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Lysmata pederseni, a protandric simultaneously hermaphroditic shrimp that inhabits the tube sponge Callyspongia vaginalis, is monogamous in the central and southeastern Caribbean Sea. We tested the null hypothesis of monogamy in a northern Caribbean population. In the Florida Keys, shrimps did not inhabit host individuals in pairs with a frequency greater than expected by chance alone. Hermaphrodites inhabited sponges solitarily and often brooded embryos. Hermaphrodites do not store sperm and need to be inseminated shortly after molting to fertilize a new batch of eggs. Thus, males and/or other hermaphrodites are likely switching among host individuals in search of sexual partners. Field experiments demonstrated low shrimp host fidelity. Host residence time was ~2 times shorter for males than for hermaphrodites. We inferred a polygynandrous mating system in L. pederseni from the Florida Keys, with male-role and young hermaphrodites often moving among sponges in search of older, more sedentary, female-role hermaphrodites. We expected shrimps to use water-borne chemical cues originating from conspecifics or sponges to locate sexual partners. Experiments demonstrated that shrimps were attracted to water-borne cues originating from sponges but not conspecifics. We have described the mating system of a reef-associated shrimp in a fast-pace shifting seascape increasingly dominated by sponges and vanishing stony corals. In the central and southeastern Caribbean Sea, with greater coral cover and lower sponge abundance than in the Florida Keys, the same species is monogamous. Whether or not similar shifts in the social organization of other coral reef-dwelling marine organisms are occurring due to contemporary changes in seascapes is a relevant topic that deserves further attention.

Habitat selection is a critical process for animals throughout their life, and adult organisms that travel to forage or mate must reselect habitat frequently. On coral reefs, competition for space has led to a high proportion of habitat specialists. Habitat selection is especially vital for organisms that require specialized habitat; however, research has primarily focused on the initial habitat choice made during the larval/juvenile stage. Here, we analyze habitat selection in the adult sponge-dwelling reef shrimp, Lysmata pederseni. Using a mark-and-recapture technique, belt transects, patch reefs, and cue isolation experiments, this study reveals that adult L. pederseni diurnally reselect habitat and a natural preference exists for specific sponge species and shapes. This natural preference is a function of chemical and morphological cues as well as sponge distribution. As habitat specialists can drive biodiversity, understanding the mechanisms behind habitat selection can inform research and management practices., Is architecture more important than smell when choosing a home? Here, we investigate the external cues involved in habitat selection of a sponge-associated shrimp after nightly forays on the reef. By tracking shrimp locations through time and isolating environmental variables, we conclude that while both sponge shape and chemical cues play a role in habitat selection, shape may be a more critical factor for resident shrimp.

Sexual dimorphism of the olfactory system is common in crustaceans; however, it has never been confirmed empirically to be sex dependent. In the current study, the growth pattern of aesthetasc (i.e., olfactory chemosensors of crustaceans) number in 4 protandric simultaneous hermaphroditic shrimp species in the genus Lysmata with 2 social systems—pair living (Lysmata amboinensis and Lysmata pederseni) and group living (Lysmata boggessi and Lysmata wurdemanni)—from male phase to euhermaphrodite phase were examined. The results show that the aesthetasc numbers of both male-phase and euhermaphrodite-phase shrimp are related in general to timing of sex change; in other words, those shrimp that change sex later have greater aesthetasc numbers than those that change sex earlier. This factor is the major reason contributing to the high variation in aesthetasc numbers in euhermaphrodite-phase shrimp. The aesthetasc number increased with shrimp growth during the male phase, but thereafter male-phase shrimp...

Sex allocation theory predicts female-biased sex allocation for simultaneous hermaphrodites with a monogamous mating system. Mating systems theory predicts that monogamy is advantageous in environments where refuges are discrete, scarce, relatively small, and when predation risk is high outside of these refuges. These predictions were tested with the Caribbean shrimp Lysmata pederseni, a simultaneous hermaphrodite which has an early male phase and lives inside tubes of the sponge Callyspongia vaginalis. This host sponge is a scarce resource that, together with the high predation risk typical of tropical environments, should favor monogamy in the shrimp. Field observations demonstrated that shrimps were frequently encountered as pairs within these tube sponges. Pairs were equally likely to comprise two hermaphrodites or one hermaphrodite and one male. Several of these pairs were observed for long periods of time in the field. Experiments demonstrated that hermaphrodites tolerated other hermaphrodites but not males in their host sponge. These results suggest that pairs of hermaphroditic L. pederseni are socially monogamous; they share the same host individual and might reproduce exclusively with their host partners for long periods of time. Nevertheless, males appeared less likely to establish long-term associations with hermaphrodites as indicated by the rate of their disappearance from their hosts (greater than that of hermaphrodites). Sex allocation was female biased in monogamous hermaphrodites. On average, hermaphrodites invested 34 times more to female than to male reproductive structures. Monogamy and female-biased sex allocation seem to be evolutionary consequences of adopting a symbiotic lifestyle in simultaneous hermaphrodites.

Attached is the complete raw data from Ashur and Dixson 2018 “Multiple environmental cues impact habitat choice during nocturnal homing of specialized reef shrimp.” Data has been inputted into Excel with five tabs corresponding to the five different experiments. Data from the mark and recapture experiment to test nocturnal vacancy rates and site fidelity has been described in the “Temporal Movements” tab. Columns C, D, and E, entitled “ Morning 1”, “Night”, and “Morning 2”, reflect the presence or absence of tagged shrimp (column B) within their original sponges on the morning following tagging (C), the subsequent night (D), and the morning following the nocturnal assessment (E). A legend is included in column G to indicate which shrimp were found outside their sponges and which shrimp were found within the same sponge individual but different tubes. The “Transects” tab describes all the data collected during the 15 x 1 m belt transects. All dimensions are recorded in centimeters. Each sponge tube is listed separately but the “Sponge ID” column indicates which tubes are from the same sponge. The “Visual_Isolation” tab refers to the data collected when shrimp were given a choice between 4 morphologies of artificial tube sponge. The chosen height (tall or short) and width (narrow or wide) are listed for each shrimp individual. Further, the “sponge origin” (column B) refers to the sponge species from which each shrimp was originally collected. The “Patch Reef” tab is similarly organized with sponge origin (column B) and sponge choice (column C) both listed. Finally, data from the fluming trials is listed in the “Chemical_Isolation” tab. The top section, labeled “chemical choice trials” (rows 2-21), refers to experiments where sponge cue is compared with seawater and includes four experiments labeled in bold font. The middle section, labeled “Chemical Preference Hierarchy” (rows 23-42), refers to trials where sponge cues from different species were compared and includes four experiments labeled in bold font. The bottom section, labeled “blank control”, refers to the blank reef water vs reef water control. Chemical choice trials consisted of marking the position of the shrimp every 5 seconds in either of the two streams of water flowing through the flume. Over the course of two minutes, 24 recordings are made, after which the water sources are switched and another two-minute trial begins with 24 additional data points. Data is organized such that each row (within each section) corresponds to an individual shrimp. The first 2-minute part of each trial is recorded in the first two columns following "shrimp #". The next two columns show the data for the second part of the trial when the water was switched. The score refers to the overall score for each cue in the trials. &nbsp

Attached is the complete raw data from Ashur and Dixson 2018 “Multiple environmental cues impact habitat choice during nocturnal homing of specialized reef shrimp.” Data has been inputted into Excel with five tabs corresponding to the five different experiments. Data from the mark and recapture experiment to test nocturnal vacancy rates and site fidelity has been described in the “Temporal Movements” tab. Columns C, D, and E, entitled “ Morning 1”, “Night”, and “Morning 2”, reflect the presence or absence of tagged shrimp (column B) within their original sponges on the morning following tagging (C), the subsequent night (D), and the morning following the nocturnal assessment (E). A legend is included in column G to indicate which shrimp were found outside their sponges and which shrimp were found within the same sponge individual but different tubes. The “Transects” tab describes all the data collected during the 15 x 1 m belt transects. All dimensions are recorded in centimeters. Each sponge tube is listed separately but the “Sponge ID” column indicates which tubes are from the same sponge. The “Visual_Isolation” tab refers to the data collected when shrimp were given a choice between 4 morphologies of artificial tube sponge. The chosen height (tall or short) and width (narrow or wide) are listed for each shrimp individual. Further, the “sponge origin” (column B) refers to the sponge species from which each shrimp was originally collected. The “Patch Reef” tab is similarly organized with sponge origin (column B) and sponge choice (column C) both listed. Finally, data from the fluming trials is listed in the “Chemical_Isolation” tab. The top section, labeled “chemical choice trials” (rows 2-21), refers to experiments where sponge cue is compared with seawater and includes four experiments labeled in bold font. The middle section, labeled “Chemical Preference Hierarchy” (rows 23-42), refers to trials where sponge cues from different species were compared and includes four experiments labeled in bold font. The bottom section, labeled “blank control”, refers to the blank reef water vs reef water control. Chemical choice trials consisted of marking the position of the shrimp every 5 seconds in either of the two streams of water flowing through the flume. Over the course of two minutes, 24 recordings are made, after which the water sources are switched and another two-minute trial begins with 24 additional data points. Data is organized such that each row (within each section) corresponds to an individual shrimp. The first 2-minute part of each trial is recorded in the first two columns following "shrimp #". The next two columns show the data for the second part of the trial when the water was switched. The score refers to the overall score for each cue in the trials., The research was funded by the Gordon and Betty Moore Foundation through Grant GBMF5464 (Dixson), Alfred P. Sloan Foundation (Dixson)