lamprey (Lampetra planeri) both ammocoetes and adults of this species have been collected in the river Yeo from 1940 onwards, and further restrictions have been placed on their distribution by pollution and by the construction of weirs and sluices.

Hypoxic Acclimation in the Lamprey, Lampetra Fluviatilis: Organismic and Erythrocytic Responses

The intraerythrocytic pH of hypoxic animals, measured with a freeze-thaw method, was higher than the plasma pH, suggesting that protons are not passively distributed, and theHypoxic animals had a higher blood O 2 affinity than the normoxic controls.

Some Aspects of Osmotic Regulation in Lampreys

Evidence has been produced to support the view that the differences observed in water, fat and Cl content of ammocoete and adult planeri and adult fluviatilis are consequences of the period of starvation preceding sexual maturity.

Osmotic Conditions During the Embryonic and Early Larval Life of the Brook Lamprey (Lampetra Planeri)

Evidence is presented which points to a decrease in the volume of the embryo at some point between gastrulation and hatching, and the evidence suggests that the ovarian egg is in osmotic equilibrium with the peritoneal fluid.