Eliecer R. Díaz

Chemical and Visual Communication During Mate Searching in Rock Shrimp

Mate searching in crustaceans depends on different communicational cues, of which chemical and visual cues are most important. Herein we examined the role of chemical and visual communication during mate searching and assessment in the rock shrimp Rhynchocinetes typus. Adult male rock shrimp experience major ontogenetic changes. The terminal molt stages (named “robustus”) are dominant and capable of monopolizing females during the mating process. Previous studies had shown that most females preferably mate with robustus males, but how these dominant males and receptive females find each other is uncertain, and is the question we examined herein. In a Y-maze designed to test for the importance of waterborne chemical cues, we observed that females approached the robustus male significantly more often than the typus male. Robustus males, however, were unable to locate receptive females via chemical signals. Using an experimental set-up that allowed testing for the importance of visual cues, we demonstrated that receptive females do not use visual cues to select robustus males, but robustus males use visual cues to find receptive females. Visual cues used by the robustus males were the tumults created by agitated aggregations of subordinate typus males around the receptive females. These results indicate a strong link between sexual communication and the mating system of rock shrimp in which dominant males monopolize receptive females. We found that females and males use different (sex-specific) communicational cues during mate searching and assessment, and that the sexual communication of rock shrimp is similar to that of the American lobster, where females are first attracted to the dominant males by chemical cues emitted by these males. A brief comparison between these two species shows that female behaviors during sexual communication contribute strongly to the outcome of mate searching and assessment.

Relevance of mytilid shell microtopographies for fouling defence - a global comparison

Prevention of epibiosis is of vital importance for most aquatic organisms, which can have consequences for their ability to invade new areas. Surface microtopography of the shell periostracum has been shown to have antifouling properties for mytilid mussels, and the topography shows regional differences. This article examines whether an optimal shell design exists and evaluates the degree to which shell microstructure is matched with the properties of the local fouling community. Biomimics of four mytilid species from different regional provenances were exposed at eight different sites in both northern and southern hemispheres. Tendencies of the microtopography to both inhibit and facilitate fouling were detected after 3 and 6 weeks of immersion. However, on a global scale, all microtopographies failed to prevent fouling in a consistent manner when exposed to various fouling communities and when decoupled from other shell properties. It is therefore suggested that the recently discovered chemical anti-microfouling properties of the periostracum complement the anti-macrofouling defence offered by shell microtopography. 1Laboratório de Manejo, Ecologia e Conservação Marinha, Instituto Oceanográfico, Universidade de São Paulo, Praça do Oceanográfico, 191, CEP 05508-900, São Paulo - SP, Brazil. 2ARONIA Coastal Zone Research Team, Novia University of Applied Sciences at Åbo akademi, Raserborgvägen 9, Ekenäs, Finland. 3Marine Science and Fisheries Department, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al-Khoud, PO Box 34, 123 Muscat, Sultanate of Oman. 4CEAZA – Centro de Estudios Avancados en Zonas Aridas, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile. 5Maritime Platforms Division, Defence Science & Technology Organisation, 506 Lorimer Street, Fishermans Bend, Vic 3207, Australia. 6Natural England, North East Region, The Quadrant, Newburn Riverside, Newcastle upon Tyne NE15 8NZ, UK.

Short‐term spatial stability in trophic interactions

Summary 1. The concept of stability in ecological theory has been a subject of debate for more than 40 years. Its value lies in being the explanatory principle underlying equilibrium in nature. Until now, the possibility of spatial stability in trophic interactions, defined as resilience of trophic activity (e.g. herbivore/algae or predator/prey) within patches after a disturbance, has not been explored. This concept requires the demonstration of two properties: (i) the return after a strong disturbance to a reference level of intensity of the trophic interaction (intensity criterion), and (ii) positive spatial correlation between pre- and post-disturbance intensity of the trophic interaction (spatial determinism criterion). 2. The first criterion can be assessed by checking the consistency of intensities of grazing effects between years and the second criterion by correlating the intensities of grazing between years on the same set of patches. We used a spatially explicit test, repeated after experimental disturbance of the same plots in two consecutive years, to test for the existence of spatial stability in the effects of grazing on rocky shore algal assemblages. 3. The detection of spatial stability depended on the level of resolution at which the prey assemblages were examined (species, functional group and trophic level) and allowed us to demonstrate stability in grazing effects, which shape the mosaic of patches on the high rocky shore at scales of 10s of meters. 4. The community analysed was highly resilient due to its domination by species that can quickly re-colonize and recover to pre-disturbance levels and showed spatial determinism because of the tendency of both grazers and algae to colonize particularly favourable areas. 5. Synthesis. The most important findings are as follows: (i) spatial stability was confirmed for a trophic interaction, and (ii) spatial determinism in these systems was detectable. We suggest that patches exhibiting predictability in trophic interaction strength can function as initiators of recovery after disturbance and at the same time represent the deterministic initial condition that might shape long-term spatial configurations within the landscape.