scholarly journals Seasonal population dynamics of Octopus vulgaris in the eastern Mediterranean

2006 ◽  
Vol 63 (1) ◽  
pp. 151-160 ◽  
Author(s):  
Stelios Katsanevakis ◽  
George Verriopoulos

Abstract The population density of Octopus vulgaris was measured by visual census with scuba diving in coastal areas in Greece (eastern Mediterranean). A time-variant, stage-classified, matrix population model was developed to interpret the seasonal variation of octopus stage densities and to estimate several life cycle parameters. An annual and a semi-annual periodic cycle were found in the stage densities. A main peak of benthic settlement was observed during summer and a secondary, irregular one during late autumn. Two spawning peaks were estimated, a main one during late winter–spring and a secondary one during late summer–early autumn. More than 50% of the just-settled individuals will eventually die after 3 months. Mortality rate declines, as individuals grow larger, reaches a minimum approximately 6 months after settlement, and then grows again probably because of terminal spawning. The life expectancy of recently settled individuals (<50 g) during their summer peak is approximately 5 months. The lifespan of the common octopus is estimated to be between 12 and 15 months. The octopuses' mean specific growth rates (±s.d.) in their natural environment were 1.61 ± 0.30 d−1 for 50–200 g individuals and 1.19 ± 0.31 d−1 for 200–500 g individuals.

2015 ◽  
Vol 147 (6) ◽  
pp. 712-722 ◽  
Author(s):  
Terry D. Galloway ◽  
Robert J. Lamb

AbstractSeasonal dynamics of louse (Phthiraptera) populations on feral pigeons, Columba livia Gmelin (Aves: Columbiformes: Columbidae) were investigated from 2003 to 2012 in southern Manitoba, Canada. Pigeons were infested with: Philopteridae – Campanulotes compar (Burmeister), Columbicola columbae (Linnaeus), and Coloceras tovornikae Tendeiro; Menoponidae – Hohorstiella lata (Piaget). We consider the hypothesis that four species living on the same host show similar seasonal dynamics, coordinated by the life history of the host. Adults of both sexes and nymphs of all four species were present on pigeons throughout the year, consistent with continuous feeding and reproduction. Campanulotes compar and C. columbae populations were low in spring and peaked in September, with C. columbae showing greater seasonal changes for all population parameters. Coloceras tovornikae showed two annual peaks in abundance in spring and late summer, and H. lata was most abundant in the cold months of the year. Over 10 years, the four species showed distinct seasonal dynamics, although they live on the same birds. Seasonal patterns provided no evidence that louse reproduction or abundance is coordinated by the long breeding and moulting seasons of the host.


2008 ◽  
Vol 99 (4) ◽  
pp. 325-335 ◽  
Author(s):  
R.V. Sequeira ◽  
A. Shields ◽  
A. Moore ◽  
P. De Barro

AbstractBemisia tabaci, biotype B, commonly known as the silverleaf whitefly (SLW) is an alien species that invaded Australia in the mid-90s. This paper reports on the invasion ecology of SLW and the factors that are likely to have contributed to the first outbreak of this major pest in an Australian cotton cropping system. Population dynamics of SLW within whitefly-susceptible crop (cotton and cucurbit) and non-crop vegetation (sowthistle, Sonchus spp.) components of the cropping system were investigated over four consecutive growing seasons (September–June) 2001/02–2004/05 in the Emerald Irrigation Area (EIA) of Queensland, Australia. Based on fixed geo-referenced sampling sites, variation in spatial and temporal abundance of SLW within each system component was quantified to provide baseline data for the development of ecologically sustainable pest management strategies. Parasitism of large (3rd and 4th instars) SLW nymphs by native aphelinid wasps was quantified to determine the potential for natural control of SLW populations. Following the initial outbreak in 2001/02, SLW abundance declined and stabilised over the next three seasons. The population dynamics of SLW is characterised by inter-seasonal population cycling between the non-crop (weed) and cotton components of the EIA cropping system. Cotton was the largest sink for and source of SLW during the study period. Over-wintering populations dispersed from weed host plant sources to cotton in spring followed by a reverse dispersal in late summer and autumn to broad-leaved crops and weeds. A basic spatial source-sink analysis showed that SLW adult and nymph densities were higher in cotton fields that were closer to over-wintering weed sources throughout spring than in fields that were further away. Cucurbit fields were not significant sources of SLW and did not appear to contribute significantly to the regional population dynamics of the pest. Substantial parasitism of nymphal stages throughout the study period indicates that native parasitoid species and other natural enemies are important sources of SLW mortality in Australian cotton production systems. Weather conditions and use of broad-spectrum insecticides for pest control are implicated in the initial outbreak and on-going pest status of SLW in the region.


2018 ◽  
Vol 17 (11) ◽  
pp. 3866-3876 ◽  
Author(s):  
Legana C. H. W. Fingerhut ◽  
Jan M. Strugnell ◽  
Pierre Faou ◽  
Álvaro Roura Labiaga ◽  
Jia Zhang ◽  
...  

Aquaculture ◽  
2004 ◽  
Vol 238 (1-4) ◽  
pp. 221-238 ◽  
Author(s):  
Paulo Vaz-Pires ◽  
Pedro Seixas ◽  
Alexandra Barbosa

2000 ◽  
Vol 53 ◽  
pp. 452-452
Author(s):  
P.P. Kyi ◽  
P.G. Long ◽  
C.F. Mercer ◽  
R.A. Skipp ◽  
G.W. Yeates

2002 ◽  
Vol 3 (1) ◽  
pp. 5 ◽  
Author(s):  
V. ZERVAKIS ◽  
D. GEORGOPOULOS

The combination of two research projects offered us the opportunity to perform a comprehensive study of the seasonal evolution of the hydrological structure and the circulation of the North Aegean Sea, at the northern extremes of the eastern Mediterranean. The combination of brackish water inflow from the Dardanelles and the sea-bottom relief dictate the significant differences between the North and South Aegean water columns. The relatively warm and highly saline South Aegean waters enter the North Aegean through the dominant cyclonic circulation of the basin. In the North Aegean, three layers of distinct water masses of very different properties are observed: The 20-50 m thick surface layer is occupied mainly by Black Sea Water, modified on its way through the Bosphorus, the Sea of Marmara and the Dardanelles. Below the surface layer there is warm and highly saline water originating in the South Aegean and the Levantine, extending down to 350-400 m depth. Below this layer, the deeper-than-400 m basins of the North Aegean contain locally formed, very dense water with different θ /S characteristics at each subbasin. The circulation is characterised by a series of permanent, semi-permanent and transient mesoscale features, overlaid on the general slow cyclonic circulation of the Aegean. The mesoscale activity, while not necessarily important in enhancing isopycnal mixing in the region, in combination with the very high stratification of the upper layers, however, increases the residence time of the water of the upper layers in the general area of the North Aegean. As a result, water having out-flowed from the Black Sea in the winter, forms a separate distinct layer in the region in spring (lying between “younger” BSW and the Levantine origin water), and is still traceable in the water column in late summer.


2019 ◽  
Author(s):  
Pamela Imperadore ◽  
Dario Parazzoli ◽  
Amanda Oldani ◽  
Michael Duebbert ◽  
Ansgar Büschges ◽  
...  

AbstractSpontaneous nerve regeneration in cephalopod molluscs occurs in a relative short time after injury, achieving functional recovery of the lost capacities. In particular, transection of the pallial nerve in the common octopus (Octopus vulgaris) determines loss and subsequent restoring of two functions fundamental for survival, i.e. breathing and skin patterning, the latter involved in communication between animals and concealing. The phenomena occurring after lesion have been investigated in a series of previous studies, but a complete analysis of the changes occurring at the level of the axons and the effects on animals appearance during the whole regenerative process is still missing. Our goal is to determine the course of events following injury. Our goal is to determine the course of events following injury, from impairment to full recovery.We observed nerve regeneration, end-target re-innervation and functional reconnections between central brain and periphery, using the contralateral nerve in the same animal as internal control. The final architecture of the regenerated nervous tissue does not mirror the original structure, however functionality returns to match the phenotype of an intact octopus, and with no visible impact on the behaviour of the animal. This provides exceptional value to these findings for future studies.Summary statementHere we report events occurring after interruption of the peripheral neural circuitry inOctopus vulgaris, from the dramatic loss of normal functioning to full recovery.


2014 ◽  
Vol 15 (3) ◽  
pp. 475 ◽  
Author(s):  
S. GARCIA-SANZ ◽  
P. G. NAVARRO ◽  
F. TUYA

Despite sea-urchins can play an important role affecting the community structure of subtidal bottoms, factors controlling the dynamics of sea-urchin populations are still poorly understood. We assessed the seasonal variation in recruitment of three sea-urchin species (Diadema africanum, Paracentrotus lividus and Arbacia lixula) at Gran Canaria Island (eastern Atlantic) via monthly deployment of artificial collectors throughout an entire annual cycle on each of four adjacent habitat patches (seagrasses, sandy patches, ‘urchin-grazed’ barrens and macroalgal-dominated beds) within a shallow coastal landscape. Paracentrotus lividus and A. lixula had exclusively one main recruitment peak in late winter-spring. Diadema africanum recruitment was also seasonal, but recruits appeared in late summer-autumn, particularly on ‘urchin-grazed’ barrens with large abundances of adult conspecifics. In conclusion, this study has demonstrated non-overlapping seasonal recruitment patterns of the less abundant species (P. lividus and A. lixula) with the most conspicuous species (D. africanum) in the study area.


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