‘Transparency’

Unidentified shrimp on unidentified Ricordea polyp

Music, Video, and Aquarium

2010 Coral Morphologic

In the second installment of the ‘Unidentified Ricordea Shrimp’ series we find the (previously featured) unidentified Ricordea shrimp upon an unusual host. While it is is most certainly on a Ricordea polyp, we are not convinced that it is in fact Ricordea florida. Over the years, we have noticed several key morphological and physiological differences that suggest that there are two genetically distinct morphs of Ricordea florida. For practical purposes, we have been referring to the morph of Ricordea seen here (under 470 nm light) as ‘inshore ricordea’.



In the Florida Keys, this morph can be found less than a mile offshore in shallow water amongst macroalgae, patches of sea grass, gorgonians, and small coral heads. In this sepia-colored aquascape, you will find the olive-green colored ‘inshore ricordea’, frequently dusted with sand to enhance its camouflage. Occasionally a neon lime-green color morph will be encountered, but for the most part the ‘inshore’ morphs are considerably less colorful than their cousins living further offshore on the reefs. Beyond a simple difference in coloration, the ‘inshore’ morphs are less colonial than their ‘offshore’ counterparts, living solitarily or in small groups. When they are encountered in colonies, the individual polyps tend to be spaced further apart from each other than the ‘offshore’ morphs that live in a jigsaw-like carpet of neatly interlocking polyps. Frequently the hypostomes (the volcano-like opening to the mouth) of these ‘inshore’ morphs are noticeably rigid; something not present with colorful ‘offshore ricordea’. The surface pseudo-tentacles of the ‘inshore’ morphs are often elongate and appearing a bit ‘raggy’ as compared to the uniformly pearl-shaped pseudotentacles of of the ‘offshore’ Ricordea. And while it seems possible that these morphological differences could be chalked up to simple adaptation to differing environments, the argument is weakened by the fact that ‘inshore’ morphs are also found offshore in the same niches as the ‘offshore’ morphs. However, the smoking gun of the genetic distinction might be the observation on two consecutive years that the release of planula (larval offspring) occurred almost exactly a full moon apart.

In the video you’ll notice a swatch of fluorescent magenta color on the surface of the oral disc. This is an unusual trait for a Caribbean Ricordea, but is not uncommon amongst the Ricordea yuma that hail from the Indo-Pacific.

Also featured in the the video is the unidentified shrimp that lives commensally on Ricordea polyps. Unlike the other commensal anemone/ corallimorph shrimp (Periclimenes pedersoni, P. yucatanicus) that are active fish cleaners, this shrimp moves considerably less. In fact it is nearly invisible. The transparency of this shrimp is such that if you look carefully in the middle of its abdomen, you’ll notice its beating heart. Even the fluorescent pink ring around the edge of the polyp’s mouth is visible through the shrimp’s tail.

We recently sent three more specimens of this unidentified Ricordea shrimp to Dr. Richard Heard, a world renowned shrimp taxonomist, at the University of Southern Mississippi’s Gulf Coast Research Lab. We look forward to his determination of species-hood in the near future.