Sifting through the mud: A tale of building the annelid Capitella teleta for EvoDevo studies

Current research status on the distribution and transport of micro(nano)plastics in hyporheic zones and groundwater

Micro(nano)plastics, as an emerging environmental pollutant, are gradually discovered in hyporheic zones and groundwater worldwide. Recent studies have focused on the origin and spatial/temporal distribution of micro(nano)plastics in regional groundwater, together with the influence of their properties and effects of environmental factors on their transport. However, the transport of micro(nano)plastics in the whole hyporheic zone-groundwater system and the behavior of co-existing substances still lack a complete theoretical interpretation. To provide systematic theoretical support for that, this review summarizes the current pollution status of micro(nano)plastics in the hyporheic zone-groundwater system, provides a comprehensive introduction of their sources and fate, and classifies the transport mechanisms into mechanical transport, physicochemical transport and biological processes assisted transport from the perspectives of mechanical stress, physicochemical reactions, and bioturbation, respectively. Ultimately, this review proposes to advance the understanding of the multi-dimensional hydrosphere transport of micro(nano)plastics centered on groundwater, the microorganisms-mediated synergistic transformation and co-transport involving the intertidal circulation. Overall, this review systematically dissects the presence and transport cycles of micro(nano)plastics within the hyporheic zone-groundwater system and proposes prospects for future studies based on the limitations of current studies.

Discovery and characterization of a transient chaetal gland during the development of Capitella teleta (Sedentaria: Annelida)

Chaetae are among the most extensively studied structures in polychaetes, serving as a defining morphological trait for annelids. Capitella teleta stands out as one of the few established annelid models for developmental and morphological studies, thus receiving significant scholarly attention. In this study, we unveil a previously unnoticed glandular structure associated with chaetae within the larvae of C. teleta. Our investigations demonstrate the absence of comparable structures in the chaetal follicles of adults and juveniles (older than 1 week), as well as during active chaetogenesis, underscoring the transient nature of these glands. This indicates that larval chaetal follicles transform into a gland that later disappears. Utilizing histology and transmission electron microscopy, we characterized these glands. Our findings underscore the diversity of chaetal ultrastructure in annelids and show that, even in well-studied species, novel morphological details can be found. We emphasize the importance of examining various life-history stages to capture such transient morphological features. This work lays a crucial morphological foundation and deepens our understanding of chaetae and chaetogenesis in C. teleta, paving the way for more accurate interpretations of future experimental studies on chaetogenesis in this species.

Journey beyond the embryo: The beauty of Pristina and naidine annelids for studying regeneration and agametic reproduction

Regeneration, asexual agametic reproduction, and other forms of postembryonic development are ecologically important and widely variable across animals, yet our understanding of this important aspect of animal diversity remains limited. A significant limitation has been the dearth of adequate study systems for exploring the mechanisms and evolution of these processes. Here I describe key parts of our journey in developing naid annelids as a study system for investigating the evolution and development of regeneration and fission. Naids are small freshwater annelids that provide numerous advantages for studying postembryonic development: they are small and reproduce readily by fission, they include species with diverse regenerative abilities, and many species are easy to culture. Among the naids, Pristina leidyi is a particularly useful study species, being largely transparent and quite robust to a variety of experimental manipulations. Building on a sparse but long history of past research on these animals, we have developed this system by establishing methods and generating resources for working with them. Naids are yielding novel insights into the evolution of regeneration and fission, providing one of many examples of the value of developing new study species to enable the exploration of fundamental and understudied questions in biology. Establishing new study systems comes with challenges but is exciting and rewarding, and I provide perspectives from my own experiences with the hope of encouraging the further expansion of study systems in biology.