Development Of Tentacles Research Articles

Early onset of zooplanktivory in equatorial reef coral recruits

Scleractinian coral recruits face multiple challenges as theyattempt to meet the metabolic demands for growth anddevelopment post-settlement. Although coral recruits ofsome scleractinian species can obtain zooxanthellae fromtheir parent colonies to enable autotrophy (Richmond 1997),the development of tentacles is essential for the capture ofparticulate matter to supplement the nutrient and energysupply of the growing juvenile coral. However, studiesexamining the onset of zooplanktivory in coral recruits arelimited (Cumbo et al. 2012).In April 2011, gravid colonies of the broadcasting coralAcropora hyacinthus were harvested from the reef off KusuIsland, Singapore (1°13′25′′N, 103°51′38′′E) for ex situspawning and establishment of larval culture (following Tohet al. 2012). The larvae were settled on tiles (2.3 cm×2.3 cm)and the recruits were tagged to determine their age. Using astereomicroscope (Nikon) with a camera setup (Canon), weobservedthat2-day-oldA.hyacinthusazooxanthellaterecruits(n=7) immobilized live 1-day-old Artemia salina naupliiwithin seconds of contact with their tentacles (Fig. 1a). The

Scleractinian corals capture zooplankton within days of settlement and metamorphosis

Corals face unique challenges in their early life stages, as their larvae lack tentacles to capture particulates to meet metabolic demands. Instead, they must meet these costs from food reserves or alternative modes of nutrition such as dissolved organic material or, when they contain Symbiodinium, autotrophy (Edmunds et al. 2001). Once settled, rapid metamorphosis and development of tentacles are advantageous, because tentacles facilitate particle capture to augment the supply of energy and nutrients necessary for polyp growth. However, it is unknown how early in their development corals begin to capture and ingest food.

Redescription of Chrysaora lactea Eschscholtz, 1829 (Cnidaria, Scyphozoa) from the Brazilian coast, with designation of a neotype

A redescription of the species Chrysaora lactea from the western South Atlantic is given based on live and preserved specimens from the Brazilian, Uruguayan and Argentinean coasts, and a neotype specimen is designated. The species is one of the commonest scyphomedusae in Brazilian coastal waters, reaching up to 25 cm in bell diameter with several different colour patterns (mainly milkywhite). The species is recorded with certainty from Jamaica to the northern coast of Argentina, and can be distinguished from its congeners primarily by the order of the development of tentacles (2nd, 3rd, 1st, 3rd, 2nd).

Is the scyphomedusa Cyanea capillata (l.) dependent on gelatinous prey for its early development?

Asbtract Newly released ephyrae ofthe scyphomedusa Cyanea capillata did not grow on either Artemia nauplii or copepod dominated mixed zooplankton, but grew with an average rate of 16.5 % day-1 (maximum of 30.6 % day-1) with a ctenophore as food. The two first food types did not generate medusae with normal development of tentacles and oral arms over a seven-week period, whereas the ctenophore food did. We suggest that availability of gelatinous prey for newly released ephyrae is a bottleneck in the development, making constraints on the population succession and at least partly explaining inter-annual variations in abundance of C. capillata.

The possible involvement of Arg-Phe-amide immunoreactive neurons during tentacle development and regeneration in the hydromedusa Polyorchis penicillatus

Descriptions of new neuropeptides are common, yet data on their biological actions are limited. Many act as neurotransmitters and neuromodulators, others appear to have morphogenetic actions, and some probably act as both transmitters and developmental regulators. Ubiquitous within the Cnidaria is a family of neuropeptides having the carboxy-terminus Arg-Xaa-NH2, where Xaa is an aliphatic or aromatic amino acid (usually Phe, Trp, Asn, Ile, Ala, or Pro). Although some of these peptides (here called RXamides) have been shown to have both excitatory and inhibitory actions on muscle and neurons in anthozoans and hydrozoans, the possibility that they have other actions has not been fully investigated. In this study we describe the normal sequence of tentacle development in Polyorchis penicillatus and compare it with the stages in regeneration of tentacles after ablation. Development of tentacles was accompanied by a characteristic sequence of appearance of neurons in the bud that were immunoreactive to antisera raised against Arg-Phe amides (RFamides). Some of these neurons were transitory and may have been giving morphogenic signals. The pattern of development of the RFamide-immunoreactive neuronal system was identical for ontogenetic development and regeneration. When early tentacle buds were treated with hydroxyurea to remove interstitial cells and neurons, the buds failed to develop. Immunocytochemistry showed that RFamide-containing neurons were absent in treated animals. Hydroxyurea treatment also prevented the regeneration of buds at the ablation site. Further studies are needed to establish whether RFamide neurons themselves, or some other neuronal types, are required for tentacle development and regeneration.

Biology and life history of the nudibranch mollusc, Coryphella stimpsoni (Verrill 1879).

1. The morphology and life history of the nudibranch mollusc, Coryphella stimpsoni (Verrill 1879) is described.2. Adults were collected in October and deposited egg strings in December.3. Development corresponds to Thompson's (1967) Type 3, i.e., juveniles crawl directly from the egg mass and begin benthic life.4. Development time from egg deposition to the benthic crawling stage was from 25 to 52 days.5. Veligers are characterized by a large amount of yolk, a reduced velum, a thin shell and no operculum.6. Sequential development of tentacles, rhinophores and cerata and the differentiation of other organs such as cnidosacs, heart and digestive structures in the juveniles are described.7. This is the first report of an eolid nudibranch from New England which crawls directly from the egg mass as a juvenile to begin benthic life.