Our investigations on different developmental stages of the jellyfish Cassiopea andromeda (Forskål, 1775) provide updated descriptions of nematocyst types and asexual reproduction modes, which were documented by drawings and high-resolution photographs. In contrast to previous studies that only described three types of nematocysts, we revealed five types: a-isorhizas, O-isorhizas, euryteles, large oval birhopaloids, and small lemon-shaped birhopaloids. Comparisons of undischarged and discharged capsules revealed significantly smaller capsule volumes (48-51 %) in the latter. We provide capsule lengths and widths ranges for each capsule type (undischarged) and developmental stage. We demonstrate that for most capsule types the calculated capsule volumes were positively correlated with the progressing development and increasing size of the five developmental stages, namely bud, polyp, strobila, ephyra, and medusa. O-isorhizas were only present in the latter three stages probably due to a change in diet related to a changing life style. Besides asexual reproduction by swimming buds and monodisc strobilation common in rhizostome Kolpophorae, we documented lateral polyp budding for the first time in this taxon. Our results demonstrate that cultivating living specimens facilitate detailed descriptions of nematocysts and reproductive modes in metagenetic cnidarians, which cannot be achieved by studies on preserved material.

Findings of a new representative of the Laophontodinae Lang, 1944 (Copepoda, Harpacticoida) from the Napoleon Reef (Gulf of Aqaba, Red Sea, Egypt) provided new insights into the systematics of the type genus Laophontodes T. Scott, 1894. Bicorniphontodes clarae gen. et sp. nov., which is described in the present contribution, shares exclusively six derived characters with Laophontodes bicornis A. Scott, 1896, L. horstgeorgei George & Gheerardyn, 2015, and partly with L. hamatus (Thomson, 1883), and L. ornatus Krishnaswamy, 1957: (1) cephalothorax medio-laterally with triangular extensions and (2) postero-laterally with paired cuticular processes, (3) free body somites except telson dorsally with hyaline frills ending in rounded lappets, (4) furcal setae I and II displaced subapically, (5) antennar allobasis lacking abexopodal seta on endopodal half, (6) outer spines of the last segment of swimming legs 2 and 3 unipinnate and comb-like, with the pinnae being extremely long and set widely apart. Thus, the named species are excluded from Laophontodes and united together with B. clarae gen. et sp. nov. in Bicorniphontodes gen. nov. as Bicorniphontodes bicornis comb. nov., B. hamatus comb. nov., B. horstgeorgei comb. nov., and B. ornatus comb. nov.. Beside the description of B. clarae gen. et sp. nov., a detailed phylogenetic discussion regarding the systematic relationships of the named species and the justification of the erection of Bicorniphontodes gen. nov. is given, including its distribution in the world’s oceans. A key to species is also provided.

Populations of harpacticoid copepods belonging to the family Phyllognathopodidae found on most continents are usually assignable to the taxon of Phyllognathopus viguieri, as it is presently diagnosed, on the basis of their morphological characters. This taxon has been considered as 'cosmopolitan' since the unifying revision of Lang in 1948. Here we reveal that Phyllognathopus viguieri is not a single biological species. Cross-breeding experiments with individuals from five different populations of Phyllognathopus viguieri obtained from Germany, Maryland and Florida in the USA, Jamaica, and Brazil indicated that two of these mutually distant populations were reproductively isolated from each other but crossed easily with others, whereas the other populations did not interbreed, with the exception of the two populations from the USA. From these results we conclude that Phyllognathopus viguieri is not a single cosmopolitan biological species. The high proportion of mutually non-reproducing populations identified in the five populations examined in this study indicate that further analysis of the micromorphology and genetic composition of populations over the entire putative range of Phyllognathopus viguieri will be necessary to clarify their interrelationships.

A re‐examination of the morphology of the female and male of Parastenocaris phyllura Kiefer, 1938 is presented using light and scanning electron microscopy. Particular attention is given to the structures of the antennae 1 and 2, the mouthparts, the pereopods, the female genital field and the caudal furcae. Five morphologically distinct copepodid stages are described. Comparative morphology and functional aspects of the adults and copepodids are discussed.

During the expedition ANT XIX/3 meiofauna samples were collected from the German research vessel Polarstern near the Shackleton Fracture Zone. During sorting of the samples 86 tantulus larvae were found. Extensive examination of the larvae revealed a high diversity of tantulocaridans in the Southern Ocean deep sea (33 species). A remarkable proportion of these were new species of Tantulacus Huys, Andersen & Kristensen, 1992. The present paper reports the discovery of three new Antarctic tantulocarids which are referred to Tantulacus. The affiliation of T. longispinosus n. sp., T. karolae n. sp. and T. dieteri n. sp. to Tantulacus is straightforward: all representatives of the Tantulocarida are characterised by the presence of 1-2 slender setae on the endopod of the second to fifth thoracopods, but in none of the hitherto described genera, other than Tantulacus, are these elements modified. Tantulacus hoegi Huys, Andersen & Kristensen, 1992 and the three new species share the possession of a distal rigid spine on the endopod of the second to fifth thoracopods as a synapomorphy and thus can be readily distinguished from other tantulocaridans. This is the first record of free-living sediment-inhabiting tantulus larvae from this area, although this probably reflects the degree of undersampling.