Slugs, seaweed shrimp and suckers

  Elysia 

Shells evolved as one (usually) effective means of defence for the soft-bodied wormlike creatures known as molluscs or more commonly, snails. But these costly investments of calcite (which can trigger an arms race of millennial proportions with crabs) are often discarded when a population of animals acquires through the emergence of novel structures and survival strategies new traits that render the hard coils redundant, even if a trace of their heritage remain embedded in the bodies of some shellless scurriers.

Sea slugs and their kin the nudibranches have ditched a hard home altogether and entrust their safety to biochemical arsenal oft obtained second-hand via the ingestion of hydroids and other sessile cnidarians whose stinging nematocysts are redistributed undischarged over the nudibranch's body. The slugs known as sap suckers also practice recycling, although their choice of food offers a more passive form of protection. Having pierced and sipped the contents of their algal feast, the chloroplasts turn the animals into the shade of their sustenance, and at least one species has somehow incorporated algae genes into its genome, giving hope to dreamers of horizontal gene transfer who hope to one day design a population of photosynthetic people.

  seaweed shrimp 

It seems to be the season for Bryopsis, a filamentous macroalgae that appears as thick clumps of thin green needles. The algal boom brings to shore a fresh batch of Elysia ornata from their pelagic larval forms as well as even smaller sapsuckers that mimic their food in both colour and form. Often the feathery strands look as if bits of dust or debris were trapped in them. But a closer glance may reveal that these minute specks have a pair of busy antennae and barely perceptible legs that cling tightly to the weed. There doesn't seem to be any local studies on these animals, but they are probably amphipods, possibly in the family Caprellidae, otherwise known as skeleton shrimps. Resembling tiny stick insects or praying mantids, caprellids congregate in large masses on various substrates from seaweed and sea stars to hydroids and gorgonians. What drives the formation of these aggregations and their phenology? How do they fend off predators when all they seem to do is hop and hide behind flimsy fronds? How do they breed and disperse to suitable habitat? But tis' all moot when their shores are dredged and dismantled for private pleasure and pernicious profit. But unlike their more charismatic reefmates, these overlooked arthropods will at least be spared the fate wrought by wildlife rescuers poachers who would justify their collectivitis with the plea of false passion, sparing neither clownfish nor croc...