[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-detail-46507-en":3,"doc-seo-46507-105":30,"detail-sidebar-cat-0-en-105":92},{"code":4,"msg":5,"data":6},0,"success",{"doc_id":7,"user_id":8,"nickname":9,"user_avatar":10,"doc_module":4,"category_id":11,"category_name":12,"doc_title":13,"doc_description":14,"doc_content":15,"file_id":16,"file_url":17,"file_type":18,"file_size":19,"view_count":20,"is_deleted":4,"is_public":21,"is_downloadable":21,"audit_status":21,"page_count":22,"language":23,"language_code":24,"site_id":25,"html_lang":24,"table_of_contents":26,"faqs":27,"seo_title":13,"seo_description":14,"update_tm":28,"read_time":29},46507,1099513958762,"Logic","https://ap-avatar.wpscdn.com/avatar/1000023916a998db790?x-image-process=image/resize,m_fixed,w_180,h_180&k=1784791008015729253",8,"Research & Report","Social behavior of the Pederson cleaner shrimp Ancylomenes pedersoni in the Caribbean Sea","Social interactions among Pederson cleaner shrimp Ancylomenes pedersoni, associates of sea anemones, likely shape cleaning services to reef fishes, yet their group-structure mechanisms are unclear. The study tests the hypothesis that shrimp dominance hierarchies are expressed through size- and gender-based behavioral interactions. Field observations of 116 shrimp show small social groups (≈3–4) per anemone and body-size ratios matching randomness. Spatial positioning depends on size, while lab trials reveal exploitation and interference competition, with large females signaling, approaching, cleaning, and attacking more than males and juveniles.","The Crustacean Society  \nJournal of Crustacean Biology  \nJournal of  \n Crustacean Biology  \nJournal of Crustacean Biology (2019) 1–13. doi:10.1093/jcbiol/ruz081  \nSocial behavior of the Pederson cleaner shrimp Ancylomenes pedersoni (Chace, 1958) (Decapoda:  \nCaridea: Palemonidae) in the Caribbean Sea: size-and gender-based dominance hierarchy  \nJessica A. Gilpin  and Nanette E. Chadwick   \nDepartment of Biological Sciences, 101 Rouse Life Sciences Building, Auburn University, Auburn, AL 36849, USA Corresponding author: J.A. Gilpin; [e-mail: jag0038@auburn.edu](e-mail: jag0038@auburn.edu)  \n(Received 5 June 2019; accepted 10 October 2019)  \nABSTRACT  \nSocial 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, asa 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  \nhealth and mobility of reef fishes.  \nKey words: anemone shrimps, aggression, behavior, cleaning symbiosis, coral reefs, coral  \nreef fishes, habitat segregation, sea anemones  \nINTRODUCTION  \nCorkscrew sea anemones Bartholomea annulata (Le Sueur, 1817) are common, large-bodied Caribbean cnidarians that host a variety of associated organisms on, among, and beneath their tentacles (Mahnken, 1972; Brooker et al., 2019) . The Pederson cleaner shrimp Ancylomenes (Periclimenes) pedersoni (Chace, 1958) are obligate  \nassociates of corkscrew anemones. The shrimp also associates with other Caribbean sea anemones, including rosetip anemones Condylactis gigantea Weinland, 1860, branching anemones Lebruniadanae (Duchassaing & Michelotti, 1861), and sun anemones Stichodactyla helianthus (Ellis, 1768) . The Pederson shrimp perch on the oral discs and tentacles of corkscrew anemones (Mahnken, 1972) and occupy reef crevices where these anemones attach  \nDownloaded from [https://academic.oup.com/jcb/advance-article-abstract/doi/10.1093/jcbiol/ruz081/5613990 by Karolinska Institutet user on 20 November 2019](https://academic.oup.com/j","cbCaip4If0WNhkcc","https://ap.wps.com/l/cbCaip4If0WNhkcc","pdf",939627,5,1,13,"English","en",105,"# Abstract\n## Hypothesis and study design\n## Field group structure and spatial patterns\n## Laboratory competition behaviors\n## Conclusions and ecological implications","[{\"question\":\"What hypothesis does the study test about Pederson cleaner shrimp dominance?\",\"answer\":\"Pederson shrimp form dominance hierarchies expressed through size- and gender-based behavioral interactions.\"},{\"question\":\"What did field observations show about social group size and body-size structure?\",\"answer\":\"Shrimp formed social groups of about 3–4 individuals per host anemone, with group body-size ratios between adjacent individuals not differing significantly from random.\"},{\"question\":\"How do male, juvenile, and large female shrimp differ in competitive behaviors toward fish and conspecifics?\",\"answer\":\"Large females more often signaled, approached, and cleaned fish models, and also approached and attacked conspecifics more than males and juveniles; smaller males/juveniles retreated more frequently as body size decreased.\"}]",1783544875,33,{"code":4,"msg":31,"data":32},"ok",{"site_id":25,"language":24,"slug":33,"title":13,"keywords":34,"description":14,"schema_data":35,"social_meta":87,"head_meta":89,"extra_data":91,"updated_unix":28},"social-behavior-of-the-pederson-cleaner-shrimp-ancylomenes-pedersoni-in-the-caribbean-sea","",{"@graph":36,"@context":86},[37,54,69],{"@type":38,"itemListElement":39},"BreadcrumbList",[40,44,48,51],{"item":41,"name":42,"@type":43,"position":21},"https://docshare.wps.com","Home","ListItem",{"item":45,"name":46,"@type":43,"position":47},"https://docshare.wps.com/document/","Document",2,{"item":49,"name":12,"@type":43,"position":50},"https://docshare.wps.com/document/research-report/",3,{"item":52,"name":13,"@type":43,"position":53},"https://docshare.wps.com/document/social-behavior-of-the-pederson-cleaner-shrimp-ancylomenes-pedersoni-in-the-caribbean-sea/46507/",4,{"url":52,"name":13,"@type":55,"author":56,"headline":13,"publisher":58,"fileFormat":61,"inLanguage":24,"description":14,"dateModified":62,"datePublished":63,"encodingFormat":61,"isAccessibleForFree":64,"interactionStatistic":65},"DigitalDocument",{"name":9,"@type":57},"Person",{"url":41,"name":59,"@type":60},"DocShare","Organization","application/pdf","2026-07-20","2026-07-08",true,{"@type":66,"interactionType":67,"userInteractionCount":20},"InteractionCounter",{"@type":68},"ViewAction",{"@type":70,"mainEntity":71},"FAQPage",[72,78,82],{"name":73,"@type":74,"acceptedAnswer":75},"What hypothesis does the study test about Pederson cleaner shrimp dominance?","Question",{"text":76,"@type":77},"Pederson shrimp form dominance hierarchies expressed through size- and gender-based behavioral interactions.","Answer",{"name":79,"@type":74,"acceptedAnswer":80},"What did field observations show about social group size and body-size structure?",{"text":81,"@type":77},"Shrimp formed social groups of about 3–4 individuals per host anemone, with group body-size ratios between adjacent individuals not differing significantly from random.",{"name":83,"@type":74,"acceptedAnswer":84},"How do male, juvenile, and large female shrimp differ in competitive behaviors toward fish and conspecifics?",{"text":85,"@type":77},"Large females more often signaled, approached, and cleaned fish models, and also approached and attacked conspecifics more than males and juveniles; 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