Lipid accumulation and metabolism in polychaete spermatogenesis: Role of the large discoidal lipoprotein

dLp/HDL-BGBP and MTP Cloning and Expression Profiles During Embryonic Development in the Mud Crab Scylla paramamosain

Lipids are the main energy source for embryonic development in oviparous animals. Prior to the utilization and catabolism, lipids are primarily transported from the yolk sac to embryonic tissues. In the present study, cDNA encoding a circulatory large lipid transfer protein (LLTP) superfamily member, the precursor of large discoidal lipoprotein (dLp) and high-density lipoprotein/β-1,3-glucan-binding protein (HDL-BGBP), named dLp/HDL-BGBP of 14,787 bp in length, was cloned from the mud crab Scylla paramamosain. dLp/HDL-BGBP was predicted to encode a 4,831 amino acids (aa) protein that was the precursor of dLp and HDL-BGBP, which were both detected in hemolymph by liquid chromatography–mass spectrometry (LC-MS/MS) analysis. For the intracellular LLTP, three microsomal triglyceride transfer protein (MTP) cDNAs of 2,905, 2,897, and 3,088 bp in length were cloned from the mud crab and were predicted to encode MTP-A of 881 aa, MTP-B of 889 aa, and MTP-C of 919 aa, respectively, which were different merely in the N-terminal region and shared an identical sequence of 866 aa. During embryonic development, the expression level of dLp/HDL-BGBP consecutively increased from the early appendage formation stage to the eye pigment-formation stage, which indicated that HDL-BGBP is probably the scaffolding protein for yolk lipid. For the MTP gene, MTP-C accounted for ~70% of MTP mRNA from the blastocyst stage to the nauplius stage, as well as the pre-hatching stage; MTP-C and MTP-A expression levels were comparable from the early appendage formation stage to the late eye pigment-formation stage; MTP-A was extremely low in blastocyst and gastrula stages; MTP-B was expressed at a relatively low-level throughout embryo development. The variations in the expression profiles among MTP transcripts suggested that MTP might play roles in the lipid droplet maturation and lipoprotein assembly during embryonic development.

Germ Cell Development in Male Perinereis nuntia and Gamete Spawning Mechanisms in Males and Females

Perinereis nuntia is a fully segmented worm with complete intersegmental septa. A previous study of females revealed that germ cells of this animal originate in the tail end segment, called the pygidium. Germ cells were duplicated in the pygidium, transferred to a newly generated segment, and then settled in the parapodia. Within each segment, the settled germ cells proliferated in the parapodia and then migrated into a body cavity area to begin meiotic development. Currently, there is not much information about differences between male and female germ cell development. Therefore, we conducted monthly in situ hybridization analyses using the germ cell marker Pn-piwi and histological examinations. Germ cells detected by Pn-piwi initially settled in the distal areas of the parapodia on both sides of each segment, then formed a large germ cell cluster in each parapodium, and finally, small germ cell clusters were formed by the separation of the large clusters. The small clusters migrated to the deeper body cavity area during growth by segment addition. Until the female germ cells began vitellogenesis, the sex of germ cells could not be identified by morphological observation. Thus, male and female P. nuntia may have the same mechanism of germ cell provision to all segments. At the time of spawning, sperm were released from nephridiopores at the 2^nd through 15^th segments from the pygidium, while eggs were released through ruptures in the skin of 2-3 segments between the 10^th and 30^th segments from the tail.

Annelid Coelomic Fluid Proteins

The coelomic cavity is part of the main body plan of annelids. This fluid filled space takes up a considerable volume of the body and serves as an important site of exchange of both metabolites and proteins. In addition to low molecular substances such as amino acids and glucose and lactate, the coelomic fluid contains different proteins that can arise through release from adjacent tissues (intestine) or from secretion by coelomic cells. In this chapter, we will review the current knowledge about the proteins in the annelid coelomic fluid. Given the number of more than 20,000 extant annelid species, existing studies are confined to a relatively few species. Most studies on the oligochaetes are confined to the earthworms-clearly because of their important role in soil biology. In the polychaetes (which might represent a paraphyletic group) on the other hand, studies have focused on a few species of the Nereidid family. The proteins present in the coelomic fluid serve different functions and these have been studied in different taxonomic groups. In oligochaetes, proteins involved antibacterial defense such as lysenin and fetidin have received much attention in past and ongoing studies. In polychaetes, in contrast, proteins involved in vitellogenesis and reproduction, and the vitellogenic function of coelomic cells have been investigated in more detail. The metal binding metallothioneins as well as antimicrobial peptides, have been investigated in both oligochaetes and polychaetes. In the light of the literature available, this review will focus on lipoproteins, especially vitellogenin, and proteins involved in defense reactions. Other annelid groups such as the Pogonophora, Echiura, and Sipuncula (now considered polychaetes), have not received much attention and therefore, this overview is far from being complete.

Combined transcriptome and proteome profiling reveals specific molecular brain signatures for sex, maturation and circalunar clock phase

Many marine animals, ranging from corals to fishes, synchronise reproduction to lunar cycles. In the annelid Platynereis dumerilii, this timing is orchestrated by an endogenous monthly (circalunar) clock entrained by moonlight. Whereas daily (circadian) clocks cause extensive transcriptomic and proteomic changes, the quality and quantity of regulations by circalunar clocks have remained largely elusive. By establishing a combined transcriptomic and proteomic profiling approach, we provide first systematic insight into the molecular changes in Platynereis heads between circalunar phases, and across sexual differentiation and maturation. Whereas maturation elicits large transcriptomic and proteomic changes, the circalunar clock exhibits only minor transcriptomic, but strong proteomic regulation. Our study provides a versatile extraction technique and comprehensive resources. It corroborates that circadian and circalunar clock effects are likely distinct and identifies key molecular brain signatures for reproduction, sex and circalunar clock phase. Examples include prepro-whitnin/proctolin and ependymin-related proteins as circalunar clock targets.

Discovery of methylfarnesoate as the annelid brain hormone reveals an ancient role of sesquiterpenoids in reproduction

Animals require molecular signals to determine when to divert resources from somatic functions to reproduction. This decision is vital in animals that reproduce in an all-or-nothing mode, such as bristle worms: females committed to reproduction spend roughly half their body mass for yolk and egg production; following mass spawning, the parents die. An enigmatic brain hormone activity suppresses reproduction. We now identify this hormone as the sesquiterpenoid methylfarnesoate. Methylfarnesoate suppresses transcript levels of the yolk precursor Vitellogenin both in cell culture and in vivo, directly inhibiting a central energy–costly step of reproductive maturation. We reveal that contrary to common assumptions, sesquiterpenoids are ancient animal hormones present in marine and terrestrial lophotrochozoans. In turn, insecticides targeting this pathway suppress vitellogenesis in cultured worm cells. These findings challenge current views of animal hormone evolution, and indicate that non-target species and marine ecosystems are susceptible to commonly used insect larvicides.

DOI:http://dx.doi.org/10.7554/eLife.17126.001

All organisms need energy to survive and grow. However, sources of energy are limited and so organisms need to decide how to spend the resources they have available. For instance, animals must choose whether they should continue to grow or if they should invest energy into reproduction instead. This decision becomes even more important for animals that reproduce in an “all-or-nothing” manner and invest all their available energy into reproduction and die soon after.

Bristle worms live in coastal areas around world. In mass spawning events, thousands of individuals raise from the sea floor to the surface, to release sperm and eggs. While the fertilized eggs start to develop in the water, the parents invariably die. The female worms spend roughly half their body mass in producing eggs and supplying them with yolk as a source of energy. It has been known for decades that the brains of bristle worms produce a master hormone that promotes growth and suppresses reproduction. Yet the identity of this hormone that controls the life-or-death decision was not clear.

Schenk et al. took advantage of new molecular tools to solve this puzzle. The experiments show that this hormone directly regulates how much yolk the female animals produce. This allowed Schenk et al. to design a new molecular assay that helped to identify the hormone itself. Unexpectedly, the hormone – called methylfarnesoate – belongs to a family of small molecules called sesquiterpenoids, which researchers previously thought were only found in insects and related groups. Hence, many insecticides have been developed to target sesquiterpenoid signaling and they are used in massive amounts to fight pests like the tiger mosquito (which transmits the Zika virus). Schenk et al. also found that these insecticides also cause severe problems in bristle-worms.

These findings challenge current views of how animal hormones have evolved and indicate that common insecticides may be harming bristle worms and other animals in marine environments. The next steps are to find out whether methylfarnesoate is found in other closely related animals, such as snails and mussels, and whether the insecticides are harmful to these animals too. Another future challenge will be to investigate how this hormone actually promotes animal growth.

DOI:http://dx.doi.org/10.7554/eLife.17126.002

Adição de óleo de palma na dieta sobre a lipidemia e a qualidade do sêmen de bubalinos (Bubalus bubalis)

O estudo visou investigar o efeito da suplementação dietética com óleo de palma sobre o perfil sérico lipídico e as características seminais de touros bubalinos (Bubalus bubalis), bem como suas correlações. Doze touros foram alocados no Grupo CONT (n=5) ou Grupo ÓLEO (n=7) e receberam alimentação isoproteica composta por silagem de milho e concentrado (milho triturado, farelo de trigo e ureia), com proporção volumoso/concentrado de 50%, durante 130 dias (Períodos 1 e 2). Diferencialmente, óleo de palma foi adicionado ao concentrado (2% MS) do Grupo ÓLEO. Sêmen e sangue foram colhidos quinzenalmente. Houve aumento nas concentrações séricas de colesterol, HDL e lipídios totais nos animais do Grupo ÓLEO, enquanto o período influenciou nas taxas de colesterol, LDL, lipídios totais e VLDL (P<0,05). Houve decréscimo no turbilhonamento e discreta redução na integridade de membranas nos animais do Grupo ÓLEO (P<0,05). Correlações significativas foram encontradas entre triglicerídeos e defeitos menores (r=-0,412; P=0,006), LDL e defeitos totais (r=-0,333; P=0,030), lipídios totais e defeitos menores (r=-0.366; P= 0,017), lipídios totais e defeitos totais (r=-0.309; P= 0,046), e VLDL e viabilidade espermática (r=0,381; P=0,012), apontando efeitos positivos da maior lipidemia na morfologia e na viabilidade espermática. O uso de óleo de palma alterou o perfil lipídico sérico, mas não favoreceu per se os parâmetros seminais relacionados com o potencial de fertilidade dos touros.