Description 

Carapace: Pale green-grey with 3 or 4 dark green bands on the dorsum. Both the light and dark zones are broken up by speckles. The dark bands extend indistinctly down the side of the carapace. Dark patch around the eye. These features are only seen in shrimps that have moulted recently otherwise the pattern is blurred or sometimes non-existent. 

Abdomen: The dorsum of each segment is bounded by dark green-grey forming a rectangle with a pale grey centre. There is a conspicuous white band on segments 1 and 4. Sometimes this may be yellow or bright orange, in which case the rostrum often has a rich red-brown colour. The lateral aspect has dark and light green blotches running through all segments. They may join up to form lines in which case the upper forms the lateral boundary of the rectangle seen in the dorsal view. 

The rostrum is grey-green and the antennae green. 

Chelae are light grey with dark green marbling not gathered into distinct bands, white or orange pollex and dactyl. 

The chelate second leg is blue. 

The walking legs are grey with yellow joints. 

The tail fan is beige with five scutes that are dark green with ill-defined yellow-green transverse bands or central patches. It usually has setae (hairs or bristles). 

Variation 

In shallow water where the silt around the mangrove roots is constantly washed by fresh seawater, the Pale Marbled Shrimp can look so clean and bright that we have questioned whether we are looking at a different shrimp. See Maude’s Shrimpgoby, Cryptocentrus maudae on the next page.

Identifying Features

Readily distinguished by its boldly marble patterned nippers that are distinctly blue-green and grey with white or orange tips. The grey green pattern on the carapace is often indistinct and dusty. This shrimp has a contrasting white bar at the junction of the carapace and abdomen. This bar may also be yellow or orange. 

Similar Shrimps

Green shrimp is freckled rather than banded, particularly on the carapace, and has distinctively bright green rostrum and antennae. 

Nomenclature

We are not at all certain about placing this shrimp in the ‘djiboutensis complex’. The markings are somewhat similar (not very) but the shrimpgoby associations do not overlap. The habitat is quite different except where the Pale Marbled Shrimp’s range extends to extremely shallow water. Even their goby associations and preferred niches are different. 

Ryanskiy (2016) p6. has images of a similar looking shrimp and gives the name Alpheus djiboutensis common name Djibouti Snapping Shrimp. Length up to 5 cm. Distribution Indo-Pacific; Red Sea, Vietnam, Philippines, Indonesia, Papua New Guinea. 

Ryanskiy’s image is similar to the brightly marked individuals found with Maude’s Shrimpgoby, Cryptocentrus maudae but is not really like the other Pale Marbled Shrimps we have found. His are more brown and strongly banded on the carapace. Ours are more green and poorly marked. 

Humann & DeLoach (2010) p85 has images of a similar looking shrimp and gives the name Alpheus species 6, common name Undetermined. Size to 4 cm. Indo-West Pacific also Japan and Hawaii. Greenish grey with blue highlights on abdomen, legs and claws. Some yellowish markings. 

There are images of the bright shallow water form of this shrimp (often identified as Alpheus macellarius) on several internet sites. It is usually with Cryptocentrus maudae, an association that we can confirm. 

The name Alpheus djeddensis-djiboutensis is of questionable status (Anker 2001).