CORE Citation and Similar Papers at Core.Ac.Uk

View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Aquatic Commons THE DEMONSTRATION OF CHEMOSENSORY FOOD DETECTION IN HYMENOCERA PICTA DANA (DECAPODA, CARIDEA), A PROPOSED PREDATOR OF THE CROWN-OF THORNS STARFISH ACANTHASTER PLANCI (L) PHILIP S. RAINBOW Cambridge Coral Starfish Research Group P.O. Box 99, Port Sudan, Democratic Republic of lhe Sudan ABSTRACT HymerlOcera pieta, the painted shrimp, is a possible predator of A canthaster planci. the Crown~of-Thorns slarfish. H. piela detects food by chemical cues alone and visual cues play no part in the initial location of prey. The presence of food in the water causes the shrimp to become more active, and distance chemoreceptors are probably present in the antennules of the shrimp. Extract of A. pfand has statistically similar attractive powers to an extract of Linckia multi/ora, the starfish supplied as food to the .<;hrimps. The painted shrimp was not attracted to fish extract (Chaetodon sp.) and may respond only to starfish. It is suggested that although H. pieta is able to kill and feed on small juvenile A. plan~i. it is probably an ineJTeclive predator against larger adult Crown·of-Thoms starfish. Present address: N.E.R.C. Unit. Department of Marine Science. U.C.N.W.• Menai Bridge, Anglesey. Wales. INTRODUCTION an Aean/haster individual, probabty as a Part of the research programme of the result of attack by the shrimps. From our Cambridge Coral Starfish Research Group own observations it seems probable that (ORMOND and CAMPBELL 1971; OR under natural conditions this shrimp would MOND et al. 1973) has been concerned cause little serious injury to adult A. planei, with an evaluation of potential predators of due to the discrepancy in she between pre Aeanthaster pland, the starfish responsible dator and prey, as the shrimps do not for widescale destruction of living coral usually exceed 5 cm in length whilst the (VINE 1972; CHESHER 1969). smallest starfish found on the reefs near Hymenoeera pieta Dana (Decapoda, Cad Port Sudan measured 15 Cln in diameter. dea, Gnathophyllidae), the painted shrimp, The ,hrimp, however, might well offer a has been suggested as one possible controlling serious threat to juvenile Aeanthaster planei predator (WICKLER and SEIBT 1970). as pairs of Hymenoeera pieta are able to These authors record the eventual death of kill other starfish species up to 10 cm such 184 PHILlP S. RAINBOW as Linekia multifora (Ll, Linekia laevigata fringing reef, to the laboratory in Port Sudan. lids (sealed witl and Fromia ghardaqana (personal observa The shrimps were kept in their natural tightly hy elaslic tions). As yet it has not been possible to pairs, one pair to an aquarium, and main· fora were placed test the effect of predation by H. piela on tained at an approximate temperature of tainers which '" A. planci of small diameter as specimens 28 0 C. The high ambient air temperature (l) Transparent of this size penetrate deeply into the corals defeated attempts to lower the temperature a clear view of n of the reef and are so well concealed that of the water to the 'lower average vC'iues otf cues alone) (2) " they are difficult to collect. Larger starfish the Kenyan coast but the shallow iagoons allowing the Line (greater than 15 em diameter) were found of the natural habitat of the shrimp vary chemical Clles to relatively easily and were thus available for considerably in temperature, higher values mental tank (vi experiment. often rising above 30" C. The salinity was (3) Painted white the passage of cI WICKLFR and SEIBT (1970) suggest that maintained at 35S'~. To avoid the necessity (chemical cues al H. pieta detect their prey .either by chance for acclimation to experimental conditions, not perforated th or more normally by chemical cues. The all experiments were conducted in the tank the enclosed stal present experiments were designed to in in which each pair of shrimps permanently ~hemosensitivity clues). A pair 0 vestigate food of the shrimp resided. The shrirn!Js were fed wi th whole one of these four and to determine whether the Crown-of .,taffish (Linekia multifora) every evening, one hour, the con Thorns starfish provides any attraction as and any food not consumed was removed a food source. 10 em from the the next day prior to any experiment close together a~ MATERlALS AND METIlODS Small transparent perspex petridishes (5 em distance between Hvmetlocera piela were transported from diameter, I cm deep) were u:,cd in the first tainer were take the .Kenyan coast where' they are found series of experiments. These dishes were the distance mm living in pmrs in the lagoons within the weigh led down by small pebbles and the preceding two m side of eaeh tanl units to facilitat, Table 1. Behavioural characteristics uf H piela evoked during 60 minute experiments. 4 pairs of shrimps were presented sequentiaHy with four different situations. of sensory cues for deteetion of food material. The number Any movements in parentheses is. the number of expcrirnemal re~lIlts averaged (totalled for antennules) to obtain the final shrimps were a1 value given. The experimen offer the shrimps Behavioural Chemical --I ------Yisua( Chemical and Concrol food 0'o.iects. CI characteristic cues alone I cues alone Visual cues I No sensory cues (2emx2cmx -'-~ I~-~ .--1----- extracts of whole LATENCY by macerating a time until 45 58 I 46 I 60 shrimp alights (max 60 25 ml of seawa min) mins. (42) (38) (30) I (33) specimens were ( Percentage time 20 3 24 0 ditcH resin 10 gi (43) (40) spent on food object (42) (33) the starfish, wi ~~ Activity chemical cues. of shrimp 1.5 0.8 1.2 0.4 behaviour of H) cm/min (41) (38) I (40) (33) apparent repelle Antennules total no of coat. The spon recordings and per were p centage Linckia moving 847 i.e. 75 313 i.e. 18 767 i.e. 74 289 i.e. 29 with the shrimps still 283 25 793 72 272 26 7DO 71 the apex of a 10 (42) (17) (41) (33) with the spong FOOD DETECTION IN HYMENOCERA PICTA 185 ilory in Port Sudan. lids (sealed with vaseline) were held on at either end of the base. Experiments again t in their natural tightly by clastic bands. Small Liuckia multi lasted one hour and at two minute intervals uarium, and rnain fora were placed in seawater in these con measurements were taken of the distance of lte temperature of taincr;, which were modified as follows: each shrimp from both sponge and starfish. nt air temperature (I) Transparent and unperforated, allowing A similar arrangement wa<; lIsed in a con· er the temperature a clear view of the starfish within (Le. visual trol experiment comparing the reactions of , average v<:!lues ofI cues alone). (2) Transparent but perforated, the shrimps to sponge soaked in starfish Ie shallow Jagoons aHowing the Unekia to be seen and allowing extract with those to sponge soaked in sea f the shrimp vary chemical cues to be released lnto the experi water, in order to discount the IX>ssibiIity ure, higher values mental tank (visual and chemical cues). of attraction to the visual s,timulus of the '. The sa linity was (3) Painted white but perforated. pennitting blue synthetic sponge. A third experiment lvoid the necessity the passage of chemical but not visual cues compared extracts of Linekia /nullilara to mental conditions, (chemical cues alone). (4) Painted white and extracts of Acunrhaster planet (the same • • lucted in the tank not perforated thus giving no indication of weight in seawater of starfish was crushed the enclosed starfish (control situation, no in 25 ml of seawater prior to soaking of the ~imps permanently -e fed with whole clues). A pair of shrimps was exposed to sponge). Final experiments compared starfish '0) eyery evening, one of these four containers for a periud of extract to fish extract (Cheatodan sp.). one hour, the container being placed initially ned was removed 10 cm from the shrimps which remained RESULTS ly experimen t. close together as a pair. Readings of the The first series of experim~nts were an x petridishes (5 em distance betw~en each shrimp and the con attempt to discover whether H. piela uses ;: used in the firs t tainer were taken every two minutes and chemical or visual cues in di'scovering its ~ese dishes were the distance moved by each shrimp in the prey. From the recordings taken it was pebbles and the preceding two minutes was estimated. The possible to estimate the average percentage side of each tank was marked off in 5 em of the experime~tal hour, spent by a shrimp airs of shrimps were units to facilitate these distance estimates. on any particular container, and -the average latt:ria1. The number Any movements of the antennules of the latency period of each situation~the time (0 obtain the final shrimps were also recorded. taken until a shrimp alighled on a container, The experiments were then redesigned to remaining there at least five minutes (this •• offer the shrimps a dir~t choice of potential latter condition overcomes errors caused by Control food ""iceIs. Cuboids of synthetic sponge chance ~ncounters). The results are shown No sensory cues (2 em x 2. em x 1 cm deep) were soaked in in Table 1. , extracts of whole Unekia /nllitilara. prepared It was noted" in preHminary observations by macerating a 5 I.:m diameter starfish in that the shrimps became more active when 25 ml of seawater. Other similar Linekia in the vicinity of food.

Load more