Mosaic Longarm Octopus

The Abdopus abaculus, commonly referred to as the Mosaic Longarm Octopus or Mosaic Drop-arm Octopus, is a small species belonging to the group of pygmy octopuses. Scientifically identified in 1997 by researchers M. D. Norman and M. J. Sweeney, the species was first documented using samples from Zamboanga del Norte in the 🇵🇭 Philippines.

This octopus thrives in tropical marine environments at shallow depths, typically between 1 and 5 meters (3 to 16 feet). It is a benthic species, meaning it lives on the ocean floor. Physically, A. abaculus is quite small, with a mantle length that can reach up to 33 millimeters (1.3 inches) and a weight of around 21 grams (0.74 ounces). Its striking appearance features a color range from dark gray to dark purple, highlighted with spots that vary from cream to light purple.

A. abaculus is gonochoric, meaning it has distinct male and female sexes. The male engages in display behaviors to attract a female, and during mating, the male uses a specialized arm, the hectocotylus, to transfer sperm into the female's mantle cavity for fertilization. Following mating, both sexes typically die shortly after spawning and brooding. The life cycle begins with embryos hatching into a planktonic stage, where the young drift in the water column before settling down to a benthic lifestyle as adults.

This species is predominantly found in the 🇵🇭 Philippines but has also been reported in other areas such as 🇹🇴 Tonga and 🇯🇵 Japan. Reproduction involves the laying of eggs, each up to 2.4 millimeters (0.09 inches) in diameter. Overall, the A. abaculus is an intriguing species notable for its striking appearance and unique reproductive behaviors.