Dosidicus gigas (Humboldt/Jumbo Squid)

DWhatley

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Inter- and intra-regional patterns of stable isotopes in Dosidicus gigas beak: biological, geographical and environmental effects
Bi Lin Liu, Jing Yuan Lin, Xin Jun Chen, Yue Jin, Jin Tao Wang 2018 (Marine & Freshwater Research subscription)

Abstract
We analysed stable carbon (δ13C) and nitrogen (δ15N) isotopes of 478 Dosidicus gigas specimens collected outside the Ecuadorian, Peruvian and Chilean exclusive economic zones in the south-eastern Pacific Ocean during 2009 to 2013. There were significant spatial differences both in δ13C and δ15N values across regions, with the lowest values off Ecuador and the highest values off Chile. A small intra-regional range of isotope values indicates that squid off Ecuador feed at the same trophic level with similar primary production. In contrast, a large intra-regional range of isotope values suggests that squid off Chile, especially Peru, migrate over a large geographic range and occupy a wide range of trophic levels. A generalised additive model was used to estimate the biological (mantle length and age), geographical (latitude, and distance to the shelf break) and environmental (sea-surface temperature and chlorophyll-a) effects on isotope values. Best fitted generalised additive models explained 54.0% of the variability in δ13C and 93.1% of the variability in δ15N. The yield relationships between isotopes and explanatory variables increase our understanding of D. gigas habitats, movement and feeding ecology in the south-eastern Pacific Ocean.
 

DWhatley

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Potential role for microRNA in regulating hypoxia-induced metabolic suppression in jumbo squids
Hanane Hadj-Moussa,, Samantha M. Logan, Brad A. Seibel, Kenneth B. Storey 2017 (ScienceDirect subscription)

Abstract
At night, Humboldt squid (Dosidicus gigas) rise to the ocean's surface to feed, but come morning, they descend into the ocean's oxygen minimum zone where they can avoid predators but must deal with severe hypoxia, high pressure, and very cold water. To survive this extreme environment, squid use various adaptations to enter a hypometabolic state characterized by metabolic rate suppression by 35–52%, relative to normoxic conditions. The molecular mechanisms facilitating this metabolic flexibility have yet to be elucidated in hypometabolic squid. Herein, we report the first investigation of the role of microRNAs, a rapid and reversible post-transcriptional master regulator of virtually all biological functions, in cephalopods. We examined expression levels of 39 highly-conserved invertebrate microRNAs in D. gigas brain, mantle muscle, and branchial heart, comparing hypoxic and normoxic conditions. Hypoxia-inducible microRNAs are potentially involved in facilitating neuroprotection, anti-apoptosis, and regenerative mechanisms in brain; inhibiting apoptosis and cell proliferation while conserving energy in heart; and limiting damage by reactive oxygen species and apoptosis in muscle. Rather than orchestrate global metabolic rate depression, the majority of hypoxia-inducible microRNAs identified are involved in promoting cytoprotective mechanisms, suggesting a regulatory role for microRNA in hypoxic marine invertebrates that sets the stage for mechanistic analyses.
 

vampyroteuthis360

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D. gigas is one of the radula specimen I have been lucky to receive as a donation from the Hopkins Marine Station Lab! The radula is so large it just fell out of the beak! Below is a photo of the radula under the SEM & a photo of the sample on an SEM stud under an automontage microscope.

For more photos: blogs.evergreen.edu/cephalopodresearch/
 

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DWhatley

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Stock assessment of jumbo squid Dosidicus gigas in northwest Mexico.
Urías-Sotomayor, Ricardo, Rivera-Parra, Gabriel Iván, Martínez-Cordero, Francisco Javier, Castañeda-Lomas, Nicolás, Pérez-González, Raúl, Rodríguez-Domínguez, Guillermo

The population dynamics of jumbo squid Dosidicus gigas from northwest Mexico was evaluated for the period 1974-2012 using Schaefer's model, where model parameters were estimated with the catch maximum sustainable yield method (Catch-MSY) using two prior intrinsic population increase rate (r) range values (1.0 to 2.0 and 1.5 to 2.0). Estimated parameters with both prior r ranges were 1.23 and 1.68 yr-1 for r and 243,836 and 190,468 ton for carrying capacity (k), respectively. Corresponding management quantities were 75,147 and 80,098 ton for the maximum sustainable yield (MSY) and 121,918 and 95,234 ton for the biomass at MSY (BMSY). Estimated jumbo squid biomass dropped below the BMSY after 2003, and near to 0.2 k in 2012. The Schaefer's model showed that declines in estimated biomass were preceded by catches that exceeded the MSY. Strong El Niño-Southern Oscillation events can change the availability of jumbo squid in northwest Mexico through migratory processes and phenotype changes in maturation size, but stock biomass variability is most likely to be caused by fishing. [ABSTRACT FROM AUTHOR]

Copyright of Latin American Journal of Aquatic Research is the property of Pontificia Universidad Catolica de Valparaiso and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
 

DWhatley

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Evidence of Iteroparity in Jumbo Squid Dosidicus gigas in the Gulf of California, Mexico
Xchel Aurora Pérez-Palafox, Enrique Morales-Bojórquez, María Del Carmen Rodríguez-Jaramillo, Juan Gabriel Díaz-Uribe, Agustín Hernández-Herrera, Oswaldo Uriel Rodríguez-García, Dana Isela Arizmendi-Rodríguez 2019
Abstract
The jumbo squid (Dosidicus gigas) has been considered a species with a semelparous life history, and this assumption has been erroneously adopted without histological evidence. Recent studies suggest that this species can spawn more than once during its life span. To identify the reproductive strategy of jumbo squid, qualitative and quantitative analyses were used in this study. Biological data were collected fortnightly from March 2008 to November 2009 off the coast of Santa Rosalía, Baja California Sur, Mexico. The histological analyses showed five stages of development: previtellogenesis, vitellogenesis, postvitellogenesis, spawning, and postspawning, with the simultaneous presence of oocytes at different substages. These results were confirmed by the presence of multiple cohorts of oocytes at each ovarian stage. Analysis applied to resting females of D. gigas confirmed that the postovulatory follicles were simultaneously found with previtellogenic oocytes denoting the ovarian recovery. The presence of postovulatory follicles at all ovarian stages and in individuals throughout the mantle length (ML) structure (from 32 to 82 cm) was an indicator of multiple spawning events. During 2008 and 2009, four ML groups (41.2, 48.5, 55.2, and 68.5 cm) and threeMLgroups (39.9, 47.8, and 53.9 cm) were observed, respectively. In conclusion, the evidence of postovulatory follicles in resting females of D. gigas indicates that the reproductive strategy of jumbo squid is iteroparity.
 

DWhatley

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The Strange Case of Mexico’s Shrinking Jumbo Squid
Too many El Niños have diminished the “diablo rojo.”

BY SABRINA IMBLERJULY 24, 2019

https://www.atlasobscura.com/articles/mystery-of-missing-jumbo-squid-solved
...
But by 2015, these large marine predators vanished—or rather, they shrank. Squid fishers who had become accustomed to hauling up catches longer than themselves found creatures barely fit for calamari. They were still Humboldt squids, but shrinky-dink versions. “You could catch 20 or 30 of them and not fill up a bucket,” says Tim Frawley, a Stanford research fellow and the lead author of a new study in ICES Journal of Marine Science that finally solves the mystery of Mexico’s missing jumbo squid.
...

https://www.atlasobscura.com/articles/mystery-of-missing-jumbo-squid-solved
https://www.atlasobscura.com/articles/mystery-of-missing-jumbo-squid-solved
 

DWhatley

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Iteroparity or Semelparity in the Jumbo Squid Dosidicus gigas: A Critical Choice
Vladimir Laptikhovsky, Alexander Arkhipkin, Marek R. Lipiński, Unai Markaida, Hilario Murua, Chingiz M. Nigmatullin, Warwick H. H. Sauer, Henk-Jan T. Hoving 2019 (BioOne subscription)
Abstract
The jumbo squid Dosidicus gigas was recently claimed to be an iteroparous species with ovaries returning to an immature, resting stage after spawning. Analysis of the data and figures presented in two recent articles revealed that this claim was based on misinterpretation of histological information and that Dosidicus is not iteroparous. Having consensus on the reproductive strategy of Dosidicus is important for the management of fisheries for this species.
 

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