| The jumbo squid, Dosidicus gigas, is a nektonic cephalopod, occurs from Baja California Peninsula(30°N) to Chile(30°S) only within the East Pacific. As a pelagic cephalopod and one of the main target species of Chinese distant water fishery, D. gigas play a major role in the marine ecosystems of the East Pacific. However, knowledge about their complex life history remained limited, especially for the feeding ecology information. With the rapidly increasing use of stable isotope analysis(SIA) in ecology, it becomes a powerful tool and complement of traditional methods for investigating the trophic ecology and migration patterns of invertebrates. The isotopic signatures of gladius have been proved to be a powerful tool to depict high resolution and ontogenic variations in individual foraging strategies of squids, which is an archival tissues with no elemental turnover after formation.In this research, the morphometric variables of D. gigas gladius and body collected off Peru were analyzed. The relationship between the morphology and growth characteristics of gladius was investigated. The ages were determined though the statolith. With the objective of exploring the feasibility of using continuous sampling hard tissue to study the feeding ecology of jumbo squids, the gladius of 35 specimens were cut successionally by the growth curve of gladius proostracum based on the age information from statolith. Inter-specific variation in isotopic niche was compared using the stable isotopic values of the profiles of gladius. In addition, the effects of lipid extraction on stable isotope values of the muscles of 53 neon flying squids were investigated and the interference mechanism of lipid in SIA were clarified with the aim of contrasting the suitability of different lipid correction models of stable carbon isotope. The results can be summarized as follows:(1) The gladius of jumbo squid is a stabilized chitinous structure, morphological characteristics can be distinguished obviously, sequential sampling along this structure gives a record of the organism throughout its life with no metabolic turnover after synthesis. For analysis of the fisheries biology and biology of jumbo squid, we determination the relationship between morphology characteristics of gladius with mantle length and body mass of jumbo squid. Results showed that thelength of cones and proostracum were significantly correlated withboth mantle length and body mass, we believe that morphology characteristics of gladius can be used to study ontogenetic growth of jumbo squid. Our results indicate that proostracum grows faster than cones, meanwhile the growth rate of vane and proostracum are same. We have speculated that morphometric variables of gladius were related to different functionalities possibly.(2)The gladius is a chitinous structure that is synthesized throughout the life of a squid, and it grows by adding chitin to the anterior ventral side of the gladius plate. The isotopic signature of gladius has been proved to be a powerful tool to depict high resolution and ontogenic variations in individual foraging strategies of squids, which is a archival tissues with no elemental turnover after formation. In this research, the gladius of jumbo squid were cut following the growth lines, and investigate the stable carbon and nitrogen isotopes of gladius profiles. The stable isotopic values of the profiles of gladius indicated that they might have different migrations patterns and foraging strategies through their life span after postnatal day 130, the food source of small group and medium group are same, and the changes in the marine environment,especially the El Nino, have an impact on life habits of jumbo squids. |
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