The bluestreak cleaner wrasse (Labroides dimidiatus) is one of several species of cleaner wrasses found on coral reefs in Maldives. Like other cleaner wrasses, it eats parasites and dead tissue off larger fishes' skin in a mutualistic relationship that provides food and protection for the wrasse, and considerable health benefits for the other fishes.
Distinctive Characters: Dorsal fin with 9 spines and 10-11 rays. Anal fin with 3 spines and 10 rays. Pectoral fin with 13 rays. Body depth 4.1-4.7 in standard length. Small scales on cheek, opercle and nape. Lips thick, the lower strongly bi-lobed. Caudal fin truncate to slightly rounded.
Bluestreak cleaner wrasse's facts
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Bluestreak cleaner wrasse (Labroides dimidiatus) enters the mouths and gill chambers of some of the larger host fishes in its cleaning operations. Also establishes “cleaning stations” on the reef to which host fishes come for its services.
Bluestreak cleaner wrasse habitat
This species inhabits coral rich areas and subtidal reef flats to seaward reefs to depths of at least 40 m. It is widely reported to be a monandric hermaphrodite but further confirmed to display bi-directional sex-change, exhibits socially controlled sex reversal and lives in single-male, multiple female social groups (Kuwamura 1984, Sadovy and Cornish 2000, Kuwamura et al. 2002, Sadovy de Mitcheson and Liu 2008). Males exhibit territoriality and the largest, oldest individual is a male which dominates all the females in the group (Robertson 1972, Nakashima et al. 2000).
It feeds on crustaceans ectoparasites and mucus of fishes which gather at specific cleaning ‘stations’ for attention (Pott 1973). Males and females are the same in colour, juveniles are black with a single blue stripe running from snout to the upper part of caudal fin.
It is active in daytime and is reported to be able to produce a protective mucous cocoon at night. Seasonal fluctuation of the activity rate has been observed with almost all individuals always active during late spring and early summer (Kuwamura 1981).
In Japan, spawning occurred within 4-5 months of the year, from late May to early September. Larvae of about 1.8 mm in total length hatch at 30 hours after spawning (Kuwamura 1981).
This species is monochromatic, spawns in harem. Spawning ascent distance was about three m with rapid ascending speed. Spawning activities were seen in March, May, June and November at Enewetak Atoll, Marshall Islands (Colin and Bell 1991). The size of eggs is approximately 0.64 mm and spherical in shape. Eggs contained multiple oil globules
Maximum size of species has been recorded at 22 cm (TL) in New Caledonia and maturity is reached at a size of about six cm TL (Kuwamura 1981, M. Kulbicki pers. comm.). All of the larger adults have an almost completely developed ventroanterior hook in the caudal fin. Maximum lifespan is estimated to be four years (Allsop and West 2003) and minimum population doubling time is approximately 1.4-4.4 years (Froese and Pauly 2008).
It shows cleaning behaviour, which only occurs during the day and particularly in the early morning (Grutter 1996). In captivity it is affected by abundance and size-frequency distribution of the monogenean parasites on the host of fishes, which was more pronounced on larger fish than on small fish (Grutter et al. 2002). It spends 60 to 154 more times cleaning larger fishes (> 12.5 cm SL) than medium (9.5 to 12.5 cm SL) or small sized fish (< 9.5 cm SL). In the Great Barrier Reef, it was found to spend 256 +/- min per day cleaning 2297 +/- 83 fish (Grutter 1996) from over 132 species (Grutter and Poulin 1998). In New Caledonia, it spent 26% of its time inspecting a large number of fish (59.5 +/- 5.1 per 15 minute) (Grutter 1999).
It consumes a large number of parasites (1218 +/- 118) each day or 4.8 +/- 0.4 parasites per minute (Grutter 1996) and most of the prey items were juvenile gnathiid isopods (Grutter 1997). The biomass of gnathiids in the diet in New Caledonia was lower than at Lizard Island, but higher than at Heron Island, suggesting that the role of gnathiids in cleaning behaviour is variable (Grutter 1999).
At One Tree Lagoon on the Great Barrier Reef, overall mortality during first year for L. dimidiatus was 50%, juveniles do not shelter within the substratum and displayed relatively high mortality over the first twelve months (Eckert 1987). The average annual mortality ofL. dimidiatus was 11.1 +/- 2.2 %.