Pteropod Species Research Articles

Pteropods and climate off the Antarctic Peninsula

Shelled (thecosome) and naked (gymnosome) pteropods are regular, at times abundant, members of Southern Ocean zooplankton assemblages. Regionally, shelled species can play a major role in food webs and carbon cycling. Because of their aragonite shells thecosome pteropods may be vulnerable to the impacts of ocean acidification; without shells they cannot survive and their demise would have major implications for food webs and carbon cycling in the Southern Ocean. Additionally, pteropod species in the southwest Atlantic sector of the Southern Ocean inhabit a region of rapid warming and climate change, the impacts of which are predicted to be observed as poleward distribution shifts. Here we provide baseline information on intraseasonal, interannual and longer scale variability of pteropod populations off the Antarctic Peninsula between 1994 and 2009. Concentrations of the 4 dominant taxa, Limacina helicina antarctica f. antarctica, Clio pyramidata f. sulcata, Spongiobranchaea australis and Clione limacina antarctica, are similar to those monitored during the 1928–1935 Discovery Investigations and reflect generally low values but with episodic interannual abundance peaks that, except for C. pyr. sulcata, are related to basin-scale climate forcing associated with the El Niño-Southern Oscillation (ENSO) climate mode. Significant abundance increases of L. helicina and S. australis after 1998 were associated with a climate regime shift that initiated a period dominated by cool La Niña conditions and increased nearshore influence of the Antarctic Circumpolar Current (ACC). This background information is essential to assess potential future changes in pteropod species distribution and abundance associated with ocean warming and acidification.

Jelly biomass sinking speed reveals a fast carbon export mechanism

Sinking of gelatinous zooplankton biomass is an important component of the biological pump removing carbon from the upper ocean. The export efficiency, e.g., how much biomass reaches the ocean interior sequestering carbon, is poorly known because of the absence of reliable sinking speed data. We measured sinking rates of gelatinous particulate organic matter (jelly‐POM) from different species of scyphozoans, ctenophores, thaliaceans, and pteropods, both in the field and in the laboratory in vertical columns filled with seawater using high‐quality video. Using these data, we determined taxon‐specific jelly‐POM export efficiencies using equations that integrate biomass decay rate, seawater temperature, and sinking speed. Two depth scenarios in several environments were considered, with jelly‐POM sinking from 200 and 600 m in temperate, tropical, and polar regions. Jelly‐POM sank on average between 850 and 1500 m d−1 (salps: 800–1200 m d−1; ctenophores: 1200–1500 m d−1; scyphozoans: 1000–1100 m d−1; pyrosomes: 1300 m d−1). High latitudes represent a fast‐sinking and low‐remineralization corridor, regardless of species. In tropical and temperate regions, significant decomposition takes place above 1500 m unless jelly‐POM sinks below the permanent thermocline. Sinking jelly‐POM sequesters carbon to the deep ocean faster than anticipated, and should be incorporated into biogeochemical and modeling studies to provide more realistic quantification of export via the biological carbon pump worldwide.

First record of the Eocene pteropodHeliconoides nitens(Gastropoda: Thecosomata: Limacinidae) from the Pacific Basin

Fossils of a single pteropod species were found in an isolated carbonate deposit within middle Eocene deep-water strata of the Humptulips Formation in western Washington State, U.S.A. The carbonate formed at a cold seep where fluids containing high concentrations of hydrocarbons, principally methane, emanated from the seafloor. Anaerobic oxidation of the methane by prokaryotes caused localized and rapid precipitation of calcium carbonate that encased biogenic detritus including wood fragments and mollusk shells; in this case even the minute and delicate aragonitic shells of the pteropod Heliconoides nitens (Lea, 1833), the first certain record of this taxon for the Pacific Basin. The presence of H. nitens in the Humptulips Formation allows us to recalibrate the age of the formation as late Lutetian or early Bartonian, up to 8 million years younger than previously thought. Heliconoides nitens has been found in temporally equivalent strata elsewhere in the world, and this is another example of some fossil pteropods having utility for long distance biostratigraphic correlations. Pteropod shells rapidly dissolve in deep-water environments, thus cold seep deposits may be a source of pteropod fossils in deep-water strata where they otherwise would not occur.

Metabolic suppression in thecosomatous pteropods as an effect of low temperature and hypoxia in the eastern tropical North Pacific

Many pteropod species in the eastern tropical North Pacific Ocean migrate vertically each day, transporting organic matter and respiratory carbon below the thermocline. These migrations take species into cold (15–10° C) hypoxic water (<20 μmol O2 kg−1) at depth. We measured the vertical distribution, oxygen consumption and ammonia excretion for seven species of pteropod, some of which migrate and some which remain in oxygenated surface waters throughout the day. Within the upper 200 m of the water column, changes in water temperature result in a ~60–75 % reduction in respiration for most species. All three species tested under hypoxic conditions responded to low O2 with an additional ~35–50 % reduction in respiratory rate. Combined, low temperature and hypoxia suppress the metabolic rate of pteropods by ~80–90 %. These results shed light on the ways in which expanding regions of hypoxia and surface ocean warming may impact pelagic ecology.

The metabolic response of pteropods to acidification reflects natural CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-exposure in oxygen minimum zones

Abstract. Shelled pteropods (Thecosomata) are a group of holoplanktonic mollusks that are believed to be especially sensitive to ocean acidification because their aragonitic shells are highly soluble. Despite this concern, there is very little known about the physiological response of these animals to conditions of elevated carbon dioxide. This study examines the oxygen consumption and ammonia excretion of five pteropod species, collected from tropical regions of the Pacific Ocean, to elevated levels of carbon dioxide (0.10%, 1000 ppm). Our results show that pteropods that naturally migrate into oxygen minimum zones, such as Hyalocylis striata, Clio pyramidata, Cavolinia longirostris and Creseis virgula, were not affected by carbon dioxide at the levels and duration tested. Diacria quadridentata, which does not migrate, responds to high carbon dioxide conditions with reduced oxygen consumption and ammonia excretion. This indicates that the natural chemical environment of individual species may influence their resilience to ocean acidification.

Comparison of the shell structure of two tropical Thecosomata (Creseis acicula and Diacavolinia longirostris) from 1963 to 2009: potential implications of declining aragonite saturation

Abstract Roger, L. M., Richardson, A. J., McKinnon, A. D., Knott, B., Matear, R., and Scadding, C. 2012. Comparison of the shell structure of two tropical Thecosomata (Creseis acicula and Diacavolinia longirostris) from 1963 to 2009: potential implications of declining aragonite saturation. – ICES Journal of Marine Science, 69: 465–474. Thecosomata (shelled pteropod molluscs) are calcifiers that play an important role in the ocean carbonate cycle. Ocean acidification as a result of the uptake of CO2 affects pteropods by increasing dissolution rates of their aragonite skeletons. Two species of pteropod found in Australian tropical waters were studied, Creseis acicula and Diacavolinia longirostris. To assess the changes in their aragonite shells, shell morphology, growth patterns, structure, size, and porosity are described for both species, from material collected at seven sites between the 1960s and the 2000s. Shell characteristics were used to explore variations over time potentially related to ocean acidification. The aragonite saturation level (Ωarag) of surface waters was hindcast and a decline equivalent to −10% (average of the seven sites) was found. Simultaneously, variations in shell thickness were recorded (C. acicula by −4.43 µm, D. longirostris by −5.37 µm) over the study period along with a significant increase in shell porosity (C. acicula: +1.43%, D. longirostris: +8.69%). The work, although not conclusive, does suggest that pteropods off Northern Australia may have been influenced by the decline in Ωarag over the past few decades. Such adverse effects could ultimately affect thecosome survival and that of their predators.

Holoplanktonic gastropoda (Mollusca) from the Miocene of Cyprus: systematics and biostratigraphy

Abstract: Eleven randomly chosen outcrops in the Miocene Pakhna Formation of Cyprus were sampled for holoplanktonic Mollusca. Four species of Heteropoda were found, and 24 of Pteropoda, a substantial increase from the two species recorded until now from the Miocene of Cyprus. One pteropod species, Peracle charlotteae sp. nov. (Gastropoda, Pseudothecosomata), is introduced. Age assignments based on holoplanktonic molluscs for the 11 localities are as follows: Langhian (Alassa 1–4), (Serravallian?) Tortonian to Messinian (Episkopi 1), Tortonian (Agios Tychon, Tokhni and the Maroni Marlstone of Khirokitia 1–2) and Tortonian to Early Messinian (Episkopi 2). These age determinations in some cases are at odds with those from previous publications based on calcareous nannofossils and Foraminifera. The sediments underlying the Amathus Channel outcrop yielded insufficient fauna for definitive dating, but we suggest are younger than Late Serravallian. At some localities, particularly in the Alassa area, pteropod assemblages are strongly variable on a bed-by-bed basis, and this offers possibilities for future refined biostratigraphical interpretations. This is the first substantial holoplanktonic mollusc fauna described from the eastern Mediterranean basin and allows correlation with assemblages in the central Mediterranean and elsewhere.

Poles Apart: The “Bipolar” Pteropod Species Limacina helicina Is Genetically Distinct Between the Arctic and Antarctic Oceans

The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five “forma”. However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (±0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems.

Annual cycle of the gelatinous invertebrate zooplankton of the eastern South Adriatic coast (NE Mediterranean)

Frequent sampling at a fixed South Adriatic station over 1996 was designed to capture the annual cycle of life-history stages of the dominant gelatinous invertebrate zooplankton, which are very seldom encountered in the world literature. Two groups of dominant species were distinguished by their periods of most intense reproduction, one in late summer‐autumn and the other in late summer‐autumn and winter. Of 66 species identified, there were 19 hydromedusae, 14 calycophores, 3 ctenophores, 2 heteropods, 12 pteropods, 8 polychaetes and 8 chaetognaths. Compared with historical data, the numerically dominant species of calycophores, pteropods and polychaetes have changed dramatically. The calycophore Muggiaea atlantica, newly observed in the Adriatic, has replaced its formerly dominant congener M. kochi; the pteropod Creseis virgula has supplanted C. acicula, and the previously very rare Pelagobia longicirrata now is the dominant pelagic polychaete. Faunal changes coincide with—and perhaps partly are owed to—newly documented circulation changes in the Eastern Mediterranean, the proximate source of southern Adriatic water. Thus, using an extended description of Adriatic zooplankton, data presented herein provide baseline information that is essential in the evaluation of biological changes in the Adriatic, which have appeared possible as a consequence of larger-scale oceanographic processes on zooplankton community structure.

Seasonal variation of pteropods from the Western Arabian Sea sediment trap

Sediment trap samples collected from the Western Arabian Sea yielded a rich assemblage of intact and non-living (opaque white) pteropod tests from a water depth of 919 m during January to September 1993. Nine species of pteropods were recorded, all (except one) displaying distinct seasonality in abundance, suggesting their response to changing hydrographical conditions influenced by the summer/winter monsoon cycle. Pteropod fluxes increased during the April–May peak of the intermonsoon, and reached maximum levels in the late phase of the southwest summer monsoon, probably due to the shallowing of the mixed layer depth. This shallowing, coupled with enhanced nutrient availability, provides ideal conditions for pteropod growth, also reflected in corresponding fluctuations in the flux of the foraminifer Globigerina bulloides. Pteropod/planktic foraminifer ratios displayed marked seasonal variations, the values increasing during the warmer months of April and May when planktic foraminiferal fluxes declined. The variation in fluxes of calcium carbonate, organic carbon and biogenic opal show positive correlations with fluxes of pteropods and planktic foraminifers. Calcium carbonate was the main contributor to the total particulate flux, especially during the SW monsoon. In the study area, pteropod flux variations are similar to the other flux patterns, indicating that they, too could be used as a potential tool for palaeoclimatic reconstruction of the recent past.

Pteropods, eddies, carbon flux, and climate variability in the Alaska Gyre

Abstract Pteropod abundances in net tows and sediment traps are used to evaluate the link between episodic pteropod carbon flux in the North Pacific Ocean and Haida eddies and climate variability. Large deposition events of Clio pyramidata (a subtropical species of pteropod) at 3800 m sediment traps at Ocean Station Papa (OSP, 50°N, 145°W; 1983–2000) lag large El Nino events, represented by the Northern Oscillation Index (NOI), in the North Pacific by 1–2 years during observations from 1983 to 2000. Strong ENSO events may inject C. pyramidata source populations into the subarctic from southern regions because of greater northward transport of water along the continental margin and in some cases, because of a northward shifting of the subarctic boundary in deeper waters. Subsequently, conditions in the North Pacific following large negative NOI events may allow C. pyramidata to build and sustain high populations in the Alaska Gyre. Several very negative NOI years coincided with strong eddy intensity. Eddies are capable of concentrating high densities of pteropods (C. pyramidata and Limacina helicina) and so may further intensify climate-driven pteropod-based carbon inputs in the North Pacific. Pteropods contribute organic (tissue) and inorganic (CaCO3=aragonite) carbon to the deep ocean, yet they are not usually included in mass flux sediment trap studies because it is difficult to distinguish “swimmers” (live at the time of capture) from “sinkers” (dead at the time of capture). At 2.5 g m−2 yr−1, CaCO3 flux due to C. pyramidata at OSP is comparable to existing pelagic estimates for all open-ocean calcifiers including coccolithophorids, foraminfera, and all pteropods. Particulate inorganic carbon (PIC) from C. pyramidata in OSP sediment traps is ∼17% of values measured in other studies that do not include pteropods in their totals. Average yearly flux of organic particulates at OSP due to C. pyramidata is 1.6 g m−2 yr−1 and is about 49% more than the annual particulate organic carbon (POC) flux estimated by Wong et al. (1999) for OSP.

Controls on modern carbonate preservation in the southern Florida Straits

The water masses in the Florida Straits and Bahamas region are important sources for the Northern Atlantic surface ocean circulation. In this study, we analyse carbonate preservation in surface sediments located above the chemical lysocline in the Florida Straits and Bahamas region and discuss possible reasons for supralysoclinal dissolution. Calcite dissolution proxies such as the variation of the foraminiferal assemblage, Fragmentation Index, Benthic Foraminifera Index, and Resistance Index displayed a good preservation in both areas. The pteropod species Limacina inflata showed very good preservation in sediments of inter-platform channels from the Great Bahama Bank (Providence Channel, Exuma Sound) above the aragonite lysocline. Supralysoclinal aragonite dissolution, however, was observed at two water depth levels (800–1000 m and below 1500 m) in the Florida Straits. Our observations suggest that the supralysoclinal dissolution in the Florida Straits is due to the degradation of organic material. The presence of Antarctic Intermediate Water (AAIW) may be a contributing factor for the significant aragonite dissolution in 800–1000 m. The comparison of modern preservation patterns of the surface sediments with hydrographical measurements shows that the L. inflata Dissolution Index (LDX) might be an adequate proxy to reconstruct paleo-water mass conditions in an area which is highly saturated with respect to calcium carbonate.

Sea-level related molluscan plankton events (Gastropoda, Euthecosomata) during the Rupelian (Early Oligocene) of the North Sea Basin

Abstract Spacio-temporal distribution patterns of North Sea Basin Early Oligocene (Rupelian) pteropoda (holoplanktonic gastropods: Mollusca, Gastropoda, Euthecosomata) are studied. These patterns indicate three short term invasions of a single pteropod species during the Rupelian. These invasions are indicated here as Clio blinkae Event, Praehyalocylis laxeannulata Event and Clio jacobae Event. The conspicuously short occurrences of the species, their abundances and some lithological features of the pteropod bearing strata lead to the conclusion that these plankton events are linked to sea level high-stands allowing currents from the worlds oceans to enter into the North Sea Basin.

Gelatinous invertebrate zooplankton of the South Adriatic: species composition and vertical distribution

The species composition and vertical distribution of gelatinous invertebrate zooplankton were investigated from April 1993 to June 1994 in the 0–1000 m water column at a deep-sea station in the northern part of the South Adriatic Pit. Fifty-seven species were identified: 11 hydromedusae, 13 calycophores, 3 ctenophores, 3 heteropods, 10 pteropods, 8 polychaetes and 9 chaetognaths. The pteropod Desmopterus papilio and the heteropod Protatlanta mediterranea were recorded for the first time in the Adriatic Sea. Data from this study differed from those of previous investigations in the South Adriatic as regards the numerically dominant polychaete and pteropod species. All investigated groups generally were more abundant in the upper 100 m and decreased with depth. Different vertical distributions of life stages were observed for those species that occupy a wide depth range: Persa incolorata, Solmissus albescens, Limacina inflata, Cymbulia peroni, Pelagobia longicirrata, Sagitta lyra and Sagitta decipiens.

Sea-level related molluscan plankton events (Gastropoda, Euthecosomata) during the Rupelian (Early Oligocene) of the North Sea Basin

Abstract Spacio-temporal distribution patterns of North Sea Basin Early Oligocene (Rupelian) pteropoda (holoplanktonic gastropods: Mollusca, Gastropoda, Euthecosomata) are studied. These patterns indicate three short term invasions of a single pteropod species during the Rupelian. These invasions are indicated here as Clio blinkae Event, Praehyalocylis laxeannulata Event and Clio jacobae Event. The conspicuously short occurrences of the species, their abundances and some lithological features of the pteropod bearing strata lead to the conclusion that these plankton events are linked to sea level high-stands allowing currents from the worlds oceans to enter into the North Sea Basin.

Impact of the Azores Front on the distribution of planktic foraminifers, shelled gastropods, and coccolithophorids

Abstract The Azores Front-Current System, south of the Azores Islands, has been studied in order to reveal the direct impact of an open oceanic thermohaline front on the distribution of the calcareous plankton. Planktic foraminifers, pteropods, heteropods, and coccolithophorids were sampled from the upper 2500 m of the water column during August 1997 and January 1999. In addition, the hydrography was recorded across the frontal jet on combined CTD and XBT transects. In August 1997, a strong seasonal thermocline capped the Azores Front (AF) at about 60–90 m water depth. Below the thermocline a distinct hydrographic front was indicated by temperature and salinity gradients. The central AF was an area of low planktic foraminiferal, gastropod, and coccolithophorid production, and was a faunal barrier for shallow- and deep-dwelling species. Highest numbers of planktic foraminifers, gastropods, and coccolithophores were recorded from above the thermocline north of the AF. The most frequent planktic foraminiferal and pteropod species were Globigerinoides ruber (white) and Limacina inflata, respectively. Below 100 m, planktic foraminifers were most frequent north of the AF and gastropod shells were rare. In particular, the deep-dwelling planktic foraminifer Globorotalia scitula was frequent only at sampling sites north of the AF. In January 1999, the surface water temperature of the Azores Front-Current System was lower and the thermocline was deeper than in August 1997. The planktic foraminiferal standing stock was three times higher than in August 1997, and no water depth related faunal changes occurred. The fauna was dominated by Globorotalia truncatulinoides, and Turborotalita humilis was frequent. During both January and August, the fauna from south of the Azores was different from that to the southeast, recording the occurrence of two different water masses. In this study we present a micropaleontological definition of the AF, in order to provide a paleoceanographic tool that may be used to decipher the late Quaternary current system of the North Atlantic Ocean.

Significance of pteropods in deciphering the late Quaternary sea-level history along the southwestern Indian shelf

The paper evaluates the usefulness of pteropods in palaeobathymetric synthesis along the southwestern continental shelf of India. Core samples collected from the shelf off north Kerala (SW coast of India) were studied for faunal assemblages (pteropods and foraminifers), calcium carbonate contents and lithological characteristics. A fundamental precept for considering any organism as a bathometer is that it should be highly sensitive to changing water depths. To ascertain this, the bathymetric distribution patterns of modern pteropods as well as planktonic and benthic foraminifers were recorded in core-top samples. The results reveal that certain pteropod species (Limacina inflata, Creseis acicula, Creseis virgula, and Creseis chierchiae) are highly depth sensitive. The response of these species to depth changes was assessed in terms of the L. inflata and Creseis spp. abundance ratio. A model for the relationship between water depths and the L. inflata/Creseis spp. ratio is proposed for the southwestern shelf of India. Variations of benthic/planktonic foraminifers (BF/PF) and pteropods/planktonic foraminifers (Pt/PF) in the modern sediments were also found to be depth controlled. Two sediment cores, representing the last 36,000 and 23,000 years, were collected to investigate past sea-level changes. These cores comprised two distinct lithological units, the upper unit corresponding to the Holocene, and the lower unit to the last glacial period. The L. inflata/Creseis spp. model was successfully applied to the fossil record for reconstructing the palaeobathymetry of the shelf study locations. Down-core variations in the BF/PF and Pt/PF ratios support these inferred sea-level changes. Major periods of sea-level oscillations were also found to have a strong influence on the calcium carbonate distribution. For both core sites, the palaeobathymetric curves reflect consistency in terms of changing sea level. The results suggest that the sea level stood around 100 m below the present mean sea level during the last glacial maximum. A rapid rise in sea level was documented between 15 and 10 ka B.P. The sea-level rise has been slower since 7 ka B.P.

Euthecosomatous gastropods (Mollusca: Heterobranchia) from Buton (SE Sulawesi, Indonesia), with notes on species from Viti Levu, Fiji; systematics, biostratigraphy

Pteropoda (Mollusca, Gastropoda, Euthecosomata) described by Beets (1943, 1950, 1953) from the alleged Late Miocene/Early Pliocene asphaltic deposits of Buton (SE Sulawesi, Indonesia) are revised. The following species are distinguished: Styliola subula (Quoy & Gaimard, 1827), Cavolinia bituminata (Beets, 1953), Cavolinia mexicana (Collins, 1934), Cavolinia vendryesiana (Guppy, 1873) and Diacria mbaensis Ladd, 1934. A comparison with the Fiji pteropod associations suggests a Miocene (Tortonian to Messinian) age for the Indonesian faunules. Pteropod species described by Ladd (1934) from Viti Levu (Fiji Islands), are revised in an appendix. Five species are distinguished, viz. Creseis acicula (Rang, 1828) (?), Cavolinia gypsorum (Bellardi, 1873), C. mexicana, C. rewaensis (Ladd, 1934) and Diacria mbaensis Ladd, 1934. The presence of Cavolina gypsorum dates this association as Miocene (Tortonian–Messinian).

Pteropods (Mollusca, Gastropoda) from the Pliocene Miyazaki Group, Miyazaki Prefecture, Japan

Twenty-four species of pteropods are described from the Pliocene Miyazaki Group in the Tsuma-Takanabe district, Miyazaki Prefecture, southwest Japan. Five are new:Clio shibatainew species,Cuvierina miyazakiensisnew species,Cavolinia floridana japonicanew subspecies,C. itoigawainew species, andC. vendryesiana hyugaensisnew subspecies.The pteropod fauna of the two lower members of the Miyazaki Group consists largely of extinct species. Whereas more than one-half of the species of the two upper members are extant.Twelve species,Limacinasp.,Clio hataii(Noda, 1972),C. shibatainew species,Cuvierina miyazakiensisnew species,Bowdenatheca?sp.,Diacria digitatasubsp. indet.,Cavolinia floridana japonicanew subspecies,C.cf.C. gypsorum(Bellardi, 1873),C. itoigawainew species,C. mexicana(Collins, 1934),C. rattoneiSimonelli, 1896, andC. vendryesiana hyugaensisnew subspecies seem to serve as good index fossils for the Pliocene.

Prey composition and daily rations of myctophid fishes in the Southern Ocean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 134:1-14 (1996) - doi:10.3354/meps134001 Prey composition and daily rations of myctophid fishes in the Southern Ocean Pakhomov EA, Perissinotto R, McQuaid CD The feeding ecology of myctophids was studied using data collected during 5 South African scientific cruises to the Southern Ocean from 1985 to 1995. A total of 362 specimens, comprising 36 species, were analyzed for gut contents. Myctophid biomass levels, estimated from Bongo net tows, are among the lowest yet recorded for the Southern Ocean. Peak biomass levels were associated with the main frontal zones and with a permanent polynya region in the Lazarev Sea. Results show that all myctophid species are opportunistic mesozooplankton feeders exhibiting a high degree of overlap in their food spectrum and consuming primarily the most abundant species of copepods, euphausiids, hyperiids and pteropods. Daily rations were estimated using 3 different approaches and ranged from 0.2 to 4.4% of dry body weights. Generally, the daily food intake was equivalent to 0.5 (lower mean) to 2.9 (upper mean) of dry body weight for Antarctic and subantarctic species, and between 1.2 and 3.8% for temperate and subtropical species. Antarctic krill, Euphausia superba, was usually poorly represented in the stomachs of all but 1 myctophid species. The results of this study therefore do not support the hypothesis that krill plays a major role in the feeding ecology and budget of myctophids. Myctophid fishes . Antarctica . Feeding . Daily ration Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 134. Publication date: April 25, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.