Larval and early post-larval shell of three deep-sea Scaphopoda (Mollusca) from the southwest Atlantic

The larval shells of Antalis circumcincta (Watson, 1879) (order Dentaliida), Pertusiconcha callithrix (Dall, 1889) (order Gadilida) and of an undetermined species of uncertain systematic position are described. The material studied comprises mainly samples from deep waters, collected by expeditions along the southeast coast of Brazil. The larval shell of the three taxa matches other types previously described in the literature. Antalis circumcincta and P. callithrix have four regions (protoconch A, protoconch B, teleoconch A, teleoconch B), but differ in dimensions and sculpture from each other, while the undetermined species has three regions (protoconch A, protoconch B, teleoconch B). A morphometric approach combined with a discriminant analysis also indicates that the three taxa are significantly distinct. This study confirms patterns of larval shells at the taxonomic rank of orders but other supraspecific patterns remain uncertain.     

Distinct protoconchs recognised in three of the larger Mediterranean Cerithium species (Caenogastropoda: Cerithiidae)

The gastropod genus Cerithium includes several polymorphic species which are hardly distinguishable using a morphological approach based on teleoconch characters. Here we show that protoconch characters can be reliably used to identify the larger Mediterranean species (Cerithium alucastrum, C. repandum and C. vulgatum), and to assess their intraspecific variability. Based on a large amount of morphological data, we show that a multispiral, strongly sculptured protoconch (traditionally associated with C. vulgatum) is found in C. alucastrum. This species originated in the Pliocene. A multispiral, weakly sculptured protoconch, not observed previously, is reported for C. vulgatum. A paucispiral protoconch, distinct from those observed previously for C. lividulum and C. renovatum, is reported for C. repandum and can be used for recognising its wide intraspecific variation and understanding its geographical distribution. Cerithium repandum, previously doubtfully recorded outside its type locality, extends back to the mid-Pliocene and is today rather widely distributed in the Mediterranean, although absent from the Aegean Sea and the Alboran Sea. We describe the larval development of C. repandum and C. vulgatum for the first time, confirming their respective non-planktotrophic and planktotrophic development previously inferred from protoconch morphology. Also, we report a possible case of morphological convergence between C. repandum and C. vulgatum occurring in harbour sites, where we found a distinct (possibly Anthropocene) shell form not described previously from other Recent or fossil material.     

Inflated protoconchs and internally dissolved, coiled protoconchs of nudibranch larvae: different developmental trajectories achieve the same morphological result

Abstract. Light and scanning electron microscopy were used to examine protoconch form in eight species of planktotrophic heterobranch larvae, including four nudibranch species with a coiled (type 1) protoconch, two nudibranch species with an inflated (type 2) protoconch, and two cephalaspid species with a coiled protoconch. The coiled protoconchs of the cephalaspids and nudibranchs have a similar form at hatching, and shell growth up to metamorphic competence is hyperstrophic. Shell added to coiled protoconchs during the larval stage overgrows all but the left wall of the initial protoconch that exists at hatching. The entire protoconch of cephalaspids, including overgrown areas, is retained through metamorphosis. However, during later larval development in nudibranchs with a coiled protoconch, overgrown shell is completely removed by dissolution. As a result, regardless of whether nudibranch larvae hatch with an inflated or coiled protoconch type, the protoconch is a large, hollow cup at metamorphic competence. The protoconch of nudibranchs is shed at metamorphosis and absence of a post-metamorphic shell is correlated with absence of visceral coiling in this gastropod group. Internal dissolution of the coiled protoconch in nudibranchs allows the left digestive gland to uncoil prior to metamorphic shell loss. Retention of overgrown protoconch whorls in cephalaspids allows the attachment plaque of the pedal muscle to migrate onto the parietal lip of the post-metamorphic shell. Release from this constraint in nudibranchs, in which the larval pedal muscles and the entire protoconch are lost at metamorphosis, may have permitted internal protoconch dissolution and precocious uncoiling of the visceral mass, as well as evolutionary emergence of the inflated larval shell type.     

Colonization history of Galapagos giant tortoises: Insights from mitogenomes support the progression rule

Galapagos giant tortoises (Chelonoidis spp.) are a group of large, long-lived reptiles that includes 14 species, 11 of which are extant and threatened by human activities and introductions of non-native species. Here, we evaluated the phylogenetic relationships of all extant and two extinct species (Chelonoidis abingdonii from the island of Pinta and Chelonoidis niger from the island of Floreana) using Bayesian and maximum likelihood analysis of complete or nearly complete mitochondrial genomes. We also provide an updated phylogeographic scenario of their colonization of the Galapagos Islands using chrono-phylogenetic and biogeographic approaches. The resulting phylogenetic trees show three major groups of species: one from the southern, central, and western Galapagos Islands; the second from the northwestern islands; and the third group from the northern, central, and eastern Galapagos Islands. The time-calibrated phylogenetic and ancestral area reconstructions generally align with the geologic ages of the islands. The divergence of the Galapagos giant tortoises from their South American ancestor likely occurred in the upper Miocene. Their diversification on the Galapagos adheres to the island progression rule, starting in the Pleistocene with the dispersal of the ancestral form from the two oldest islands (San Cristóbal and Española) to Santa Cruz, Santiago, and Pinta, followed by multiple colonizations from different sources within the archipelago. Our work provides an example of how to reconstruct the history of endangered taxa in spite of extinctions and human-mediated dispersal events and provides a framework for evaluating the contribution of colonization and in situ speciation to the diversity of other Galapagos lineages.     

Description of a New Galapagos Giant Tortoise Species (Chelonoidis; Testudines: Testudinidae) from Cerro Fatal on Santa Cruz Island

The taxonomy of giant Galapagos tortoises (Chelonoidis spp.) is currently based primarily on morphological characters and island of origin. Over the last decade, compelling genetic evidence has accumulated for multiple independent evolutionary lineages, spurring the need for taxonomic revision. On the island of Santa Cruz there is currently a single named species, C. porteri. Recent genetic and morphological studies have shown that, within this taxon, there are two evolutionarily and spatially distinct lineages on the western and eastern sectors of the island, known as the Reserva and Cerro Fatal populations, respectively. Analyses of DNA from natural populations and museum specimens, including the type specimen for C. porteri, confirm the genetic distinctiveness of these two lineages and support elevation of the Cerro Fatal tortoises to the rank of species. In this paper, we identify DNA characters that define this new species, and infer evolutionary relationships relative to other species of Galapagos tortoises.     

Systematics and phylogenetic species delimitation within Polinices s.l. (Caenogastropoda: Naticidae) based on molecular data and shell morphology

Here, we present the first phylogenetic analysis of a group of species taxonomically assigned to Polinices sensu latu (Naticidae, Gastropoda) based on molecular data sets. Polinices s.l. represents a speciose group of the infaunal gastropod family Naticidae, including species that have often been assigned to subgenera of Polinices [e.g. P. (Neverita), P. (Euspira), P. (Conuber) and P. (Mammilla)] based on conchological data. The results of our molecular phylogenetic analysis confirm the validity of five genera, Conuber, Polinices, Mammilla, Euspira and Neverita, including four that have been used previously mainly as subgenera of Polinices s.l. Our results furthermore indicate a close relationship of members of the Polinicinae to Sinum??a genus traditionally placed in the naticid subfamily Sininae. We furthermore present conchological analyses to determine the validity of shell characters used traditionally in species designation in the genus Polinices. Our data reveal several characters (e.g. protoconch, operculum colour, parietal callus) to be informative, while many characters show a high degree of homoplasy (e.g. umbilicus, shell form). Among the species arranged in the genus Polinices s.s., four conchologically very similar taxa often subsumed under the common Indo-Pacific species P. mammilla are separated distinctly in phylogenetic analyses. Despite their striking conchological similarities, none of these four taxa are related directly to each other. Additional conchological analyses of available name-bearing type specimens and type figures reveal the four ??mammilla??-like white Polinices species to include true P. mammilla and three additional species, which could be assigned to P. constanti (replacement name for P. dubius), P. jukesii and possibly P. tawhitirahia, based on protoconch and operculum characteristics.     

29种中国野豌豆属植物叶表皮微形态特征及其系统学意义

应用光学显微镜和扫描电子显微镜对29种野豌豆属植物叶表皮微形态特征进行了观察。结果显示:叶表皮细胞形状有无规则形和多边形2种,垂周壁式样有深波状、浅波状和平直-弓形;表皮角质层纹饰微形态多样,大多数植物叶片表面不具有腺毛或仅中脉有,少数植物叶片表面具腺毛;部分叶表皮上有柔毛,少数植物无毛。气孔器存在于上表皮、下表皮、或上下表皮均有,形状为椭圆形、卵圆形,均为无规则型。野豌豆属植物叶表皮的这些微形态特征,在属内组间没有明确的规律性,但可为探讨该属种间的分类学及亲缘关系提供依据。     

Local parasite lineage sharing in temperate grassland birds provides clues about potential origins of Galapagos avian Plasmodium

Oceanic archipelagos are vulnerable to natural introduction of parasites via migratory birds. Our aim was to characterize the geographic origins of two Plasmodium parasite lineages detected in the Galapagos Islands and in North American breeding bobolinks (Dolichonyx oryzivorus) that regularly stop in Galapagos during migration to their South American overwintering sites. We used samples from a grassland breeding bird assemblage in Nebraska, United States, and parasite DNA sequences from the Galapagos Islands, Ecuador, to compare to global data in a DNA sequence registry. Homologous DNA sequences from parasites detected in bobolinks and more sedentary birds (e.g., brown‐headed cowbirds Molothrus ater, and other co‐occurring bird species resident on the North American breeding grounds) were compared to those recovered in previous studies from global sites. One parasite lineage that matched between Galapagos birds and the migratory bobolink, Plasmodium lineage B, was the most common lineage detected in the global MalAvi database, matching 49 sequences from unique host/site combinations, 41 of which were of South American origin. We did not detect lineage B in brown‐headed cowbirds. The other Galapagos‐bobolink match, Plasmodium lineage C, was identical to two other sequences from birds sampled in California. We detected a close variant of lineage C in brown‐headed cowbirds. Taken together, this pattern suggests that bobolinks became infected with lineage B on the South American end of their migratory range, and with lineage C on the North American breeding grounds. Overall, we detected more parasite lineages in bobolinks than in cowbirds. Galapagos Plasmodium had similar host breadth compared to the non‐Galapagos haemosporidian lineages detected in bobolinks, brown‐headed cowbirds, and other grassland species. This study highlights the utility of global haemosporidian data in the context of migratory bird–parasite connectivity. It is possible that migratory bobolinks bring parasites to the Galapagos and that these parasites originate from different biogeographic regions representing both their breeding and overwintering sites.     

Cyclops predation on ciliates: species.specific differences and functional responses

Experiments were conducted to measure to what extent cyclopoidcopepods ingest ciliated protists. Five freshwater ciliate species,ranging in size from 22 to 120 µm diameter, were testedwith two species of cyclopoids: Cyclops abyssorum and Cyclopskolensis. Ingestion rates were measured by radiolabeling ciliateswith ¹⁴C, and from these, functional response curves (the changein ingestion rate with changing cell densities) were constructed.Cyclopoids ingest ciliates with very high estimated maximalrates of >200 cells cyclopoid^–1 h^–1 However,there are large differences in ingestion rates that are notpredictable by the size of predator or prey. One ciliate speciesof intermediate size, Coleps hirtus, is nearly immune from cyclopoidpredation at all measured ciliate densities. Three other smallciliate species that move in rapid jumps elicit Honing type3 functional responses, with very little change in ingestionrates at low ciliate densities. Thus, while cyclopoids are capableof having a very considerable impact on ciliate populations,some ciliate species appear to have behavioral, morphologicalor chemical defenses to reduce their vulnerability. This callsinto question the practice of considering ciliates a homogeneousgroup when constructing food web models.     

HETEROSTOPHIC SHELLS AND PELAGIC DEVOLOPMENT IN TROCHOIDEANS: IMPLICATIONS FOR CLASSIFICATION, PHYLOGENY AND PALAEOECOLOGY

Four species of archeogastropods, presumed members of threesubfamilies of the trochidae, exhibit significant differencesin developmental modes and shell coiling. All four species havelecithotrophic development which is reflected in their inflatedpausispiral protoconchis; however, Margarites marginatus andLirularia succincta have benthic development in gelatinous masses,while Margarites pupillus and Calliostoma ligatum have pelagicembryos and swimming larvae with a potential for dispersal overa period of a week or longer. These modes cannot be deducedfrom the size of the egg, the size or shape of the protoconch,or the size or relative prominence of female pallial reproductivestructures. The protoconch of C. ligatum is orthostrophicallycoiled, but the protoconchs of the other three species are hyperstrophicallycoiled although their teleconchs are orthostrophic. These threetrochoidean species thus share with architectonicoideans, pyramidelloideans,opisthobranchs, and pulmonates the distinctive shell characterof heterostrophy, previously unreported for archaeogastropods. These observations, considered together with others reportedin the literature, show: (1) that developmental mode (pelagicor benthic) cannot be inferred from protoconch appearance ortaxonomy in major trochoidean ganera; (2) that significant dispersalpotential is present in the histories of some trochoidean archeogastropoids;and (3) that character sets (pallial reproductive structures,pairing during spawning, heterostrophic shell coiling) thoughtnot to occur below the mesogastropod level are found in theTrochoidea. These conclusions bring into question the usefulnessof these characters in defining higher gastropod taxa and raiseadditional questions concerning the ancestry of the higher gastropods. (Received 16 February 1989; accepted 25 June 1989)     

Molecular Evidence for an Old World Origin of Galapagos and Caribbean Band-Winged Grasshoppers (Acrididae: Oedipodinae: Sphingonotus)

Patterns of colonization and diversification on islands provide valuable insights into evolutionary processes. Due to their unique geographic position and well known history, the Galapagos Islands are an important model system for evolutionary studies. Here we investigate the evolutionary history of a winged grasshopper genus to infer its origin and pattern of colonization in the Galapagos archipelago. The grasshopper genus Sphingonotus has radiated extensively in the Palaearctic and many species are endemic to islands. In the New World, the genus is largely replaced by the genus Trimerotropis. Oddly, in the Caribbean and on the Galapagos archipelago, two species of Sphingonotus are found, which has led to the suggestion that these might be the result of anthropogenic translocations from Europe. Here, we test this hypothesis using mitochondrial and nuclear DNA sequences from a broad sample of Sphingonotini and Trimerotropini species from the Old World and New World. The genetic data show two distinct genetic clusters representing the New World Trimerotropini and the Old World Sphingonotini. However, the Sphingonotus species from Galapagos and the Caribbean split basally within the Old World Sphingonotini lineage. The Galapagos and Caribbean species appear to be related to Old World taxa, but are not the result of recent anthropogenic translocations as revealed by divergence time estimates. Distinct genetic lineages occur on the four investigated Galapagos Islands, with deep splits among them compared to their relatives from the Palaearctic. A scenario of a past wider distribution of Sphingonotus in the New World with subsequent extinction on the mainland and replacement by Trimerotropis might explain the disjunct distribution.     

Internal embryonic brooding and development in the southern Australian micro-snail Tricolia rosea (Angas, 1867) (Vetigastropoda: Phasianellidae: Tricoliinae)*

ABSTRACT

Internal embryonic brooding has been suggested as an adaptation to enhance reproductive success in minute gastropods. It is rare in vetigastropods, previously known in only two species of Spectamen Iredale, 1924 (Solariellidae) from South Africa. Herein it is confirmed in the temperate Australian micro-snail Tricolia rosea (Angas, 1867), with up to 46 embryos observed within a gravid female. Embryos are brooded to an advanced stage, possessing a translucent, calcified shell and a calcified operculum. The initial protoconch is colourless, spirally sculptured and delineated by a consistent axial demarcation at the 0.75 whorl mark, when it measures 320?µm across. Beyond this, the second part of the protoconch is tinted pink, the strong spiral sculpture continues but the ribs and interstices are broader, with smoother surface microsculpture. At the 1.1 to 1.125 whorl mark the protoconch measures 400?µm across when transition to smooth teleoconch sculpture occurs. No brooded embryos possessed teleoconch sculpture. The potential relationship of protoconch morphology to embryonic development, hatching, feeding and release are considered. The mechanism of fertilisation is unknown, but embryos in a brood are at the same developmental stage. Unanswered questions in embryonic development and problems with protoconch terminologies in vetigastropods are also discussed.     

Some heterostrophic gastropods from Triassic St. Cassian Formation with a discussion on the classification of the Allogastropoda

Fifteen species of Heterostropha are described, 12 of them for the first time. All are newly interpreted with regard to their taxonomic relation to fossil and living gastropods. The Streptacidoidea with long Paleozoic history are represented in the Late Triassic St. Cassian Formation by several genera that can be differentiated into four families. The Ebalidae are represented byEbala, with smooth protoconch, Cassianebalidae byCassianebala andLoxebala with axially ornamented protoconch. The Donaldinidae of St. Cassian are represented by one species ofDonaldina and two ofNeodonaldina that stand in the continuation of Paleozoic species ofDonaldina. Architectonicoidea with shells coiled in a plane and Valvatoidea appear in the St. Cassian fauna without known Paleozoic relation. In the former superfamily the Architectonicidae can be recognized in the genusRinaldoconchus with two species. Cassianaxidae withCassianaxis, Amphitomariidae withAmphitomaria, Stuoraxidae withStuoraxis andAmpezzogyra have a sinistral protoconch and planispirally coiled dextral teleconchs. They all resemble different modern species that have similarly small shells. Modern Hyalogyrinidae have withAlexogyra a new representative from the Triassic. The Valvatoidea are represented with the generaCarboninia andBandellina of the Cornirostridae in the Triassic representatives. The relation of described species in the system of the Heterostropha is discussed.     

The origin and diversification of Galapagos mockingbirds

Abstract Evolutionary radiations of colonists on archipelagos provide valuable insight into mechanisms and modes of speciation. The apparent diversification of Galapagos mockingbirds (Nesomimus) provoked Darwin's initial conception of adaptive radiation, but the monophyly of this historically important exemplar has not been evaluated with molecular data. Additionally, as with most Galapagos organisms, we have a poor understanding of the temporal pattern of diversification of the mockingbirds following colonization(s) from source populations. Here we present a molecular phylogeny of Galapagos and other mockingbird populations based on mitochondrial sequence data. Monophyly of Galapagos mockingbirds was supported, suggesting a single colonization of the archipelago followed by diversification. Our analyses also indicate that Nesomimus is nested within the traditional genus Mimus, making the latter paraphyletic, and that the closest living relatives of Galapagos mockingbirds appear to be those currently found in North America, northern South America, and the Caribbean, rather than the geographically nearest species in continental Ecuador. Thus, propensity for over‐water dispersal may have played a more important role than geographic proximity in the colonization of Galapagos by mockingbirds. Within Galapagos, four distinct mitochondrial DNA clades were identified. These four clades differ from current taxonomy in several important respects. In particular, mockingbirds in the eastern islands of the archipelago (Española, San Cristóbal, and Genovesa) have very similar mitochondrial DNA sequences, despite belonging to three different nominal species, and mockingbirds from Isabela, in the west of the archipelago, are more phylogenetically divergent than previously recognized. Consistent with current taxonomy is the phylogenetic distinctiveness of the Floreana mockingbird (N. trifasciatus) and close relationships among most mockingbirds from the central and northern region of the archipelago (currently considered conspecific populations of N. parvulus). Overall, phylogeographic patterns are consistent with a model of wind‐based dispersal within Galapagos, with colonization of more northerly islands by birds from more southern populations, but not the reverse. Further radiation in Galapagos would require coexistence of multiple species on individual islands, but this may be prevented by relatively limited morphological divergence among mockingbirds and by lack of sufficient habitat diversity in the archipelago to support more than one omnivorous mimid     

Revision of the genus Thetidos Hedley, 1899 (Gastropoda: Conoidea: Raphitomidae) in the Indo-Pacific with descriptions of three new species

The genus Thetidos was established to accommodate a single species Thetidos morsura, a minute turriform conoidean with an unremarkable paucispiral protoconch, but possessing characteristic globose whorls of the teleoconch and three strong denticles on the inside of outer apertural lip. Subsequently, Thetidos was considered synonymous with Lienardia, and has rarely been mentioned in literature until the recent discovery of a remarkably similar species Thetidos tridentata, though it is different in protoconch morphology. Both molecular data and protoconch morphology unequivocally suggested placement of the new species in Raphitomidae. Examination of shells from the Indo-Pacific identified a number of similar forms, all referable to the genus Thetidos. Six species are now recognized within the genus; of them three, Thetidos puillandrei n. sp., Thetidos minutissima n. sp., Thetidos pallida n. sp., are here described as new. Thetidos species are now known from subtidal depths from the Philippines and Sulawesi to French Polynesia. Thetidos morsura is the only species of the genus that possesses a paucispiral protoconch suggestive of a non-planktotrophic development, although it displays a wide geographic range and a high morphological variability.

http://zoobank.org/urn:lsid:zoobank.org:pub:1F2001CC-6BEA-4B26-AFB8-6B337E101FDB     

The distribution of mosquitoes across an altitudinal gradient in the Galapagos Islands

An avian malaria parasite (genus Plasmodium) has been detected consistently in the Galapagos Penguin (Spheniscus mendiculus) and less frequently in some passerines. We sampled three resident mosquito species (Aedes taeniorhynchus, Culex quinquefasciatus, and Aedes aegypti) using CDC light and gravid traps on three islands in 2012, 2013, and 2014. We sampled along altitudinal gradients to ask whether there are mosquito‐free refugia at higher elevations as there are in Hawaii. We captured both Ae. taeniorhynchus and Cx. quinquefasciatus at all sites. However, abundances differed across islands and years and declined significantly with elevation. Aedes aegypti were scarce and limited to areas of human inhabitation. These results were corroborated by two negative binomial regression models which found altitude, year, trap type, and island as categorized by human inhabitation to be significant factors influencing the distributions of both Ae. taeniorhynchus and Cx. quinquefasciatus. Annual differences at the highest altitudes in Isabela and Santa Cruz indicate the lack of a stable highland refuge if either species is found to be a major vector of a parasite, such as avian malaria in Galapagos. Further work is needed to confirm the vector potential of both species to understand the disease dynamics of avian malaria in Galapagos.     

Ty1-copia group retrotransposon sequences in amphibia and reptilia

We have isolated sequences belonging to Tyl-copia group retrotransposons from the genomes of an amphibian (Pyxicephalus adspersa) and three reptiles (Conolophus subscristatus, Amblyrynchus cristatus and Pytas mucosus). Two different seqences were found in the amphibian (Tpa1 and Tpa2). Each is present in several copies per genome and absent from the genomes of two other amphibian species. The C. subcristatus sequence Tcs1 is present in multiple copies in both its host genome (Galapagos land iguana) and the genome of the related Galapagos marine iguana (A. cristatus). There is little or no polymorphism in Tcs1 insertions between different individual animals, suggesting that this sequence is not transposing rapidly in either iguana genome. The P. mucosus sequence Tpm1 shows a discontinuous distribution in snake species, suggesting that it has either been lost from many lineages during vertical germline transmission or has been transferred horizontally in some snake species. Phylogenetic comparisons of all these sequences with each other and with other members of this retrotransposon group from other animals and plants show that sequences within a particular vertebrate species are most closely related to each other, consistent with a vertical transmission model for their evolution.     

Ty1-copia group retrotransposon sequences in amphibia and reptilia

We have isolated sequences belonging to Tyl-copia group retrotransposons from the genomes of an amphibian (Pyxicephalus adspersa) and three reptiles (Conolophus subscristatus, Amblyrynchus cristatus and Pytas mucosus). Two different seqences were found in the amphibian (Tpa1 and Tpa2). Each is present in several copies per genome and absent from the genomes of two other amphibian species. The C. subcristatus sequence Tcs1 is present in multiple copies in both its host genome (Galapagos land iguana) and the genome of the related Galapagos marine iguana (A. cristatus). There is little or no polymorphism in Tcs1 insertions between different individual animals, suggesting that this sequence is not transposing rapidly in either iguana genome. The P. mucosus sequence Tpm1 shows a discontinuous distribution in snake species, suggesting that it has either been lost from many lineages during vertical germline transmission or has been transferred horizontally in some snake species. Phylogenetic comparisons of all these sequences with each other and with other members of this retrotransposon group from other animals and plants show that sequences within a particular vertebrate species are most closely related to each other, consistent with a vertical transmission model for their evolution.     

Drastic effects of El Niño on Galapagos pinnipeds

Summary Population dynamics of pinnipeds living in the tropical upwelling ecosystem of the Galapagos were strongly influenced by the 1982–83 Southern Oscillation-El Niño (EN) event which was the strongest recorded in this century. The Galapagos fur seal (Arctocephalus galapagoensis) population lost the four youngest year classes (1980–1983) almost entirely and approximately 30% of the adult females and non-territorial males. Mortality of large territorial males was almost 100%. Most of the 1982 year class of Galapagos sea lions (Zalophus californianus wollebaeki) died and there was a much lower pup production in the breeding season following EN. Recurrent EN events must strongly influence age structure and average population size of these and other otariid species depending on tropical upwelling ecosystems.