Friday, 19 September 2014

Ghost shrimp

The latest addition to my tank is a small group of Ghost shrimp (Palaemonetes sp.). I like the idea of having shrimp in my community tanks, and Ghost shrimp are both large enough to coexist with the fish I have, and cheap enough that I can afford to keep them in conditions where successful recruitment of offspring is unlikely.

Fish are most interesting if they're are active swimmers. The appeal of shrimp, on the other hand, lies in the fact that they don't move much. They tend to spend much of their time in one spot, feeding on whatever detritus or algae is at hand. Being translucent, Ghost shrimp may not be the ideal aquarium shrimp, but they make up for this limitation by being cheap enough to stock at relatively high densities. They also happen to be large enough to coexist with the fish I have in my community tank - Glowlight tetras, imperfectly identified Blood tetras, two species of Corydoras, some Otocinclus and several kuhli loaches.

I decided to use my algae issues as an excuse to add a few Ghost shrimp to my tank. After all, there tends to be a relationship between species diversity and stability in ecological systems. I can't say it helped (I would honestly be very surprised if eight shrimp - or fewer - could make any change in a 55-gallon aquarium, especially given less than a week to work at it). Not to mention that they are supposed to feed primarily on algae.

After a week there are between five and seven survivors. I found one shrimp dead the morning after I purchased them (the smallest of the group); I'm hoping the rest of them made it. I saw five of them together yesterday - that sets the lower limit on the number of survivors - but generally I only see two or three of them at a time.
Palaemonetes paludosus, the eastern Grass Shrimp.
Public domain image. Original image by Joseph Stansbury Rosin, cropped and sharpened by Kazvorpal.
The Ghost shrimp available in pet stores in the US appears to be Palaemontest paludosus, the eastern or riverine Grass shrimp. One of the most interesting things about these shrimp are that they apparently dig quite extensive burrows. Via The Aquarium Wiki
The Ghost Shrimp burrows to feed and digs its two to three foot deep burrow with the claws of the first and second legs. It uses these legs to draw the sandy mud backward and collect it in a receptacle formed by another pair of legs. When the receptacle is full, the shrimp crawls backward, reverses itself in a special turn around chamber and then deposits its load outside. The burrows are not permanent. A number of branches and turnaround chambers are found in the burrows and they have at least two openings to the surface. The shrimp use their pleopods to produce some circulation of sea water through the burrows. The pencil-sized openings of the burrows are typically in the middle of little piles of sand or sand with small pebbles.
This would suggest that tanks with coarse gravel bottoms may not be ideal for keeping these shrimp. It might also explain why I rarely see more than one or two of them at a time. It does seem hard for me to envision how such a small shrimp would build and maintain such an extensive system of burrows.

Female carrying eggs. Public domain image courtesy Vlad at The Aquarium Wiki.


Fern said...

Wow Ghost shrimps are very pretty.

Fern said...
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Ian said...

Yep, they are. But they tend to disappear amongst all the logs, rocks and vegetation.