Question of the Month

FEBRUARY: What is the weirdest creature in the Estuary and why?

Your Response?

Estuary's Question of the Month: What is the weirdest species in the Estuary and why?

Response #1: The bug-eyed, fat-faced, glowing midshipman
By Bruce Herbold

“Plainfin midshipmen are a pretty weird fish. They’re named after the most junior officers in the British Royal Navy, who worked and berthed amidship between the mizzen and main masts. The outstanding feature of these officer’s uniforms were the brightly polished buttons, but the corresponding dots on our estuary fish don’t need elbow grease to shine. They’re ‘photophores’ that glow in the dark. What are photophores for? Some claim that the lights help these fish attract prey or make them blend into the starlit ocean, but most of the time midshipmen stay half buried in the ocean floor ooze with their pretty buttons invisible. To add further mystery, this species doesn’t make its own glowing chemical, luciferin; it comes from the kind of plankton they eat. And some populations live in places without this kind plankton, so they don’t glow, but they seem to do fine. Even more mysterious is the noticeable noise made by the mating midshipmen (also known as ‘humming toadfish’). When Sausalito houseboat residents first noticed this loud, constant, humming from dusk until dawn, theories abounded: Secret military sonic weapons? Involuntary experiments in sleep deprivation? Illegal sewage pumps to escape the evil Clean Water Act? CIA spying techniques? But, it was our horny hero the plainfin midshipman calling to his love.  Courting male midshipmen create nests in the intertidal zone and start their boring concerts, vibrating their muscles against their swim bladder to attract females. The muscles used are among the most rapidly moving muscles of any vertebrate. For years, the good people of Marin celebrated their noisy weird friend with the Sausalito Humming Toadfish Festival.”

 

 
Bruce Herbold is a fish biologist and consultant since retiring from US EPA in 2013. He also enjoys Scottish country dance and rock and roll drumming.

Top Art: Brennan Greedy

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