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 dont eat Aiptasia but are 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. In a picture of 1 of each species next to each other 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.
True L. wurdemanni has always eaten Aiptasia,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.
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.
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.
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.
