Sailfin Shrimpgoby
Amblyeleotris randalli
Sailfin Shrimpgoby
Amblyeleotris randalli
Hoese and Steene, 1978
Description
Body design
A medium-sized shrimp, 12 cm in length, white with 7 narrow, bright orange bars along its body. These are all parallel save the first, which runs from the lower margin of the eye to the angle of the jaw. The second bar crosses the operculum, the third, fourth and fifth are below the dorsal fins, the sixth lies on the midpoint of the caudal peduncle and the seventh is a crescent-shaped bar at the base of the caudal fin with extensions along the upper and lower margins. All the bars cross the dorsum to join the corresponding bar on the other side, In the case of the first bar forms a dorsal bar between the eyes
There is a barely perceptible orange spot behind the eye and even less distinct blotches forming vertical rows along the body are described.
Fin design
The first dorsal fin is large and striking. It is beige with a white edge and irregular white spots surrounding a white-edged basal black patch at the level of the third lateral bar of the body pattern.
On the second dorsal fin, the pattern is repeated with smaller basal dark patches centred on the fourth and fifth body bars and the pale markings running more longitudinally, sloping downward and back but the whole pattern is less defined so the fin can appear translucent.
The pelvic and pectoral fins are transparent with a pale blue-green. The anal fin is blue with a purple margin and a pale leading edge. The caudal fin is transparent.
In juveniles, the first dorsal fin is disproportionately large, with a reduced number of spots.
Diagnostic features
The flamboyant dorsal fin is unique among shrimpgobies.
Similar species
None
Taxonomy
Other common names: Randall’s Shrimpgoby
Type description Hoese and Steene (1978) Rec. West. Aus. Mus. 6(4)
Holotype from the Philippine Islands, Paratypes from Guadalcanal, New Britain, Admiralty Islands, Palau, Ambon.
Natural History
Habitat
Variable depth and habitat 5 to 35 metres. From the outer reef front to the sheltered fringing reef.
May be found on flat rubble, sand between scattered small coral rock outcrops on patch reefs, and also on black sand slopes.
Though this is the usual habitat we have also seen them at 30 m on sand with small coral rock fragments in parallel rows on the seaward side of Ribbon Reef #3. The Yellow Pyjama Shrimp is the partner in this habitat.
Natural History
Behaviour
When approached or while being observed this goby repeatedly raises and lowers the first dorsal fin in a nervous fashion. The repeated appearance and disappearance of a large eye probably disconcerts the potential predator.
The response to intrusion by other gobies is a full-on open-mouthed threat display which is all the more dramatic for the size of the dorsal fin.
Habitat
Depth Range 15 to 48 metres, mostly between 10 and 30 metres, usually in the sandy base of small caves or overhangs of high-profile reef slopes. May be on unstable-looking sand slopes between rocky outcrops, but still on high-profile reefs.
There is not much sand in these locations and the burrow is constructed close to a side wall with relatively large coral fragments. Although the caves are small it is common to find more than one pair in residence. This may result from a lack of suitable sites or because there is little current to carry away all the planktonic stage shrimps and gobies so they settle nearby.
Distribution
Published distribution:
Indonesia and the Philippines north to the Ryukyu Islands, south to Great Barrier Reef east to New Caledonia and Fiji.
Roger Steene photographed the species off Cairns (in type description 1978)
Our records:
Solomon Islands: Ndende, Nggella Islands and Kolombangara Island.
Associated Shrimp species
Associated Shrimps (two shrimps)
Usual association
Sandy Snapping Shrimp, Alpheus species 12
Occasional association
Yellow Pyjama Snapping Shrimp, Alpheus ochrostriatus