ASK THE EXPERT! Magnificent Shrimps Neville Coleman

 ASK THE EXPERT?

MAGNIFICENT SHRIMPS

Just when you think its all sorted out, another expedition, or a friend comes along with more photographs resulting in more questions and more investigation.
 
The facts are that we really know so little. If my collected and cross-referenced species over the many years have proved difficult for the experts to effectively sort out, the difficulty for photographers and naturalists has been decidedly more confusing.

In many of the identification guides of the past, authors or compilers have selected a single photo to illustrate the species, rarely giving any indication of sex of the species, or declaring if it was a day time or night time shot. (Some common species with night colours shown as new species?). No consistency of selection has been attempted, with dorsal and lateral perspectives being used in different books with no idea of whats required to actually identify the species.

Then there is the question of comparison.  To really compare day time colour patterns the shrimp needs to be photographed from a dorsal perspective with the tail flared. Unfortunately, most commensal Anemone Shrimps of the genus Periclimenes spp. do not remain still.  They continually rock from side to side, forward, backward and up and down, hardly enabling a consistent dorsal image to be taken by any but the most patient and dedicated photographer.

If there are 10 or 20 specimens (males, females and juveniles) inhabiting the same Sea Anemone it is even more difficult to organise consistent imagery of each example. It is difficult enough trying to sort out some when dorsal comparisons are available, but when attempting to compare a dorsal image with lateral image in a book, guesses become the norm.

Magnificent Shrimp

Ancylomenes magnificus

At one time this once very distinctively coloured, behaviourally consistent shrimp with a single type of associate host was easy.  Today, there is more than meets the eye.

In the early years of underwater recording the magnificent shrimp was only observed on or around tube anemones Cerianthus sp. which were generally associated with sand, mud or rubble bottom. In general, the shrimp kept its nippers in front of its head appearing as if its arms were folded. The entire area forward of the white line joining the eyes was light blue and the shrimp rocked from side to side.

Since 1996, expeditions across the Indo-Pacific have shown that this shrimp has been observed in association with Tube Anemones, Sea Anemones, Upside down Sea Jellies, Stony Corals and Sea Pens. It also appears that there may be several species or a complex of sibling species ranging across the Asia/Indo-Pacific region.

Mature female Magnificent Shrimp Ancylomenes magnificus? with distinctive purple edges to the dorsal hump (day time) and two males. 18m, Milne Bay, Papua New Guinea.
(Photo Neville Coleman) 

Typical male Magnificent Shrimp with standard day time colour pattern. 
Loloata Island, Papua New Guinea.
(Photo Neville Coleman)