International Journal for Parasitology 17 "0887# 0302Ð0313 Symbioses in Amphipholis squamata "Echinodermata\ Ophiuroidea\ Amphiuridae#] geographical variation of infestation and e}ect of symbionts on the host|s light production Dimitri Deheyna\"\ Nikki A[ Watsonb\ Michel Jangouxa\ c aLaboratoire de Biologie marine "CP 059:04#\ Universite# Libre de Bruxelles\ 49 av[ F[D[ Roosevelt\ B!0949 Bruxelles\ Belgium bDivision of Zoology\ School of Biological Sciences\ University of New England\ Armidale\ NSW 1240\ Australia cLaboratoire de Biologie marine\ Universite# de Mons!Hainaut\ 08 av[ Maistriau\ B!6999 Mons\ Belgium Received 16 March 0887^ received in revised form 02 May 0887^ accepted 02 May 0887 Abstract Populations of the polychromatic and bioluminescent species Amphipholis squamata from eight locations were examined for internal and external symbionts[ At three locations "two in the United Kingdom and one in Papua New Guinea#\ no symbionts were present\ while four species were recovered from the remaining locations] Cancerilla tubulata and Parachordeumium amphiurae "copepods#\ Rhopalura ophiocomae "orthonectid# and an undescribed species of rhabdocoel turbellarian[ No ophiuroid individual hosted more than one symbiont species\ despite the presence of two or more within a population[ Symbiont presence and prevalence varied with location\ and with colour variety\ but with no apparent pattern or trends[ Light!production characteristics of the host were a}ected by the presence of all symbionts except C[ tubulata[ These e}ects\ however\ did not vary between colour varieties or between geographical locations\ but were speci_c to the symbiont species] the presence of P[ amphiurae resulted in enhanced intensity of light production\ while that of R[ ophiocomae and the turbellarian species resulted in reduced intensity[ The kinetics of light production "time until maximum output# were altered only by the presence of the turbellarian[ Changes in the light!production characteristics are discussed in relation to morphological\ energetical and physiological e}ects of the symbioses[ Þ 0887 Australian Society for Parasitology[ Published by Elsevier Science Ltd[ All rights reserved[ Keywords] Amphipholis squamata^ Echinoderm symbioses^ Geographical distribution^ Host luminescence^ Ophiuroid symbionts^ Physio! logical reaction 0[ Introduction of the nature of the hostÐsymbiont relationship ð0\ 1Ł[ One echinoderm species may host a parasite\ a Echinoderms act as hosts to a wide variety of commensal\ or both\ and most symbionts do not symbionts\ separately or simultaneously\ regardless appear to be mutually exclusive ð0\ 2Ł[ Echinoderm symbionts vary in degree of host speci_city from monoxenous symbionts\ such as copepods\ to polyxenous symbionts\ such as ciliates[ Multiple " Corresponding author[ Tel] "¦21# 1 549 11 23^ Fax] "¦21# hosts\ however\ are always of the same echinoderm 1 549 16 85^ e!mail] ddeheynÝulb[ac[be[ class ð1Ł[ 9919!6408:87:,08[99 Þ 0887 Australian Society for Parasitology[ Published by Elsevier Science Ltd[ All rights reserved[ PII] S9919!6408"87#99008!1 0303 D[ Deheyn et al[ : International Journal for Parasitolo`y 17 "0887# 0302Ð0313 The cosmopolitan ophiuroid Amphipholis squa! mata has a wide range of tolerance towards symbionts\ with as many as 04 di}erent organisms reported in association with individuals[ These con! sist of copepods "seven species#\ ciliates "four species#\ polychaetes "two species#\ orthonectids "one species# and a turbellarian "one species\ _rst mentioned here#[ The associations have been reported from individuals of various seas and oce! ans in accordance with the wide distribution of this ophiuroid ð0\ 3Ł[ Symbiont life!cycles and the _ne morphological interface of the hostÐsymbiont relationship have been investigated for several spec! ies ð1\ 4Ł[ Impacts of infestation on the ophiuroid population structure have also been examined\ notably by investigating the in~uence of symbiont infestations on the ophiuroid life!cycle\ and its brooding and regenerative abilities ð5Ð09Ł[ E}ects on the ophiuroid physiology or metabolism\ however\ have been little studied as indicated by the fact that only one symbiont species has been assessed for its e}ect on the energetical activity of Fig[ 0[ Amphipholis squamata[ The eight geographical locations the ophiuroid ð6Ł[ that were investigated\ and occurrence of the four symbionts Amphipholis squamata is a polychromatic species considered] "0# Cancerilla tubulata "copepod#^ "1# Para! with various colour varieties present in distinct chordeumium amphiurae "copepod#^ "2# Rhopalura ophiocomae numbers and proportions at di}erent locations ð00\ "orthonectid#^ "3# the new species of rhabdocoel turbellarian^ "9# Absence of symbionts[ 01Ł[ Individuals have long been reported to produce light ð02\ 03Ł\ with light!production characteristics varying between colour varieties\ and between brooding and non!brooding individuals ð01Ł[ Other biological features\ such as concentration of neuro! from eight di}erent locations in various peptides\ types of neuroreceptors on photocytes\ geographical regions "Fig[ 0#\ i[e[ in France life!cycle\ reproductive pattern and genotype\ are "Langrune!sur!Mer and Rosco}#\ the U[K[ known to di}er between individuals of di}erent "Wembury\ Prawle Point\ Millport and varieties ð04Ł\ and also between individuals from New Haven#\ New Zealand "Portobello# and Papua widely distant locations "ð05Ł^ D[R[ Murray\ New Guinea "Laing Island#[ All locations were Macrogeographic genetic variation in the cosmo! politan brooding brittle star\ Amphipholis squa! intertidal "from mid! to upper!intertidal\ except for mata[ Master thesis\ Mount Allison University\ Prawle Point where specimens were collected from 0878#[ We aimed to determine whether symbioses tidal pools#\ and individuals were collected at low in A[ squamata varied with host colour variety or tide by hand using _ne forceps "the ophiuroid is geographic location of the population\ and what small\ adult specimens having a disc diameter of e}ect the di}erent symbionts had on the host light! approx[ 2 mm with arms approx[ 04 mm long#[ The production characteristics[ habitats consisted of muddy or detritic sand under boulders or mussels beds\ except for Prawle Point 1[ Materials and methods were the ophiuroid was found amongst algae Coral! lina of_cinalis[ All individuals found at each search Individuals of A[ squamata "Delle Chiaje\ 0717# were collected\ regardless of microhabitat\ size or were collected between March 0882 and June 0885 colour variety[ D[ Deheyn et al[ : International Journal for Parasitolo`y 17 "0887# 0302Ð0313 0304 1[0[ Measurement of infestation variety\ and examined within 01 h for the presence of the following four symbionts] "0# the copepod Collected individuals were transported to the Cancerilla tubulata Dalyell\ 0740 "Fig[ 1#\ which is laboratory in seawater\ sorted according to colour an ectosymbiont that clings to the oral base of the Figs 1Ð4[ Scanning electron micrographs of the four symbionts from Amphipholis squamata "As#[ Fig[ 1[ Cancerilla tubulata "Ct# attached to the host[ Fig[ 2[ Parachordeumium amphiurae "isolated specimen#[ Fig[ 3[ Rhopalura ophiocomae "Ro# in the host[ Fig[ 4[ The new rhabdocoel turbellarian species "isolated specimen#[ 0305 D[ Deheyn et al[ : International Journal for Parasitolo`y 17 "0887# 0302Ð0313 ophiuroid arm ð06Ł^ "1# the copepod Para! 1[2[ Measurement of bioluminescence chordeumium amphiurae He#rouard\ 0895 "Fig[ 2#\ which lives in the bursa of infested individuals Only arms produce light in the ophiuroid^ there! that are then recognisable by an external swelling fore light production was measured from isolated and a pore that the symbiont induces on the ophi! arms of infested individuals[ "When the symbiont uroid disc\ and also by an orange tint of the sym! C[ tubulata occurred it was removed prior to light biont visible through the ophiuroid skin ð5Ł^ "2# measurement[# Light production was also measured the orthonectid Rhopalura ophiocomae Giard\ 0766 from 01 to 04 non!infested individuals of each "Fig[ 3#\ which infests the coelom and the coelom variety\ from each collection[ When locations were wall ð4Ł^ and "3# a new species of rhabdocoel tur! sampled several times\ results from the di}erent bellarian "in course of description# that occurs in collections were pooled[ Light production was the ophiuroid haemal system "Fig[ 4#[ There are always measured within 01 h of collection\ from no external signs of the presence of the orthonectid adult individuals with intact arms "i[e[ non!regen! and the turbellarian "ð4Ł^ Deheyn\ personal obser! erating# with disc diameter 1Ð2 mm[ Individuals vation^ respectively#[ The disc of every ophiuroid were anaesthetised by immersion for 2 min in a was therefore dissected to check for their presence\ 2[4) MgCl1 solution and the length of arms mea! which allowed simultaneous detection\ under the sured before separation from the disc using a _ne compound microscope\ of gonads and brooded scalpel[ The disc was dissected for symbionts\ and juveniles[ the presence of brooded juveniles and developed gonads determined\ while each isolated arm was measured for bioluminescence[ The luminous reac! 1[1[ Morphological observation tion was triggered using KCl 199 mM so that light production was maximal and unimodal\ and Infested ophiuroids were investigated by light occurred within 079 s following KCl addition ð01\ microscopy to precisely localize the symbionts and 19Ł[ Light was detected in a dark room at each to determine