1. General Description
2. Anatomy

General Description

Illustration of Fangtooth from plate 55 of Oceanic Ichthyology by G. Brown Goode and Tarleton H. Bean, published 1896. The fangtooth family Anoplogastridae (sometimes incorrectly written Anoplogasteridae), comprises two species of bathypelagic fishes in the Pacific, Atlantic and Indian Ocean (Nelson, 2006). The common name for the family comes from the numerous elongate fanglike teeth projecting out of the mouths of adults. Their enormous heads are about 1/3 of their body length. Their heads are punctuated by equivalently enormous jaws of equal length (Hulley, 1986). These fishes are voracious sit-and-wait predators and swallow their prey whole (Childress, 1973); they have been observed feeding on fish 1/3 of their own size (Davenport, 1993). Despite their formidable appearance and disposition these fishes reach only about 16cm in length and are generally only a threat to the smaller fish upon which they prey. Anoplogaster is itself a common prey of tunas and marlins (Shimizu, 1977). This specimen from the South Pacific (SW of the Society Islands) is deposited in the Scripps Institution of Oceanography Marine Vertebrate Collection (SIO 72-303) and is 13.8 cm in standard length.

Anatomy

Digital Fish Library's rendering of a segmented FangtoothThe light purple organ is the kidney; the dark purple is the ovary. Also highlighted are the eyes (the two turquoise orbs) and the brain (yellow). The associated spinal cord (in white) is the rod like projection posterior to the rest of the brain. The two small fingerlike projections of the brain near the eyes are the optic nerves. The large saddle-shaped object is the liver and the small red object below the liver is the heart. The large reddish mass above the abdomen is the lateral musculature. This specimen is a gravid female; the large, oval structure (dark purple) behind the liver is the ovary. Because this female is gravid, many of the other internal organs are pushed together and crowded in the abdominal cavity.

The unusual anatomy of this species is additionally notable because the juveniles look very different. Juveniles lack the enormous fangs and mouth characteristic of the adults. Juveniles are commonly found near the waters surface while adults are generally found in deep waters. This is facilitated by the presence of a swim bladder (which provides buoyancy control) in juveniles and ensuing regression of the swim bladder in adults (Kotlyar, 2003). Adults occupy a deep water habitat between 500 and nearly 5000m in depth (FishBase).

The juveniles of this species were misidentified and placed in a separate family until the work of Grey in 1955. Notably it was mainly on distinct juvenile features, that the two species of Anoplogaster were distinguished. Juveniles of Anoplogaster cornuta have long temporal spines protruding off the body, while A. brachycera lack these long spines (Kotlyar, 1986). These characters gave rise to the common names for these respective species, the longhorn fangtooth and shorthorn sabertooth; these fishes are also commonly known as ogrefishes, sabretooth fishes and in Japan as the devil berycoid, “Oni-kinme” (Shimizu, 1978; Kotlyar, 2003).

Despite its worldwide occurrence little is known about this family and its phylogenetic position within Beryciformes. These scans allow for greater anatomical detail than previously available to morphologists. (Much of the details from these scans await further research.) With the growing base of comparative material available using this resource, we may soon be able to better explain the unique ontogeny and phylogeny of these interesting fishes.

Literature Cited

Childress, J.J. 1973. Observations of the feeding behavior of a mesopelagic fish Anoplogaster cornuta: Beryciformes. Copeia 1973, 602-603.

FishBase.2003. Froese, R. and D. Pauly. (eds) 2003. World Wide Web electronic publication. www.fishbase.org, version 22 March 2007

Grey, M. 1955. Notes on a collection of Bermuda deep-sea fishes. Fieldiana 37, 265-302.

Hulley, P.A. 1986. Anoplogasteridae. In: Smith, M.M., and Hemmstra, P.C. (eds.) Smiths’ Sea Fishes. Macmillan South Africa Ltd., Johannesburg

Kotlyar, A.N. 1986. Classification and distribution of fishes of the family Anoplogasteridae (Beryciformes). Journal of Ichthyology 26, 133-152.

Kotlyar, A.N. 2003. Family Anoplogastridae Gill 1893 — fangtooths. California Academy of Sciences Annotated Checklists of Fishes 20, 1-3.

Shimizu, T. 1978. Record of the Beryciform fish, Anoplogaster cornuta, from the Western North Pacific. Japanese Journal of Ichthyology 25, 65-67.