Dopamine-Derived Guanidine Alkaloids from a Didemnidae Tunicate: Isolation, Synthesis, and Biological Activities.

Mellpaladines A-C (1-3) and dopargimine (4) are dopamine-derived guanidine alkaloids isolated from a specimen of Palauan Didemnidae tunicate as possible modulators of neuronal receptors. In this study, we isolated the dopargimine derivative 1-carboxydopargimine (5), three additional mellpaladines D-F (6-8), and serotodopalgimine (9), along with a dimer of serotonin, 5,5'-dihydroxy-4,4'-bistryptamine (10). The structures of these compounds were determined based on spectrometric and spectroscopic analyses. Compound 4 and its congeners dopargine (11), nordopargimine (15), and 2-(6,7-dimethoxy-3,4-dihydroisoquinolin-1-yl)ethan-1-amine (16) were synthetically prepared for biological evaluations. The biological activities of all isolated compounds were evaluated in comparison with those of 1-4 using a mouse behavioral assay upon intracerebroventricular injection, revealing key functional groups in the dopargimines and mellpaladines for in vivo behavioral toxicity. Interestingly, these alkaloids also emerged during a screen of our marine natural product library aimed at identifying antiviral activities against dengue virus, SARS-CoV-2, and vesicular stomatitis Indiana virus (VSV) pseudotyped with Ebola virus glycoprotein (VSV-ZGP).

Temporal and Spatial Site Sharing during Spawning in Snappers Symphorichthys spilurus and Lutjanus bohar (Pisces: Perciformes: Lutjanidae) in Waters around Peleliu Island, Palau.

Jiro Sakaue, Hiroshi Akino, Manabu Endo, Hitoshi Ida, and Takashi Asahida (2016) Two species of Lutjanidae, Symphorichthys spilurus and Lutjanus bohar, form spawning aggregation, a large school specifically formed for reproduction. Although they share the same spawning site at the southernmost reef in Peleliu Island, Palau, timing of spawning and their behaviors in the spawning and resting sites differ. Although the spawning behaviors have reported previously, long term and integrated observations documenting the size of the aggregation, exact spawning duration and timing, detailed behavioral profiles, as well as oceanic conditions upon spawning have never been reported. Here, we conducted a comparative study for these species and found behavioral and environmental cues that might be key to differentiate their ecological characteristics. S. spilurus begun to aggregate at full moon. Aggregations of L. bohar on the other hand, started from four days before full moon. Size of the aggregation was > 50,000 in S. spilurus, but about 7,000 in L. bohar. Both species migrated from the resting area to the spawning site in a diel rhythm. S. spilurus started spawning every half- moon, between the full moon and the new moon, while L. bohar spawns on every full moon. The first spawning took place at around dawn but the time shifted. S. spilurus spawned only when the current directs toward the southeast (offshore flow), while L. bohar spawns only when the current directs toward the southwest (tidal flow). Characteristic swimming behavior was observed for S. spilurus, in that, one or few males that could successfully chase the quick-swimming female fish could fertilize the eggs. In contrast, the behavior of L. bohar, was in a manner typical of several other lutjanid fish. The comparative and long-term field observation conducted over 10 years identified clear differences in the spawning behaviors of S. spilurus and L. bohar. Key behavioral and environmental factors found here might be key determinants for the ecology of these species.

A 'living fossil' eel (Anguilliformes: Protanguillidae, fam. nov.) from an undersea cave in Palau.

We report the discovery of an enigmatic, small eel-like fish from a 35 m-deep fringing-reef cave in the western Pacific Ocean Republic of Palau that exhibits an unusual suite of morphological characters. Many of these uniquely characterize the Recent members of the 19 families comprising the elopomorph order Anguilliformes, the true eels. Others are found among anguilliforms only in the Cretaceous fossils, and still others are primitive with respect to both Recent and fossil eels. Thus, morphological evidence explicitly places it as the most basal lineage (i.e. the sister group of extant anguilliforms). Phylogenetic analysis and divergence time estimation based on whole mitogenome sequences from various actinopterygians, including representatives of all eel families, demonstrate that this fish represents one of the most basal, independent lineages of the true eels, with a long evolutionary history comparable to that of the entire Anguilliformes (approx. 200 Myr). Such a long, independent evolutionary history dating back to the early Mesozoic and a retention of primitive morphological features (e.g. the presence of a premaxilla, metapterygoid, free symplectic, gill rakers, pseudobranch and distinct caudal fin rays) warrant recognition of this species as a 'living fossil' of the true eels, herein described as Protanguilla palau genus et species nov. in the new family Protanguillidae.