Sunday, January 18, 2015

Fish Geek's Pick of the Week! Hawaiian Dascyllus!

Video: Hawaiian Dascyllus with Eggs: Laying? Fertilizing? Protecting!, by Rebekah Kaufmann

Hawaiian Dascyllus

Latin: Dascyllus albisella (from Latin alba or white)
Hawaiian: 'alo'ilo'i (bright and sparkling)
Common: "Hawaiian Domino" or "Hawaiian White Spotted Damsel" or "Snowball Damsel"
Juvenile Hawaiian Dascyllus in the shelter of an urchin. Photo by Robyn Smith

We love "spotting" this awesome fish in both it's cute juvenile phase and its fascinating adult phase. Juveniles are small, black, with a bright white spot on each side, and a bright blue spot on their forehead. They often seek shelter in antler corals, urchins, or anemones (and are immune to anemone stings like their Damsel cousin Clown fish). As an adult, the blue spot disappears, and the white spot blends out into the greyer-black sides.
John P. Hoover says, "They can lighten or darken their color; while spawning they become almost entirely white. As with all damselfishes, the females lay eggs on the bottom while the males follow closely behind to fertilize them. When disturbed they make a chirping sound"
Kelleen says, "These guys are one of my favorites: I like pointing out the tiny ones and watching as they flit in and out of their protective homes. I also like approaching the adults and listening as they grunt in warning! We are used to listening for dolphins and whales underwater, but listen closer- these fish talk!"
The sounds of the Hawaiian Dascyllus have been described as "grunts", "chirps", or "pops", and when approaching a larger adult or a nest, divers can hear these sounds in a series of repetitive pops, along with aggressive darting from the defensive fish. A study by David A. Mann and Phillip S. Lobel recorded and analyzed these sounds, and found "Males produced pulsed sounds during the courtship behavior known as the signal jump, visiting by females (during pseudospawning), mating, aggression to heterospecifics and conspecifics, and nest preparation. Females made only aggressive sounds." Scuba divers, being not in the same species, will only hear the aggressive sounds.
Damsel Fish have one nostril instead of two! Hawaiian Dascyllus portrait by Robyn Smith.

Kama'aina? Endemic. Only found in Hawai'i and Johnston Island. They are very similar to another Damsel, the Threespot or Domino (Dascyllus trimaculatus), which lacks the neon-blue.
Size: To about 5" as adults. Juveniles are adorably tiny.
Depth: Around 30 feet- Adults like coral dropoffs for spawning, and juveniles like the protection of an antler coral or similar structure or animal.
White List? Yes. Damsel fish are generally popular in the aquarium trade because of their beauty and relative resiliancy, although Hoover warns, "One drawback is their aggressive nature...the strongest will often pick mercilessly on the others."

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