Transcriptional Response of Two Core Photosystem Genes in Symbiodinium spp. Exposed to Thermal Stress

Mutualistic symbioses between scleractinian corals and endosymbiotic dinoflagellates (Symbiodinium spp.) are the foundation of coral reef ecosystems. For many coral-algal symbioses, prolonged episodes of thermal stress damage the symbiont\u27s photosynthetic capability, resulting in its expulsion from the host. Despite the link between photosynthetic competency and symbiont expulsion, little is known about the effect of thermal stress on the expression of photosystem genes in Symbiodinium. This study used real-time PCR to monitor the transcript abundance of two important photosynthetic reaction center genes, psbA(encoding the D1 protein of photosystem II) and psaA (encoding the P700 protein of photosystem I), in four cultured isolates (representing ITS2-types A13, A20, B1, and F2) and two in hospite Symbiodinium spp. within the coral Pocillopora spp. (ITS2-types C1b-c and D1). Both cultured and in hospite Symbiodinium samples were exposed to elevated temperatures (32°C) over a 7-day period and examined for changes in photochemistry and transcript abundance. Symbiodinium A13 and C1b-c (both thermally sensitive) demonstrated significant declines in both psbA and psaA during the thermal stress treatment, whereas the transcript levels of the other Symbiodinium types remained stable. The downregulation of both core photosystem genes could be the result of several different physiological mechanisms, but may ultimately limit repair rates of photosynthetic proteins, rendering some Symbiodinium spp. especially susceptible to thermal stress

Maximum quantum yield of PSII (F_v/F_m) and the effective absorption cross-section of PSII (σ_PSII) during the simulated bleaching event.

<p>(a.) Maximum quantum yield of PSII (F_v/F_m) and (b.) the effective absorption cross-section of PSII (<b>σ</b>_PSII) for <i>Symbiodinium</i> C1b-c and D1 after Day 1 and 7 of thermal stress (32<b>°</b>C). Asterisks (*) represent statistically significant differences between controls and treatments for each <i>Symbiodinium</i> type at a time point (Mann-Whitney U test; p<b><</b>0.05). For each point, n = 3–6 <b>±</b>SD.</p

Relative expression of <i>psbA</i> and <i>psaA</i> for <i>Symbiodinium</i> C1b-c and D1 during the simulated bleaching event.

<p>Each bar represents the mean expression value (logarithmic scale; <b>±</b>SE) relative to the untreated controls (28<b>°</b>C) for four biological replicates. Asterisks (*) represent values that statistically differed from the untreated controls sampled the same day (REST; p<b><</b>0.05).</p

Chlorophyll <i>a</i> fluorescence measurements of cultured <i>Symbiodinium</i> during the thermal stress treatment.

<p>(a.) Maximum quantum yield of PSII (F_v/F_m) and (b.) the effective absorption cross-section of PSII (<b>σ</b>_PSII) across four <i>Symbiodinium</i> phylotypes, prior to (Day 0) and during (Day 1–7) thermal stress (32<b>°</b>C). Asterisks (*) represent statistically significant values that differed from the untreated controls (One-way ANOVA; p<0.05). For each point, n = 4 ±SD.</p

Target gene, encoded protein, and primer sequence used for real-time PCR.

<p>F designates the forward primer; R designates the reverse primer.</p

Complete mitochondrial genomes of the black corals Alternatipathes mirabilis Opresko & Molodtsova, 2021 and Parantipathes larix (Esper, 1788) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae)

We describe the complete mitogenomes of the black corals Alternatipathes mirabilis Opresko & Molodtsova, 2021 and Parantipathes larix (Esper, 1790) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae). The analysed specimens include the holotype of Alternatipathes mirabilis, collected from Derickson Seamount (North Pacific Ocean; Gulf of Alaska) at 4,685 m depth and a potential topotype of Parantipathes larix, collected from Secca dei Candelieri (Mediterranean Sea; Tyrrhenian Sea; Salerno Gulf; Italy) at 131 m depth. We also assemble, annotate and make available nine additional black coral mitogenomes that were included in a recent phylogeny (Quattrini et al. 2023b), but not made easily accessible on GenBank. This is the first study to present and compare two mitogenomes from the same species of black coral (Stauropathes arctica (Lütken, 1871)) and, thus, place minimum boundaries on the expected level of intraspecific variation at the mitogenome level. We also compare interspecific variation at the mitogenome-level across five different specimens of Parantipathes Brook, 1889 (representing at least two different species) from the NE Atlantic and Mediterranean Sea

Complete mitochondrial genomes of the black corals Alternatipathes mirabilis Opresko & Molodtsova, 2021 and Parantipathes larix (Esper, 1788) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae)

We describe the complete mitogenomes of the black corals Alternatipathes mirabilis Opresko & Molodtsova, 2021 and Parantipathes larix (Esper, 1790) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae). The analysed specimens include the holotype of Alternatipathes mirabilis, collected from Derickson Seamount (North Pacific Ocean; Gulf of Alaska) at 4,685 m depth and a potential topotype of Parantipathes larix, collected from Secca dei Candelieri (Mediterranean Sea; Tyrrhenian Sea; Salerno Gulf; Italy) at 131 m depth. We also assemble, annotate and make available nine additional black coral mitogenomes that were included in a recent phylogeny (Quattrini et al. 2023b), but not made easily accessible on GenBank. This is the first study to present and compare two mitogenomes from the same species of black coral (Stauropathes arctica (Lütken, 1871)) and, thus, place minimum boundaries on the expected level of intraspecific variation at the mitogenome level. We also compare interspecific variation at the mitogenome-level across five different specimens of Parantipathes Brook, 1889 (representing at least two different species) from the NE Atlantic and Mediterranean Sea

Mitogenomics reveals low variation within a trigeneric complex of black corals from the North Pacific Ocean

A 2013 study revealed that three morphologically distinct antipatharian genera (Dendrobathypathes, Lillipathes, Parantipathes) from the eastern North Pacific (ENP) are genetically indistinguishable using three mitochondrial and four nuclear markers (7,203 bp). To investigate whether this lack of molecular variability extends beyond three mitochondrial genes, we sequenced the complete mitogenome of a single representative within each genus. Dendrobathypathes was the only specimen from the 2013 study containing high molecular weight (HMW) DNA. In terms of geographic proximity to the ENP, the closest Lillipathes and Parantipathes yielding HMW DNA were from the central North Pacific near Hawai'i. Based on cox3-IGR-cox1, Lillipathes and Parantipathes each contained two variable sites and thus were not equivalent substitutes for specimens from the ENP. Nonetheless, variation was extremely low when comparing the mitogenomes, with 32 variable positions across 17,687 bp. Pairwise comparisons revealed 18 (Dendrobathypathes and Parantipathes) and 23 (Lillipathes and Parantipathes;Lillipathes and Dendrobathypathes) variable sites. An ML-based phylogenetic reconstruction using 13 protein-coding genes and two rRNAs revealed that the three North Pacific genera grouped in a clade with Atlantic Dendrobathypathes, while Atlantic Parantipathes spp. formed a sister clade. Previous research hypothesized that hybridization with subsequent introgression was responsible for the lack of variability among genera. Due to uniparental inheritance and lack of recombination, mtDNA cannot identify hybrids; however, finding Pacific Parantipathes grouping with Dendrobathypathes and Lillipathes rather than Atlantic Parantipathes suggests that the trigeneric complex has a unique evolutionary history. If high-resolution nuclear markers support hybridization, it will be important to elucidate the molecular mechanism that maintains three distinct morphological forms occurring in sympatry

Reproductive inequality in humans and other mammals

To address claims of human exceptionalism, we determine where humans fit within the greater mammalian distribution of reproductive inequality. We show that humans exhibit lower reproductive skew (i.e., inequality in the number of surviving offspring) among males and smaller sex differences in reproductive skew than most other mammals, while nevertheless falling within the mammalian range. Additionally, female reproductive skew is higher in polygynous human populations than in polygynous nonhumans mammals on average. This patterning of skew can be attributed in part to the prevalence of monogamy in humans compared to the predominance of polygyny in nonhuman mammals, to the limited degree of polygyny in the human societies that practice it, and to the importance of unequally held rival resources to women's fitness. The muted reproductive inequality observed in humans appears to be linked to several unusual characteristics of our species-including high levels of cooperation among males, high dependence on unequally held rival resources, complementarities between maternal and paternal investment, as well as social and legal institutions that enforce monogamous norms