Description

Carapace: The carapace is medium brown, with ten pairs of longitudinal darker brown stripes that give it an overall brown look. These stripes are continued on the abdomen giving it a similar brown appearance. The same lines are usually present on the sides of the carapace but may be absent or replaced by brown speckling. 

The abdomen has a pattern that is a repeat of the carapace, in the same colours. It is intersected by a conspicuous white band on segment 1 and white spots on segments 4 and 5. 

The rostrum is a contrasting yellow but the antennae are grey. 

The chelae have yellow-green carpus and merus but the Pincers are dark brown, sometimes stippled with paler grey-brown. 

The chelate second legs are yellow-green. 

The walking legs are yellow, contrasting with the brown body. 

The tail fan has yellow scutes. 

Identifying Features 

This has the typical pattern of a pyjama shrimp, just the colours vary. The carapace, abdomen and pincers are brown with the rostrum, legs and tail dull yellow-green. 

It is very similar to the Yellow Pyjama Shrimp but can be distinguished by its plain brown, lightly stippled pincers. The Yellow Pyjama Shrimp has pale yellow pincers decorated with reddish lines. 

Similar Shrimps

We identify three main groups of Pyjama Shrimp based on colour. They differ consistently in colour, habitat and associations. Pair formation only involves individuals of the same colour form. 

The Yellow Pyjama Shrimp group, to which the Brown Pyjama Shrimp belongs, includes all forms with yellow or green legs, tail and rostrum and a pale ochre to dark brown carapace and abdomen. The Yellow Pyjama Shrimp itself may be confused with this species but is more grey with brighter yellow appendages and pale pincers. The primary distinction lies in ecology and shrimp associations. (There is also an orange form that belongs to this group). 

The Pink Pyjama Shrimp group (includes a grey type) is grey with pink extremities and can also be differentiated by habitat and associations. All grey forms are currently included in this designation although we have not recorded them forming mixed pairs with the pink form. 

The Red Pyjama Shrimp has a distinctively different dark red carapace and has different geographical distribution, habitat and associations. 

Taxonomy

This is one of the shrimps commonly grouped under the species name Alpheus ochrostriatus (itself an invalid name). The group can be split into four, possibly more, by colour, habitat and associations. These are the Yellow Pyjama Shrimp, the Pink Pyjama Shrimp, the Brown Pyjama Shrimp and the Red Pyjama Shrimp. 

Ryanskiy (2016) p6. has images of a similar-looking shrimp and gives the name Alpheus ochrostriatus, with the common name White Saddle Snapping Shrimp. Length up to 7 cm. 

He presents a second image, supposedly of the same species, but we would call it the Pink Pyjama Shrimp. 

We have not seen this shrimp form a pair with any of the other coloured Pyjama Shrimp species described on this website.