Feeding ecology and diet

Hemichordates may be either suspension- or sedimentfeeders. The latter, like Balanoglossus clavigerus, take in sediment and obtain nutrients from the organic matter contained

Acorn worms, such as Balanoglossus australiensis are named for their acorn shaped head. They dig a U-shaped burrow, and live there with only the head sticking out of one opening, eating bacteria, micro-algae, and detritus. (Photo by Animals Animals ©Joyce & Frank Burek. Reproduced by permission.)

Acorn worms, such as Balanoglossus australiensis are named for their acorn shaped head. They dig a U-shaped burrow, and live there with only the head sticking out of one opening, eating bacteria, micro-algae, and detritus. (Photo by Animals Animals ©Joyce & Frank Burek. Reproduced by permission.)

in it. The suspension-feeding adult hemichordates, as well as the filter-feeding tornaria larvae, gather their meals by generating currents with the cilia located on their bodies and drawing in organic matter. There is some uncertainty about the role their mucus plays in prey capture. Some scientists believe food sticks to the mucus-covered proboscis, and the cilia then beat in a pattern that draws the mucus and the food together to the mouth at the bottom of the proboscis. Researchers studying such species as Rhabdopleura normani, on the other hand, have found that normal feeding does not involve mucus; instead, the organism relies on the cilia to change direction in movements called local reversals and thereby directs food particles to its mouth.

Indirect-developing species have free-swimming tornaria larvae that live on plankton for weeks to months. Some species, like Saccoglossus horsti, have free-swimming larvae that obtain all their nutrition from their yolk, and within a few days take up the sessile (permanently attached) lifestyle. Studies of P. pelagica larvae indicate that their mucus may facilitate feeding, although the details are unclear and several alternative hypotheses have been suggested for the mucus.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Post a comment