Electric eel organ description, structure, function and developmental origin

This blog and all posts associated are part of a histology assignment at Memorial University of Newfoundland

The electric eel is an apex predator capable of shocking both prey and predators, due to a composite "electric organ" containing ~6000 electrocytes (Electric Eels, n.d., para. 2), the working man of these organs and their tissues. In a situation of conflict, all the electrocytes in the organ will simultaneously discharge this electroshock of at least 600V(Electric Eels, n.d., para. 2.), subsequently dazing their opponents, to put it lightly. From the literature cited, the video above, and from simple inference as well, it is clear that the electric organ, and its tissues has a function directly related to predation and defense(Electric Eels, n.d., para. 1, 2 & 3); which is most likely the reason why it is an apex predator. A shocking revelation!

The electric organ is divided into three parts(hence why it was initially mentioned as a composite organ): The main organ, the Sachs' organ and the Hunter's organ(Szabo, T., 1966). It is believed that all three organs was originally striated muscle fibers, as there is a striated structure in undeveloped electroplates(Szabo, T., 1966). The three organs develop in succession, starting with the Sachs' organ, then the main organ and ending with the Hunter's organ(Szabo, T., 1966). Electroplates, the basic unit of the electric organs, have been shown through histological study, to originate from muscle tissue(Szabo, T., 1966). Fully developed electroplate is composed of thin electroplasm, filling only ~one tenth of the connective tissue area(Szabo, T., 1966), as one progresses anteriorly, the processes of the plates disappear and the electroplasm becomes increasingly structured. At the 10cm level, a clearly defined striation can be seen, similar to what is present in neighboring striated muscle. Tangential sections showed large amounts of nuclei in the electro-(sarco) lemma(Szabo, T., 1966). (Szabo, T., 1966) The strited structure in the ventral region of the main organ, is a primitive form of electric tissue, suggesting that this is the germinative region of electric tissue. In the anterior pole of the Sachs' organ, at the ventral border, some undeveloped electric tissue, which bears a similar appearance to that of very large muscle fibers, with some striations present (Szabo, T., 1966). The cell membrane is also crowded by nuclei (Szabo, T., 1966). This structure appears very similar to undeveloped electroplates and is enclosed in the general connective tissue envelope of the Sachs' organ(Szabo, T., 1966). These are the only indications of muscular origin in this specific organ(Szabo, T., 1966). From Szabo's findings, it was determined that all three organs originated from striated muscle fibers, originally(Szabo, T., 1966), which change fundamentally during development. They also do not form from myoblasts, but from well formed striated muscle fibers(Szabo, T., 1966). Moreover, electric organ development appears to be a mainly post-embryonic style of development(Szabo, T., 1966)

Fig 1. the picture above depicts the anatomy of the electric organ within the fish, while the chart below shows the number of electroplates in 12, 23, 38 and 140cm fish; more detailed figure information is given above ;Szabo, T., 1966

 

Fig. 2 Histological section showing eel electrocytes stained with a monoclonal antibody

References: http://www.jneurosci.org/content/3/11/2300.full.pdf+html

http://animals.nationalgeographic.com/animals/fish/electric-eel/

http://www.youtube.com/watch?v=AktTpy5_39g

Szabo, T., 1966, The Origin of Electric Organs in Electrophorus electricus, Anatomical Record vol. 155 p. 103-110, John Wiley and Sons Inc.

Disclaimer: I, Erik Barnable deserve and reserve no rights, or real credit for this blog post--all credit should go to my informative sources