Multi-omic characterization of the thermal stress phenome in the stony coral Montipora capitata

Background Corals, which form the foundation of biodiverse reef ecosystems, are under threat from warming oceans. Reefs provide essential ecological services, including food, income from tourism, nutrient cycling, waste removal, and the absorption of wave energy to mitigate erosion. Here, we studied the coral thermal stress response using network methods to analyze transcriptomic and polar metabolomic data generated from the Hawaiian rice coral Montipora capitata. Coral nubbins were exposed to ambient or thermal stress conditions over a 5-week period, coinciding with a mass spawning event of this species. The major goal of our study was to expand the inventory of thermal stress-related genes and metabolites present in M. capitata and to study gene-metabolite interactions. These interactions provide the foundation for functional or genetic analysis of key coral genes as well as provide potentially diagnostic markers of pre-bleaching stress. A secondary goal of our study was to analyze the accumulation of sex hormones prior to and during mass spawning to understand how thermal stress may impact reproductive success in M. capitata. Methods M. capitata was exposed to thermal stress during its spawning cycle over the course of 5 weeks, during which time transcriptomic and polar metabolomic data were collected. We analyzed these data streams individually, and then integrated both data sets using MAGI (Metabolite Annotation and Gene Integration) to investigate molecular transitions and biochemical reactions. Results Our results reveal the complexity of the thermal stress phenome in M. capitata, which includes many genes involved in redox regulation, biomineralization, and reproduction. The size and number of modules in the gene co-expression networks expanded from the initial stress response to the onset of bleaching. The later stages involved the suppression of metabolite transport by the coral host, including a variety of sodium-coupled transporters and a putative ammonium transporter, possibly as a response to reduction in algal productivity. The gene-metabolite integration data suggest that thermal treatment results in the activation of animal redox stress pathways involved in quenching molecular oxygen to prevent an overabundance of reactive oxygen species. Lastly, evidence that thermal stress affects reproductive activity was provided by the downregulation of CYP-like genes and the irregular production of sex hormones during the mass spawning cycle. Overall, redox regulation and metabolite transport are key components of the coral animal thermal stress phenome. Mass spawning was highly attenuated under thermal stress, suggesting that global climate change may negatively impact reproductive behavior in this species.

Moonrise timing is key for synchronized spawning in coral Dipsastraea speciosa

Synchronized mass coral spawning typically occurs several days after a full moon once a year. It is expected that spawning day is determined by corals sensing environmental change regulated by the lunar cycle (i.e., tide or moonlight); however, the exact regulatory mechanism remains unknown. Here, we demonstrate how moonlight influences the spawning process of coral, Dipsastraea speciosa. When corals in the field were shaded 1 and 3 d before the full moon or 1 d after the full moon, spawning always occurred 5 d after shading commenced. These results suggest moonlight suppresses spawning: a hypothesis supported by laboratory experiments in which we monitored the effects of experimental moonlight (night-light) on spawning day. Different night-light treatments in the laboratory showed that the presence of a dark period between day-light and night-light conditions eliminates the suppressive effect of night-light on spawning. In nature, moonrise gets progressively later during the course of the lunar cycle, shifting to after sunset following the day of the full moon. Our results indicate that this period of darkness between sunset and moonrise triggers synchronized mass spawning of D. speciosa in nature.

Revisiting the Spawning Pattern of Nyale Worms (Eunicidae) Using the Metonic Cycle

Mass spawning dates of nyale worms (Eunicidae) have been scientifically predictable since 2019. The month of spawning is consistently following the pattern of the February full moon, while the date of spawning is consistently on the 20th of the lunar calendar. There are particular years with February only spawning, March only spawning, and split spawning in both February and March. The existing prediction of the split spawning, however, was constructed with very little available data. The present study aimed to revisit the split spawning prediction using the Metonic cycle, a 19-year lunisolar cycle. The results show that the spawning prediction very much follows the Metonic Cycle. There are minor dates on split spawning to be revised, when February full moon rises on 14th February. The revised hypothesis is that split spawning is very likely to occur when the full moon rises between the 7th to 13th of February. When February full moon appears before the 7th of February, single spawning will take place on the fifth day after the March full moon. When February full moon befalls after the 13th of February, single spawning will occur on the fifth day after the February full moon. The revised prediction method has only 2 (two) deviances in 114 years of simulation dates. The present study is the first to suggest the link between Polychaete spawning patterns and the Metonic Cycle.

Quantitative study of the behavior of two broadcast spawners, the sea urchins Strongylocentrotus intermedius and Mesocentrotus nudus, during mass spawning events in situ

Background The spatial distribution of spawners and temporal parameters of spawning in motile invertebrates with external fertilization might influence reproductive success. However, to date, data on the prespawning and spawning behaviors of broadcast spawners in the field have been scarce and mostly qualitative. The present study was intended to clarify the behavioral adaptations of two sea urchin species, Strongylocentrotus intermedius and Mesocentrotus nudus, using quantitative analysis of their behavior during mass spawning events under natural conditions. Methods We analyzed in situ video recordings of sea urchin behavior obtained during six spawning seasons (2014–2019). The total number of specimens of each sea urchin species and the numbers of spawning males and females were counted. Quantitative parameters of sea urchin spawning (numbers of gamete batches, release duration of one gamete batch, time intervals between gamete batches and total duration of spawning) and movement (step length of spawners and nonspawners before and during spawning and changes in distances between males/nonspawners and females) were determined. Results For each species, 12 mass spawning events were recorded in which 10 or more individuals participated. The temporal dynamics of the numbers of males and females participating in mass spawning were well synchronized in both species; however, males began to spawn earlier and ended their spawning later than females. In both species, the most significant intersex difference was the longer spawning duration in males due to the longer pause between gamete batches. The total duration of gamete release did not differ significantly between sexes. The average duration of sperm release during mass spawning events was longer than solitary male spawning. Males and females showed significant increases in the locomotion rate 35 min before the start of spawning and continued to actively move during spawning. An increase in movement rate before spawning in males and females was induced by environmental factor(s). Nonspawners of both species showed increased locomotion activity but in the presence of spawning neighbors and less prominently than spawners. On a vertical surface, both echinoids moved strictly upward. On flat surfaces, males, females and nonspawners of both echinoids became closer during spawning. Discussion We showed that two sea urchin species with planktotrophic larvae display similar behavioral adaptations aimed at enhancing reproductive success. The high sensitivity of sea urchins, primarily males, to some environmental factors, most likely phytoplankton, may be considered a large-scale adaptation promoting the development of mass spawning events. The longer spawning duration in males and increased movement activity before and during spawning in both sexes may be considered small-scale adaptations promoting approach of males and females and enhancing the chances of egg fertilization.

Multi-omic characterization of the thermal stress phenome in the stony coral Montipora capitata

We used network methods to analyze transcriptomic and polar metabolomic data generated from the stress resistant stony coral Montipora capitata. Corals were exposed to ambient or thermal stress conditions over a five-week period that coincided with a mass spawning event of this species. Gene co-expression networks showed that the early thermal stress response involves downregulation of growth and DNA replication, whereas signaling and the immune response are strongly upregulated. Later stages are dominated by suppression of metabolite transport and biomineralization and enhanced expression of transcriptional regulators. Integration of gene-metabolite data demonstrates that the major outcome of the thermal treatment is activation of animal redox stress pathways with detoxification of reactive oxygen species being dominant. Differential regulation of the highly conserved cytochrome P450 gene family was of particular interest with downregulation of CYP1A1, involved in progesterone metabolism, potentially explaining the attenuated mass spawning observed during the sampling period.

PEMIJAHAN INDUK, PROFIL KOLESTEROL, DAN ASAM LEMAK TELUR LOBSTER PASIR (Panulirus homarus) HASIL BUDIDAYA

Pembenihan lobster pasir (Panulirus homarus) belum berkembang di Indonesia karena terbatasnya teknik pemijahan induk dan belum diketahuinya tingkat keberhasilan induk betina membawa telur dan profil telur hasil pemeliharaan. Penelitian bertujuan untuk mempelajari pengaruh ablasi satu tangkai mata, metode pemijahan massal dan individual pada bulan gelap dan terang pada induk berganti kulit dan membawa telur, serta konsentrasi kolesterol dan asam-asam lemak telur pada lama pengeraman berbeda. Induk betina dan jantan dipakai secara terus-menerus saat percobaan pemijahan. Pemijahan pertama menggunakan pemijahan dengan rasio 2:1 pada bulan gelap. Percobaan kedua dan ketiga menggunakan pemijahan massal selama bulan terang dan gelap. Profil telur dibandingkan konsentrasi kolesterol dan asam lemaknya pada 1, 2, dan 3-4 minggu pengeraman. Hasil penelitian menunjukkan ablasi tangkai mata dapat menstimulasi pemijahan individual dan massal yang didahului dengan ganti kulit pada induk betina sebagai indikator pemijahan. Pemijahan massal pada bulan gelap menghasilkan induk betina membawa telur terbanyak dibandingkan pemijahan individual pada bulan gelap dan pemijahan massal pada bulan terang. Konsentrasi kolesterol dan asam-asam lemak telur mengalami perubahan mengikuti lama pengeraman oleh induk yang menunjukkan terjadinya peningkatan kematangan telur (P<0,05).Spiny lobster (Panulirus homarus) hatchery has not been developed in Indonesia. Major constraints were limited broodstock spawning techniques, low incidence of eggs-berried broodstock, and unknown eggs profile. This study aimed to evaluate the effects of eyestalk ablation, spawning methods and moon circulation to molted, the number of eggs berried of females, and eggs-berried cholesterol and fatty acids profiles. Individual and mass spawning during full and new moon were used in this studies. Female and male broodstocks were used for consecutive spawning with ratio 2:1. The first study was used individual spawning during new moon. The second and third studies were used mass spawning during full moon and new moon, respectively. Eggs-berried profile compared concentration of cholesterol and fatty acids during 1, 2, and 3-4 weeks. Results showed eyestalk ablation stimulated individual or mass spawned and molted of female as early indicator of spawning. Full moon and mass spawning supported more eggs-berried female broodstock than that of other methods. Cholesterol and fatty acids showed different concentration within 1, 2, and 3-4 weeks of eggs-berried that supported eggs maturity (P<0.05).