A conserved strategy for inducing appendage regeneration in moon jellyfish, Drosophila, and mice

Can limb regeneration be induced? Few have pursued this question, and an evolutionarily conserved strategy has yet to emerge. This study reports a strategy for inducing regenerative response in appendages, which works across three species that span the animal phylogeny. In Cnidaria, the frequency of appendage regeneration in the moon jellyfish Aurelia was increased by feeding with the amino acid L-leucine and the growth hormone insulin. In insects, the same strategy induced tibia regeneration in adult Drosophila. Finally, in mammals, L-leucine and sucrose administration induced digit regeneration in adult mice, including dramatically from mid-phalangeal amputation. The conserved effect of L-leucine and insulin/sugar suggests a key role for energetic parameters in regeneration induction. The simplicity by which nutrient supplementation can induce appendage regeneration provides a testable hypothesis across animals.

Jellyfish Bioprospecting in the Mediterranean Sea: Antioxidant and Lysozyme-Like Activities from Aurelia coerulea (Cnidaria, Scyphozoa) Extracts

Marine invertebrates represent a vast, untapped source of bioactive compounds. Cnidarians are represented by nearly 10,000 species that contain a complex mixture of venoms, collagen, and other bioactive compounds, including enzymes, oligosaccharides, fatty acids, and lipophilic molecules. Due to their high abundance in coastal waters, several jellyfish taxa may be regarded as candidate targets for the discovery of novel lead molecules and biomaterials and as a potential source of food/feed ingredients. The moon jellyfish Aurelia coerulea is one of the most common jellyfish worldwide and is particularly abundant in sheltered coastal lagoons and marinas of the Mediterranean Sea, where it first appeared—as an alien species—in the last century, when Pacific oyster cultivation began. In the present study, the antioxidant and lysozyme antibacterial activities associated with extracts from different medusa compartments—namely the umbrella, oral arms, and secreted mucus—were investigated. Extracts from the oral arms of A. coerulea displayed significant antioxidant activity. Similarly, lysozyme-like activity was the highest in extracts from oral arms. These findings suggest that A. coerulea outbreaks may be used in the search for novel cytolytic and cytotoxic products against marine bacteria. The geographically wide occurrence and the seasonally high abundance of A. coerulea populations in coastal waters envisage and stimulate the search for biotechnological applications of jellyfish biomasses in the pharmaceutical, nutritional, and nutraceutical sectors.

The importance of molecular characters when morphological variability hinders diagnosability: systematics of the moon jellyfish genus Aurelia (Cnidaria: Scyphozoa)

Cryptic species have been detected across Metazoa, and while no apparent morphological features distinguish them, it should not impede taxonomists from formal descriptions. We accepted this challenge for the jellyfish genus Aurelia, which has a long and confusing taxonomic history. We demonstrate that morphological variability in Aurelia medusae overlaps across very distant geographic localities. Even though some morphological features seem responsible for most of the variation, regional geographic patterns of dissimilarities are lacking. This is further emphasized by morphological differences found when comparing lab-cultured Aurelia coerulea medusae with the diagnostic features in its recent redescription. Previous studies have also highlighted the difficulties in distinguishing Aurelia polyps and ephyrae, and their morphological plasticity. Therefore, mostly based on genetic data, we recognize 28 species of Aurelia, of which seven were already described, 10 are formally described herein, four are resurrected and seven remain undescribed. We present diagnostic genetic characters for all species and designate type materials for newly described and some resurrected species. Recognizing moon jellyfish diversity with formal names is vital for conservation efforts and other studies. This work clarifies the practical implications of molecular genetic data as diagnostic characters, and sheds light on the patterns and processes that generate crypsis.

Observations on the Surface Structure of Aurelia solida (Scyphozoa) Polyps and Medusae

The surface structures and mucus layers that form an interface between the epithelial layer of organisms and their external environment were studied in the bloom-forming moon jellyfish (Aurelia solida, Scyphozoa) from the northern Adriatic. The surface of the polyps revealed epithelial ciliated cells and numerous nematocysts, both non-discharged and discharged. Cilia were also the most prominent features on the surface of adult medusa, protruding from the epidermal cells and with microvilli surrounding the base. Histochemical methods and various microscopy techniques (light/epifluorescence and electron microscopy) confirmed the presence of abundant mucus around polyps and on the surfaces of adult medusa, and that the mucus contained acidic and neutral mucins. The observed mucus secretions on the exumbrella surface of the medusae were in the form of granules, flocs, and sheets. Scanning electron microscopy and transmission electron microscopy analyses confirmed the presence of various microbes in the mucus samples, but not on the epithelial surfaces of the polyps or the exumbrella of the medusae.

Dissolved Oxygen-And Temperature-Dependent Simulation of the Population Dynamics of Moon Jellyfish (Aurelia coerulea) Polyps

As the extent of hypoxia in coastal waters increases, the survivorship of jellyfish polyps relative to that of competing sessile organisms often increases, enabling them to reproduce more prolifically, leading to a medusa bloom in the following year. Quantifying the population of polyps can be used to predict when these blooms will occur. We used a time-delayed logistic equation to quantify the response to variable dissolved oxygen (DO) concentrations and temperatures in a population of moon jellyfish (Aurelia coerulea) polyps on substrates that carried competing sessile organisms. The availability of substrate depends on the DO threshold for each competitor, and substrates only become available to the polyps during hypoxic periods. We used the median sublethal concentration (SLC50) thresholds of hypoxia for different groups of benthic organisms to calculate the DO-dependent survivorship of A. coerulea polyps competing on the substrate. Since the median lethal time (LT50) for cnidarians is close to 240 h, we chose a 10-day delay in the time-delayed logistic equation. The carrying capacity is determined every 10 days depending on DO concentrations and temperature. The polyps reproduce by budding at a temperature-dependent rate after settling on the substrate during the hypoxic period, and thus, the annual polyp reproduction rate is determined by multiplying the temperature-dependent budding rate by the DO-dependent survivorship. The duration of hypoxia is a key factor determining the polyp population, which can increase more as the duration of hypoxia increases. Modeling simulations were compared to observed data. In this model, the DO and temperature distribution data make it possible to quantify variations in the population of the A. coerulea polyps, which can be used to predict the abundance and appearance of medusa the following year.