hectocotylus | Okinawa Nature Photography

The spotty bobtail squid ( Eumandya parva ) is a small cephalopod found in the beautiful waters surrounding Okinawa. They are hard to find due to their small size. Persistence, patience, and diving with a buddy with good eyes will increase your chances of finding them.

Scientific name: Eumandya parva
Common Name: Bobtail Squid
Found: Ryukyu Islands
Habitat: Open water @ night
Average Size: 15mm – 25mm

Bobtail squid have eight arms and two tentacles used to capture prey. They have a two part parrot-like beak used for feeding. They primarily feed on small crustaceans free swimming in open water.

What’s really impressive about cephalopods is that they are masters of evasion. They are equipped with advanced mirroring cells. These cells can change shape and color to match their surrounding. These vibrant chromotophores are also used for communication and attracting a mate.

The bobtail squid has the ability to produce a large ink cloud (smoke screen) when in danger. This cloud of ink will confuse predators and give the squid a chance to escape safely.

Squid have wing-like fins used for precision movement through the open water. Their siphon is used for jet propulsion, allowing a clean getaway from predators.
They can also evade predators by covering up with sand to avoid detection.

I found this large Euprymna brenneri covering itself with sand to avoid detection. I have only seen two of these in the waters of Okinawa. A new species decribed in December 2019.

Mating season occurs in the summer months.

Look close and you can see the white bundle of spermatophores produced during the mating process. The eggs will be fertilized and attached to a safe location under a reef ledge. Tiny bobtail squid will hatch from their eggs in three weeks.

If you would like to learn more about the Cephalopods of Okinawa, check out my previous posts on the blue-ringed octopus, pygmy squid, pharaoh cuttlefish and the shell eating octopuses of Okinawa.

My Mission: To Document and Preserve the Wildlife of the Ryukyu Islands

This site is also designed to help people identify the beautiful animals of Okinawa, basically to serve as an online nature reference guide. If you would like to make a contribution to support my mission, please click on the donation link paypal.me/maketheswitch4nature

Your donations will help conservation initiatives as well as bring solutions to the worldwide pollution issues on our beautiful shorelines. Thank you for your support, Shawn M Miller.

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In the summer of 2018, I documented some exciting animal behavior underwater. While searching for the blue-ringed octopus in a shallow reef cut, I stumbled upon the elusive pygmy squid (Idiosepius sp). I first photographed the Ryukyuan pygmy squid back in 2012 and was excited to see another one. This undescribed pygmy squid is only 10mm-14mm in size. It can be difficult to get an acceptable photograph of it free-swimming through the water.

Its amazing how fast squid can change color to blend into the sounding background. Look at that camouflage.

The pygmy squid has defined white nodules on the posterior end of the mantle used for attaching to seaweed and rocks.

I took a few photographs of the tiny squid and it eventually retreated into fireweed (Aglaophenia cupressina).

The fireweed looks like a harmless piece of seaweed but its actually a dangerous stinging hydroid. The fireweed delivers a painful sting causing redness, irritation and infection.

I returned to the exact location a few days later in search of the pygmy squid. I found the fireweed but it was much smaller, as if it was purposely cut down. These fireweed colonies have been in the same reef cut for over six years. What could have caused this devastation? Was it possible that a Scuba Instructor cut down the fireweed colonies for the safety of their students? I mention this because the hydroids are in a high-traffic swim-through area, and some days literally hundreds of divers swim through this reef cut.

My first thought was someone cut down the fireweed but I was wrong. It was actually a brightly colored nudibranch named Tenellia yamasui (Hamatani, 1993). The fireweed was infested with juvenile nudibranchs feeding on it.

You would think that the nudibranchs would be conservative and keep some food for the future. The sea slugs devoured the entire fireweed.

Ever wonder what this stinging hydroid can do to your skin? To learn more about the dangerous animals and treatments, check out my post on The Hazardous Marine Life of Okinawa.

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Okinawa Nature Photography

沖縄自然写真 By Shawn Miller

Tag Archives: hectocotylus

Masters of Evasion – The Bobtail Squid of Okinawa

Ryukyuan Pygmy squids and hydroid-eating nudibranchs