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Peppermint Shrimp

By Stephen Hopkins and Keith Redfield. Posted to Reefkeepers emailing list, Tuesday 2nd November 1999.

Keith Redfield

There are 2 similar species, one nearly indistinguishable.

Rhynchocinetes spp (there are many but most reference uritai) is also known as the "Camel" shrimp and has a highly pronounced hump. They eat Aiptasia but are also confirmed coralivores.

Lysmata rathbunae is found off eastern Florida (as opposed to the largely Carribean/Gulf L. wurdemanni ). About the only external difference between the two is tail-fan patterning, and that is subtle. I have a picture of 1 of each species next to each other and in that context, the differences are quite apparent, but in an LFS it would be difficult to tell. Basically L. rathbunae has a darker tail fan, with no visible striping, and a darker, more opaque body. L. rathbunae has no interest whatsoever in Aiptasia in my experience. I am not a taxonomist, and these are my lay interpretations of readings on the subject, as well as personal experience watching both varieties (or what I think are both varieties) in my tanks.

True L. wurdemanni has always eaten Aiptasia IME, but it is fairly localized to their territory (about 1sq foot), so you need enough shrimp to cover the tank. It is reasonable to suspect that anything that will eat one Cnidarian will eat others as well, and their have been reports of L wurdemanni eating coral. I've not seen that, but I have never kept SPS much.

I believe much of the debate on their abilities is simply mis-identification (or overly well-fed shrimp -- they do not prefer Aiptasia over other more readily available foods). L. rathbunae are quite common in the trade, as they are collected in lobster traps in droves.

Tank raised L. wurdemanni are now available commercially via ORA. It would be nice if they grow them out on Aiptasia, but I doubt it.

Stephen

I have been laboring for months to learn how to raise peppermint shrimp. The good news is that I have several hundred shrimp about an inch long which were raised from egg. The bad news is that I probably have ten times more time and supplies invested in them than they are worth.

So, you can imagine the horror when reading Keith's about the two species which are easily confused. But Keith's description was not good enough to tell the two apart without having one of each in hand. Today I finally made it to the library and dug up Austin Williams book on the decapod crustaceans of the Atlantic. He provides a very simple and non-subjective way to tell the two species apart, to wit:

Lysmata rathbunae - rostrum reaching as far as, or beyond, end of antennular peduncle; antennal scale 5 times as long as wide.

Lysmata wurdemanni - rostrum reaching not much, if at all, beyond second article of antennular peduncle; antennal scale less than 4 times as long as wide.

Yeah, Greek huh?? The book has nice line drawings to show the difference but let me attempt to explain. The ''rostrum'' is that sharp horn-looking projection on the top of the head which protrudes out the front like a serrated spear. Lysmata have three sets of antennae, and where the two front pair of antennae join is the end of the ''antennular peduncle''. The ''second article of the antennal peduncle'' is the second joint in that appendage the antennae arise from. The ''antennal scales'' are two flat blade-like projections sticking out the front of the head. They seem use these blades to help steer themselves when swimming.

So, if the end of the rostrum spear sticks out as far as where the front two pair of antennae join together, then it is a Lysmata rathbunae . If the tip of the rostrum does not reach as far forward as the point where the first two pair of antennae join, then it is a Lysmata wurdemanni . The antennal scale lengthwidth ratio is difficult to determine without catching the shrimp and measuring carefully, but the the length of the rostrum relative to the base of the front two pair of antennae is pretty much fool-proof.

While Williams spends most of several pages describing the anatomy in cryptic detail, he also provides some interesting comments which are excerpted below.

L. rathbunae

  • Variation - There are 2 varieties of L. rathbunae with the most obvious difference being the number of rostral teeth (number of serrations on that spear).
  • Habitat - Sometimes from sponges; the typical from generally occurs from 13 to 119 meters but the form with more rostral teeth generally occurs in depths of 9 meters or less.
  • Known Range - Range of the typical form is SE Cape Fear, NC , east coast of Florida to Yucatan. The range of the form with more numerous rostral teeth is Bermuda, Miami and Venezuela.

L. wurdemanni

  • Variation - There are also two forms in this species and they too are most easily differentiated by the number of teeth on the upper margin of the rostrum, the thickness of the second leg, and other stuff.
  • Habitat - Commonly found on stone jetties or AMONG HYDROIDS growing on piles or buoys, or in sponges. The EMPHASIS is mine but it may provide a clue to the food preferences of this species.
  • Known Range - Great Egg Harbor NJ to Port Aransas TX; Surinam; French Guiana; Mamanguape and Sao Paulo, Brazil
  • Remarks - When approached by a spiny boxfish or filefish, this shrimp begins rhythmically rocking to and fro; ascending vertically in a peculiar walking motion, it mounts its ''host'' and begins picking off parasites. The shrimp will swarm over the fingers of a person, picking at cuts and dead skin.

Mine turn out to definitely be L. wurdemanni and are probably of the typical form. Mine eat every small anemone in sight.

Created by liquid
Reefs.org
Last modified 2006-11-24 18:40
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