Reproductive cycle of edible echinoderms from the Southwestern Indian Ocean I: Tripneutes gratilla L. (Echinoidea, Echinodermata)

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Feeding preferences, seasonal gut repletion indices, and diel feeding patterns of the sea urchin Tripneustes gratilla (L.) (Echinodermata, Echinoidea) on a coastal habitat off Toliara (Madagascar)

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Reproductive cycle of edible echinoderms from the Southwestern Indian Ocean II: The sandfish Holothuria scabra

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Lecithotrophic development and metamorphosis in the Indo-West Pacific brittle star Ophiomastix venosa (Echinodermata: Ophiuroidea)

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Population dynamics, infestation and host selection of Vexilla vexillum, an ectoparasitic muricid of echinoids, in Madagascar.

The symbiotic interaction, population and infestation dynamics of the muricid Vexilla vexillum (Gmelin, 1791) on 2 echinoid species, Tripneustes gratilla (Linnaeus, 1785) and Echinometra mathaei (Blainville, 1825), was investigated on the barrier reef off Toliara (Madagascar). V. vexillum is an ectoparasitic muricid which was exclusively found in association with sea urchins, on which it moves freely and browses over the integument. Host recovery from damage caused by muricid grazing was dependent on lesion size. Small lesions regenerated while larger ones were subjected to secondary infections, which led to host death. A 27 mo survey (2000 to 2003) of the muricid's population dynamics revealed annual recruitment episodes during the mid-summer season (December to January). Patterns of recruitment peaks were apparently linked to its reproductive cycle. Demographic parameters including growth and mortality rates of the muricid were estimated from analysis of size-frequency distributions. Growth was described by the von Bertalanffy function. The model predicts that V. vexillum is a fast-growing species in which asymptotic shell length (L infinity = 1.024 cm) is reached 6 to 7 mo after recruitment. The growth rate constant K, and shell length at settlement L0, were estimated from the model. Estimated mortality rate was 55% yr(-1); V. vexillum has a short lifespan. The observed high growth rate together with the high mortality rate suggest that V. vexillum is a semelparous species. A field survey of the infestation dynamics of V. vexillum was performed during 3 consecutive years, with seasonal variation in parasite prevalence on both echinoid host species. Although both T. gratilla and E. mathaei were infested, a preference towards T. gratilla was noted. This was attributed to T. gratilla's test morphology (which allows better accessibility for grazing), to the muricid's higher recognition capacity of T. gratilla (as determined by olfactory experiments) and to the high recruitment predictability of that particular host. This study provides novel information on the biology of V. vexillum, an echinoid epidermal grazer, and its relationship with 2 ecologically and economically important echinoid species.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

The Role of visual and chemical cues in host detection by the symbiotic shrimp Gnathophylloides mineri

The use of visual and chemical cues in host detection is regarded as important but relatively unknown for many symbionts. The small circumtropical caridean shrimp Gnathophylloides mineri forms a close symbiotic association with sea urchins, particularly Tripneustes gratilla, in many parts of the world. G. mineri is known to occur in temperate eastern Australia but the breadth of host use and selection of hosts amongst different species of sea urchins is relatively unknown. The abundance of G. mineri on three co-occurring species of sea urchins, T.gratilla, Heliocidaris tuberculata and Pseudoboletia indiana were measured in eastern Australia. These species of sea urchins were chosen because of either a known prior association with this shrimp elsewhere in the world, or due to their abundance in the area in temperate Australia where the shrimp occurs. Field collections showed that the association between shrimp and sea urchin appears extremely host-specific, with G. mineri only observed on T. gratilla, at an average density of two shrimp per sea urchin. Moreover, the majority of symbionts occurred on the underside (oral region) of T. gratilla. A visual laboratory experiment showed that G. mineri would actively move towards T. gratilla in preference to the other potential host species in the absence of chemical signals. Using a Y-maze, we tested the reaction of G. mineri to the absence of visual signals but the presence of chemical signals originating from their host, and from other species of potential host sea urchins. Seawater alone was used as a negative control. We demonstrated that G. mineri could detect T. gratilla from a distance, the same host that the shrimp are associated with in the field, using visual and chemical cues. Moreover, G. mineri react quickly to visual and chemical host signals by moving towards T. gratilla in preference to other species of sea urchins or in the absence of a signal. The relative importance of visual versus chemical cues is, however, unknown.6 page(s

Effects of delayed metamorphosis and food rations on the perimetamorphic events in the echinoid Paracentrotus lividus (Lamarck, 1816) (Echinodermata)

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Land-based, closed-cycle echiniculture of Paracentrotus lividus (Lamarck) (Echinoidea: Echinodermata): A long-term experiment at a pilot scale

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