Dosidicus gigas (Humboldt/Jumbo Squid)

Paralarvae of the complex Sthenoteuthis oualaniensis-Dosidicus gigas (Cephalopoda: Ommastrephidae) in the northern limit of the shallow oxygen minimum zone of the Eastern Tropical Pacific Ocean (April 2012) (subscription)

Abstract
The three-dimensional distribution of the paralarvae of the complex Sthenoteuthis oualaniensis - Dosidicus gigas (Cephalopoda: Ommastrephidae) was analyzed at the northern limit of the shallow oxygen minimum zone in the Eastern Tropical Pacific in April, 2012. The hypoxic water (∼ 44 μmol/kg or 1 mL/L) rises from ∼ 100 m depth in the entrance of the Gulf of California to ∼ 20 m depth off Cabo Corrientes. Most of the paralarvae of this complex, dominated by D. gigas, were concentrated in the Gulf entrance, between the thermocline (∼20 to ∼ 50 m depth) and the sea surface, in the warmest (> 19°C) oxygenated (> 176 μmol/kg) layer. The highest abundance of paralarvae was detected in an anticyclonic eddy (∼120 km diameter and > 500 m deep), which contained lower salinity water (< 35 g/kg), consistent with formation in the California Current. Lower paralarvae abundance was recorded further south off Cabo Corrientes, where hypoxic layers were elevated as water shoaled near shore. Almost no paralarvae were found in the north of the study area beyond the strong salinity front (∼ 34.8 - 35.4 g/kg) that bounded the anticyclone. These results showed an affinity of the paralarvae for lower salinity, oxygenated water, illustrated by the influence of the mesoscale anticyclonic eddy and the salinity front in their distribution. Based on this study, it can be concluded that the expansion of the depth range of hypoxic water observed in the Eastern Tropical Pacific may be increasing environmental stress on the paralarvae by vertically restricting their habitat, and so affecting their survival. This article is protected by copyright. All rights reserved.
 
POPULATION DYNAMICS OF JUMBO SQUID DOSIDICUS GIGAS IN PACIFIC ECUADORIAN WATERS
ENRIQUE MORALES-BOJORQUEZ, JOSE LUIS PACHECO-BEDOYA 2016 (PDF Journal of Shellfish Research, Vol. 35, No. 1, 1–14)

ABSTRACT Population dynamic studies of Dosidicus gigas have not been reported in Ecuadorian waters. The number of cohorts in the population and reproductive features such as sex ratio, seasonal changes in maturity stages, and size at first maturity are unknown. This knowledge is crucial in the study area, because it can provide fishery management support to Ecuadorian stakeholders. Biological data from 2013 (March–December) and 2014 (January–December) in Ecuadorian waters were analyzed. Biological sampling per month was carried out during every year in different coastal waters off of Ecuador. The biological findings indicated the presence of three size groups in the Ecuadorian squid stock, which estimated to be individuals less than 50 cm mantle length (ML). The monthly size groups changed between one and three size groups in 2013 and 2014. The ML at first maturity for females of jumbo squid estimated in 2013 was L50% ¼ 32.4 cm ML, and L50% ¼ 35.5 cm ML in 2014. For both fishing seasons, the ML–mantle weight relationship estimated for jumbo squid presented isometric growth, and the sex ratio for D. gigas showed that females were more abundant than males. This study found that the ML structure of jumbo squid, the number of size groups, and ML at first maturity are different from that previously estimated in traditional fishing areas of D. gigas in the eastern Pacific Ocean.
 
Characterization of the northernmost spawning habitat of Dosidicus gigaswith implications for its northwards range extension
Jorge E. Ramos, Alejandro Ramos-Rodríguez, Gastón Bazzino Ferreri, J. Alejandro Kurczyn, David Rivas, César A. Salinas-Zavala 2017 (subscription Marine Ecology)

ABSTRACT: The jumbo squid Dosidicus gigas is an ecologically and commercially important species whose northernmost geographic limit is the Gulf of California. However, over the last decades this species has extended its geographic distribution polewards, with associated impacts on the ecosystem. The origin of range-shifting individuals is poorly understood; therefore, we aimed to identify and characterize the northernmost spawning habitat of this species. Implications of the location and oceanographic conditions of the spawning habitats, migration capacity and life history characteristics of D. gigas are also discussed to elucidate its migration pattern. The northernmost spawning area was located between the biological activity centres (BACs) around the Gulf of Ulloa at the west coast of southern Baja California Peninsula during winter, summer and autumn 2005. Generalized linear models indicated that the interaction of sea surface salinity and thermocline depth, and the effect of latitude and sea surface temperature explained most of the variability in paralarval presence, whereas chlorophyll a and latitude explained paralarval abundance. Simulations indicated that paralarvae were dispersed towards the southwest or temporarily remained between BACs. The northwards incursion of D. gigas may be favoured by BACs and upwelling events along the coast of the northeastern Pacific. In warm years, D. gigas is likely to spawn off the Baja California Peninsula, it may actively migrate as far north as Alaska (USA) tracking BACs and upwelling conditions in search of feeding grounds, and it may return from different areas along the northeastern Pacific to spawn off the Baja California Peninsula.
 
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.
 
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.
 
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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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.)
 
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.
 
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
 
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.
 
The breeding strategy of female jumbo squid Dosidicus gigas: energy acquisition and allocation
Xinjun Chen, Fei Han, Kai Zhu, André E. Punt, Dongming Lin 2020 (full report, Nature)

Abstract
Reproductive investment generally involves a trade-off between somatic growth and energy allocation for reproduction. Previous studies have inferred that jumbo squid Dosidicus gigas support growth during maturation through continuous feeding (an “income” source). However, our recent work suggests possible remobilization of soma during maturation (a “capital” source). We used fatty acids as biochemical indicators to investigate energy acquisition and allocation to reproduction for female D. gigas. We compared the fatty acid profiles of the ovary to those of the mantle muscle (slow turnover rate tissue, representing an energy reserve) and the digestive gland (fast turnover rate organ, reflecting recent consumption). For each tissue, the overall fatty acids among maturity stages overlapped and were similar. The changes with maturation in fatty acid composition in the ovary consistently resembled those of the digestive gland, with the similarity of fatty acids in the mantle muscle and the ovary increasing during maturation, indicating some energy reserves were utilized. Additionally, squid maintained body condition during maturation regardless of increasing investment in reproduction and a decline in feeding intensity. Cumulatively, D. gigas adopt a mixed income-capital breeding strategy in that energy for reproduction is mainly derived from direct food intake, but there is limited somatic reserve remobilization.
 

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