Examinando por Autor "Carrasco, Sergio A."
Mostrando 1 - 5 de 5
Resultados por página
Opciones de ordenación
Ítem Discrete Spawning Aggregations of the Loliginid Squid Doryteuthis gahi Reveal Life-History Interactions of a Dwarf Morphotype at the Center of Its Distribution Range(Frontiers Media S.A., 2021-01) Carrasco, Sergio A.; Bravo, Macarena; Ibáñez, Christian M.; Zapata Hernández, GermánHeterogeneous environmental conditions along the Humboldt Current System (HCS) influence the life-history strategy of a variety of species in different ways. There is limited information on latitudinal traits of coastal cephalopods as part of the interacting species in pelagic and benthic environments. The present study used the loliginid squid Doryteuthis gahi as a model organism to: (1) evaluate latitudinal traits on egg laying patterns, (2) characterize a particular spawning ground, (3) quantify the isotopic variation from different tissues, (4) evaluate potential trophic ontogenetic changes, (5) determinate trophic position, and (6) isotopically estimate the relative importance of putative preys in the squid’s assimilated diet. Results evidenced that egg-masses collected between 2014 and 2020 presented similar patterns along northern-central Chile (27–36°S), with females attaching small egg-capsules (10–50 mm length) through the year and over a variety of anthropogenic and natural substrates. At a small scale (Coquimbo; 29°S), early life history traits showed distinct patterns depending on SST, with warmer collection periods (∼18°C) evidencing larger capsules and smaller embryos, although small paralarvae were obtained over the 4-year sampling period. In this site, sampling of older ontogenetic stages supported the constant presence of small-sized squids (19–77 mm ML). Males had larger mean sizes compared to females and undetermined specimens, with a high proportion of mature stages. Observations in captivity were extended for up to 110 d, validating that small females (45–64 mm ML) spawn the small egg-capsules typically observed in the field. Differences in stable isotope composition between beaks and soft tissues of adult squids were lower for δ13C values (1.1 vs. 1.4‰, respectively) and higher for δ15N values (5.3 vs. 4.7‰, respectively). Isotopic composition through ontogeny found similar δ13C and δ15N values, suggesting that carbon sources (pelagic origin) and trophic position did not change significantly, with copepods, euphausiids and nereid polychaetes being the most important preys. This study unveils the permanent occurrence of a small reproductive morphotype of D. gahi in shallow coastal habitats of northern-central Chile (i.e., center of the distribution range), providing the first insights for understanding the species’ potential adaptations to heterogeneous conditions in the HCS and the unexplored distribution gap between the two centers of abundance (Peru and the Falkland/Malvinas islands). © Copyright © 2021 Carrasco, Bravo, Ibáñez and Zapata-Hernández.Ítem Environmental and ecological factors mediate taxonomic composition and body size of polyplacophoran assemblages along the Peruvian Province(Nature Publishing Group, 2019-12) Ibáñez, Christian M.; Waldisperg, Melany; Torres, Felipe I.; Carrasco, Sergio A.; Sellanes, Javier; Pardo-Gandarillas, M. Cecilia; Sigwart, Julia D.Intertidal communities’ composition and diversity usually exhibit strong changes in relation to environmental gradients at different biogeographical scales. This study represents the first comprehensive diversity and composition description of polyplacophoran assemblages along the Peruvian Province (SE Pacific, 12°S–39°S), as a model system for ecological latitudinal gradients. A total of 4,775 chitons from 21 species were collected on twelve localities along the Peruvian Province. This sampling allowed us to quantitatively estimate the relative abundance of the species in this assemblage, and to test whether chitons conform to elementary predictions of major biogeographic patterns such as a latitudinal diversity gradient. We found that the species composition supported the division of the province into three ecoregional faunal groups (i.e. Humboldtian, Central Chile, and Araucanian). Though chiton diversity did not follow a clear latitudinal gradient, changes in species composition were dominated by smaller scale variability in salinity and temperature. Body size significantly differed by ecoregions and species, indicating latitudinal size-structure assamblages. In some localities body size ratios differed from a random assemblage, evidencing competition at local scale. Changes in composition between ecoregions influence body size structure, and their overlapping produce vertical size segregation, suggesting that competition coupled with environmental conditions structure these assemblages. © 2019, The Author(s).Ítem Macroevolutionary Trade-Offs and Trends in Life History Traits of Cephalopods Through a Comparative Phylogenetic Approach(Frontiers Media S.A., 2021-09) Ibáñez, Christian M.; Díaz-Santana-Iturrios, Mariana; Carrasco, Sergio A.; Fernández-Álvarez, Fernando A.; López-Córdova, David A.; Cornejo, Claudio F.; Ortiz, Nicolás; Rocha, Francisco; Vidal, Erica A. G.; Pardo-Gandarillas, María CeciliaOne of the major mechanisms responsible for the animals’ fitness dynamics is fecundity. Fecundity as a trait does not evolve independently, and rather interacts with other traits such as body and egg size. Here, our aim was to correctly infer the macroevolutionary trade-offs between body length, egg length, and potential fecundity, using cephalopods as study model. The correlated evolution among those traits was inferred by comparative phylogenetic methods. Literature data on biological and reproductive traits (body length, egg length, and potential fecundity) was obtained for 90 cephalopod species, and comparative phylogenetic methods based on a previous molecular phylogeny were used to test the correlated evolution hypothesis. Additionally, we estimated the phylogenetic signal and fitted five different evolutionary models to each trait. All traits showed high phylogenetic signal, and the selected model suggested an evolutionary trend toward increasing body length, egg length, and fecundity in relation to the ancestral state. Evidence of correlated evolution between body length and fecundity was observed, although this relationship was not detected between body length and egg length. The robust inverse relationship between fecundity and egg length indicates that cephalopods evolved a directional selection that favored an increase of fecundity and a reduction of egg length in larger species, or an increase in egg length with the concomitant reduction of fecundity and body length in order to benefit offspring survival. The use of phylogenetic comparative methods allowed us to properly detect macroevolutionary trade-offs. © Copyright © 2021 Ibáñez, Díaz-Santana-Iturrios, Carrasco, Fernández-Álvarez, López-Córdova, Cornejo, Ortiz, Rocha, Vidal and Pardo-Gandarillas.Ítem Sexual Selection and the Evolution of Male Reproductive Traits in Benthic Octopuses(Frontiers Media S.A., 2019-11) Ibáñez, Christian M.; Pérez-Álvarez, Javiera; Catalán, Jennifer; Carrasco, Sergio A.; Pardo-Gandarillas, Cecilia; Rezende, Enrico L.Competition between same-sex organisms, or intra-sexual selection, can occur before and after mating, and include processes such as sperm competition and cryptic female choice. One of the consequences of intra-sexual selection is that male reproductive traits tend to evolve and diverge at high rates. In benthic octopuses, females often mate with more than one male in a single reproductive event, opening the venue for intra-sexual selection at multiple levels. For instance, males transfer spermatophores through hectocotylus, and can remove the spermatophores left by other males. Considering the limited evidence on post-copula competition in benthic octopuses, and the potential to affect the evolution of reproductive traits within octopodids, we put this hypothesis to a test employing a phylogenetic comparative approach. We combined data on hectocotylized arm length (HAL), ligula length (LL), spermatophore length (SL) with a Bayesian molecular phylogeny of 87 species, to analyze how reproductive traits have diverged across lineages and covary with body size (mantle length; ML). First, additionally to ML, we estimated the phylogenetic signal (λ) and mode of evolution (κ) in each reproductive trait. Second, we performed phylogenetic regressions to quantify the association among reproductive traits and their co-variation with ML. This analysis allowed us to estimate the phenotypic change along a branch into the phylogeny, and whether selection may have played a role in the evolution and diversification of specific clades. Estimations of λ were always high (>0.75), indicating concordance between the traits and the topology of the phylogenetic tree. Low values of κ ([removed] 0.5 in all cases). Overall, evolutionary rate models applied to the SL-ML regression suggested that octopuses of the family Megaleledonidae have evolved larger spermatophores than expected for their size. The regression HAL-ML indicated that HAL was more variable in Megaleledonidae than in the remaining clades, suggesting that the high divergence across species within this group might partially reflect intra-sexual selection. These results support the hypothesis that, at least in some lineages, sexual selection may account for the divergence in reproductive traits of male octopuses. © Copyright © 2019 Ibáñez, Pérez-Álvarez, Catalán, Carrasco, Pardo-Gandarillas and Rezende.Ítem Systematics and Phylogenetic Relationships of New Zealand Benthic Octopuses (Cephalopoda: Octopodoidea)(Frontiers Media S.A., 2020-03) Ibáñez, Christian M.; Fenwick, , Mark; Ritchie, Peter A.; Carrasco, Sergio A.; Pardo Gandarillas, M. CeciliaThe systematics of the New Zealand octopods have only been reviewed twice in the last 100 years. In these revisions many species have been provisionally classified in the genus Octopus. Recent genetic studies have synonymized some New Zealand species with octopuses from other regions. The present study investigates the systematics and phylogeny of octopuses from New Zealand using eighty eight specimens, three mitochondrial genes (16S rRNA, cytochrome c oxidase subunit I, and cytochrome c oxidase subunit III) and one nuclear gene (Rhodopsin). Forty-four new octopod DNA sequences (belonging to 13 species) were included, adding to the 83 existing sequences from GenBank. All sequences were used to generate phylogenetic trees based on Maximum Likelihood (ML) and Bayesian inference (BI), with a data set composed by 97 species, including octopod sister groups and Vampyroteuthis infernalis as an outgroup. Gene tree and species delimitation analyses revealed a distinct genetic difference between two sympatric Graneledone subspecies, which we propose as valid species. Muusoctopus tangaroa is a sister species of M. thielei from Kerguelen; while Enteroctopus zealandicus forms a clade with E. megalocyathus from South America and E. dofleini from the North Pacific. Similarly, Octopus campbelli, O. huttoni, and O. mernoo form a monophyletic group with Robsonella fontaniana from South America, Scaeurgus unicirrhus from the Atlantic and O. pallidus from Australia. Pinnoctopus cordiformis is close to Grimpella thaumastocheir and several species of Octopus sensu lato as in previous phylogenetic studies. This study suggests that octopuses from New Zealand have different phylogenetic and biogeographic origins and represent independent radiations into this region. © Copyright © 2020 Ibáñez, Fenwick, Ritchie, Carrasco and Pardo-Gandarillas.