I'm not the most observant person in the world when it comes to slithery slimey things, so imagine my surprise when I saw this Yellow-shelled Semi-slug (Parmarion martensi) crossing the walkway outside the lab, likely flushed out of the Kent Ridge forest by the heavy rain this morning.
This species is supposed to be a common native resident of parks and gardens in Singapore (and an invasive pest species in the US), but this is my first time ever seeing this species.
An opalescent nudibranch (Hermissenda crassicornis) glides elegantly along a kelp blade in the tidepools at Cannon Beach, Oregon. Nudibranchs are soft-bodied marine relatives of snails and slugs that have traded their shell for a more exotic defense--those tranquilly-billowing orange-tipped cerata on the opalescent nudibranch’s back are in fact filled with stinging cells they have appropriated from their prey. The opalescent nudibranch lives in the intertidal zone and down to a depth of 37m up and down the Pacific shore from Alaska to Northern California. The seemingly placid beauty of this ethereal creature belies its fiercely predatory and cannibalistic nature. Hermissenda crassicornis feeds primarily on hydroids and bryozoans, somehow untouched by the stinging nematocysts that these marine animals use for defense. The nematocysts pass unscathed through the opalescent nudibranch, migrating to the tips of the cerata on its back, where their vibrant orange serves as a visual cue to would-be predators of the potent venom within. Nudibranchs exchange gas throughout their entire body surface, so the cerata also serve to increase surface area for exchange. Many nudibranch also sport feathery plumes of gills. The name "nudibranch" means "naked gill." At the head of the nudibranch, two sensory tentacles contain both tactile and visual receptors. Posterior to this are the two upward-projecting rhinophores--olfactory tentacles that help to identify prey and potential mates. Nudibranchs are hermaphroditic but cannot self-fertilize--they must mate to reproduce. A curious observation is that though the nudibranch is hermaphroditic and therefore lacks competition for females, Hermissenda crassicornis is known to attack and eat other members of its species that it encounters if it is not ready to mate. There is an interesting video clip of this at themarinedetective.com if you’d like to see more. Thanks to Steve @intertidal_zone for opening my eyes to the presence of the nudibranch in our Oregon tidepools and for teaching me about these and other Oregon intertidal creatures. Check out his feed for beautiful photos and engaging writing about life on the Oregon coast.