crustacean

Seashore Critters

The beach may be a nice place to visit, but you wouldn’t want to live there. Windy, hot, dry, barren and occasionally flooded by seawater, it’s a hostile environment for small animals. And yet there are some species that manage to make the beach their home. I spent a day at Mōwhanau recently with children from Brunswick School, turning over driftwood and logs and looking for interesting critters.

1. hopper

A common beach sandhopper (Bellorchestia quoyana), when examined closely, reveals its crustacean nature.

Photo: Crispychipp / Wikimedia Commons CC-BY-SA

Sandhoppers are the most abundant denizen of the beach. Under every piece of driftwood or seaweed is a multitude, which spring away or scurry down burrows when disturbed. These little creatures, properly known as amphipods, are actually crustaceans, not insects. They are cousins to crabs, crayfish and even the slaters in your garden. Like all crustaceans, they breathe through gills which they have to keep moist. Most of the roughly 10,000 species live in the sea, but amphipods can be found in any damp environment. Some Southern Hemisphere hoppers even live far from the coast in forest leaf litter.

2. log

A log, like this one found on Mōwhanau Beach, is like a tiny oasis, providing shelter and food for a whole community of invertebrates
Photo: Whanganui Regional Museum

 

On the beach amphipods burrow down to damp sand during the day and come out at night to feed on anything the tide has washed up. Close up, they resemble tiny humpbacked shrimps, ranging in colour from dark grey to pinkish-orange, and have powerful hind legs for jumping. Sandhoppers are an important part of the beach ecosystem, not just as food for larger animals, but as scavengers that break down seaweed and carry those nutrients as deep as 30 cm into the sand.

Another creature found under beach logs is the native seashore earwig (Anisolabis littorea). These are flightless, and much larger than the introduced European earwigs in your garden. Their Māori name, matā, is also the word for obsidian – black volcanic glass – because they’re similarly shiny and black.

Seashore earwigs are omnivores, feeding on seaweed or catching amphipods with their nippers. Unlike most insects, they take good care of their young; after mating, the female drives off the male and guards her clutch of eggs and helpless babies. Once the baby earwigs get large enough to fend for themselves, all bets are off. They can flee the nest, eat each other, or eat their mum (and she’ll happily snack on them if they try). Female matā have long straight nippers while males have curved asymmetrical ones.

3. earwig

The native seashore earwig or matā (Anisolabis littorea) is a beautiful glossy black creature found under beach debris all around Aotearoa
Photo: Lisa Bennett / NatureWatchNZ CC-BY-NC, with permission

Although they look fearsome, curving their pincers over their back like a scorpion, I’ve handled earwigs for years and never been nipped. The kids from Brunswick School were initially cautious, but when I showed them how you can gently let a big coastal earwig crawl from hand to hand, they all wanted to try.

The “ooh yuck!” response when presented with a creepy-crawly is not innate in children, but learned from their parents, peers and authority figures. There are native invertebrate species going extinct right now. Voters don’t care because bugs are “yucky”. Museums like Te Papa and Puke Ariki are putting on insect exhibitions to help fight this perception. If we adults are frightened of harmless little insects, it’s not the insect’s fault. We need to get over our irrational fears, model good behaviour for kids, and, on our next visit the beach, turn over some logs with them and see what we find.

 

Dr Mike Dickison is Curator of Natural History at Whanganui Regional Museum.