ABSTRACT
Three species of Spinoncaea Böttger-Schnack, 2003 are newly recorded in three locations of the equatorial and temperate Pacific Ocean collected by using a net of 60 µm mesh size. For all three species, morphological characters and patterns of ornamentation were analyzed in detail and illustrations of both sexes, also including form variants of the females, are provided. For the first time, information about the variability of various continuous (morphometric) characters are given, such as the spine lengths on the rami of the swimming legs or the proportions of urosomites. The complementary morphological descriptions of the Pacific specimens focus on similarities or modifications of characters as compared to earlier descriptions of these species from the type locality and various other localities. For S. ivlevi (Shmeleva, 1966), originally but insufficiently described from the Adriatic Sea, the Pacific material is similar in most aspects to the comprehensive redescription of the species from the Red Sea and from the type locality, except for a difference in the morphometry of the distal endopod segment on the antenna, which is discussed here. For S. tenuis Böttger-Schnack, 2003, and S. humesi Böttger-Schnack, 2003, the Pacific material mostly coincides with the characteristic features as described in the original account from the Red Sea. For all three species, differences and/or additions in ornamentation details were found in Pacific specimens (e.g., on the intercoxal sclerite of the first swimming leg or on the genital somite of the male) and females with aberrant morphology were detected. Genetic analyses based on 12S srRNA revealed for two species, S. ivlevi and S. humesi, little or no differences in genetic sequences between Pacific specimens and those recorded from the Mediterranean Sea, thus demonstrating that specimens from both locations are conspecific. For S. tenuis, for which no comparable genetic data are available, 12S srRNA amplification was unsuccessful as was the amplification of mitochondrial COI (barcoding) for all three species. The applicability of using COI amplification for barcoding of oncaeid copepods is discussed.
ABSTRACT
In order to expand the fragmentary knowledge on the interactions between the environment and copepod distribution in the deep offshore Adriatic Sea, microcopepod assemblages were investigated during 31 cruises in the 1200-m deep central part of the South Adriatic Pit (SAP), from May 1998 to December 2009. Samples were collected in 8 depth layers, using a 53-µm mesh Nansen net equipped with a closing system. The taxonomic composition and vertical and temporal distributions of copepod abundances were analyzed, considering naupliar stages for all species combined, total calanoid copepodites, copepodite stages and adults separately for oithonids and oncaeids, and all post-naupliar stages combined of harpacticoids and mormonilloids. Corycaeid copepods are not considered in the present study. Data are presented for 41 non-calanoid copepod species, as well as for 7 undetermined morphospecies. Within the family Oncaeidae, four species new to the Adriatic Sea fauna are registered. Nauplii were generally the numerically dominant group, especially in the upper epipelagic layers, where they outnumbered all total post-naupliar stages by a factor of an average 3.5. Oncaeids were notably abundant, accounting in total post-naupliar copepods for an average proportion of 33% in the upper 50 m and 74% between 300- and 400-m depth. In the epipelagic zone, copepod abundances were enhanced by the cyclonic circulation which enriches the central part of the SAP with new primary production. A strong advection of Levantine Intermediate Water (LIW) influenced the post-naupliar abundances also in mesopelagic and deeper layers, by promoting the sinking of heavy water mass from the connected middle Adriatic sub-basin which enhances the trophic conditions and transports new organisms into the deeper layers of the SAP. Therefore, the variability in copepod abundances was influenced not only by the seasonal temperature fluctuations but also by the productivity conditions in the SAP which are connected to the movements of regional water masses and the resulting effects on the internal Adriatic circulation.
