The genus Muricea, a highly speciose gorgonian coral group in the Tropical Eastern Pacific (TEP), is commonly found on shallow rocky reefs including Machalilla National Park (MNP), El Pelado Marine Reserve (REMAPE) and Galápagos Marine Reserve (GMR). Here, we report the presence of M. hebes, M. echinata and M. robusta, which have been not previously reported at the REMAPE area and along the Ecuadorian region. These new records for Muricea hebes (Verril, 1864) in Ecuador broaden the known geographical distribution of these species across the tempered waters of California and Mexico, and the Tropical Eastern Pacific, belonging to Panama and Ecuador. Muricea robusta (Verril, 1864) was previously recorded in Mexico and Colombia, whereas M. echinata (Verril, 1866) was only found in Panama. This report contributes to increasing the knowledge of marine diversity in Ecuador, and broadens the previously recorded geographic distribution of the genus Muricea throughout the TEP. ARTICLE HISTORY

The Equatorial Front, in the southern part of the Tropical Eastern Pacific (TEP) region, has been characterized as a hotspot of functional biodiversity due to the mixing of warm and cold waters. Nevertheless, the biogeographic patterns for some organisms, such as octocorals, remain unknown in some coastal regions. Therefore, we aimed to assess the distribution of two common octocoral genera in this area, Muricea and Leptogorgia, including 14 species based on museum specimen records, along the mainland coast of Ecuador. Statistical analyses were performed on the environmental and geographical patterns (Sea Surface Temperature (SST), bathymetry, chlorophyll (CHL-a), and Photosynthetic Active Radiation (PAR)) that influence the Equatorial Front, which is subdivided into five biogeographic regions. Our results showed two hotspots of octocoral biodiversity. The SST was found to be the main environmental factor related to octocoral distribution along the Equatorial Front. Finally, the highest abundance of Muricea over Leptogorgia suggests the former species' higher resilience to thermal fluctuations. We discuss the possible role of substrates at suitable depths, active photosynthetic radiation, and temperature in the occurrence of octocorals in the two hotspots.

The vibrios carrying the pirA and pirB toxin genes cause acute hepatopancreatic necrosis disease (AHPND) in cultivated shrimp, significantly affecting the yield. The use of probiotic strains is a promising strategy to prevent vibriosis in shrimp cultures. The microbial consortium formulated with three strains, Vibrio diabolicus (Ili strain), Vibrio hepatarius (P62 strain), and Bacillus cereus sensu stricto (P64 strain), is used to control vibriosis. Despite the effectiveness of these probiotics, until now there is not a description of the cellular structures necessary to help shrimp colonization, an important process to exclude pathogenic vibrios. Initially, the three probiotic strains were characterized by scanning electron microscopy, which allowed us to observe that Ili has numerous flagella and P62 has numerous fimbriae, while P64 has both flagella and fimbriae. Next, the colonization capacity of the three probiotic strains in P. vannamei shrimp larvae was determined by direct exposure of the shrimp larvae to probiotics previously stained with fluorochrome dyes, orange acridine, Evans blue, and DAPI. The larvae were observed using epifluorescence and confocal microscopy, which showed the three probiotics adhered to the body cuticle and internal gut lining. Larvae exposed to AHPND-causing V. parahaemolyticus stained with acridine orange were quickly and completely colonized, however, the previous treatment of larvae with probiotic consortium limited the colonization of the pathogenic Vibrio. The ability of probiotic strains to exclude pathogenic vibrio from shrimp surfaces could be explained by the cell surface appendages observed in probiotic strains, thus limiting the free spaces for pathogenic vibrios. Finally, the probiotic consortium in P. vannamei larvae was evaluated in a larviculture (Nauplii 5 to postlarvae 8), where the three probiotics were applied daily. The trial included a control group without the application of the probiotic. After 16 days of culture, the larvae treated with the microbial consortium and the control group were challenged with a pathogenic, the AHPND-causing V. parahaemolyticus strain. We registered a significant (P < 0.05) higher survival in the larvae treated with the microbial consortium 75.33 ± 12.62% compared to the control group 32.27 ± 9.57%. These results indicate that the preventive use of probiotic strains with colonization capacity increase larvae protection. This may be a good strategy for the control of AHPND in shrimp larvae hatcheries.

The emergence of new virulent Vibrio strains resistant to common antibiotics has caused significant economic losses to shrimp farming worldwide. It is mandatory to adopt new strategies to control shrimp farming related vibriosis. Essential oils (EOs) have several biological properties among of which the quorum sensing (QS) inhibitory activity is appealing for vibriosis control. In this work, we evaluated QS inhibitory activity of five EOs obtained from oregano (Organum vulgare), tea tree (Melaleuca alternifolia), lemongrass (Cymbopogon citratus), cinnamon (Cinnamomum verum) and thyme (Thymus vulgaris), at sublethal doses. EOs involvement in bioluminescence shutdown, biofilm formation and swarming motility was evaluated in four Vibrio strains of aquaculture interest including V. harveyi, V. campbellii, V. vulnificus, and V. parahaemolyticus. Oregano oil (EOOv) and tea tree oil (EOMa) were further tested in in vivo assays due to their significant effects (P < 0.05) on QS inhibition. EOOv was the most efficient one and exerted a comparable QS inhibitory effect to EOMa at a lower concentration in vivo (2.5 μg mL⁻¹ of EOMa versus 1.0 μg mL⁻¹ of EOOv). The lowest active doses of EOOv and EOMa that inhibited QS had no toxic effects on hemocytes and larvae of P. vannamei. A challenge test was performed in P. vannamei postlarvae (PL8) with V. campbellii, grown previously in the presence of EOOv or EOMa at sublethal active doses. Our results indicated that both EOs affected the virulence of V. campbellii and were able to significantly (P < 0.05) reduce shrimp mortality (EOOv in a 40% while EOMa in a 32%). A field bioassay was also carried in earthen ponds to test two different concentrations of EOOv and EOMa for feed supplementation (2.5 and 5.0 mg kg⁻¹ respectively). EOOv increased significantly (P < 0.05) shrimp survival and yield at both doses, whereas EOMa increased shrimp survival and yield only at the highest dose. In conclusion, EOOv and EOMa constitute suitable alternatives to reduce vibrios virulence and to increase yield in shrimp culture systems.