Typical 2-Cys Peroxiredoxins as a Defense Mechanism against Metal-Induced Oxidative Stress in the Solitary Ascidian Ciona robusta

Typical 2-Cys peroxiredoxins (2-Cys Prdxs) are proteins with antioxidant properties belonging to the thioredoxin peroxidase family. With their peroxidase activity, they contribute to the homeostatic control of reactive oxygen species (ROS) and, therefore, participate in various physiological functions, such as cell proliferation, differentiation, and apoptosis. Although Prdxs have been shown to be potential biomarkers for monitoring aquatic environments, minimal scientific attention has been devoted to describing their molecular architecture and function in marine invertebrates. Our study aims to clarify the protective role against stress induced by exposure to metals (Cu, Zn, and Cd) of three Prdxs (Prdx2, Prdx3, and Prdx4) in the solitary ascidian Ciona robusta, an invertebrate chordate. Here, we report a detailed pre- and post-translational regulation of the three Prdx isoforms. Data on intestinal mRNA expression, provided by qRT-PCR analyses, show a generalized increase for Prdx2, -3, and -4, which is correlated to metal accumulation. Furthermore, the increase in tissue enzyme activity observed after Zn exposure is slower than that observed with Cu and Cd. The obtained results increase our knowledge of the evolution of anti-stress proteins in invertebrates and emphasize the importance of the synthesis of Prdxs as an efficient way to face adverse environmental conditions.

Morphological Study and 3D Reconstruction of the Larva of the Ascidian Halocynthia roretzi

The swimming larva represents the dispersal phase of ascidians, marine invertebrates belonging to tunicates. Due to its adhesive papillae, the larva searches the substrate, adheres to it, and undergoes metamorphosis, thereby becoming a sessile filter feeding animal. The larva anatomy has been described in detail in a few species, revealing a different degree of adult structure differentiation, called adultation. In the solitary ascidian Halocynthia roretzi, a species reared for commercial purposes, embryogenesis has been described in detail, but information on the larval anatomy is still lacking. Here, we describe it using a comparative approach, utilizing 3D reconstruction, as well as histological/TEM observations, with attention to its papillae. The larva is comparable to those of other solitary ascidians, such as Ciona intestinalis. However, it displays a higher level of adultation for the presence of the atrium, opened outside by means of the atrial siphon, and the peribranchial chambers. It does not reach the level of complexity of the larva of Botryllus schlosseri, a phylogenetically close colonial ascidian. Our study reveals that the papillae of H. roretzi, previously described as simple and conform, exhibit dynamic changes during settlement. This opens up new considerations on papillae morphology and evolution and deserves to be further investigated.

Typical 2-Cys Peroxiredoxins as a Defense Mechanism against Metal-Induced Oxidative Stress in the Solitary Ascidian Ciona robusta

Typical 2-Cys peroxiredoxins (2-Cys Prdxs) are proteins with antioxidant properties belonging to the thioredoxin peroxidase family. With their peroxidase activity, they contribute to the homeostatic control of reactive oxygen species (ROS) and, therefore, participate in various physiological functions such as cell proliferation, differentiation, and apoptosis. Although Prdxs have been shown to be potential biomarkers for monitoring the aquatic environments, minimal scientific attention has been devoted to describing their molecular architecture and function in marine invertebrates. Our study aims to clarify the protective role against stress induced by exposure to metals (Cu, Zn, and Cd) of three Prdxs (Prdx2, Prdx3, and Prdx4) in the solitary ascidian Ciona robusta, an invertebrate chordate. Here we report a detailed pre- and post-translational regulation of the three Prdx isoforms. Data on intestinal mRNA expression, provided by qRT-PCR analyses, show a generalized increase for Prdx2, 3, and 4, which is correlated to metal accumulation. Furthermore, the increase in tissue enzyme activity observed after Zn exposure is slower than that observed with Cu and Cd. The obtained results increase our knowledge of the evolution of anti-stress proteins in invertebrates and emphasize the importance of the synthesis of Prdxs as an efficient way to face adverse environmental conditions.

A new species of Microcosmus (Tunicata: Ascidiacea: Bolteniidae) from the Sea of Okhotsk

A large solitary ascidian Microcosmus armatus sp. nov., described from the Sea of Okhotsk, represents the first record of the genus Microcosmus Heller, 1877 in the cold waters of the Northwestern Pacific. The genus belongs to the family Bolteniidae formerly known as Pyuridae.

Occurrence and Habitat Characteristics of Aurelia sp. Polyps in a High-Latitude Fjord

Causes and consequences of jellyfish bloom formation are subject to controversial discussions worldwide. While medusae have been studied to a broader extent, the knowledge on polyp stages of scyphozoans is limited thus hampering reliable prediction of jellyfish bloom formation. This study describes the occurrence, abundance, habitat characteristics and interactions of scyphozoan Aurelia sp. polyp colonies with other fouling organisms in intertidal and subtidal sectors of Trondheimsfjorden (Norway). In total, 982 polyps were found on 70 substrata of varying material types during a field survey in spring-summer 2018 along a longitudinal gradient within and outside Trondheimsfjorden. The polyps were identified as Aurelia sp. based on molecular species identification. Most polyps were found in bays with macroalgae canopy on the down facing side of artificial and natural substrata (rocks, concrete, iron) and inside rock cracks. Polyp microhabitats included the surface of Ascidia mentula (solitary ascidian), increments of Pomatoceros triqueter (polychete) tubes and dead Balanus balanoides (barnacle) shells. Based on the deployment of settling plates, abundance of Aurelia sp. polyps ranged from 1.2 (± 0.7) to 0.12 (± 0.07) polyps cm–2. Settlement occurred either directly on the PVC settling plates or as epibionts on the ascidian Ascidia mentula and on barnacle shells of Balanus balanoides. This study provides insights into the potential of local Aurelia sp. polyps contributing to the seasonal occurrence and abundance of Aurelia sp. in fjord systems, where intensive blooms occur annually.

And Then There Were Three…: Extreme Regeneration Ability of the Solitary Chordate Polycarpa mytiligera

Extensive regenerative ability is a common trait of animals capable of asexual development. The current study reveals the extraordinary regeneration abilities of the solitary ascidian Polycarpa mytiligera. Dissection of a single individual into separate fragments along two body axes resulted in the complete regeneration of each fragment into an independent, functional individual. The ability of a solitary ascidian, incapable of asexual development, to achieve bidirectional regeneration and fully regenerate all body structures and organs is described here for the first time. Amputation initiated cell proliferation in proximity to the amputation line. Phylogenetic analysis demonstrated the close affinity of P. mytiligera to colonial species. This evolutionary proximity suggests the ability for regeneration as an exaptation feature for colonial lifestyle. P. mytiligera’s exceptional regenerative abilities and phylogenetic position highlight its potential to serve as a new comparative system for studies seeking to uncover the evolution of regeneration and coloniality among the chordates.