Biología y ecología del calamar Dosidicus gigas (Cephalopoda) en aguas chilenas: una revisión

Indexación: Web of Science; Scielo.ABSTRACT. 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.RESUMEN. Dosidicus gigas, es el calamar más abundante en el Pacífico suroriental, manteniendo la mayor pesquería mundial de cefalópodos. Su creciente importancia económica, ha motivado el aumento de estudios asociados al crecimiento de sus poblaciones y su expansión geográfica. Sin embargo, algunas características biológicas básicas de esta especie son desconocidas o escasamente estudiadas. En esta revisión, se resume la información sobre la biología y ecología de esta especie para el Pacífico suroriental y se proponen hipótesis y líneas de investigación para el mejor entendimiento de su historia de vida. Los datos sobre estructura de tamaños, reproducción y aspectos genéticos de la especie, permiten avanzar en las hipótesis relacionadas con la historia de vida de estos rasgos. Hipótesis 1: Los calamares maduran a gran tamaño y desovan en aguas oceánicas con temperaturas cálidas, donde paralarvas y juveniles se desarrollan. Los calamares inmaduros migran hacia la costa para alimentarse, crecer y madurar, y luego vuelven a los sitios en alta mar para desovar. Hipótesis 2: Alternativamente, los juveniles de D. gigas en la zona oceánica no migran a las aguas costeras y maduran pequeños en comparación a los individuos que viven cerca de la costa que maduran a un tamaño más grande y migran a las aguas oceánicas para desovar. Se proponen dos hipótesis acerca de la variación espacial de la historia de vida. Además, se proporciona el marco relativo a la alimentación y parasitismo del calamar, que coloca a D. gigas como un importante nexo trófico en los ecosistemas marinos del Pacífico suroriental. No obstante, se necesitan más estudios relacionados con alimentación, reproducción y carga parasitaria del calamar para poner a prueba las hipótesis propuestas en este trabajo.http://ref.scielo.org/hpft7

Environmental and ecological factors mediate taxonomic composition and body size of polyplacophoran assemblages along the Peruvian Province

Indexación: ScopuIntertidal 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).https://www-nature-com.recursosbiblioteca.unab.cl/articles/s41598-019-52395-

Tropical polyplacophoran diversity from south of the Panamian Province Diversidad de poliplacóforos tropicales del sur de la Provincia Panameña

© 2016, Escuela de Ciencias del Mar. All rights reserved. For the first time a comprehensive record on the diversity of polyplacophorans in the south of the Province of Panama (Ecuador-Peru), corresponding to the Guayaquil ecoregion, was made. Chitons were collected from five locations and their diversity and the similarity of the assemblies were estimated. During winter 2013 and summer 2013-2014 a total of 539 chitons belonging to 11 species were collected. The diversity decreases from north to south due to a strong replacement of species and to the local dominance of some taxa. The ordination analysis suggests two faunal groups, one composed of the locations of Montañita and Santa Rosa form Ecuador, and Bonanza from Peru, while the second is composed of the Peruvian locations of Pocitas and Lobitos. The species that contribute most to the differentiation are Ischnochiton dispar, Acanthopleura echinata and Acanthochitona ferreirai. Polyplacophorans diversity at this part of Province

Morphological and molecular description of a new record of Graneledone (Cephalopoda, Octopodidae) in the southeastern Pacific Ocean

Octopuses of the genus Graneledone inhabit in the deep-sea and are composed of 8 recognized species. Here we conduct phylogenetics analyses of 4 species of Graneledone using 2 molecular markers (16S and COI), and report a new record of Graneledone for the Pacific Ocean off south-central Chile. Four specimens of Graneledone sp. were collected from 436 to 1482 m depth. These octopuses are medium sized, have no ink sac and bear only one row of suckers in their arms, which are of similar length. They are characterized by having 43 to 45 suckers in the hectocotylized arm (third right); 6 to 7 lamellae per demibranch; VV-shaped funnel organ and 5 to 7 transverse creases in the ligulae. Some morphological traits show great variation compared with species from Pacific, Atlantic and Antarctic oceans. Molecular phylogenetic analysis supports the hypothesis of monophyly of Graneledone.Los pulpos del género Graneledone habitan en aguas profundas y constituyen 8 especies reconocidas. Se realizaron análisis filogenéticos de 4 especies de Graneledone con 2 marcadores moleculares (16S y COI), y se informa sobre un nuevo registro de Graneledone para el Océano Pacífico frente a la zona centro-sur de Chile. Se obtuvieron 4 ejemplares de Graneledone sp. entre 436 y 1482 m de profundidad. Estos pulpos son de tamaño medio, no tienen saco de tinta y tienen una sola fila de ventosas en sus brazos, que son de igual longitud. Se caracterizan por tener de 43 a 45 ventosas en el brazo hectocotilizado (tercero derecho); 6 a 7 laminillas por demibranquia; órgano del sifón en forma VV y de 5 a 7 pliegues transversales en la lígula. Algunos rasgos morfológicos muestran una gran variación en comparación con las especies del Pacífico, Atlántico y la Antártida. Los análisis filogenéticos moleculares apoyan la hipótesis de monofilia de Graneledone

Diet of juvenile blue sharks Prionace glauca (Linnaeus, 1758) (Carcharhiniformes: Carcharhinidae) in coastal waters off central-south Chile Dieta de tiburones juveniles Prionace glauca (Linnaeus, 1758) (Carcharhiniformes: Carcharhinidae) en la zona litora

Feeding studies of pelagic sharks in Chilean - waters are rare because of the difficulty in accessing and collecting stomachs. This paper is the first contribution to the knowledge of the diet of juvenile P. glauca (Linnaeus, 1758), caught in the coastal zone of central-southern Chile. We described the diet of 13 juvenile P. glauca using frequency of occurrence, percent by number and weight quantitative indexes. The relationship between prey size and number and predator size was quantified with correlation analysis. Only 77% of stomachs had food contents. One hundred percent of stomachs contained Engraulis ringens and 60% had Dosidicus gigas. The relationship found between predator and prey size reinforces the hypothesis of positive relationships between predator and prey body size

First record of parasites of Dosidicus gigas (d' Orbigny, 1835) (Cephalopoda: Ommastrephidae) from the Humboldt Current system off Chil

Se describió y cuantificó la fauna parasitaria de 124 calamares (Dosidicus gigas) capturados en aguas oceánicas y costeras en Chile Central (32ºS - 40ºS). El 97% de los calamares presentó al menos un taxón parásito. Se determinó la prevalencia y abundancia para cada especie de parásito. Cada taxón parasitario se describió en base a microscopía de luz e imágenes de microscopía electrónica de barrido. La fauna parasitaria estuvo compuesta por céstodos larvales: Hepatoxylon trichiuri (Abundancia: 2,6; Prevalencia: 70,2%), Tentacularia coryphaenae (Abundancia: 0,1; Prevalencia: 5,6%), plerocercoide Tetraphyllidea (Abundancia: 9,1; Prevalencia: 83,1%), Pelichnibothrium speciosum y los nemátodos Anisakis Tipo I (Abundancia: 0,06; Prevalencia: 6,5%) y Tipo II (Abundancia: 0,52; Prevalencia: 17,7%). Se han descrito alrededor de 9 taxa parasitarios en D. gigas, todos encontrados en calamares menores a 40 cm de longitud del manto, y de los cuales cinco (plerocercoide Tetraphyllidea, Tentacularia coryphaenae Pelichnibothrium speciosum y Anisakis Tipo I y II), se registraron en este estudio, pero en calamares de mayor tamaño. El parásito H. trichiuri es un nuevo registro para D. gigas en estas latitudes del Pacífico Sur, comprendiendo el límite sur de su rango de distribución. El plerocercoide Tetraphyllidea, por tener un órgano apical con la misma forma y tejido celular que una ventosa accesoria, podría pertenecer al género Phyllobothrium. Los Anisakis Tipo I y II, sólo se pueden distinguir por la forma de la cola y la presencia-ausencia del mucrón. Se sugiere la realización de análisis moleculares cuando hay carencia de caracteres morfológicos de diagnósticos en los estados larvale

Dieta de tiburones juveniles Prionace glauca (Linnaeus, 1758) (Carcharhiniformes: Carcharhinidae) en la zona litoral centro-sur de Chile

Feeding studies of pelagic sharks in Chilean waters are rare because of the difficulty in accessing and collecting stomachs. This paper is the first contribution to the knowledge of the diet of juvenile P. glauca (Linnaeus, 1758), caught in the coastal zone of central-southern Chile. We described the diet of 13 juvenile P. glauca using frequency of occurrence, percent by number and weight quantitative indexes. The relationship between prey size and number and predator size was quantified with correlation analysis. Only 77% of stomachs had food contents. One hundred percent of stomachs contained Engraulis ringens and 60% had Dosidicus gigas. The relationship found between predator and prey size reinforces the hypothesis of positive relationships between predator and prey body size

Updated molecular phylogeny of the squid family Ommastrephidae: insights into the evolution of spawning strategies

Two types of spawning strategy have been described for ommastrephid squids: coastal and oceanic. It has been suggested that ancestral ommastrephids inhabited coastal waters and expanded their distribution into the open ocean during global changes in ocean circulation in the Oligocene. This hypothesis could explain the different reproductive strategies in oceanic squids, but has never been tested in a phylogenetic context. In the present study, we assess the coastal-to-open-ocean hypothesis through inferring the evolution of reproductive traits (spawning type) of ommastrephid squids using the phylogenetic comparative method to estimate ancestral states and divergence times. This analysis was performed using a robust molecular phylogeny with three mitochondrial genes (COI, CYTB and 16S) and two nuclear genes (RHO and 18S) for nearly all species of ommastrephid squid. Our results support dividing the Ommastrephidae into the three traditional subfamilies, plus the monotypic subfamily Todaropsinae as proposed previously. Divergence times were found to be older than those suggested. Our analyses strongly suggest that early ommastrephid squids spawned in coastal areas, with some species subsequently switching to spawn in oceanic areas, supporting previous non-tested hypotheses. We found evidence of gradual evolution change of spawning type in ommastrephid squids estimated to have occurred since the Cretaceous.FONDECYT 311015