Morphology and gut contents of anguillid and marine eel larvae in the Sargasso Sea

Publication date: Available online 2 February 2019Source: Zoologischer AnzeigerAuthor(s): Michael J. Miller, Lasse Marohn, Klaus Wysujack, Marko Freese, Jan-Dag Pohlmann, Håkan Westerberg, Katsumi Tsukamoto, Reinhold HanelAbstractThe head morphology and body shapes of anguilliform larvae (leptocephali) vary widely by having fewer, much longer teeth in the small larvae and more numerous, but relatively smaller teeth in larger developmental stages. The feeding ecology of leptocephali has been difficult to understand because they do not appear to feed on typical zooplankton like other fish larvae but are mostly found with amorphous organic material in the gut. Observations of the basic morphology of mainly the head and gut contents of anguillid larvae and several families of larger marine eel larvae were made using photographs taken during three recent sampling surveys for leptocephali in the Sargasso Sea spawning area of the European, Anguilla anguilla, and American, A. rostrata, eels. The gut contents of leptocephali consisted of amorphous material that sometimes flowed out of the intestine, and like in the Indo-Pacific, appendicularian houses and fecal pellets and other visible objects were sometimes present. High-magnification microscope images showed the presence of many spherical objects, amorphous and other materials that were likely related to bacteria, protists, fungi, or other organisms. The presence of filter structures confirmed that large oval objects were appendic...

Source: A Journal of Comparative Zoology - February 2, 2019 Category: Zoology Source Type: research