Octopus Vulgaris (Common Octopus) Cuvier, 1797

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CIRCADIAN RHYTHMS IN OCTOPUS VULGARIS
D. V. Meisel, R. A. Byrne, M. Kuba, U. Griebel, J. A. Mather 2003 (full pdf)

ABSTRACT Biological rhythms enable organisms to measure time and to synchronize their endogenous behavior and physiology with the time constraints of their environment. Since the inhabitants of the littoral zone of marine environments are exposed to complex temporal and environmental changes, biological rhythms play an important role in their lives. Timekeeping is especially important for those with short lives like octopuses. Circadian rhythms, which are rhythms of about a day, are one of the most prominent of biological rhythms. They are ubiquitous through all phyla of the animal kingdom, light being one of the most important “Zeitgebers” for almost all of them. To examine the function of light as a synchronizer for their activity, four octopuses were held in a potentially entrained state with a 24-hour L:D (light/dark) cycle. After this phase the animals were placed in constant conditions to document free running activity with circadian components. The results of this study clarify why publications up to now show conflicting results about circadian aspects of Octopus vulgaris activity. While light was used inefficiently as a Zeitgeber for activity the results of our study proved the presence of an endogenous circadian rhythm in O. vulgaris. These generalistic and opportunistic animals may use several different time cues to synchronize their activity and behavior with the time constraints of their environment
 

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Behavioral Sleep in Octopus Vulgaris
D. V. meiSel, r. A. BYrne, J. A. mAtHer 3, m. KuBA

BSTRACT. – Sleep is a ubiquitous phenomenon, found in animals of many different phyla.
While in the past sleep has been defined through studies on mammals and birds, it has recently
appeared that invertebrates might show this behavioural state. The present behavioral study on
sleep in Octopus vulgaris demonstrates its presence in a cognitively advanced invertebrate. We
studied resting states in sixteen adult Octopus vulgaris to determine the presence of behavioural
sleep. Animals were filmed day and night in isolation and before and after they were restdeprived mechanically. Activity cycles were under circadian control and quiescent animals
showed an elevated arousal threshold, which was determined by exposing them to growing levels of vibratory stimulation, and state reversibility with intense stimulation. Behavioral observations also demonstrated that octopuses chose a preferred resting place, actively built a den site
and assumed a typical posture. The quiescence of the subjects often coincided with random
movements of the suckers on the arms. Octopuses also showed a typical ‘half-and-half’ skin
pattern during the periods of rest, which was not camouflage matched to the environment. Rest
deprivation during nighttime led to a rest rebound, while daytime rest deprivation reduced quiescent time. All these findings lead us to the conclusion that, although brain physiological
changes might not be parallel, Octopus vulgaris shows typical behavioral sleep.
 

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Reproductive Biology of the Common Octopus (Octopus vulgaris Cuvier, 1797) in South Kenya
G.M. Kivengea1 , M.J. Ntiba1,2, D.O. Sigana1 and A.W. Muthumbi 2014 (full pdf)

Abstract — Although common octopus catches are increasing globally, lack of information on the reproductive biology of the species has been a major concern in its management, particularly in Kenya. The present study aimed to investigate the reproductive biology of common octopus at Shimoni and Vanga on the Kenyan south coast. Sampling was undertaken monthly from November 2010 to November 2012 using a traditional fishing spear. The body weight (BW), total length (TL), dorsal mantle length (DML), ventral mantle length (VML) and gonad weight was recorded for each specimen. Maturity stages and gonadosomatic indices (GSI) were determined using standard methods. A total of 1 599 specimens (746 males and 853 females) were collected. The sex ratio was 1:1.1 (males: females) at both Shimoni and Vanga during the study period. Sexual staging of gonads indicated that the common octopus was breeding year round with a spawning peak from June to August. Fecundity estimates ranged from 5 200 to 389 000 oocytes (mean 154 057.6 ± 29 132). The lowest gonadosomatic index values were recorded during the month of September, indicating the end of the spawning period. The female length at first maturity (DML50%) was 10.8 cm, that for the male was 10.5 cm.
 

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Morphological assessment of the Octopus vulgaris species complex evaluated in light of molecular-based phylogenetic inferences
Michael D. Amor, Mark D. Norman, Alvaro Roura, Tatiana S. Leite, Ian G. Gleandall, Amanda Reid, Catalina Perales-Raya, Chung-Chen Lu, Colin J. Silvey, Erica A. G. Vidal, Frederick G. Hochberg, Xiaodong Zheng, Jan M. Strugnell 2016 (Wiley Subscription)

Abstract
Cryptic species are common in the ocean, particularly among marine invertebrates such as octopuses. Delineating cryptic species is particularly problematic in octopus taxonomy where the plasticity recorded among taxonomic characters often results in low resolution at the species level. This study investigated the morphological relationships among seven phylogenetic clades (identified using cytochrome c oxidase subunit I) of the broadly distributed Octopus vulgaris species complex and close relatives. Morphological analyses in this study were successful in delimitingO. sinensis, Brazilian O. vulgaris and O. vulgaris sensu stricto, which was congruent with the molecular findings of this study. Analyses based on male morphology were successful in distinguishing 14 of 15 total pairwise comparisons and proved to be a more reliable indicator of species-level relationships in comparison with female morphology. The majority of characters with the greatest discriminatory power were male sexual traits. Significant morphological differences were also recorded among sampling localities of conspecifics, with phenotype showing correlation with local environmental data. The findings of this study support the hypothesis that multiple O. vulgaris-like species are currently being incorrectly treated under a single species name, O. vulgaris. Octopuses being exported globally under the name O. vulgaris are of extremely high fisheries market value and profile. Our findings have potentially significant implications for the naming and conservation of commercially harvested members of this species complex throughout their ranges.
 

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Short comment about the octopus life cycle in the northern Alboran Sea (western Mediterranean Sea)
Maria del Carmen Garcia Martinez, Francina Moya, Maria Gonzalez, Pedro Torres, Sara Farzaneh, Manuel Vargas-Yanez 2017 (Full Article from Allied Academies Journal of Fisheries Research)

Abstract
Octopus vulgaris is a plastic species capable of adapting to different environmental conditions. The different phases of its life cycle seem to be highly influenced by suchenvironmental variables. Therefore the reproductive season and the length of its embryonic and planktonic phases can differ substantially for different geographicalareas. The Mediterranean Sea is one of the regions were the octopus life cycle is not yet well known. Biological data in the Alboran Sea (Western Mediterranean) in the present work show the existence of migration movements to coastal waters for the breeding season during spring and mainly during summer. Water temperature measurements show that the length of the embryonic and paralarval phases arearound 120 days and new individuals incorporate to fisheries from autumn to winter.These results coincide with landings time series allowing the full description of theO. vulgaris life cycle.
 

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Diet of Octopus vulgaris from the Moroccan Mediterranean Coast
Rabia Ajana, Mohamed Techetach, Younes Saoud 2018 (subscription Thalassas via Springer )

Abstract
In this paper the diet of octopus was studied by analyzing the stomach contents of 365 specimens obtained throughout the year from commercial catches. Different prey items, belonging to three taxa (Mollusca, Crustacea and Teleostei) were found, indicating opportunistic feeding behavior. The most important prey species were Callista chione (62.1% IRI, index of relative importance) and Liocarcinos (23.83% IRI). Mollusks (bivalves) were the most frequently found prey group in octopus stomachs according to the index of occurrence and the index of importance in weight and number, followed by crustaceans (brachyurans) and teleosts. The diet was examined in relation to size, sex and seasons. For small O. vulgaris, crustaceans were more important, whereas for larger specimens, bivalves were dominant. The change of the frequency of prey in stomach of octopus by sex and seasons is not significantly different.
 

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