Eel Blog

A natural history blog dedicated to the Anguilliformes

[muraenidae]

A young cusk eel (Brotulotaenia sp) by artour_a on Flickr.

Hello, new followers! Here's a juvenile cusk eel (not technically an eel, but still an awesome fish) for your viewing pleasure, while I go write more about true eels. Also, if you have questions, please submit them, so that I have ideas of what people find interesting!

[muraenidae]

Moray eels have a problem. Like other eels, they are the descendants of fish that use a method called gape suction feeding in order to gather food. Essentially, this requires a mouth that can expand very rapidly, creating a huge rush of water into the fish's mouth, and dragging along any prey item caught in the wake. Eels, though, because of their slender bodies and specialized skull, don't have the gape to create the suction needed to eat this way. So, in order to pull food into their mouths and down into their throats, moray eels have evolved a second set of jaws. Derived from gill arches, these jaws sit in the back of the moray's throat. When an eel bites down on a prey item, these jaws swing forward, grasp the prey, and then move backwards in order to pull the food down into the eel's throat.

[muraenidae]

Depending on whose evolutionary tree you believe, gulper and pelican eels ('saccopharyngiformes') are either closely related to true eels, but outside of the crown group, or nested within the order anguilliformes (which would make them true eels in their own right). These deep-sea specialists have a unique, highly derived anatomy, with V-shaped muscle segments (in all other fish, the muscles are W-shaped), no swim bladder, and a specialized skull. Gulper eels have reduced or lost many cranial elements, but the jaw is greatly enlarged, allowing these animals to swallow organisms larger than their own bodies. Saccopharynx sp.

[muraenidae]

This is an evolutionary tree showing the relationships between all of the major groups of eels. Based on mitochondrial DNA, this tree suggests that freshwater eels (family Anguillidae) are descendants of organisms that were originally deep-ocean specialists, like snipe eels and sawtooth eels. The authors of this study used a maximum likelihood method to reconstruct ancestral adult habitat. A pie chart at each node indicates the likelihood that an ancestor occupied one four habitat types: Light blue circle, shallow water; brown circle, outer shelf and slope; dark blue circle, oceanic midwater; red circle, freshwater. This tree also shows that the traditional classification of eels probably does not reflect evolutionary history well. None of the current suborders of eels are a natural group, and even some families of eel, like the conger eels, are more closely related to other eel families than to members of their own family. (Jun G. Inoue, Masaki Miya, Michael J. Miller, Tetsuya Sado, Reinhold Hanel, Kiyotaka Hatooka, Jun Aoyama, Yuki Minegishi, Mutsumi Nishida, and Katsumi Tsukamoto Deep-ocean origin of the freshwater eels Biol. Lett. rsbl20090989; published ahead of print January 6, 2010, doi:10.1098/rsbl.2009.0989 1744-957X)

[muraenidae]

Snake eel by jasdivr on Flickr.

I believe that this is the Reptilian Snake Eel, Brachysomophis henshawi

[muraenidae]

Moray eels are important predators in tropical marine ecosystems. While they are normally nocturnal, and hunt primarily from holes and caves, scientists have observed moray eels (Gymnothorax pictus) leaving the water to capture shore crabs (Grapsus tenicrustatus), consuming their prey while totally or partially emerged from the water.

Diurnal, land-based predation on shore crabs by moray eels in the Chagos Archipelago (2009) N. J. Graham, S. J. Purkis and A. Harris. Coral Reefs 28:397-397

[muraenidae]

Protanguilla palau is the only member of the family Protanguillidae. These small eels share a number of features that were only known from fossils prior to its discovery in 2011. It's thought to have split from the other living eels around the early Triassic, although the first fossil eels are only known from the early Cretaceous - 100 million years after this hypothesized divergence. Because it looks so much like some fossil animals, it's tempting to think of Protanguilla as primitive, but just like the coelacanth, tuatara, and other 'living fossils,' it's important to remember that this animal is probably highly derived compared to the ancestor of all eels.

[muraenidae]

Nemichthys scolopaceus - credit Sandra J. Raredon, Division of Fishes, NMNH by Smithsonian National Museum of Natural History on Flickr.

Nemichthys scolopaceus, preserved specimen in the Smithsonian collections Snipe eels (family Nemichthyidae) are pelagic hunters with a global distribution. These eels have a unique morphology - they are characterized by slender, curving jaws and an anus located directly behind their pectoral fins. Snipe eels are very slender-bodied fish: adults can reach over a meter in total length, but rarely attain a body mass of more than a few hundred grams.

[muraenidae]

This video shows large leptocephali that were filmed by divers at 3 locations within the Indonesian Archipelago from 2009 - 2011. These leptocephali were observed in Lembeh Strait adjacent to northeastern Sulawesi Island, at Ambon Island and at Bali, from December to April. These leptocephali are about 300 - 400 mm long and appear to be metamorphosing larvae of some type of moray eel of the family Muraenidae. The morphological similarities between these leptocephali and ribbon eels, Rhinomuraena quaesita, suggest they may be ribbon eel larvae. This video clip showing the four leptocephali that were filmed by various divers is associated with an unpublished manuscript: Observations of large muraenid leptocephali in coastal Indonesia: locations of sightings and behavior of the larvae, Miller et al.

[muraenidae]

23 Leptocephalus-eel by Mang Idol on Flickr.

The larvae of eels are known as leptocephali (singular = leptocephalus). These marvelous creatures have flattened, leaf-shaped bodies; because they have no red blood cells, tiny organs, and only a very small layer of muscle, leptocephali are almost completely transparent, although some may have reflective chromatophores in their skin. Eels may remain in this stage for up to a year, and many leptocephali migrate vast distances before metamorphosing into adult eels.

[muraenidae]

Reptilian snake eel (Brachysomophis henshawi) by echeng on Flickr.

Brachysomophis henshawi, Lembeh Strait, Indonesia.

Snake eels are a primarily tropical group. While most spend their time burrowed in sediment, emerging to hunt fish and crustaceans, some are active pelagic hunters.

[muraenidae]

mustache conger by shappell on Flickr.

Conger cinereus, Makena, HI, USA Conger eels are found primarily in deep and temperate zones of the Atlantic, Indian and Pacific Oceans, where they eat mostly smaller fish and crustaceans.