Luidia

Abstract: Sea star larvae (Echinodermata: Asteroidea), collected from the subtropical Northwest Atlantic Ocean, exhibited three distinct modes of asexual reproduction. A number of different bipinnariae and brachiolariae reproduced by paratomous cloning of the posterolateral arms. This morphogenesis was identical to that of larvae assignable to the genus Luidia. A second mode of asexual reproduction involves the autotomization of an anterior portion of the preoral lobe. Primary larvae with preoral lobes of varying sizes and free-swimming preoral lobes of various stages of morphological development were simultaneously collected. The free-swimming preoral lobes developed complete digestive systems and ultimately assumed the form of typical bipinnaria larvae. Asexual reproduction by larvae may also take the form of budding. The released individual is either a blastula- or gastrulastage embryo. Subsequent development to a bipinnariastage secondary larva, with the possible exception of coelom formation, appears to occur ...

Abstract: Cloning among metazoan larvae is rare and generally restricted to a few phyla with parasitic or colonial life-histories. Echinoderms are all non-colonial animals, and although cloning is well docu-mented for some adults, its occurrence in larval stages has not been previously observed1–3. Here we describe a novel mode of cloning by fission in planktotrophic bipinnaria larvae of the sea star Luidia sp. from the Sargasso Sea and the Gulf Stream. Reproductive larvae were widely distributed, comprising about 30% of sample populations. This represents an extensive multi-plicative potential whereby the pelagic life of the genet is prolonged and the potential of recruitment into benthic adult populations can be enhanced.

Abstract: A population of the sea-star Luidia sarsi Duben & Koren, which probably metamorphosed in the spring of 1963 and which was first found in the fall of 1963, was followed in the Oresund during a two-year period. The irregular appearance of Luidia sarsi in the Oresund is discussed and it is concluded that it is due to -1. That larval invasions do not occur every year, -2. That larvae of an already existing population in the Oresund will be killed in the brackish water of the Baltic Sea. -3. That low salinity may reduce or eradicate the populations especially in winters, and -4. That the life length probably does not exceed 4–5 years. The stomach contents of 42 specimens were examined; it was found that L. sarsi feeds exclusively on the brittlest ars Ophiura albida and Amphiura filiform is and the sea-urchin Echinocardium cordatum, the first mentioned being by far the most important. These results were verified experimentally. Starved Luidia will also eat certain other species of brittlestars but at a...

Abstract: Luidia ciliaris (Philippi) has intraoral digestion and was found to be a selective feeder on echinoderms. In 258 specimens from the Irish Sea, echinoderms occurred in 97·4% of all stomachs containing food and contributed 92% of the food volume (estimated by points method). The most important food items were Psammechinus miliaris, Ophiothrix fragilis, Ophiura albida and Ophiocomina nigra. Ophiocomina nigra did not occur as frequently as would be expected from their availability. Observation in situ revealed that large specimens had efficient escape response to moving Luidia and aquarium experiments showed that O. nigra deprived of their moving ability were readily eaten. However, the Luidia showed clear preference to Ophiothrix fragilis. There was no distinct seasonal difference in the composition of the diet, but a tendency to a minimum feeding activity in May-June, probably connected with the spawning period.