Amphipods Rule!

Photos from UAB in Antarctica group on Flickr, related to this post
By Maggie
Posted on 02/14/07

… project activities these days. Chuck described making funnel traps for amphipods. For an entire Tuesday, my home office was a sweat shop as I with the aid of my old Singer sewing machine transformed slippery window sheer fabric into pillowcase-size collecting bags for amphipods. Six queen size pillowcase bags, 6 more bags of about one third size. James Taylor’s “me and my machine for the rest of the morning, for the rest of the afternoon…..” played over and over above the whine of a tired engine which slowly but faithfully punched needle and thread along the yards of fine meshed fabric.

Fortunately, this seamstress masquerade lasted just one day and admittedly the most taxing part of it was threading the ultra fine needle with eyes that don’t focus so well anymore on tiny objects!

The bags however are not ready for action. The finishing touches, flexible plastic coated wire cable that will hold the bag open and then twisted and closed, need to be handstitched on during the long 4 days on the ship to reach Palmer Station. To be sure, I and perhaps our team members will be kept in stitches during the voyage!

Future entries will describe how we use these bags in Antarctica. In the meantime, you may be wondering why we are putting all this effort into designer traps and bags?? In short it is because we believe that …..

Amphipods rule….

….the marine benthic communities in Antarctica.

You may also be wondering, just what are amphipods???

Amphipods are cousin to the more familiar crustaceans like lobster and shrimp. Generally smaller than their edible kin, most amphipods are 1- 40mm in body length. Those tiny sand hoppers or beach fleas encountered on sandy beaches right at the water line are amphipods.

Over 7000 species of amphipods have been described from primarily marine habitats, but freshwater and even some terrestrial representatives exist. You would be correct in assuming with so many species living in such different environments that there would be a lot of variability in their appearance.

Like all crustaceans, amphipods are covered by an exoskeleton (sort of a shell) made of a compound called chitin which is also used in the exoskeletons of some insects like ants and beetles. The body of a generalized amphipod is composed of a head, a tail, and 10 segmented portions between them (7 “thoracic” segments and 3 “abdominal” segments). Amphipods are laterally compressed like a shrimp which means that their bodies are taller than they are thick. (Other crustaceans are dorsoventrally compressed – that means flattened.)

Amphipod eyes (if present – deep living species and those found in cave waters may be blind or may appear to have one giant eye atop the head) are not stalked like the beady eyed shrimp. Most amphipods bear 2 pair of antennae on the head. The first thoracic segment bears complex mouth parts which differ greatly depending on the amphipods diet.

There are also two sets of distinctive thoracic appendages used for grasping onto things called gnathopods, and 5 sets of pereopods which assist in swimming along with the 3 sets of pleopods on the abdominal segments. The telson and uropods, comprise the tail end. Glad you asked??

I’ve posted three pictures of some of the pretty ‘pods’ as we call them for short. Gondogeneia (Gondo for short) is the largest of this trio, reaching a total body length of 25mm (about the length of a skinny jelly bean). Due to their size amphipods are referred to ecologically as mesograzers. Some species feed primarily on algae are thus called herbivores or mesoherbivores. Gondo however, is also known to eat smaller animals, so it is referred to as an omnivore.

Other amphipods in the Antarctic (over 800 species!) are detritovores, feeding on algal or animal debris; carnivorous amphipods prey on other animals; and nercophagous pods feed on animal carcasses. Those sand fleas you see hopping on the beach feed on the dead animals and seaweed washed ashore.

Amphipods rule…..

….often on algae as pictured. In our previous work, we have recorded as many as 300,000 of them per square meter of bottom in patches of their favorite macroalgal species - think about arranging that many skinny jelly-sized bean amphipods within a square made with 4 yardsticks (aka meter sticks)! We have also observed large numbers of amphipods on and in other sessile, attached organisms - like sponges.

It is this incredible abundance and the variations in feeding habits that have drawn our focus to how amphipods can influence the shape of benthic communities. We hope to discover some clues by enticing pods into our custom made funnel traps. Divers will gently pry loose attached seaweed and sponges without disturbing the associated amphipods and enclose the assemblage in our designer drapery sheer collecting bags for analysis back in the laboratory. Stay tuned for our next installment in the investigation of ….

Amphipods rule!

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