Comparative cleaning behaviour of Pederson's cleaner shrimp (Ancylomenes pedersoni) between geographically close yet ecologically dissimilar coral reef habitats

Cleaning mutualisms are important interactions on coral reefs. Intraspecific variation in cleaning rate and behaviour occurs geographically and is often attributed to local processes. However, our understanding of fine-scale variation is limited, but would allow us to control for geography and region-specific behavioural patterns. Here, we compare the cleaning activity of Pederson's cleaner shrimp (Ancylomenes pedersoni) on two neighbouring, yet ecologically dissimilar, reef systems in Honduras: Banco Capiro, an offshore bank close to significant land runoff with high coral cover but a depleted fish population, and an oligotrophic fringing reef around the island of Utila, with lower coral cover but high fish abundance and diversity. The proportion of realized to potential fish clientele was <60% at both sites, and the composition of clientele was neither reflective of the demographics of the resident assemblages at each site nor similar between sites. Parrotfishes represented 13–15% of total fish abundance at both sites yet accounted for >50% (Banco Capiro) and 10% (Utila) of all cleans. Conversely, the schoolmaster snapper (Lutjanus apodus) represented ~1% of total fish abundance at both sites yet accounted for 40% (Utila) and 1% (Banco Capiro) of all cleans. After standardizing our cleaning rate data by clientele abundance, we find that clientele at Banco Capiro engage in over four times as many cleaning encounters per hour with A. pedersoni than at Utila. Our study highlights the variable nature of coral reef cleaning interactions and the need to better understand the ecological and environmental drivers of this biogeographic variation.

The Spotted Cleaner Shrimp, Periclimenes yucatanicus (Ives, 1891), on an Unusual Scleractinian Host

The spotted cleaner shrimp, Periclimenes yucatanicus (Ives, 1891), forms symbioses with sea anemones that may serve as cleaning stations for reef fishes [...]

Social behavior of the Pederson cleaner shrimp Ancylomenes pedersoni (Chace, 1958) (Decapoda: Caridea: Palemonidae) in the Caribbean Sea: size- and gender-based dominance hierarchy

Social interactions among Pederson cleaner shrimp Ancylomenes pedersoni (Chace, 1958), an associate of sea anemones, likely affect cleaning services to reef fishes, but major aspects of their social group structure and behavior remain unknown. We hypothesized that Pederson shrimp form dominance hierarchies expressed through size- and gender-based behavioral interactions. Observation of 116 shrimp on coral reefs at St. Thomas, US Virgin Islands, revealed that they formed social groups of ~3 or 4 individuals (range 1–9) per host sea anemone, as a mix of large females, medium-size males, and/or small juveniles. Social groups were not rigidly size-structured, in that body size ratio between adjacent individuals did not differ significantly from random. Individuals, however, were spatially structured such that distance between shrimp and the tentacles of the host anemone decreased significantly with shrimp body size; large individuals occupied the anemone tentacle crown, whereas smaller shrimp perched on reef or sand substrates adjacent to the anemone. During laboratory experiments, shrimp exhibited five types of exploitation competition behaviors toward client fish models (signal, approach, clean, no response, retreat), and four types of interference competition behaviors toward conspecific shrimp (approach, attack, no response, retreat). Large females more frequently signaled toward, approached, and cleaned fish models than did males and juveniles, which did not respond or retreated. Females also approached and attacked conspecifics more than did males and juveniles, which retreated at frequencies that increased with decreasing body size. We conclude that Pederson shrimp form gender and size-based hierarchies in which large females monopolize food resources (ectoparasites on client fishes), and interfere with resource access by smaller males and juveniles. These behaviors cause them to spatially partition microhabitats on anemones, and hypothetically could lead to males and juveniles dispersing among anemones more frequently than females. These shrimp social interactions may thus enhance spatial and temporal variation among cleaning stations, with consequences for the health and mobility of reef fishes.

Effects of 17β-estradiol injection and red-spectrum light on eyestalk hormones and vitellogenesis of the ornamental cleaner shrimp Lysmata amboinensis (De Man, 1888) (Decapoda: Caridea: Lysmatidae)

We analyzed the effects of 17β-estradiol (E2) injection and red light on the sexual maturation and vitellogenesis of the cleaner shrimp Lysmata amboinensis (De Man, 1888) by measuring the change of mRNA expression levels of eyestalk and vitellogenesis-related hormones induced by both factors. We examined the eyestalk crustacean hyperglycemic hormone (CHH) and vitellogenesis-inhibiting hormone (VIH) genes. The E2 injection did not affect changes of eyestalk hormones. The red light, however, caused a significant increase (P &lt; 0.05) of CHH promoting maturity and a significant decrease of VIH, which suppressed vitellogenesis. The vitellogenin receptor (VTG-R) and mRNA expression (in situ hybridization) also caused the E2 injection and red-wavelength irradiation to induce synthesis of vitellogenin (VTG). Red-light-induced gonadal maturation, promoting hormone and VTG synthesis, but E2 did not change the eyestalk hormone. Red-light irradiation could thus be used as a novel, maturity-promoting alternative method in the culture of the species, which is different from the eyestalk-ablation method that has so far been used.

The cleaner shrimp Lysmata amboinensis adjusts its behaviour towards predatory versus non-predatory clients

In cleaning mutualisms, small cleaner organisms remove ectoparasites and dead skin from larger clients. Because cheating by predatory clients can result in cleaner death, cleaners should assess the potential risk of interacting with a given client and adjust their behaviour accordingly. Cleaner shrimp are small marine crustaceans that interact with numerous client fish species, many of which are potential predators. We use in situ observations of cleaner–client interactions to show that the cleaner shrimp Lysmata amboinensis adjusts several behaviours when interacting with predatory versus non-predatory clients. Predatory clients were cleaned in a significantly lower proportion of interactions than non-predatory clients, and cleaners also exhibited a leg rocking behaviour—potentially signalling their identity or intent to clean—almost exclusively toward predatory clients. Incidence of leg rocking was positively correlated with client size, and laboratory experiments showed that it can be elicited by dark visual stimuli and decreases in illumination level. Thus, cleaners clean less frequently when predation risk is higher, and may use leg rocking as a signal advertising cleaning services and directed specifically at predators.