Search

The biodiversity of mollusks, particularly cephalopods, has not been exhaustively determined in the Revillagigedos ecoregion, which is a biodiversity hotspot for several marine groups located in the Tropical East Pacific Province. In our study, we detected and examined ocellate octopuses from Socorro and Clarion Islands, and determined their identity using morphological criteria and molecular data from two mitochondrial genes (COIII and COI). The taxon identified was Octopus oculifer, a species considered endemic to the Galapagos Archipelago. In addition, according to our analyses, O. mimus, O. hubbsorum and O. oculifer are very closely related and may represent a species complex comprised of three morphotypes. We found that the evolutionary relationships among octopuses are not determined by the presence of ocelli. This study is the first to report a clade represented by ocellate and non-ocellate species, in addition, the identity of cephalopods in the Revillagigedos was determined with analytical support.

Cephalopods are important in midwater ecosystems of the Gulf of Mexico (GOM) as both predator and prey. Vertical distribution and migration patterns (both diel and ontogenic) are not known for the majority of deep-water cephalopods. These varying patterns are of interest as they have the potential to contribute to the movement of large amounts of nutrients and contaminants through the water column during diel migrations. This can be of particular importance if the migration traverses a discrete layer with particular properties, as happened with the deep-water oil plume located between 1000 and 1400 m during the Deepwater Horizon (DWH) oil spill. Two recent studies focusing on the deep-water column of the GOM [2011 Offshore Nekton Sampling and Analysis Program (ONSAP) and 2015–2018 Deep Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND)] program, produced a combined dataset of over 12,500 midwater cephalopod records for the northern GOM region. We summarize vertical distribution patterns of cephalopods from the cruises that utilized a 10 m2 Multiple Opening/Closing Net and Environmental Sensing System (MOC10). About 95% of the cephalopods analyzed here either move through or live within 1000–1400 m zone. Species accounts include those with synchronous (e.g., Pterygioteuthis sp.) and asynchronous (e.g., Stigmatoteuthis arcturi) vertical migration. Non-migration patterns of some midwater cephalopods (e.g., Vampyroteuthis infernalis) are also highlighted. Ontogenic shifts are noted for some species examined.

Species of the genus Octopus from the northeastern Pacific are ecologically and economically important; however, their taxonomy is confusing and has not been comprehensively assessed. In this study, we performed a taxonomic evaluation of these species considering the morphological characteristics of the original descriptions, a molecular analysis of partial COI-gene sequences, and a traditional morphometry analysis of nine body measurements. Several interesting findings were obtained with our results: for instance, we updated the diagnoses of some species by including characters such as the number of lamellae per demibranch and the presence of chromatophores in the visceral sac; we deposited partial COI-gene sequences of species that had not been incorporated into the GenBank repository; and according to the morphometric analysis, we confirmed that the lengths of arms I–IV are relevant to discriminate the species under study. The taxa evaluated were morphologically, molecularly and morphometrically well-delimited; however, features such as funnel organ shape and arm length proportions in regard to dorsal mantle length are either not included in the diagnosis of the genus Octopus or overlap with other genera. Hence, this information, combined with the results obtained from the molecular analysis, supports the generic re-assignation of two of the species evaluated.

Species of the genus Octopus from the northeastern Pacific are ecologically and economically important; however, their taxonomy is confusing and has not been comprehensively assessed. In this study, we performed a taxonomic evaluation of these species considering the morphological characteristics of the original descriptions, a molecular analysis of partial COI-gene sequences, and a traditional morphometry analysis of nine body measurements. Several interesting findings were obtained with our results: for instance, we updated the diagnoses of some species by including characters such as the number of lamellae per demibranch and the presence of chromatophores in the visceral sac; we deposited partial COI-gene sequences of species that had not been incorporated into the GenBank repository; and according to the morphometric analysis, we confirmed that the lengths of arms I–IV are relevant to discriminate the species under study. The taxa evaluated were morphologically, molecularly and morphometrically well-delimited; however, features such as funnel organ shape and arm length proportions in regard to dorsal mantle length are either not included in the diagnosis of the genus Octopus or overlap with other genera. Hence, this information, combined with the results obtained from the molecular analysis, supports the generic re-assignation of two of the species evaluated.

The Southern Ocean hosts a rich and diverse fauna that required specialist adaptations to colonize and persist at temperatures close to freezing. While much has been revealed about key adaptations in Antarctic fishes little is known about evolutionary strategies of other Antarctic ectotherms, particularly the abundant benthic incirrate octopods. Their oxygen demand is largely fuelled by the blue oxygen transporter haemocyanin that however, due to its increasing functional failure towards colder temperatures, poses a prime target for cold-adaptive adjustment. While haemocyanin structure has been well understood it remains unclear which molecular features and evolutionary trajectories explain functional properties of octopod haemocyanin. This thesis thus aimed to unravel cold-adaptive features of octopod haemocyanin and the underlying molecular features that evolved to sustain oxygen supply at sub-zero temperatures. Haemocyanin function is best assessed by oxygen binding experiments, which however was challenged due to the minute haemolymph volumes non-model organisms like Antarctic octopods, yield. I thus upgraded an oxygen diffusion chamber with a broad range fibre optic spectrophotometer and a micro-pH optode and tested the setup for Octopus vulgaris, the Antarctic eelpout and a Baikal amphipod. This technical advancement enabled simultaneous recordings of pH and oxygen dependent pigment absorbance in only 15 microliter of sample. Results were highly reproducible and accurate and provided detailed insight to the complex and dynamic spectral features of three diverse blood-types. To identify cold-adaptive functional traits of blood oxygen transport this study compared haemocyanin oxygen binding properties, oxygen carrying capacities and haemolymph protein and ion composition between the Antarctic octopod Pareledone charcoti, the temperate Octopus pallidus and the subtropical Eledone moschata. Compared to octopods from warmer climates, Pareledone charcoti showed incomplete but significantly reduced oxygen affinity, which together with increased haemocyanin concentrations and high physically dissolved oxygen levels supported oxygen supply at zero degree Celsisu. Therefore, unlike many Antarctic fishes Pareledone charcoti continued to rely on an oxygen transporting pigment. High temperature sensitivity of oxygen binding enabled Pareledone charcoti to utilise most of the oxygen bound by haemocyanin at 10 degree celsius. The concomitant relief for the circulatory system at warmer temperatures promotes warm tolerance and thus eurythermy in Pareledone charcoti. Underlying molecular mechanisms were studied by comparing 239 partial haemocyanin sequences of the functional unit f and g of 28 octopods species of polar, temperate, subtropical and tropical origin. Despite high conservation of these haemocyanin regions several sites were positively selected for their charge properties at the molecule's surface. Net surface charges were generally elevated in polar octopods suggesting that charge-charge interactions raise intrinsic pK values to stabilise quaternary structure against higher ambient pH present in cold waters. The presence of at least two haemocyanin isoforms and high allelic variation in polar octopods indicate sustained genetic diversity of haemocyanin and thus the genetic potential to regulate blood oxygen transport in the cold. Further, amino acid variability located within a potential metal binding site suggests regulation of blood oxygen transport in octopods via altered intrinsic sensitivity to allosteric ligands In conclusion, this study revealed significant adaptations of octopod haemocyanin at the functional and molecular level that support oxygen supply at near freezing temperatures. However, "imperfect" functional adaptation and ensuing reliance on high haemocyanin levels in Pareledone charcoti seems to add to the various design constraints of octopods compared to fishes. Hence, at second glance functional oxygen reserves indicate a higher capacity to sustain oxygen transport at warmer temperatures and together with a potential ability to regulate and reverse cold-adaptive molecular traits may be key to determine future winners and losers in an ecosystem facing radical environmental change.

Using a combination of diverse large predatory fishes and one seabird, we collected information on the cephalopod fauna of the western Indian Ocean. We analyzed the stomach contents of 35 fishes representing ten families (Xiphiidae, Istiophoridae, Scombridae, Carangidae, Coryphaenidae, Alepisauridae, Dasyatidae, Carcharhinidae, Alopiidae and Sphyrnidae) and of the sooty tern Onychoprion fuscata of the Mozambique Channel from 2000 to 2010. Both fresh and accumulated beaks were used for identifying cephalopod prey. Cephalopods were important prey for twelve predators; swordfish Xiphias gladius had the highest cephalopod proportion; sooty tern (O. fuscata) and bigeye tuna (Thunnus obesus) had high proportions too. We recovered 23 cephalopod families and identified 38 species. Ten species from four Teuthida families (Ommastrephidae, Onychoteuthidae, Histioteuthidae and Ancistrocheiridae) and two Octopoda families (Argonautidae and Bolitaenidae) occurred very frequently in the stomach contents, while Sepiida were rare. Ommastrephidae were the most cephalopod food sources: the purpleback flying squid Sthenoteu this oualaniensis was the most prevalent prey by far, Ornithoteuthis volatilis was important for eleven predators and few but large specimens of the neon flying squid Ommastrephes bartramii were recovered in the stomachs of swordfish in the Indian South Subtropical Gyre province only. Predators' groups were identified based on cephalopod prey composition, on depth in which they forage, and on prey size. Surface predators' diets were characterized by lower cephalopod diversity but greater average numbers of cephalopod prey, whereas the deep-dwelling predators (swordfish and bigeye tuna) preyed on larger specimens than surface predators (O. fuscata or yellowfin tunas Thunnus albacares). Our findings emphasized the usefulness of a community of marine predators to gain valuable information on the biology and the distribution of the cephalopod forage fauna that are discussed with regard to biogeographic province, marine predator, fishing gear to catch the large pelagic fishes, and size of the beaks recovered in the stomachs.