July 2018 Biodiversity Spotlight

Rattails and Grenadiers (Family Macrouridae)

Images courtesy of NOAA Okeanos Explorer

Contributed by Randy Singer

When scientists explore the sea floor with remote operated vehicles (ROVs), seeing deep-sea fishes is always an uncommon treat. The most commonly observed deep-sea fishes are grenadiers or rattail fishes, which are in the family Macrouridae. These fishes get their name from their unique body morphology. Typified by large heads with large mouths and eyes, grenadiers have slender bodies that taper greatly to thin caudal peduncles or tails. Their family name gives homage to their tails as it is derived from the Greek makros meaning "great" and oura meaning "tail. While they are not the most diverse family of deep-sea fishes (28 genera), they are certainly the most abundant on the sea floor and have dynamic and interesting swimming behaviors. They do not have numerous, flashy photophores (light producing organs) like some other deep sea fishes, but the ones they do have are usually on the midline of the abdomen just in front of the anus. The function of the placement of these photophores is still somewhat of a mystery. Most species of grenadier are benthic (found on the bottom) between 200 and 7,000 meters. These benthic species have gas bladders with unique muscles attached to them that allow them to move up and down in the water column.

You can take a look at these wild and crazy fishes yourself as they are frequently seen on Okeanos Explorer research expeditions. The purpose of these expeditions is to explore previously unvisited areas of the ocean.  You can learn more about the program and find videos, data, and other resources by visiting their website. You can also check out a sighting of an interesting rattail in the genus Gadomus in this highlights reel. This sighting was from one of the first ever dives to an unexplored area in the Gulf of Mexico. This and other rare and wonderful encounters await you on every Okeanos dive.

There are iDigBio resources available to use these dives to teach students about natural history, engineering, computer science, and more! Bring Okeanos Explorer dives and natural history collections into your classroom with this lesson plan.

Lesson objective(s):

  • Upon completion of this lesson, each student should be able to:
  • Explain how scientists explore the deep sea.
  • Find valid scientific names for deep sea animals.
  • Search for digitized natural history collection data in an online aggregated database.
  • Evaluate the effectiveness of different search strategies.
  • Discuss the different types of biodiversity data (remote sensing and collections).
  • Discuss the importance of deep sea discovery.

Lesson Materials:

Please contact us if you would like Word versions of any of the lesson materials.