Petromyzontidae, Bonaparte, 1831

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 37-39

Family Petromyzontidae

Lampreys

Lampreys are not fishes. They are a distinct lineage of vertebrates traditionally associated with fishes. Lampreys evolved in the marine environment and originated in the Ordovician period, at least 450 million years ago. This makes them survivors of five of the Earth’s great extinction events. Lampreys are often thought to be related to hagfish ( Myxiniformes ), which are a sister group to lampreys. Ammocoetes, the filter-feeding worm-like larval stage of modern lampreys, have long influenced hypotheses of vertebrate ancestry. The life history of modern lampreys, from a superficially amphioxus-like ammocoete to a specialised predatory adult, was thought to exemplify the origin of vertebrates. However, recent analyses of immature specimens of Palaeozoic stem lampreys show that they lack an ammocoete larval stage.Ammocoetes are specialisations of the life history of modern lampreys rather than relics of vertebrate ancestry. Since modern hagfish also lack a larval stage, the last common ancestor of hagfish and lampreys was probably a macrophagous predator without a filter-feeding larval stage. The earliest known record of the ontogenic transition from ammocoete to adult is Mesomyzon from Early Cretaceous lake beds in China. All modern lamprey lineages have evolved in freshwater within the last 200 million years. The derived state of an ammocoete and the prolonged filter-feeding larval phase undoubtedly delayed the need for the endocrine function of a thyroid gland in iodine-poor freshwater environments. This is one of the mechanisms that allowed lampreys to evolve in freshwater.

Lampreys are jawless and eel-like animals with seven roundish gill openings behind the eye but lacking paired fins. They have a very distinctive oral disc armed with rows of horny teeth, which they use to attach themselves to surfaces and prey. The dentition of the oral disc is an important character in identifying genera ( Figure 26–27). All lampreys are found in cooler waters above 20° northern and southern latitudes. Petromyzontidae are found in the north, while a few species of other families are found in the southern hemisphere.

Lampreys spawn in spring and die shortly after spawning. They spend several years in a larval stage (ammocoete). The duration of the ammocoete stage is still controversial, but we know that lamprey species in West Asia undergo metamorphosis between late summer and early winter. Juveniles are always shorter than adult ammocoetes (larvae shrink during metamorphosis). Migrating Petromyzon marinus are attracted by steroidal pheromones released by stream-dwelling larvae, which indicate habitat suitability. These compounds are detected at extremely low concentrations and are released in large quantities. Laboratory experiments show that each Petromyzon larva activates at least 400 l of water per hour. Spawning lampreys cease their normal daylight avoidance and spawn on sunny days. The male arrives first at the spawning site and releases a bile acid that acts as a sex pheromone, inducing the ovulated female to search for him. Spawning generally occurs in fast-flowing water, often at the head of riffles in streams. During spawning, the male attaches to the female’s neck and wraps his body around her. The female then deposits the eggs in the gravel with her belly.

Open Access. © 2025 JÖrg Freyhof, Baran Yoğurtçuoğlu, Arash Jouladeh-Roudbar and Cüneyt Kaya, published by De Gruyter. the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

https://doi.org/10.1515/9783111677811-002

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Of the four species from West Asia, two are anadromous: Caspiomyzon wagneri and Petromyzon marinus . Caspiomyzon is a predatory species, and Petromyzon is parasitic. The two species of Lampetra in West Asia are sedentary; they do not feed after metamorphosis. Instead, they spawn in the spring after metamorphosis. Other species of Lampetra are found in Europe.

Further reading. Vladykov & Kott 1979 (diversity, distribution); Hardisty & Potter 1971–1982, Hardisty 1979, Hardisty 1986a (biology); Youson & Sower 2001 (thyroid hormones); Gills et al. 2003 (phylogeny); Sorensen et al. 2005 (pheromone); Gess et al. 2006 (fossils);Lang et al.2009 (phylogeny); Docker et al. 2015 (review); Miyashita et al. 2021 (evolution of ammocoetes); Hughes et. al. 2025 (generic concept).

Caspiomyzon wagneri ; Tajan, Iran; ~ 400 mm TL. Caspiomyzon wagneri ; Samur, Russia; 247 mm TL. © A. Naseka.