Papers by Roger Sepúlveda
Rocky shores are areas of high diversity and productivity providing goods and services. Since hum... more Rocky shores are areas of high diversity and productivity providing goods and services. Since humans are altering nature at an unprecedented rate, producing shifts in important parameters for life such as temperature, habitat availability, water quality, among others, it is expected that species will respond by changing their natural distributions and/or abundances. To understand how species will respond to such changes, it is necessary to learn the processes that determine these patterns. The South American Research Group on Coastal Ecosystems was established to assess marine diversity and biomass along both coasts of South America through an international collaboration. The main goals of SARCE are to: (1) Test hypotheses about latitudinal gradients and patterns of local and regional biodiversity, (2) Identify the relationship between biodiversity and ecosystem functioning, (3) Assess the effect of environmental gradients and anthropogenic stressors, (4) Carry out capacity building and training activities aimed to solve environmental problems for the benefit of society. The SARCE network has sampled the coasts of nine countries around South America with a standardized protocol in more than 150 sites (2010-2014), ranging from 11º North to 55º South. This chapter provides a description of the biodiversity of the sites sampled by SARCE, along with a review of the uses and services that these ecosystems provide to human populations and the main threats and impacts these uses have caused.
Latin American Journal of Aquatic Research, May 25, 2016
The jumbo squid Dosidicus gigas is the most abundant cephalopod species in the southeastern Pacif... more The jumbo squid Dosidicus gigas is the most abundant cephalopod species in the southeastern Pacific Ocean, which supports the biggest cephalopod fishery in the world. Due to its growing economic importance, the population growth and distributional expansion of this squid is being increasingly studied. Nevertheless, some basic features of the biology of D. gigas are still unknown or have been poorly investigated. In this review we summarize the known information regarding the biology and ecology of this species in the southeastern Pacific Ocean; we focus on the Chilean region in order to propose hypotheses and research lines for a better understanding the life history of this organism. Available data on the size structure, reproduction and genetics of D. gigas allows us to propose hypotheses related to the squid's life history traits. Based on the current literature and publications of colleagues, we propose two hypotheses regarding the effect of spatial variation on the life history of D. gigas. Hypothesis 1: Squids mature at large sizes and spawn in oceanic waters with warm temperatures where paralarvae and juveniles develop. Immature squids migrate near shore to feed, grow and mature, and then return to the offshore sites to spawn. Hypothesis 2: Alternatively, juvenile D. gigas in the oceanic zone do not migrate to coastal waters and mature at small sizes compared to individuals living near the coast that mature at larger size and migrate to oceanic waters to spawn. We provide background information about the feeding behavior and parasitism of this species, suggesting that D. gigas is an important trophic link in the southeastern Pacific marine ecosystem. However, more studies on the feeding habits, reproduction and parasite load are needed not only to test hypotheses proposed in this study, but also to advance the overall knowledge of this species.
Regional Studies in Marine Science, Jul 1, 2021
DOAJ (DOAJ: Directory of Open Access Journals), 2003
Biological Research, 2011
Respiration and energy metabolism are key processes in animals, which are severely constrained by... more Respiration and energy metabolism are key processes in animals, which are severely constrained by the design of physical structures, such as respiratory structures. Insects have very particular respiratory systems, based on gas diffusion across tracheae. Since the effi ciency of the tracheal respiratory system is highly dependent on body shape, the pattern of morphological variation during ontogeny could have important metabolic consequences. We studied this problem combining through-fl ow respirometry and geometric morphometrics in 88 nymphs of the sand cricket, Gryllus fi rmus. After measuring CO 2 production in each individual, we took digital photographs and defi ned eight landmarks for geometric morphometric analysis. The analysis suggested that ontogenic deformations were mostly related to enlargement of the abdomen, compared to thorax and head. We found that (controlling for body size) metabolic variables and especially resting metabolism are positively correlated with a shape-component associated to an elongation of the abdomen. Our results are in agreement with the mechanics of tracheal ventilation in orthopterans, as gas circulation occurs by changes in abdominal pressures due to abdominal contractions and expansions along the longitudinal axis.
DOAJ (DOAJ: Directory of Open Access Journals), 2005
Regional Studies in Marine Science, 2021
Latin American Journal of Aquatic Research, 2016
The jumbo squid Dosidicus gigas is the most abundant cephalopod species in the southeastern Pacif... more The jumbo squid Dosidicus gigas is the most abundant cephalopod species in the southeastern Pacific Ocean, which supports the biggest cephalopod fishery in the world. Due to its growing economic importance, the population growth and distributional expansion of this squid is being increasingly studied. Nevertheless, some basic features of the biology of D. gigas are still unknown or have been poorly investigated. In this review we summarize the known information regarding the biology and ecology of this species in the southeastern Pacific Ocean; we focus on the Chilean region in order to propose hypotheses and research lines for a better understanding the life history of this organism. Available data on the size structure, reproduction and genetics of D. gigas allows us to propose hypotheses related to the squid’s life history traits. Based on the current literature and publications of colleagues, we propose two hypotheses regarding the effect of spatial variation on the life history...
Revista de biología marina y oceanografía, 2009
In this study we analyzed the natural diet and the dietary preferences of the octopus Robsonella ... more In this study we analyzed the natural diet and the dietary preferences of the octopus Robsonella fontaniana (d'Orbigny, 1834). Twenty-seven individuals were collected at San Vicente Bay, Chile, to study their stomach contents, and other 12 individuals were used in laboratory experiments for dietary selection tests. In the stomach contents 11 prey types were found, from which brachyuran crabs were the most frequent item. For preference tests, the animals were acclimated to constant temperature, air and water. Two experiments were performed: i) selection test on two gastropod species and three crustacean species, resulting in consume of crustaceans only (66.7% crustaceans and 0% gastropods), and ii) selection test on five crustaceans species, showing high preference for those highly motile (i.e. E. analoga was consumed 75% of the times offered). The scaling relationship between octopuses and preys showed a positive relationship between the size of octopuses and the fed preys. From field and experimental evidence we suggest that R. fontaniana has a selective hunting behavior and specialized diet with a narrow trophic niche breadth.
Gayana (Concepción), 2005
Se presentan los resultados de dos cruceros de pesca de investigación de la jibia, Dosidicus giga... more Se presentan los resultados de dos cruceros de pesca de investigación de la jibia, Dosidicus gigas (Orbigny 1835) realizados entre julio de 1993 y enero de 1994 en la Zona Económica Exclusiva de Chile comprendida entre los 29º S y 40º S. En cada lance se registró el día, hora, duración del lance, así como el volumen de la captura por lance y máquina potera, para efectuar estimaciones de abundancia relativa. A los ejemplares capturados se les determinó la longitud dorsal del manto (LDM), peso total, peso eviscerado, peso manto, sexo y se les extrajo el tracto digestivo, para un análisis del contenido estomacal. Las jibias sólo fueron capturadas entre los 29º S y los 30º S. En el primer crucero (invierno) se registraron ejemplares grandes (71 a 98 cm LDM) y chicos (< 44 cm LDM) de ambos sexos, mientras que en el segundo crucero (primavera) se capturaron sólo jibias de tamaño intermedio (26 a 60 cm LDM). Las distribuciones de frecuencias de tamaños determinadas en los cruceros muestran dos cohortes de D. gigas en la zona de pesca. La dieta no varió entre las estaciones y estuvo compuesta principalmente por peces pelágicos y demersales, secundariamente cefalópodos y ocasionalmente crustáceos pelágicos, incluyendo también canibalismo. Las relaciones longitud-peso fueron similares en ambos sexos y se corrobora que las jibias registradas en aguas de Chile, alcanzan pesos mayores a la misma longitud que las poblaciones de jibia de México y Perú.
Helgoland Marine Research, 2007
Despite a large amount of climatic and oceanographic information dealing with the recurring clima... more Despite a large amount of climatic and oceanographic information dealing with the recurring climate phenomenon El Niño (EN) and its well known impact on diversity of marine benthic communities, most published data are rather descriptive and consequently our understanding of the underlying mechanisms and processes that drive community structure during EN are still very scarce. In this study, we address two questions on the effects of EN on macrozoobenthic communities: (1) how does EN affect species diversity of the communities in northern Chile? and (2) is EN a phenomenon that restarts community assembling processes by affecting species interactions in northern Chile? To answer these questions, we compared species diversity and co-occurrence patterns of soft-bottoms macrozoobenthos communities from the continental shelf off northern Chile during (March 1998) and after (September 1998) the strong EN event 1997-1998. The methods used varied from species diversity and species cooccurrence analyses to multivariate ordination methods. Our results indicate that EN positively affects diversity of macrozoobenthos communities in the study area, increasing the species richness and diversity and decreasing the species dominance. EN represents a strong disturbance that affects species interactions that rule the species assembling processes in shallow-water, sea-bottom environments.
Helgoland Marine Research, 2006
We conducted an ecological study of a population of the polychaete Abarenicola affinis chiliensis... more We conducted an ecological study of a population of the polychaete Abarenicola affinis chiliensis in the shallow subtidal zone of Caleta Guardiamarina Riquelme in northern Chile. The study area is characterized by a hypoxic bottom consisting of fine sands and a silt-clay mixture, with high values of total organic matter content (TOM > 20%). During the two study periods (spring 1996 and 1997), the numerical contribution of A. affinis chiliensis to the total macrofauna was greater than 80%. A similar pattern was recorded for biomass, with A. affinis chiliensis surpassing 95% of the total macrofauna biomass. Statistical analyses did not detect significant differences in environmental and biotic variables between years (with the exception of salinity, which increased slightly), indicating temporal stability of these variables over the study period. Our results do not support the hypothesis of Wells that seawater temperatures act as a physical barrier impeding the dispersal of Abarenicola species. This hypothesis should be reexamined for some representatives of Abarenicola on the Pacific coast of South America.
Biological Research, 2011
Respiration and energy metabolism are key processes in animals, which are severely constrained by... more Respiration and energy metabolism are key processes in animals, which are severely constrained by the design of physical structures, such as respiratory structures. Insects have very particular respiratory systems, based on gas diffusion across tracheae. Since the effi ciency of the tracheal respiratory system is highly dependent on body shape, the pattern of morphological variation during ontogeny could have important metabolic consequences. We studied this problem combining through-fl ow respirometry and geometric morphometrics in 88 nymphs of the sand cricket, Gryllus fi rmus. After measuring CO 2 production in each individual, we took digital photographs and defi ned eight landmarks for geometric morphometric analysis. The analysis suggested that ontogenic deformations were mostly related to enlargement of the abdomen, compared to thorax and head. We found that (controlling for body size) metabolic variables and especially resting metabolism are positively correlated with a shape-component associated to an elongation of the abdomen. Our results are in agreement with the mechanics of tracheal ventilation in orthopterans, as gas circulation occurs by changes in abdominal pressures due to abdominal contractions and expansions along the longitudinal axis.
Se presentan los resultados del análisis taxonómico y ecológico de los poliquetos bentónicos subm... more Se presentan los resultados del análisis taxonómico y ecológico de los poliquetos bentónicos submareales obtenidos durante el crucero CIMAR 11 Fiordos. Las muestras fueron obtenidas en el mar interior de los fiordos magallánicos entre el seno Reloncaví (41° 40' S) y golfo Corcovado (43° 43' S), Pacífico suroriental, Chile, con un box-corer, entre 16 y 357 m de profundidad. Se recolectaron un total de 1.608 ejemplares de poliquetos pertenecientes a 7 clados, 30 familias y 57 especies. Los grupos funcionales que presentaron mayor abundancia fueron los depositívoros superficiales con un 41%, seguido por los omnívoros/carnívoros con un 27%. Los valores de diversidad específica fueron moderados entre 0,71 y 2,43; siendo la dominancia de Berger-Parker entre 0,18 y 0,86 que refleja una relación inversa con los valores de diversidad. Las especies más abundantes fueron Capitella capitata con un 15,92%, seguido de Maldane chilensis con un 10% y Eranno chilensis con un 9,3%. Las especies Amphicteis chilensis, Glycinde armata, Prionospio orensanzi y Thelepus * Proyectos CONA-C11F 05-15.
Intertidal zones are represented by sand, rock, or the interface between both. Sand flooding is a... more Intertidal zones are represented by sand, rock, or the interface between both. Sand flooding is a periodic physical disturbance affecting sandy beaches and adjacent rocky shores. The interaction of these disturbances with additional, stochastic disturbances is unclear. Here, we investigate the response of intertidal rocky-shore macrobenthic communities to both, periodic and unpredictable disturbances; i.e. seasonal sand flooding and the Maule 8.8 M w mega-earthquake, respectively, in the southern central coast of Chile. A 13-month hierarchical monitoring programme was started in February 2010 (i.e. before the earthquake), and included six intertidal rocky shores nested within “zones” (either affected or not affected by flooding) and within “area” (either the earthquake “rupture” area located 400 km south). The analysis of our beyond BACI design showed different effects of sand floodings and the earthquake on mid-intertidal species richness, abundance, and structure. Species richness...
Organisms Diversity & Evolution
Zoomorphology
Allometry involves the study of the relationship between size and shape of an individual, and in ... more Allometry involves the study of the relationship between size and shape of an individual, and in particular, the manner in which shape depends on size. Animals with multi-element skeletons may have differing growth allometries in different parts of the body. Chitons, for example, have eight overlapping shell plates or valves of three distinct types: head (one plate), intermediate (six plates), and tail (one plate). The overall chiton body is ellipsoidal and different species differ in their eccentricity. The aim of this study was to examine overall allometry in size and shape over adult ontogeny, and how these patterns vary among four closely-related species of intertidal chitons from Southeastern Pacific Ocean. For each specimen (n=407), measurements were taken of total body length and the exposed anterio-posterior lengths of the eight shell plates. Multivariate allometry was evaluated by means of a Principal Component Analysis for each species separately, and for the total. The results showed differential allometric growth of specific skeletal elements, which varied among species; however, there was no clear evidence for specific differentiable growth stages. The overall trend among the combined species was for weakly positive allometry of shell plate widths, but isometric growth of total length and width; thus, the lateral proportion of the animal occupied by shell increases over growth and conversely "thinner looking" girdles may be generally indicative of older animals.
Uploads
Papers by Roger Sepúlveda