The morphology of sperm and early embryo development of shellfish can provide guidance for classification and biological reproduction. In this study, scanning electron microscopy and light microscopy were used to determine the shape of the sperm, characterize the embryonic development, and measured the size of the mature eggs and the D-shape larvae of four different clam species (Paphia schnelliana, Lutraria sieboldii, Antigona lamellaris, and Paphia textzle). The results showed that these four clam species differ in sperm morphology and the size of the mature eggs and the Dshape larvae (P<0.01). There were also differences in embryonic development time and morphology. This analysis of spermatozoa morphology, egg size, D-shaped larvae size, and embryo development in these four different clam species provides the basis for classification and future breeding efforts.

Pulsed aerial exposure (PAE) is a major stressor for submerged macrophytes in tidal river networks, yet species-specific physiological mechanisms remain unclear. We conducted a 7-day PAE mesocosm experiment using Hydrilla verticillata (L.f.) Royle and Vallisneria denseserrulata (Makino) Makino to compare their photosynthetic performance, pigment retention, and oxidative defense. Hydrilla maintained lower baseline Y(II) and reliable EC₅₀s (64.6–85.7 min/d). In contrast, Vallisneria showed higher baseline Y(II) but a transient Y(NPQ) increase peaking at 120 min/d that subsequently collapsed, greater pigment loss (total chlorophyll −68% vs. −44%), and highly uncertain or out-of-range EC₅₀s. Although antioxidant enzyme activities were higher in Vallisneria, MDA accumulation was comparable between species. Principal component analysis (87.14% total variance) revealed that PC1 (42.03%) separated pigments from antioxidant enzymes, and PC2 (26.46%) captured photochemical efficiency. PC3 (18.65%) further indicated a transient oxidative burst and subsequent defense breakdown in Vallisneria under severe stress. These results suggest that Hydrilla exhibits a low light-capture strategy to mitigate PAE pressure, while Vallisneria exhibits an inducible defense that becomes overwhelmed. The quantitative parameters provide baseline data for macrophyte growth models, though field validation is required to confirm long-term ecological implications.

The PfPGRP gene from the pearl oyster Pinctada fucata was cloned and expressed in different tissues with and without stimulation by Vibrio alginolyticus, LPS, and Poly (I:C) to investigate its role in the immune response. The cDNA sequence of PfPGRP was 789 bp long, containing an open reading frame of 591 bp that encoded 196 amino acids. Phylogenetic analysis showed that the genetic distance between vertebrate and invertebrate PGRPs was significant, and the homology of PGRP gene sequences in mollusks was around 50%. The PfPGRP gene had the highest homology with the PGRP gene from Crassostrea gigas, at 72.9%. Protein domain prediction identified a conserved canonical PGRP domain and an Ami_2 domain in PfPGRP, suggesting that it could hydrolyze invading bacteria and terminate the immune response. Quantitative PCR showed that PfPGRP was expressed constitutively in all tissues, with the highest levels in the mantle, followed by the gonad and hepatopancreas. The expression of PfPGRP in the mantle was significantly upregulated after LPS injection, indicating that this tissue is more sensitive to LPS and plays a crucial role in defending against bacterial invasions. Similarly, the expression of PfPGRP in the hepatopancreas was significantly upregulated after both Vibrio and LPS injections, but reached its maximum later in the Poly (I:C) group, suggesting that it is more sensitive to bacteria and may be involved in bacterial elimination.Overall, these results suggest that PfPGRP plays an essential role in the innate immune system of P. fucata and is involved in defense against bacterial and viral invasions.