Friday, February 05, 2021

Green ropes and clumsy grabbers

Nothing in the biosphere is ever simple. It's all complicated, intertwined, inter-dependent, busy. Nothing is just one thing. Not even me, or you. Well, in some sense, you're a separate person, but really, you're (and I'm) a community, a city with billions of inhabitants. You wouldn't survive without your critters; they wouldn't survive without you.

You have to start somewhere. I'll start in my tank, with hermits. Hermits are messy eaters. They grab food with their pincers; awkward things, without the useful fingers and thumbs we have. Food gets transported to the first set of mouth appendages, spilling crumbs as it goes. These mini-hands break it up (spilling more, of course), and pass it on to the smaller mouth parts. And so it goes.

In the tank, I feed the hermits and crabs, and some of the larger anemones. And a busy community thrives because the hermits are messy eaters.

I was taking photos of the barnacles, trying to catch one with it's legs stretched out at full length. (They catch their food with those legs, remember.) I wasn't having much luck, but I processed a few of the photos and looked them over.

Barnacles in community

And there again, there are layers upon layers. And each layer has its story. 

The barnacles arrived on an oyster. Every now and then, I find on the beach a pile of empty oyster shells, usually up high above the tide line, sometimes near the remains of a bonfire. The leftovers of a human party? Or were they raccoons? It's usually too late to see tracks. A couple of times, in the pile, I've found a live oyster, forgotten by the diners. This one, in my tank, was one of those. It came with a planting of barnacles and mussels.

The oyster is a filter feeder. It brings in water from its surroundings (carrying with it fragments of hermit food), then spits it out, clamping the shell shut, then opening up again. The barnacles comb the water with their legs, catching smaller critters and hermit leftovers. The mussels filter the water, like the oyster does.

Look at the photo. Two barnacles are still alive. In the mouth of the one on the left, its coiled legs look like a roll of green rope.

Two barnacles are empty. Whelk snails bore through their armoured plates and eat the animal inside. In the few weeks the oyster has been here, half the barnacles have been eaten, as well as all but one of the mussels. The blue patch on the far left is an empty mussel shell.

Look again. on the sides of the barnacles, there are tiny tentacles reaching out into the water. These are two-tentacled tube worms. They somehow burrow into shells (barnacle, oyster, hermit crab, clam: any shell will do.) and reach out into the water with those two tentacles, capturing floating bits of food stuffs. I see four worms here. (The tangled fibers on the right are probably eelgrass roots.)

In front, a bit blurry, there's an orange-striped green anemone, also catching bits of hermit leftovers, and anything the oyster spat out.

And then, there's the sand. Not visible here, but certainly under a lens, there are crowds of amphipods, copepods, and yesterday's isopods, all busy keeping the sand clean.

And behind the anemone, on the left, look closely: there's a leg of one of the tinier hermits, the source, with his larger cousins, of most of the food the rest of the community harvests. Because they're messy eaters.

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Nada, nunca, en la biósfera es sencillo. Todo es complicado, enredado, complejo. Nada existe como una sola cosa. Ni tú, ni yo. En algún sentido, eres una sola persona, pero en verdad, eres (y soy) una comunidad, una ciudad con billones de habitantes. Sin tus comensales, no sobrevivirías; sin ti, ellos tampoco vivirían.

Hay que empezar en alguna parte. Yo empezaré hoy en mi acuario, con los cangrejos ermitaños. Los ermitaños son desordenados, descuidados. Agarran su comida con las pinzas, "manos" torpes, sin los dedos tan útiles que tenemos nosotros. Con ellas, mueven la comida hacia las primeras apéndices de la boca, dejando caer migajas en camino. Estas agarraderas rompen los pedazos de comida (tirando aún más) y los transportan a la tercera nivel del aparato bucal. Y así sigue.

En el tanque, les doy de comer a los cangrejos y ermitaños y al algunas de las anémonas más grandes. Y a base de eso, una comunidad amplia y variada vive, porque los ermitaños son descuidados.

Estaba sacando fotos de los bálanos, tratando de agarrar uno con sus cirros (patas) al agua, estirados a lo máximo. (Capturan su comida con esas patas.) Es difícil, y no me ayudó la suerte esta vez, pero abrí unas de las fotos y las examiné.

La foto: bálanos y su comunidad.

Y ahí, como siempre, had capas y capas. Y cada individuo tiene su historia.

Los bálanos llegaron aquí en un ostión. De vez en cuando, encuentro en la playa, bien arriba del nivel de la marea alta, a veces cerca de una vieja fogata, un montón de conchas vacías de ostiones. ¿Serán lo que dejaron un grupo de gente comiendo en la playa? O si no, ¿una familia de mapaches? Siempre ha sido demasiado tarde para encontrar huellas.

En unos de esos montones, he encontrado ostiones vivos, y los he traído a casa. El que ahora vive en mi tanque fue uno de estos. Llegó con su propia carga de bálanos y mejillones.

El ostión come filtrando el agua, capturando cualquier fragmento de comida que trae, y luego escupiendo lo demás, cerrando y abriendo su concha. En su lado, los bálanos cuelan el agua con sus cirros para capturar animalitos más pequeños y los restos de la comida de los ermitaños. Los mejillones filtran el agua, al igual que el ostión.

Miira la foto. Dos de los bálanos todavía viven. En la boca de aquel a la izquierda, se le ven los cirros, como una rueda de cuerdas verdes. 

Dos de los bálanos están vacíos. Los buccinos (caracoles carnívoros) taladran la concha y se comen el animal escondido adentro. En las pocas semanas que ha estado en el tanque el ostión, los caracoles han comido la mitad de los bálanos, y dejaron solo un mejillón con vida. La mancha azul a la izquierda es la concha vacía de un mejillón.

Mira otra vez. En los lados de los bálanos se ven unos tentáculos muy pequeños. Estos son tentáculos de gusanitos que viven en tubos; estos tienen dos tentáculos cada uno. De alguna manera, hacen agujeros en las conchas (cualquier concha; ostión, almeja, bálano, caracol; les da lo mismo), y de allí extienden sus tentáculos al agua, agarrando pedacitos de materia comestible. Aqí veo cuatro de estos gusanitos. (Las fibras enredadas a la derecha son raices de hierba zostera.)

Un frente, un poco borrosa, se ve una anémona de rayas anaranjadas, también ocupada en buscar comida flotante en el agua; los deshechos de los ermitaños y cualquier cosa que haya escupido el ostión.

Y queda la arena. No se ven aquí, pero si con una lente, se encontrarán muchos anfípodos, copépodos e isópodos como el de ayer, todos activamente limpiando la arena.

Y atrás de la anémona, a la izquierda; mira con cuidado; verás una pata de uno de los más pequeños de los ermitaños, el responsable, con la ayuda de todos sus primos, de proveer la mayoría de la comida de que vive la comunidad. Porque son tan descuidados.


6 comments:

  1. Your aquarium posts fascinate me; every time I read one I learn about some new animal (this time it was the tubeworms).

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    1. You might like this post from 10 years ago, with a video of one of these tubeworms catching food. YouTube doesn't like these old videos, and flashes the text away too soon. Sorry about that!
      https://wanderinweeta.blogspot.com/2011/02/its-living-tubeworm-video.html

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    2. This one's newer, but shorter. https://wanderinweeta.blogspot.com/2017/02/gone-fishing.html

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    3. How cool! Neat how much those tentacles are like conveyor belts, yet they don't get noticeably shorter; I guess they are passing the bits along from one section to another? And are the sparkly bits mica flakes in your sand?

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    4. I don't know if it's mica, or fragments of shell lining, which is also reflective.
      There's supposed to be a groove in the tentacles. An object in the groove, if the tentacle is vibrating, will move along as gravity pulls it. My son used to work designing belt systems that worked on this principle; quite effective, with no rollers or other moving parts, apart from the belt as a whole that vibrated. He made some as toys in our home workshop. I don't know if the worm uses this technique or some other.

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  2. I suppose you have to start somewhere - coincidentally, the opening words of my first book! I love the way that you see so much the details - and yes, we are all of us interconnected - in a sense we're all spun from one thread that stretches back billions of years...

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I'm having to moderate all comments because Blogger seems to have a problem notifying me. Sorry about that. I will review them several times daily, though, until this issue is fixed.

Also, I have word verification on, because I found out that not only do I get spam without it, but it gets passed on to anyone commenting in that thread. Not cool!