Description and female genital structures of a new species of the demersal calanoid copepodRidgewayiafrom southern Japan

Investigation of the reproductive system in calanoid copepods: A new approach using 3D reconstructions from serial semi-thin cross-sections in Calanus glacialis and Metridia longa

The structure of the female reproductive system of the calanoid copepods Calanus glacialis and Metridia longa from the White Sea was studied using light microscopy, scanning and transmission electron microscopy, as well as confocal laser scanning microscopy. For the first time, we applied also the method of 3D reconstructions from semi-thin cross-sections to visualize the general plan of the reproductive system in both species. The application of a combination of methods provided novel and detailed information on the genital structures and muscles located in the genital double-somite (GDS) as well as structures used for the reception and storage of spermatozoa, fertilization and release of eggs. An unpaired ventral apodeme and associated muscles located in the GDS are described for the first time for calanoid copepods. The role of this structure in copepod reproduction is discussed. Stages of oogenesis and the mechanism of yolk formation in M. longa are studied using semi-thin sections for the first time. A combination of non-invasive (LM, CLSM, SEM) and invasive techniques (semi-thin sections and TEM) applied in this study substantially improves our understanding of the functioning of the genital structures in calanoid copepods and could be recommended as a standard set of methods for future research in the reproductive biology of copepods.

First record of the genus Boholina (Copepoda, Calanoida, Pseudocyclopidae) in Vietnam, with description of a new species from an anchialine cave in Tra Ban Island

A new species, Boholinareductasp. nov., was found in a brackish pool within an anchialine cave in Tra Ban Island in Bai Tu Long Bay, north Vietnam. The new species is clearly distinguished from all the six species currently known in the genus Boholina by the following unique characteristics: reduction of the septum between gonopores; narrow and pointed rostrum; basal segment of mandibular palp armed with three setae; maxillule without seta on the basal exite, and exopod with 11 setae; second and third endopodal segments of the maxilliped bearing three setae each; exopod of male right leg 5 2-segmented, with two strong and one vestigial spines on the outer margin of the distal segment; and last exopodal segment of female leg 5 bearing only one spine on the outer margin. We provide a description of the new species, along with detailed illustrations and scanning electron microscopy photographs. The identification key to Boholina species is updated as well. This is the first record of the genus Boholina from Vietnam.

A new species of Labidocera (Copepoda, Calanoida, Pontellidae) collected from Okinawa, southwestern Japan, with establishment of five Indo-West Pacific species groups in the L.detruncata species complex

Labidocerachuraumisp. n. is described from Okinawa, southwestern Japan. The female of the new species differs from other congeners in genital compound somite with right postero-lateral and left antero-lateral processes. The male is distinguished from other congeners by the structure of the fifth leg. This new species is assigned to a newly proposed species group, the Labidoceramadurae species group, within the Labidoceradetruncata species complex. In this species complex five Indo-West Pacific species groups are recognized (cervi, detruncata, gangetica, madurae, and pavo) and defined on the basis of difference in sexual dimorphism.

Cladistic analysis of the calanoid Copepoda

Calanoid copepods are extremely successful inhabitants of marine, brackish and freshwater plankton. Morphological data are used to arrive at a first, parsimony-based phylogeny for the calanoid copepods. Each family is represented by at least one exemplar, typically a recognised plesiomorphic species. The Epacteriscidae are sister to all other calanoid copepods – an observation that brings into question the concept of an Epacteriscoidea that includes the Ridgewayiidae. The monophyly of the Augaptiloidea, Centropagoidea, Clausocalanoidea and Pseudocyclopoidea is corroborated. The current analysis suggests there may be two major clades, one containing the Augaptiloidea, Centropagoidea and possibly the Pseudocyclopoidea and Ridgewayiidae and the other including the Megacalanidae, Calanidae/Paracalanidae, Bathypontioidea, Eucalanoidea, Ryocalanoidea, Spinocalanoidea and Clausocalanoidea. The relationships of the Pseudocyclopidae, Boholinidae, and Ridgewayiidae to the Centropagoidea/Augaptiloidea clade received low nodal support. Monophyly of an enlarged Bathypontioidea (including the Fosshageniidae) is proposed. A monophyletic Megacalanoidea is not retrieved. The nature of the inferred ancestral Calanoida is discussed. New evolutionary series are proposed for the female genitalia (including several losses and regaining of seminal receptacles, and independent losses of the genital operculum – once lost it is never regained) and leg 1 endopod. Paedomorphosis appears to be a dominant process in the evolution of the Calanoida.

The shell glands in some calanoid copepods (Crustacea)

This study represents the first structural, ultrastructural, and biochemical investigation of the shell glands in calanoid copepods. These glands, located inside the points of the last prosomal segment, constitute voluminous syncytial secretory units, each of which extends into an excretory canalicule with a cellular or syncytial wall. The canalicules merge into two collector canals, or shell ducts, that rejoin the oviducts and then open into the egg-laying ducts. Each secretory unit synthesizes heterogeneous granules containing both light and predominantly dense material. Exocytosis of these mature secretory granules occurs in an apical excretory chamber. In freshwater species, the modifications observed during the secretory cycle emphasize a gradual discharge from the secretory units in the hours following laying. Cytochemical and biochemical studies of the secretions reveal the presence of N-acetylglucosamine, galactose, and N-acetylgalactosamine glycoconjugated proteins.