Natural Feeding and Description of Clausocalanus furcatus Order Calanoida (Copepoda) in the coastal waters of Baniyas City (Eastern Mediterranean): التغذية الطبيعية ووصف النوع Clausocalanus furcatus رتبة Cyclopoida (Copepoda) في المياه الشاطئية لمدينة بانياس (شرق المتوسط)

This study, included the feeding of Clausocalanus furcatus of crustacean zooplankton (Calanoida), by studying the structure of the mandible and the gut content of this previous species to determine their favorite food. 93 samples have been collected vertically in period between March and October 2020. The samples were also accompanied with different hydrophysical and hydrochemical measurements in three regions that differ from each other with their environmental properties. The number of members of (C.furcatus) that were studied reached (64) individuals, of which (44) are female and (20) are male. On the other hand, determining the morphology, studying its structure, and knowing the content of the gut of the aforementioned species helped in expanding knowledge about the conditions and strategies of feeding it under the influence of environmental factors. The number of algae species (phytoplankton) that C.furcatus fed reached (9) species, of which (6) belong to the Dinophyceae, (2) species to Bacillariophyceae earth, and (1) only one species to the group Cryptophyceae. The highest average number of Dinophyceae was (1755), followed by Bacillariophyceae (505) individuals, then the group of Cryptophyceae (189) individuals.

Zooplankton Abundance and Diversity in the Tropical and Subtropical Ocean

The abundance and composition of zooplankton down to 3000 m depth was studied in the subtropical and tropical latitudes across the Atlantic, Pacific and Indian Oceans (35 °N–40 °S). Samples were collected from December 2010 to June 2011 during the Malaspina Circumnavigation Expedition. Usually, low abundances were observed with the highest values found in the North Pacific Ocean, Benguela, and off Mauritania, and the lowest in the South Pacific Ocean. No significant differences in abundance and zooplankton composition were found among oceans, with depth being consistently the most important factor affecting their distribution. Each depth strata were inhabited by distinct copepod assemblages, which significantly differed among the strata. The contribution of copepods to the zooplankton community increased with the depth although, as expected, their abundance strongly decreased. Among the copepods, 265 species were identified but 85% were rare and contributed less than 1% in abundance. Clausocalanus furcatus and Nannocalanus minor dominated the epipelagic strata. Pleuromamma abdominalis and Lucicutia clausi were of importance in the mesopelagic layer, and Pareucalanus, Triconia, Conaea and Metridia brevicauda in the bathypelagic layer. Our results provide a global-scale assessment of copepod biodiversity and distribution, providing a contemporary benchmark to follow future ocean changes at low latitudes.

Copepod community along the Mediterranean coast of Morocco (Southwestern Alboran Sea) during spring

Copepod community along the Mediterranean Moroccan coast was investigated, for the first time, during April 2013. Total abundance varied from 53 to 4557 ind. m-3 and high values were found in coastal waters. Oithona nana and Paracalanus parvus dominated in the entire area and species diversity was decreasing from the West to the East. Hierarchical clustering revealed three groups of stations, depending on their geographic position (western, central and eastern areas). Indicator species analysis pointed out that Clausocalanus furcatus and Gaetanus sp. were significantly associated with Group I, Clausocalanus sp., Centropages sp. and Centropages chierchiae with Group II, whereas Temora longicornis was significantly associated with Group III. Detrended Correspondence Analysis based on the species abundance and environmental variables (temperature, salinity, chlorophyll-a), highlighted a more or less similar setting of stations which was related to salinity and temperature. The presence of three anticyclonic gyres at the northern part of the study area is suggested as the major factor acting on the variability of copepod community along the Mediterranean Moroccan coast.

What are the factors leading to the success of small planktonic copepods in the Gulf of Gabes, Tunisia?

An oceanographic cruise conducted during June 2008 in the Gulf of Gabes revealed the existence of different water masses; the Modified Atlantic Waters (MAW) circulated in the upper 100 m in the offshore area, the Mixed Mediterranean Water (MMW) was confined to the inshore region and the Ionian Water (IW) was in deep offshore water. The thermal stratification was indicated by the vertical profiles of temperature generated from a coast-offshore section. Phosphorus limitation was induced by the thermal stratification as shown by the high N/P ratio. Heterotrophic and mixotrophic dinoflagellates were the major contributors to total phytoplankton biomass. Ciliates were less abundant and dominated by tintinnids. Small planktonic copepods (≤1.45 mm) contributed to 93.64% of total copepod abundance in the inshore area as a result of the high density of Oithona similis, Oithona nana, Clausocalanus furcatus and Euterpina acutifrons in this area characterized by warm and salty MMW. In fact, small copepods were significantly correlated to both temperature and salinity. Small copepod fraction prevailed also in the MAW contributing to 71.05% of total copepod abundance as a result of the dominance of O. nana and C. furcatus. Nonetheless, the large copepod Nannocalanus minor was more adapted to the deep IW where it contributed to 44.05% of total copepod abundance. Invasive species were encountered in the offshore region intruded by the Atlantic waters. The Atlantic copepods were scarce and less abundant reflecting the weakening of the Atlantic flow in the eastern basin of the Mediterranean.

Morphology of antennular sensors in Clausocalanus furcatus (Copepoda: Calanoida)

The success of planktonic copepods in aquatic environments is dependent on efficient sensing of their three-dimensional surroundings. The detection of external cues is of importance for the localization of other organisms (prey, predators and mates), and is mediated by an array of mechano- and chemoreceptors located on the paired antennules (A1).We investigated the morphology and distribution pattern of A1 sensory structures in the adult female of Clausocalanus furcatus (Copepoda: Calanoida) using different techniques (camera lucida, scanning and transmission electron microscopy and laser scanning confocal microscopy) each focusing on a specific aspect of the structures analysed. Integration of the information collected shows that C. furcatus possesses an array of mechanical, chemical and dual-function sensors over its A1, by which the copepod can detect different stimuli from the environment. Results are discussed in the light of the unique swimming behaviour displayed by this widespread epipelagic copepod.