I found this little creature at the LFS I worked at and acquired it when they shut down. I never knew what it was until I was able to snap a good photo of it in my aquarium. She's known as Bonellia Viridis AKA the Green Spoonworm! Not a very common hitchhiker but it's wide-ranging, found in the north-eastern Atlantic Ocean, Indian and Pacific Oceans, and the Mediterranean and Red seas.
"The same chemical plays a unique role in the worm's sexual differentiation. The planktonic, free-swimming Bonellia larvae are initially sexually undifferentiated. Larvae which land on unoccupied sea-floor mature, over the period of years, into adult females. Most larvae, however, come in contact with the bonellin in the skin of an adult female—its body or its roving, bonellin-rich proboscis—and are masculinised by this exposure. The chemical causes these larvae to develop into the tiny males, which cling to the female's body or are sucked inside it by the feeding tube, to spend the remainder of their lives inside her genital sac, producing sperm to fertilize her eggs, reliant on her for all other needs.
The sex of a Green Spoonworm is thus determined by external, environmental factors (the presence or absence of bonellin), not by internal, genetic factors (chromosomes), as is the case with most other sexually-differentiated organisms. This environmental sex determination helps Green Spoonworm populations respond to the availability of burrows." - Wikipedia
And here's a video of it in my hand:
Green spoon worm - YouTube
"The same chemical plays a unique role in the worm's sexual differentiation. The planktonic, free-swimming Bonellia larvae are initially sexually undifferentiated. Larvae which land on unoccupied sea-floor mature, over the period of years, into adult females. Most larvae, however, come in contact with the bonellin in the skin of an adult female—its body or its roving, bonellin-rich proboscis—and are masculinised by this exposure. The chemical causes these larvae to develop into the tiny males, which cling to the female's body or are sucked inside it by the feeding tube, to spend the remainder of their lives inside her genital sac, producing sperm to fertilize her eggs, reliant on her for all other needs.
The sex of a Green Spoonworm is thus determined by external, environmental factors (the presence or absence of bonellin), not by internal, genetic factors (chromosomes), as is the case with most other sexually-differentiated organisms. This environmental sex determination helps Green Spoonworm populations respond to the availability of burrows." - Wikipedia
And here's a video of it in my hand:
Green spoon worm - YouTube
