Lipid and protein utilization during lecithotrophic development in the asteroid Stegnaster inflatus, with a review of larval provisioning in lecithotrophic echinoderms

The eggs of echinoderms with lecithotrophic development provide structural and nutritional materials (lipids, proteins) to complete development without any external sources of nutrition. Previous studies have suggested that a relatively large proportion of the maternal lipid reserves remain after settlement to provision the early post-metamorphic juvenile. Here we examined lipid and protein utilization during lecithotrophic development of the asterinid starfish Stegnaster inflatus which has large (~400 µm diameter), negatively buoyant eggs. S. inflatus produces eggs with a large amount of lipid (mean ± SD: 2047 ± 315 ng egg-1), with 26% structural lipids and 74% energetic lipids dominated by diacylglycerol ether (DAGE; 66%). Similar amounts of protein were present in the egg (mean ± SD: 2143 ± 157 ng egg-1), with a lipid:protein ratio of 0.96. Approximately 80% of the egg protein is used prior to settlement. In contrast, 51.0% of the energetic lipids provided in the egg, and 40.3% of the DAGE remain for provisioning of the early juvenile. A review of lecithotrophic development in echinoderms reveals that asteroid, echinoid and ophiuroid species have an excess of 50% of the maternal lipids remaining in the settled post-larva. When considering maternal investment in offspring for lecithotrophic developers, we need to consider energetic use during the short dispersal period, as well as provisioning for post-metamorphic early juvenile life.

The planktonic stages of the salmon louse (Lepeophtheirus salmonis) are tolerant of end-of-century pCO2 concentrations

The copepod Lepeophtheirus salmonis is an obligate ectoparasite of salmonids. Salmon lice are major pests in salmon aquaculture and due to its economic impact Lepeophtheirus salmonis is one of the most well studied species of marine parasite. However, there is limited understanding of how increased concentration of pCO2 associated with ocean acidification will impact host-parasite relationships. We investigated the effects of increased pCO2 on growth and metabolic rates in the planktonic stages, rearing L. salmonis from eggs to 12 days post hatch copepodids under three treatment levels: Control (416 µatm), Mid (747 µatm), and High (942 µatm). The pCO2 treatment had a significant effect on oxygen consumption rate with the High treatment animals exhibiting the greatest respiration. The treatments did not have a significant effect on the other biological endpoints measured (carbon, nitrogen, lipid volume, and fatty acid content). The results indicate that L. salmonis have mechanisms to compensate for increased concentration of pCO2and that populations will be tolerant of projected future ocean acidification scenarios. The work reported here also describes catabolism during the lecithotrophic development of L. salmonis, information that is not currently available to parameterize models of dispersal and viability of the planktonic free-living stages.

Early development of twoCapitellaspecies (Annelida: Capitellidae) from the Gulf of Mexico

Early development of the polychaetesCapitellasp. TF from Tampa, Florida andCapitellasp. TV from Tamiahua Lagoon, Veracruz was studied under laboratory conditions. Our observations indicate that hermaphrodites occur inCapitellasp. TF, but not inCapitellasp. TV. Length and volume of larvae and early juveniles were measured daily. Both species appear to have lecithotrophic development. Sizes and duration of the developmental stages varied widely, as in most known species ofCapitella. Characteristic features ofCapitellasp. TF include very small hermaphrodites with a distinct dorsal pigmentation pattern and characteristically shaped brood tubes with a centrally thickened region. Embryos forced to abandon the brood did not survive more than 3 days, and handling the brood produced alterations in timing. Ciliated metatrochophores fromCapitellasp. TV survived inside the brood without the female for at least 14 days and some larvae hatched and died during settling. Some of these larvae were abnormal, with two rounded protuberances in the two ends. Mortality was high. Fungi and protozoans appeared in the dishes and probably partially induced the production of thicker mucus in the brood tubes, delay in metamorphosis, juvenile mortality, worm length and failure in coupling. Size and duration of the developmental stages were distinctly different from the other putative lecithotrophic species of the complex. These differences and other characteristics of each species discard the possibility that they belong to a previously described species. Our results are applicable to future ecological, morphological and molecular studies of each species, habitat and phylogenetics.

Laboratory development of Capitella sp. A (Annelida: Capitellidae) from a NW Mediterranean fish farm reared under different organic enrichment conditions

The polychaete Capitella sp. A, collected in a NW Mediterranean fish farm (Les Cases d’Alcanar, Tarragona, Spain), was cultured for the first time under experimental conditions with different organically enriched sediments to study the differences in development and growth. The species proved to be dioecious and had lecithotrophic development. Sizes of individuals and duration of the developmental stages varied widely, as in most known species of Capitella. In organically enriched sediments, the juveniles were seen one day after hatching and immature females (i.e. with yellow ovaries) after 52 days. Females may reach maturity (i.e. show white intra-coelomic oocytes) at about 64 days old, and the species had a life span of 167 days. According to its development, Capitella sp. A differs from all known lecithotrophic species of the genus. The results also proved that organically enrichment enhanced growth and survival, whereas lowering food can cause morphological alterations such as reduced size in male genital spines.

First record of the genusOnchidoris(Gastropoda: Nudibranchia: Onchidorididae) from the South Atlantic Ocean, with the description of a new species from Brazil

A new species of the genusOnchidorisis described from the south-western Atlantic, on the coast of Brazil, in the States of Rio de Janeiro and São Paulo. To date, the genusOnchidorisis known almost exclusively from the northern hemisphere, especially the Atlantic coast of Europe and the Mediterranean Sea. The single previous record from the southern hemisphere isOnchidoris maugeansis, described from Australia. This is the first record of the family Onchidorididae from the coast of Brazil.Onchidoris brasiliensissp. nov. is very similar toOnchidoris depressa, from England and the northern coast of Spain, but is distinguished by the presence of a triangular protuberance on the edge of the inner lateral radular tooth and a wide closed branchial circle with tubercles inside. Furthermore, the egg mass of O.brasiliensissp. nov. contains a single row of eggs, whereas that ofO. depressahas multiple rows.Onchidoris brasiliensissp. nov. has lecithotrophic development, the first record of this type of development in the genus. There is a relationship betweenO. brasiliensissp. nov. and the bryozoanParasmittina protecta.

Reproductive ecology of the pedunculate barnacle Scalpellum stearnsii (Cirripedia: Lepadomorpha: Scalpellidae)

The sexuality of large (non-dwarf) individuals and the characteristics of eggs, larvae and dwarf males were investigated in the pedunculate barnacle Scalpellum stearnsii. All 103 large individuals collected in this study were not hermaphrodites but females. The major length axis of the egg was on average 0.50 mm, which was larger than that in most thoracican barnacles with planktotrophic larvae. The larvae hatched as nauplii and metamorphosed into cyprids without feeding (i.e. lecithotrophic development). There was a positive relationship between body weight and egg mass weight in ovigerous females. The number of males attached per female ranged from 0 to 35 (average: 5.9) and there was a positive relationship between the number of males and female body weight. The distribution of dwarf males was skewed significantly towards the lower part of the occludent margin, which is near the fertilization site.

Life cycle of Capitella sp. Y (Polychaeta: Capitellidae) from Estero del Yugo, Mazatlán, Mexico

The development of the polychaete Capitella sp. Y from Estero del Yugo, Mazatlán, Mexico was studied under culture conditions. Capitella sp. Y has a lecithotrophic development with the production of ciliated metatrochophore larvae. A high variation in size and duration of the different developmental stages was observed, as with most of the Capitella species previously described. The median survival time was estimated as six months. The Capitella sp. Y population consists of males, females and hermaphrodites (protandrous and proteroginous individuals). Differences in developmental modes among the Capitella capitata species-complex have indicated that Capitella sp. Y do not belong to any of these previously described species. This study has shown that hermaphroditism is favoured when density of individuals is low, especially in protandrous specimens. It is suggested that hermaphroditism, as well as the ability of self-fertilization observed in Capitella sp. Y enhances the success of the population in natural environments.

The morphology of the foregut of larvae and postlarva of Sesarma curacaoense De Man, 1892: a species with facultative lecithotrophy during larval development

Previous study on the resistance of larvae of Sesarma curacaoense submitted to starvation has revealed a facultative lecithotrophy during zoeal stages, but megalopa and first juvenile stages are exclusively feeding stages. In the present study, the gross morphology and fine structure of the foregut of S. curacaoense were investigated during larval, megalopa and first juvenile stages. The foregut of the zoea I show specific setae and a filter press apparently functional. The foregut undergoes changes in the zoea II (last larval stage) with increment of setae number, mainly on the cardiopyloric valve and complexity of the filter press. After metamorphosis to megalopa stage the foregut become rather complex, with a gastric mill supporting a medial and two lateral teeth well-developed. The foregut of the first juvenile is more specialized compared to the previous stage, showing similar characteristics of the decapod adults. These results provide further evidence of facultative lecithotrophic development in the larvae of S. curacaoense.

Developmental morphology of mouthparts and foregut of the larvae and postlarvae of Lepidophthalmus siriboia Felder & Rodrigues, 1993 (Decapoda: Callianassidae)

In this study, the gross morphology of the mouthparts and foregut of the ghost shrimp Lepidophthalmus siriboia were investigated from larvae and postlarvae reared in the laboratory. The mouthparts (maxillae and maxillipeds) of the zoeae have a reduced number of setae and spines (or is absent in some individuals), and the foregut, under developed, have few minute setae in the cardiac and pyloric chambers. In contrast, after the metamorphosis into megalopa stage, all feeding appendages have many setae and, the foregut shows a well-developed gastric mill with strong lateral teeth. In the juvenile stage occurs an increase of setae and spines in the mouthparts and the foregut becomes more specialized. These observations strongly suggest that a lecithotrophic development occurs during all zoeal stages but the megalopa and juvenile stages are feeding animals. The functional morphology of the feeding structures of L. siriboia and other decapods will be briefly discussed.