VARIATIONS IN CLIENT BASE WITH SIZE AND MATURITY IN THE BLUESTREAK CLEANER WRASSE LABROIDES DIMIDIATUS

Introduction:

Bluestreak cleaner wrasse participate in a cleaning symbiosis with client species, receiving nutrition from the removal of ectoparasites, mucus and dead tissue from the surface of the fish. Although this has previously been assumed to be a mutualistic relationship, with the reduction in parasites increasing client fitness, this has yet to be proved conclusively; it is possible that this interaction may actually represent behavioural parasitism on the part of the cleaners (Grutter, 1999).

The cleaner station comprises a focal area, where the majority of the activity takes place, surrounded by a larger domain, through which the cleaner wrasse may swim to attract clients. This territory may be patrolled either singly or as a pair; occasionally multiple wrasse occupy the same area.

Their distinctive colouration is thought to play a role in client enticement, together with a characteristic dance. Client fish swim into the station and will often pose to solicit cleaning, typically adopting an immobile head or tail stand position which may be species specific. This may result in a cleaning event, recognised as oral contact between the cleaner and the surface of the client, the outcome of which is assumed to be removal of ectoparasites and other material.

There is much inter-specific variation in tendency of fish to pose; however, this is unrelated to the probability of being cleaned. Likelihood of posing also appears to be unrelated to body size of trophic type, refuting the hypothesis that posing may be a form of appeasement by piscivorous fish that represent a threat to the wrasse.

Intra-specific variation in tendency to pose seems to indicate that for a particular species, posing increases the probability of being cleaned (Cote et al, 1998).

It is possible that tendency to pose may instead be related to attractiveness of the client to the cleaner fish. It is thought that attractiveness is determined by several factors, and is the basis for the observed selectivity of the cleaner wrasse. The most crucial element appears to be ectoparasite load, which in turn will depend on both host surface area and mean parasite intensity harboured by a particular species; the latter may be associated with particular lifestyles. Attractiveness may also be determined to some degree by the nutritional value of the client's surface mucus, and may also incorporate behavioural features of the client, such as tendency to pose and aggression.

Aims:

To investigate differences in client choice between juvenile and adult bluestreak cleaner wrasse. To determine any significant preference in client choice based on size and species of fish.

Objectives:

• Record any soliciting and cleaning at an adult and a juvenile cleaning station.
• Record any soliciting that occurs and fails to elicit a cleaning response.

Methods:

This study was carried out at Pulau Hoga, Wakatobi National Marine Park, S-E Sulawesi. An adult and a juvenile cleaner station were selected at Kaledupa reef, buoy 1. Both sites were chosen to be at approximately the same depth, with similar background fish. Surveys were carried out by a buddy pair of SCUBA divers at different time of day for approximately 40 minutes at a time. Divers were trained in fish identification and sizing was performed using the method set out by English (1997). Recording began after approximately a minute to allow the fish to become acclimatised to the presence of divers. Recordings were taken of any fish that solicited (to family), the outcome of the soliciting and the length of the client. Each diver recorded the activities and combined their results afterwards to aid identification and size estimation.

Analysis of results:

• The results will be analysed at the client family level to reduce possible errors that could have been introduced at species level.
• The client sizes will be divided into ranges produced by calculating the quartile ranges of all the length data and compared between juveniles and adults.
• Client family preference between juveniles and adults will also be compared.

Expected results:

• There appears to be a difference in the clients soliciting cleaning at juvenile and adult stations.
• Numbers of fish soliciting, but not being cleaned at both adult and juvenile stations appear to be similar.
• Average client size appears to reflect the size of the cleaner wrasse but the size range of clients appears to be similar.
• Juvenile cleaner wrasse appear to be more selective with regard to clients, perhaps targeting only those that actively solicit while adults appear to clean anything that remains in their territory for any significant length of time.

Report

A report entitled "Variations in client base with size and maturity in the Bluestreak Cleaner Wrasse, Labroides dimidiatus" will be produced by Thomas Mullier, University of Southampton by May 2002