The diel vertical dynamics of gelatinous zooplankton in physically stratified conditions over the 100-m isobath (~110 km offshore) in the South Brazilian Bight (26°45'S; 47°33'W) and the relationship to hydrography and food availability were analyzed by sampling every six hours over two consecutive days. Zooplankton samples were taken in three depth strata, following the vertical structure of t...

We raised leatherback posthatchlings in the laboratory for up to 7 weeks to study the role of visual and chemical cues in food recognition and food-seeking behavior. Turtles were reared on a formulated (artificial gelatinous) diet and had no contact with test materials until experiments began. Subjects were presented with visual cues (a plastic jellyfish; white plastic shapes [circle, square, d...

Insight into the origin and early evolution of the animal phyla requires an understanding of how animal groups are related to one another. Thus, we set out to explore animal phylogeny by analyzing with maximum parsimony 138 morphological characters from 40 metazoan groups, and 304 18S rDNA sequences, both separately and together. Both types of data agree that arthropods are not closely related ...

The bioluminescence of the ctenophore Mnemiopsis takes place when the photoprotein mnemiopsin in the photocytes reacts with Ca2+. The luminescence is inhibited in sunlight and this photoinhibition is reversible by keeping the live specimens in the dark. The extracts of mnemiopsin are similarly photoinhibited, but the photoinhibition cannot be reversed in the dark. We have found that photo-inhib...

Lobate ctenophores (tentaculates) generally exhibit a remarkable ability to regenerate missing structures as adults. On the other hand, their embryos exhibit a highly mosaic behavior when cut into halves or when specific cells are ablated. These deficient embryos do not exhibit embryonic regulation, and generate incomplete adult body plans. Under certain conditions, however, these deficient ani...

We describe the effect of gelatinous plankton – Aurelia aurita and invaders Mnemiopsis leidyi and Beroe ovata – on fish (eggs, larvae, feeding, and stocks) in the Black Sea and Sea of Azov, based on field data and the relevant literature. Representatives of three ecological groups of fish were chosen as examples: planktivorous anchovy typical of warm-water conditions, planktivorous sprat of tem...

Gelatinous zooplankton outbreaks have increased globally owing to a number of human-mediated factors, including food web alterations and species introductions. The invasive ctenophore Mnemiopsis leidyi entered the Black Sea in the early 1980s. The invasion was followed by the Azov, Caspian, Baltic and North Seas, and, most recently, the Mediterranean Sea. Previous studies identified two distinc...

Identifying causes of structural ecosystem shifts often requires understanding trophic structure, an important determinant of energy flow in ecological communities. In coastal pelagic ecosystems worldwide, increasing jellyfish (Cnidaria and Ctenophora) at the expense of small fish has been linked to anthropogenic alteration of basal trophic pathways. However, this hypothesis remains untested in...

When teaching an introductory zoology course, it is always entertaining to show students some specimens of the only described species of placozoans—Trichoplax adhaerens, a tiny, simple, nearly worldwide marine organism (Figure 1) [1,2]. The inevitable disbelief—those are animals?—leads naturally to enumerating the shared derived features of all animals (Box 1) and in turn to discussing the rela...

Human-induced stresses of overfishing, eutrophication, climate change, translocation and habitat modification appear to be promoting jellyfish (pelagic cnidarian and ctenophore) blooms to the detriment of other marine organisms. Mounting evidence suggests that the structure of pelagic ecosystems can change rapidly from one that is dominated by fish (that keep jellyfish in check through competit...