Food preferences of larvae of Antarctic silverfish Pleuragramma antarcticum Boulenger, 1902 from Terre Adélie coastal waters during summer 2004

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1 Available online at Pola Siene ( e Food pefeenes of lavae of Antati silvefish Pleuagamma antatium Boulenge fom Tee Adélie oastal wates duing summe Caole Vallet abd * Cistina Beans e Philippe Koubbi fg Luie Couot bd JeanHeni Heq e Anne Goffat e a UAtois Cente IUFM Nod e Pas de Calais Cente IUFM d Outeau F Outeau Fane b Univ Lille Nod de Fane F Lille Fane ULCO LOG F Wimeeux Fane d CNRS UMR F Wimeeux Fane e Laboatoie d Oéanologie MARE Cente Univesité de Liège Bat. B Allée de la Chimie Liège Belgium f UPMC Univesité Pais UMR Laboatoie d Oéanogaphie de Villefanhe BP VillefanhesuMe Fane g CNRS UMR LOV BP VillefanhesuMe Fane Reeived August ; evised Deembe ; aepted Deembe Available online Januay Abstat Ihthyoplankton samples wee olleted fom to Januay in the Dumont d Uville Sea (East Antati shelf. The Nototheniidae Pleuagamma antatium ompised moe than of the sampled lavae. Gut ontents of P antatium lavae wee examined. Most lavae fed on phytoplankton espeially diatoms wheeas some othe speimens had a mixed diet with phyto and zooplankton pey. A single speimen fed exlusively on opepods. The stomah ontents was dominated by thee diatoms taxa suh as Thalassiothix antatia Fagilaiopsis spp. and Chaetoeos spp. Pey seletion was appaently food density dependent with an invese elationship between food abundane and seletion feeding. Lavae seleted positively some diatoms suh as Cosinodisus spp. and T. antatia pesenting a low onentation in the wate olumn ompaed to Fagilaiopsis spp. whih wee stongly negatively seleted. Duing summe lavae wee oppotunisti feedes with a boad tophi nihe whih allowed them to swith between diffeent food types. Ó Elsevie B.V. and NIPR. All ights eseved. Keywods: Antatia; Feeding stategy; Food seletion; Food size; Genealist feedes. Intodution * Coesponding autho. Univesité du Littoal Maison de la Rehehe en Envionnement avenue Foh F Wimeeux Fane. addess: aole.vallet@univlittoal.f (C. Vallet. The Antati silvefish Pleuagamma antatium belongs to the impotant nototheniid family and is the most abundant pelagi fish with a iumantati distibution (De Witt and Hopkins ; Hubold and Ekau ; Wöhmann et al.. This pelagi fish /$ see font matte Ó Elsevie B.V. and NIPR. All ights eseved. doi:./j.pola...

2 C. Vallet et al. / Pola Siene ( e is onsideed to be a possible key speies in the food web of ontinental shelf wates (Fuiman et al. ; La Mesa et al. whee adults ae eaten by seals (abeate Weddell and fu seals penguins (empeo gentoo Adélie as well as othe speies of fish (Chionodao hamatus Cyodao antatius Neopagetopsis spp. Dissostihus mawsoni (Casaux et al. ; Cheel and Kooyman ; Danei ; Danei and Calini ; Fuiman et al. ; Knox ; Mille. Thee is also a high pedation pessue on lavae and postlavae whih ae usually eaten by seabids (snow petel Pagodoma nivea postlavae and juveniles of othe fish (Chionodao myesi and even oasionally by adult P. antatium (Hubold ; Kellemann ; Mille. In spite of its impotant tophi ole in Antati eosystem and its lage distibution in ihthyoplankton at many loations aound Antatia (Koubbi et al. ; MoalesNin et al. thei laval suvival onditions ae pooly undestood. Gut analyses of laval and juvenile P. antatium in diffeent Antati aeas evealed a mixed diet of seveal diffeent zooplanktoni taxa suh as eggs and lavae of euphausiids opepods amphipods Limaina heliina and tintinnids (De Witt and Hopkins ; Kellemann ; Noth ; Noth and Kellemann. Howeve obsevations of diatoms in gut ontents of P. antatium ae ae exept duing the ihthyoplankton suvey in Tee Adélie whee diatoms wee thei ommon food (Koubbi et al.. Often gut ontents of laval fish ae obseved by steeomiosope whih is not appopiate to obseve phytoplankton (Kellemann. Consequently Sanning Eleton Miosope (SEM aleady used to pefom study on gut miofloa (Jolly et al. ; Mendez et al. has also been used to study gut ontents of P. antatium (Koubbi et al.. This method enables detemination of the vauity of laval fish guts and diet omposition moe peisely. Applying this method Koubbi et al. ( onluded that lavae of P. antatium ae not simply anivoous as peviously thought (Kellemann but omnivoous. Moeove Kellemann ( demonstated that lavae and juveniles of P. antatium ould selet thei zooplanktoni pey. Beause gazing on phytoplankton has been epoted by Koubbi et al. ( one of the main question is to know whethe lavae of P. antatium also atively selet phytoplankton. To answe to this question it is neessay to examine the laval diet and the food availability in the natual envionment espeially phytoplankton abundane. This study pesents data on diet feeding stategy and food pefeenes of lavae of P. antatium in the Dumont d Uville Sea.. Mateials and methods.. Field sampling The suvey took plae onboad the Fenh RV l Astolabe fom to Januay aoss the aea e E (Fig. whih oesponds with the Collaboative East Antati Maine Census (CEA MARC suvey aea of /. It is a pat of the ICO TA Fenh pojet (Integated Coastal Oean Obsevations in Tee Adélie. The aea was fee of sea Fig.. Loations of sampling stations duing the suvey (data soue: ETOPOv. NOAA. GDC.

3 C. Vallet et al. / Pola Siene ( e ie while iebegs wee only obseved aound the glaies. Eleven tansets wee aied out geneally set nothwad fo a maximum of nautial miles based on sea ie onditions o navigational safety onstaints. Oveall stations wee sampled (Fig. of whih in the Astolabe basin (zone wee seleted to sample the foaging aea of Adélie penguins whih feed thei hiks at the olony nea Dumont d Uville station (fom station to nine on the Adélie bank (fom to zone and in the Adélie depession (fom stations to zone. Eah zone was defined by Beans et al. ( in elation to diatom assemblages. Niskin bottles wee used to sample wate at diffeent depths fo eah station (appoximately m m m and m to study onentations of oxygen nutients total abon and nitogen photosyntheti pigments and abundane in the mioplankton ommunity (Beans et al.. Vetial hauls of a WP net of mm mesh size wee made at eah station down to m depth to ath zooplanktoni oganisms suh as opepods eggs amphipods and Limaina heliina. Maoplankton samples wee olleted in stations out of by oblique tows of a doublefamed bongo net with mm mesh and m mouth diamete (Smith and Rihadson. Station was exluded fom analyses as we ould not sample thee due to ough sea onditions. Tows wee aied out at a speed of knots fom the sufae to the sea bed at a maximum depth of m. The volume of wate filteed by eah net was measued with a HydoBios flowmete and used to alulate standadized ihthyoplankton abundanes. Samples wee fixed immediately onboad with neutal fomalin in seawate... Diet In the laboatoy fish lavae wee soted identified aoding to Kellemann ( and ounted unde a steeomiosope. Fo eah station a maximum of five speimens wee andomly seleted fo dissetion. Total length of lavae was measued to the neaest. mm with a digital alipe. The whole digestive tat was emoved fom the fish lavae unde a steeomiosope and opened. The gut ontents of lavae wee analysed using a steeomiosope and also using a Sanning Eleton Miosope (SEM to bette identify small mioplanktoni individuals when they wee pesent. Lage pey wee identified when the state of digestion was not too advaned. Food items of eah speimen wee insed in MilliQ wate (Millipoe. Eah gut ontent was filteed on. mm filte (Millipoe polyabonate put on a abon tape attahed to a metal stub ( mm diamete. Stubs wee died unde lamina flow hood duing h. Afte dying stubs wee palladiumgoldoated (Polaon SC and obseved with a LEO SEM (VP. Mioplankton genus identifiation was made aoding to Sott and Mahant (. The valve diamete of the enti diatoms the length of the pennate diatoms and the diamete of the silioflagellates wee measued using an image analyse LEO with an auay of. mm. The length of the diatoms of the genus Thalassiothix ould not be measued beause the ells in the gut wee boken. Thus fo this genus only the width was measued. The individual length of this genus is usually e mm (Sott and Mahant. Data wee pooled and the numbe of food items (n the fation of a food item in the gut ( and the fequeny of ouene in guts ontaining food item expessed as peentage (O wee alulated fo eah taxon. Feeding inidene efes to the peentage of guts that ontained at least one food item... Feeding stategy To detemine the feeding stategy of lavae the modified Costello gaphial method (Amundsen et al. was used. In this gaphial method the peyspeifi abundane was alulated as follows: X si p i ¼ P ðþ st whee P i is the food itemspeifi abundane of food item i S i the numbe of gut ontents omposed of food item i and S t the total numbe of food items in all guts. The food itemspeifi abundane was plotted against the ouene in guts ontaining food items (O poviding a twodimensional diagam (Amundsen et al.. The intepetation of the diagam (food item impotane feeding stategy and nihe beadth an be obtained by examining the distibution of points along the diagonals and the axes of the gaph. The food item impotane was epesented in the diagonal fom lowe left (ae food item to uppe ight (dominant food item. The vetial axis epesents the feeding stategy of the pedato in tems of speialisation o genealisation. Pedatos have speialised on food items if positioned in the uppe pat of the gaph while food items positioned on the lowe pat have been eaten only oasionally (genealisation. As fo nihe beadth a population with a high betweenphenotype omponent as diffeent

4 C. Vallet et al. / Pola Siene ( e individuals speialize on diffeent esoues types was haateized by food item points loated at the uppe left of the diagam wheeas a population with a high withinphenotype omponent that is most individuals utilize many esoue types simultaneously was haateized by pey points loated at the lowe ight of the diagam... Food seletion A numbe of indies ae available to measue seletive feeding. Jaobs ( poposed an index to analyse feeding habits and food pefeene. This seletivity index D deives fom the Eletivity index poposed by Ivlev (Jaobs : D ¼ p ðþ þ p whee p is the fation of a food item in the gut is the fation of that food item in the wate olumn. The elative diffeene D vaies fom to fo negative seletion and fom to þ fo positive seletion... Food divesity The Shannon divesity index (H was estimated to haateize the spatial distibution of food divesity in gut ontents of P. antatium. H ¼ X N i N log N i ðþ N whee N i was the individual numbe of food item i and N was the total numbe of food items.. Results.. Distibution and size of P. antatium lavae Lavae of P. antatium wee sampled at stations and wee the most abundant ove the Adélie Bank (Fig. with a maximum abundane of ind. m at station. The size of lavae vaied fom. mm at station ove Adélie Bank to. mm at station nea the Metz Glaie Tongue (MGT. The most abundant size lasses wee mm and mm TL oesponding to and of the total lavae measued espetively (Fig.... Geneal food omposition The gut ontents of lavae wee analysed. Thei diet ompised taxa phytoplankton and thee zooplankton taxa (Table Fig.. Feeding inidene among the speimens obseved was aound. Among them fed exlusively on diatoms two individuals only fed on opepods five on diatoms and opepods and one on diatoms and eggs. A single lavae ate zooplanktoni pey whih ould not be identified due to the advaned state of digestion. One gut was empty. The diatom Thalassiothix antatia was the most abundant food epesenting of the total food items. The small olonial diatoms Fagilaiopsis spp. wee seond in abundane ompising about of the diet. The hainfoming Chaetoeos spp. epesented moe than of the food items (Table Fig. a. These thee taxa wee the most fequently Fig.. Spatial distibution of fish lavae in the oastal zone fom Tee Adélie to the Metz glaie in. P. antatium abundanes wee mapped by kiging.

5 ontibuted substantially to the diet and wee ingested by and of lavae espetively... Food omposition by zone n ( o i C. Vallet et al. / Pola Siene ( e n = t o p o P Total length (mm Fig.. Length fequeny distibution of laval P. antatium in summe. ingested food with espetively and of ouene (Table Fig. a wheeas unidentified eggs and zooplanktoni individuals wee of mino impotane. Othe fequently eaten items wee the enti diatoms Thalassiosia spp. and the silioflagellate Dityoha speulum eah of them ingested by of lavae. Lage diatoms suh as Coethon pennatum Asteomphalus spp. o Cosinodisus spp. The diet of lavae vaied spatially and signifiantly as a funtion of sampling zone (KuskalleWallis test p ¼.. In the Astolabe Basin to the shelf beak (zone Fig. b diet was omposed of taxa out of while seven and taxa wee pesent in guts at zones and espetively (Fig. and d. The Shannon index distibution showed that highest divesity in gut ontents was loated in the Astolabe basin with the maximum value at station (H ¼. wheeas zone (Adélie Bank pesented gut ontents with the lowest divesity at station (H ¼ Table. The KuskalleWallis test showed signifiative diffeene between Shannon indexes at eah zone (p ¼.. A BonfeonieDunn test showed two goups of zones goup inluding zones and with highest divesity in gut ontents and goup with zone whih is epesented by the lowest divesity in gut ontents and dominated by a single taxon i.e. Chaetoeos spp. Feeding inidene was fo zones and and fo zone beause of one empty gut obseved at station. At this station othe lavae fed only on opepods. Thee diatoms taxa suh as T. antatia Fagilaiopsis sp. and Chaetoeos spp. wee the most abundant and the most fequently ingested food in the Table Food omposition of laval Pleuagamma antatium in summe. Columns ae ode fo eah taxa aveage size standad deviation size numbe of items (n foodspeifi abundane (P i and ouene (O of eah food taxa. Feeding inidene efes to the peentage of guts with at least one food item (n ¼. Food taxa Code Aveage size (mm Standad deviation size (mm n P i ( O ( Phytoplankton Centi diatoms Atinoylus spp..... Asteomphalus spp..... Chaetoeos spp..... Coethon pennatum.... Cosinodisus spp..... Thalassiosia spp..... Pennate diatoms Fagilaiopsis spp..... Nitzshia spp..... Rhizosolenia spp..... Thalassiothix antatia.... Unidentified diatoms.. Silioflagellates Dityoha speulum.... Zooplankton Unidentified eggs. e.. Unidentified Copepods.... Unidentified individuals. e.. Feeding Inidene.

6 C. Vallet et al. / Pola Siene ( e Fig.. Sanning Eletoni Miosope pitues of the food items found in the gut of laval P. antatium in summe. Numbe in the uppe left of the pitue oesponded to the ode of the food taxa epoted in Table.

7 C. Vallet et al. / Pola Siene ( e Fig.. (ontinued. diet. Within zones and peyspeifi abundane was espetively and fo T. antatia and fo Fagilaiopsis spp. and and fo Chaetoeos spp. Howeve thei Table Numbe of food items (S and Shannon index (H at eah station in summe. Zone Stations S H ouene was vey diffeent spatially. T. antatia was ingested by of lavae at zone of lavae at zone and at zone ; Fagilaiopsis spp. was eaten by moe than of lavae at both zones and and by about at zone ; Chaetoeos spp. was fed by of lavae at zone at zone and at zone (Fig.. Othes fequently eaten food (> wee the enti diatoms C. pennatum Thalassiosia spp. and Cosinodisus spp. and the silioflagellate D. speulum at zone unidentifiable opepods at zone and the enti diatom Thalassiosia spp. and D. speulum at zone... Feeding stategy Diet omposition of lavae based on the modified Costello method was summaized in Fig.. The twodimensional plot povides infomation on food item impotane feeding stategy and nihe beadth ontibution of between and/o withinphenotype omponents. Fo food item impotane most items wee loated in the loweleft one of the plot thus epesenting ae food with low fequeny ouene and low foodspeifi abundane. The less ae food items wee Chaetoeos spp. Fagilaiopsis spp. and T. antatia owing to thei high fequeny of

8 ouene ompaed to othe taxa (Fig.. In elation to the feeding stategy axis lavae of P. antatium ould be onsideed as genealist feedes as all food items wee loated in the lowe pat of diagam attaining a low foodspeifi abundane. As fa as the nihe width ontibution is onened the loation of main food taxa Chaetoeos spp. Fagilaiopsis spp. and T. antatia within the twodimensional plot indiated a elatively highe withinphenotype omponent in the utilization of food esoues than betweenphenotype omponent. These taxa showed a low speifi abundane and a high ouene (lowe ight indiating that they wee eaten by most individuals along with othe pey... Food seletion Fo the whole study aea the density of suitable food was ells pe lite fo phytoplankton and individuals pe m fo zooplankton. The pennate diatom T. antatia was the main omponent of the diet. Howeve this speies did not ou in the diet at the same popotion than found in situ ( ells pe lite. Positive seletion was found fo this speies (D ¼. as its abundane in the wate olumn epesented aound of the total abundane of the phytoplankton and its ouene in gut ontents was (Fig. a. Two othe phytoplanktoni taxa Nitzshia spp. ( ells pe lite and Cosinodisus spp. ( ells pe lite epesented less than of the total phytoplankton abundane but they wee positively seleted by P. antatium (Fig. a. Positive seletion was also obseved fo Asteomphalus spp. Thalassiosia spp. and D. speulum as well as fo Chaetoeos spp. at a lesse extent (Fig. a. On the othe hand some phytoplanktoni taxa exhibit a high negative seletion suh as Rhizosolenia spp. o a low negative seletion like the small olonial Fagilaiopsis spp. and the ental diatoms Atinoylus spp. and C. pennatum (Fig. a. Among zooplanktoni oganisms eggs and opepods wee highly positively seleted. Foodspeifi abundane ( e ( n e u O a Foodspeifi abundane ( e ( n e u O b Foodspeifi abundane ( e ( n e u O Foodspeifi abundane ( e ( n e u O d Fig.. Feeding stategy diagam fo laval P. antatium (a fom Tee Adélie to Metz Glaie Tongue (MGT and in (b Astolabe basin (zone ( Adélie Bank (zone and (d Adélie depession (zone. Numbes in eah gaph oesponded to the ode of eah food taxon epoted in Table C: phytoplankton; B: zooplankton. C. Vallet et al. / Pola Siene ( e

9 Food seletion by laval fish was analysed at eah diffeent zone. The total phytoplankton onentation was. and times highe at zone nea the MGT ( ells pe lite than at both zones ( ells pe lite and ( ells pe lite espetively. Howeve the total zooplankton onentation was the same ode of magnitude fo both zones ( ind. m and ( ind. m and. time lowe at zone ( ind. m. At zone Cosinodisus spp. Nitzshia spp. T. antatia opepods and eggs wee stongly positively seleted Fagilaiopsis spp. showed low pefeene while highest value of negative indies was obseved fo Rhizosolenia spp. (Fig. b. At zone whee phytoplankton abundane was the lowest and zooplankton abundane the highest opepods and T. antatia showed high value of positive indies wheeas values wee lose to zeo fo Fagilaiopsis spp. and Chaetoeos spp. (Fig.. Values fo D. speulum wee of modeate pefeene. Zone was vey diffeent ompaed to both zones and (Fig. d. Seveal taxa (Asteomphalus spp. Chaetoeos spp. Cosinodisus spp. and Thalassiosia spp. showed value of index D highe than. suggesting that all these taxa wee ingested pefeentially D. speulum was modeately ingested wheeas Fagilaiopsis spp. was stongly negatively seleted (Fig. d... Food size The size distibution of the total food ingested by the lavae was polymodal with the mm size lass ompising lage potions of thei diet (Fig. a. At zone P. antatium lavae fed on the lowe size ange of pey (fom to mm while at zone they fed mainly on the mm lass and ingested lage food items (e mm Fig. a. At zone the mm size lass epesented the main food items ingested. The mean food size vaied little in elation to the laval length (Fig. b. Howeve exteme values ineased with laval length whih suggest that lage lavae of P. antatium wee able to ingest lage food items. Thus whateve thei size all lavae of P. antatium wee able to ingest pey of size highe than mm (i.e. the mean food size of eah length lass. Seletivity index D a Seletivity index D b Seletivity index D e ( n e u O Seletivity index D e ( n e u O d Fig.. Seletivity index (D as a funtion of ouene of eah food item in summe in (a the Dumont d Uville Sea (b Astolabe basin (Zone ( Adélie Bank (Zone and (d Adélie depession (Zone. Numbes in eah gaph oesponded to the ode of eah food taxon epoted in Table C: phytoplankton; B: zooplankton. C. Vallet et al. / Pola Siene ( e

10 C. Vallet et al. / Pola Siene ( e Fig.. (a Pey size fequeny fo eah zone loated fom Tee Adélie to Metz Glaie Tongue (MGT in summe ; (b Food size laval P. antatium size elationship obseved in summe ( mean food size.. Disussion.. Distibution of lavae of P. antatium Lavae of P. antatium dominated the neiti assemblage in Tee Adélie oastal wates duing summe as aleady shown by Koubbi et al. ( o elsewhee epoted ove the Antati ontinental shelf (Hoddell et al. ; Ganata et al.. Ou esults showed that total length of lavae anged between and mm suggesting that they ould ome fom oastal epodutive aeas whee hathing takes plae in Novembe fo lage individuals and at the beginning of Januay fo smalle ones. The same peiod of hathing was obseved in othe aeas of the Southen Oean (Hubold ; Kellemann ; Vahi et al.. Moeove Koubbi et al. ( demonstated that epodution oued in deep oastal anyon o in oastal zones nea ieshelves glaies. Hubold ( and La Mesa et al. ( stated that laval suvival was elated to the development of oastal polynya whih ould povide favouable onditions fo ealy laval stages gowth. Distibution of lavae of P. antatium

11 C. Vallet et al. / Pola Siene ( e in Tee Adélie oastal wates duing summe oinided with aeas of both high pimay podution and diatom divesity whih povide the neessay nutients fo ealy stages of P. antatium (Beans et al. ; Koubbi et al.... Gut ontents Ou esults onfimed that laval P. antatium fed on both phyto and zooplankton. Compaed to pesent data feeding inidene was simila in Tee Adélie duing summe ( (Koubbi et al. and lowe in the pak ie zone off the Antatia Peninsula ( (Kellemann. These diffeenes ould be explained by the diffeene of methodology used. Kellemann ( obseved the digestive tat unde a steeomiosope while in this study and the pevious one (Koubbi et al. we used a Sanning Eleton Miosope whih allowed us to obseve smalle food items (fom mm Table and thus to get a moe auate food identifiation. Howeve it was vey diffiult to detemine speies among opepods even with a steeomiosope beause of the state of digestion. No iliate was obseved in guts of P. antatium lavae whih was diffeent fom speimens olleted off the Bisoe Islands in the southen ontinental shelf of Bansfield Stait (Kellemann. This is also ontay to obsevations by Beans et al. ( who found that iliates wee dominated by tintinnids (. of all iliates duing summe in the Dumont d Uville Sea. Howeve iliate abundane was vey low with an aveage of ells pe lite and seveal samples had no iliate (Beans et al.. The low abundane of euphausiids lavae eoded in summe (<. of total zooplankton (Vallet et al. might explain the absene of this pey in the gut ontents of Pleuagamma found in the pesent study... Food seletion In aquaultue maine mioalgae ae widely used in the fist feeding stages of maine fish lavae (Jones et al. ; Lubzens ; Naas et al. ; Reitan et al.. In ou study diatoms pobably stimulate feeding behaviou in lavae of P. antatium as many ompounds suh as betaine o aminoaids natual onstituents of phytoplankton (Dabowski and Ruseik ae onsideed to be the most effetive feeding stimulants (Lazo et al.. Ou esults showed that some diatoms suh as Cosinodisus spp. o T. antatia wee highly positively seleted by P. antatium lavae. Diatoms espeially Cosinodisus spp. ae known to have a high amount of fee amino aids (Baven et al. whih ould atively ontibute to the fee amino aid pool in gut ontents of lavae theefoe playing an impotant ole in enegy podution and potein synthesis (Fyhn. Lazo et al. ( demonstated that the pesene of phytoplankton in thei ultue esulted in ineased gowth suvival and enzyme ativity in fish lavae. It ould be possible that in exteme onditions as in the Antati wates P. antatium lavae need to feed fist on phytoplankton fo a shot peiod to get a bette digestive system to subsequently assimilate lage zooplanktoni pey suh as opepods o euphausiid lavae. Moeove fatty aid omposition in P. antatium lavae fom Tee Adélie showed that they ae omnivoous with a maked diatom food soue and a slight ontibution of small opepods like Oithonidae (Tavenie and Mayzaud unpublished. The seletivity index indiated that lavae of P. antatium wee able to selet positively some food items suh as Cosinodisus spp. T. antatia and opepods. Howeve the seletive feeding tightly depended on the onentation of food items in the plankton. Futhemoe food sizes wee vey diffeent between diatoms and opepods. Although P. antatium lavae wee able to ingest lage pey the width of thei mouth ontol the maximum food size (Kellemann... Feeding stategy In oastal wates of Tee Adélie lavae of P. antatium fed on thee dominant phytoplanktoni food items T. antatia Chaetoeos spp. and Fagilaiopsis spp. All othe food items wee onsumed oasionally by a few individuals. The feeding stategy of Pleuagamma was shifted towads a withinphenotype ontibution to the nihe beadth as most food items pesented a low foodspeifi abundane and high ouene. Lavae of P. antatium an be onsideed as genealist feedes as thei diet onsisted of a few dominant pey and a elatively high numbe of othe food items eithe zooplankton o phytoplankton. As a onsequene lavae of P. antatium should have a high toleane of vaiable envionmental onditions being able to swith between seveal pey types (Rihmond et al.. Othe studies aleady epoted that lavae of P. antatium wee welladapted to feed on a wide spetum of food depending on seasonal availability (Hubold and Hagen. Although many authos hypothesized that physiologial plastiity ineased enegeti osts (e.g. Agawal ; Coustau

12 C. Vallet et al. / Pola Siene ( e et al. ; De Witt et al. ; van Kleunen et al. genealist feedes ae favoued in flutuating envionments ompaed to speialist feedes (Rihmond et al.. Aknowledgements This atile is a ontibution to the Census of Antati Maine Life and to ANR GLIDES (PI: ChalesAndé Bost. We thank the Captain Yvon Guédez and the ew of the RV l Astolabe Alain Pottie Alain Piee and Patie Godon fo logistis onboad and adaptation of l Astolabe to allow sientifi wok. We also thank Patie Puvost and Camille White fo help with the field wok. The authos ae gateful to Gegoy Beaugand fo omments and help in oeting the English text. Funding was povided by IPEV and Zone Atelie Antatique (INSUCNRS. This wok was suppoted by the Austalian Govenment s Coopeative Reseah Centes Pogamme though the Antati Climate and Eosystems Coopeative Reseah Cente (SW Wight. Wok of Anne Goffat (MARE publiation no. was suppoted by BELSPO (Belgium unde ontats PELAGANT (EV/ /A and PADI (SD/BA/. Refeenes Agawal A.A.. 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