Chordata · chordates

Silver hatchetfish

Argyropelecus aculeatus

Sternoptychidae · marine hatchetfishesIUCN: Least Concern
Silver hatchetfish
Photo: SEFSC Pascagoula Laboratory; Collection of Brandi Noble, NOAA/NMFS/SEFSC · Public domain · Wikimedia Commons · resized

A flat, mirror-sided twilight-zone fish with light organs along its belly.

Fun factIts belly lights hide its silhouette from predators below.

Waters
Worldwide
Depth zone
Twilight zone, 200–1,000 m
Diet
Zooplankton
Size
Up to 8 cm

Classification

Chordata › Actinopterygii › Stomiiformes › Sternoptychidae

  1. Kingdom Animalia animals
    • Many-celled organisms that eat other living things for energy (heterotrophs)
    • Cells have no cell walls
    • Most can move at some stage of life
  2. Clade Bilateria bilateral animals
    • Body has a left and right side that mirror each other (bilateral symmetry)
    • Head end with concentrated nerves; three tissue layers
    • Includes about 99% of all living animal species
  3. Clade Deuterostomia deuterostomes
    • In the embryo, the first opening becomes the anus and the mouth forms second
    • Includes echinoderms and chordates
  4. Phylum Chordata chordates
    • At some stage of life: a stiffening rod along the back (notochord)
    • A hollow nerve cord along the back (dorsal)
    • Slits in the throat (pharyngeal slits) and a tail past the anus
  5. Subphylum Vertebrata vertebrates
    • A skull (cranium) protecting a brain
    • Backbone or similar support around the nerve cord
    • Includes fishes, amphibians, reptiles, birds, and mammals
  6. Infraphylum Gnathostomata jawed vertebrates
    • Jawed vertebrates: jaws formed from gill arches
    • Paired fins or limbs
    • Includes all fishes except hagfish and lampreys, plus all tetrapods
  7. Superclass Osteichthyes bony vertebrates
    • Bony vertebrates: skeleton made largely of bone
    • Most have a lung or swim bladder
    • Includes ray-finned and lobe-finned fishes and all tetrapods
  8. Class Actinopterygii ray-finned fishes
    • Ray-finned fishes: fins are webs of skin held up by thin bony rays
    • Usually a gas-filled swim bladder for buoyancy
    • About half of all vertebrate species
  9. Infraclass Teleostei teleost fishes
    • Teleosts: symmetrical tail fin
    • Jaws that can push forward to grab prey (protrusible)
    • About 96% of all living fishes
  10. Cohort Euteleostei salmon, cod, perch & kin
    • A huge group that includes salmon, cod, and all spiny-finned fishes
  11. Order Stomiiformes dragonfishes & hatchetfishes
    • Deep-sea fishes with rows of light organs (photophores) on the belly
    • Many have huge mouths and fangs
    • Includes bristlemouths, possibly the most numerous vertebrates
  12. Family Sternoptychidae marine hatchetfishes
    • Hatchetfishes: very thin, silver bodies
    • Belly lights hide their silhouette from below
  13. Genus Argyropelecus
    • Species in the same genus are very close relatives and often look alike.
  14. Species Argyropelecus aculeatus Silver hatchetfish

Closest relatives in the guide