Teleost fish, or eels, have longer bodies than other fish. • They lack a pelvic girdle and a ventral fin. • The eel's elongated body shape gives it a narrow head that aids in hiding in mud, sand, and small openings. • They consist of marine morays and freshwater eels.Electric Eels are not true eels, they belong to order Gymnotiformes. • There are over 800 species of eels so they are very diverse. • Eels do not have pelvic fins. They have continuous dorsal, anal, and caudal fins. • The Asian swamp eel is a facultative air-breathing fish with reduced gills (Damsgaard et al., 2014). • Eels have a keen sense of smell and have a highly developed olfactory system.

1. University of Chakwal, Pakistan

2. Department of Zoology
Presented by: Sadia Altaf
Reg. no.: 20M-UOC/ZOL-01
BS Zoology
Session: 2020-24
Subject: Endocrinology
Submitted to: Dr. Syeda Nadia Ahmad
Topic: The Eel

3. Introduction to Eel
• Teleost fish, or eels, have longer bodies than other
fish.
• They lack a pelvic girdle and a ventral fin.
• The eel's elongated body shape gives it a narrow
head that aids in hiding in mud, sand, and small
openings.
• They consist of marine morays and freshwater eels
(Tesch & Bartsch, 2003).
Figure 1: Freshwater eel. Source:
https://images.app.goo.gl/4ZuoMVE4PS
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Figure 2: Marine moray. Source:
https://images.app.goo.gl/vKzYFr51N4
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4. Taxonomy
Kingdom Animalia
Phylum Chordata
Class Actinopterygii
Infraclass Teleostei
Order Anguilliformes
Suborders Anguilloidei
Nemichthyoidei
Congroidei
Synaphobranchoidei

5. Distribution
• Except in West Africa and South America, they are widely dispersed in
most tropical and subtropical regions of the world.
• Based on their geographic ranges, tropical and temperate species of
freshwater eels were distinguished.
• There are eleven species of tropical eels and five species of temperate eels,
respectively.
• Except for the European eel, A. Anguilla, most temperate species are found
along the western shores of the Atlantic, Indian, and Pacific oceans.
• Their continental ranges are thought to be connected to the subtropical
circulation of the oceans (Arai, 2016).

6. Importance
• The European eel is mostly cultured in
southern Europe.
• The Japanese eel, A. japonica, is an
important cultured fish in several Asian
countries including Japan, China, and
Taiwan.
• Eels are a vital source of food for
numerous birds, animals, and huge fish.
• They are considered to be a nutrient flux to
and from the sea both as predator and prey
(Tesch & Bartsch, 2003).
Figure 3: Japanese Eel dish. Source:
https://images.app.goo.gl/ktRFZmbE7AjtnxM78

7. Unique Facts
Figure 4: Electric Eel. Source:
https://images.app.goo.gl/uf6pYx1WpCDJUmab8
Figure 5: Asian Swamp Eel. Source:
https://images.app.goo.gl/6ZArz5uFjQ75HTK76
• Electric Eels are not true eels, they belong to
order Gymnotiformes.
• There are over 800 species of eels so they are
very diverse.
• Eels do not have pelvic fins. They have
continuous dorsal, anal, and caudal fins.
• The Asian swamp eel is a facultative air-breathing
fish with reduced gills (Damsgaard et al., 2014).
• Eels have a keen sense of smell and have a highly
developed olfactory system (Catania, 2016).

8. Morphology
• Eels (Anguilliformes) lack a pelvic girdle and a
ventral fin. Certain taxa, like the Muraenoidei,
have smaller pectoral fins.
• The eel's relatively narrow head, which helps it
conceal itself in sand, mud, and small holes, is
located beneath its elongated body structure.
• They have thick skin to avoid harsh
environments.
• They have embedded rudimentary scales (Tesch
& Bartsch, 2003).
Figure 6: Pectoral fins of Eel. Source:
https://images.app.goo.gl/w8ksLS91g8WEj46F7
Figure 7: Skin of Eel. Source:
https://images.app.goo.gl/oGeo7nNGwfW63E3
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9. Behavior
Migratory Behavior
• Eels are catadromous that perform
extensive migrations between continental
growing habitats and oceanic spawning
sites (Verhelst et al., 2023 and Feunteun et al.,
2003).
Parental Care
• The parental care of A. platysoma is
characterized by females laying eggs and
males guarding in a deep hole on a rock
until the independence of the young (Abe,
1998).
Figure 8: Migration of Eels. Source:
https://images.app.goo.gl/R9KeCG5ToUE2
bxCS6

10. Recent Findings
• The presence of bioactive compounds in European eel (Anguilla anguilla) skin was
studied. Proximate and lipid class compositions and analysis of the fatty acid (FA) profile
were determined.
• Higher levels of proteins, lipids, ash, and ω6 FAs were observed in the skin tissue. The
muscle tissue showed higher moisture, ω3 FA, and ω3/ω6 ratio values.
• Regarding lipid classes, a higher proportion of phospholipids, free sterols, α-
tocopherol, and free FAs was observed in the skin tissue.
• It was concluded that European eel skin, a by-product resulting from commercial
processing, can be considered a valuable source for the food and pharmaceutical
industries by providing value-added constituents such as proteins, lipids, ω3 FAs,
phospholipids, and α-tocopherol (Bote et al., 2024).

11. References
Abe, N. (1998). Parental care and social organization of the spiny eel, Aethiomastacembelus platysoma, in Lake
Tanganyika. Environmental biology of fishes, 52(1), 271-280.
Arai, T. (2016). Biology and ecology of anguillid eels (Vol. 340). Boca Raton, FL, USA: CRC Press.
Bote, A., Trigo, M., Martínez, S., & Aubourg, S. P. (2024). The Presence of Bioactive Compounds in European Eel
(Anguilla anguilla) Skin: A Comparative Study with Edible Tissue. Marine Drugs, 22(3), 105.
Catania, K. C. (2019). The astonishing behavior of electric eels. Frontiers in Integrative Neuroscience, 13, 23.
Damsgaard, C., Findorf, I., Helbo, S., Kocagoz, Y., Buchanan, R., Weber, R. E., ... & Wang, T. (2014). High blood
oxygen affinity in the air-breathing swamp eel Monopterus albus. Comparative Biochemistry and Physiology
Part A: Molecular & Integrative Physiology, 178, 102-108.
Feunteun, E., Laffaille, P., Robinet, T., Briand, C., Baisez, A., Olivier, J.-M., & Acou, A. (2003). A Review of Upstream
Migration and Movements in Inland Waters by Anguillid Eels: Toward a General Theory. Eel Biology, 191–213.
Nielsen, M. E., & Esteve‐Gassent, M. D. (2006). The eel immune system: present knowledge and the need for
research. Journal of Fish Diseases, 29(2), 65-78.
Tesch, F. W., & Bartsch, P. (2003). The eel (Vol. 15). Oxford: Blackwell Science.
Verhelst, P., Westerberg, H., Coeck, J., Harrison, L., Moens, T., Reubens, J., ... & Righton, D. (2023). Tidal and
circadian patterns of European eel during their spawning migration in the North Sea and the English
Channel. Science of the total environment, 905, 167341.

12. Thank you!