Shy Polly

In the sand at the bottom of my aquarium, there lives a polychaete worm. I don't know how old she* is; I saw her first months ago; then she was just a few inches long. The last time I took her out of the sand, cleaning the tank, she was around 6 or more inches long. Hard to measure, because she squirms around constantly, trying to bury herself again. She's a shy critter, rarely shows her face above the sand, and at the least movement nearby, instantly retreats.

Sometimes she tunnels close to the glass. Then I drop some goodies; shrimp pellets usually, nearby, and sit watching, hoping to see her come out to grab a pellet. Usually, she's too fast for me, but I caught her on camera last week.

Looking for that shrimp pellet

Fat, isn't she? This is just about 1 inch at the head end. The rest stays under the sand unless she's really hungry and the food is far away.

The worms are segmented, like our common earthworm, but each segment has a pair of "paddles". Here you can see 6 of these paddles, each with from 3 to about 6 "fingers". 

On the head, she has four eyes and a collection of antennae and palps. And a big mouth, that she can open wide to grab a pellet as fat as she is.

Wide mouth and flexible jaw.

While I watched, she tentatively eased out, waving around to smell where the food was, retreating several times because a small crab walked by. She found the food and opened her mouth wide, wide, grabbed the pellet and disappeared into her tunnel.

When I checked an hour later, she'd filled in the tunnel.

*These worms may be male or female: I don't really know which this one is, but since I've named her Polly (for polychaete, which means "many bristles"), I give her female pronouns.

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Bajo la arena en mi acuario, vive un poliqueto, un anélido común en nuestras playas. Cuando lo vi por primera vez, hace unos meses, medía unos cuantos centímetros. La última vez que la saqué del tanque para hacer la limpieza, ya medía 15 cm. o más. Es difícil medirlo, ya que continuamente se retuerce, tratando de enterrarse otra vez en la arena. Es un animal muy tímido; pocas veces sale a la superficie, y al notar cualquier movimiento, rápidamente se vuelve a esconder.

A veces hace sus túneles cerca de la pared de vidrio. Entonces, coloco un bocadito de camarón cerca. Y me siento a esperar. Muchas veces sale; apenas veo un tentáculo cuando se espanta y desaparece. Pero la semana pasada logré capturarlo con la cámara.

Es un anélido con segmentos, como los de la lombriz de tierra común, pero en cada segmento tiene un par de parápodos (como patitas) con extensiones, de 3 a 6 o más, los que usa para nadar, y también sirven para respirar.

En la cabeza tiene cuatro ojos, varios tentáculos y órganos de tacto. Y una gran boca, que se abre a todo lo ancho del animal.

Mientras miraba esta vez, salió al agua, meneándose para olfatear la comida, regresando varias veces a su túnel cuando pasó cerca un cangrejito. Encontró la comida, abrió la boca bien grande, agarró el bocado y se desapareció.

Cuando pasé una hora más tarde, había rellenado su túnel.