Abstract To elucidate the effects of pathogenic infection on the muscle quality and tissue structure of the shrimp, we explored the changes in muscle tissue quality and structure of the ridgetail white prawn (Exopalaemon carinicauda) after infection with Vibrio parahaemolyticus, WSSV, and co-infection with V. parahaemolyticus and WSSV, all through intramuscular injection of pathogens. Our results reflected that muscle tissue of healthy shrimps was tightly arranged and had neat muscle fibres and uniform texture. While compared with the control group, the muscle hardness, adhesiveness, elasticity, and chewiness of the shrimp in both single and co-infected groups were significantly decreased (). In addition, microscopic observation indicated that in each infected group, the muscle fibre gaps in the muscle tissue of the shrimp increased, the muscle density decreased, and even some muscle fibres swelled and broke. The above results suggested that the infection of pathogens significantly affected the shrimp’s muscle quality and tissue structure, which may be related to the pathogenic mechanisms of these pathogens. In actual shrimp farming, we should improve the shrimp’s muscle quality through a series of measures, such as enhancing disease resistance.

Abstract Coastal lagoons of Southeastern Brazil are highly unstable environments mainly due to abrupt salinity changes. The species Quadrivisio lutzi is the unique amphipod inhabiting the water column of unstable coastal closed lagoons at the north of Rio de Janeiro State. This study determined temperature and salinity range of tolerance and identified osmoregulatory strategies for survival. Bioassays were performed with gradual and non-gradual increases of salinity within the range of 0-60 mg/l. The median lethal salinity concentration in 48 h was evaluated. Haemolymph and water osmolality at different salinities were determined. Temperature tolerance in 48 h was evaluated with gradual increments/decreases of temperature in the range of 3-39°C. Results showed two osmoregulatory strategies in the amphipod Q. lutzi: hyper-regulation in freshwater and brackish water (0.5-11 ppt); and passive isosmotic condition at higher salinity (>11-21 ppt). The LC50 for the species was 23.8 ppt with salinity range of tolerance of 0.5-21 ppt for 48 h. The amphipod tolerated in 48 h a temperature range of 8-32°C. Tolerance to temperature increased to 35°C when the amphipod is in passive isosmotic condition. The amphipod Q. lutzi is an euryhaline and eurythermic species. The range of environmental tolerance of the amphipod Q. lutzi allows it to overcome salinity changes determined by sea sand-bar opening; and to tolerate seasonal temperature variations characteristic of tropical regions. The euryhaline and eurythermal capacity of the species suggest that it may survive to climate changes.

Abstract A new species of amphipod, Maera epuwingkul sp. nov. (Maeridae), is described from San Matías Gulf in Río Negro, Argentina. The species was first found during surveys focused on the analysis of diversity associated with the introduced macroalga Undaria pinnatifida. After its dissection and morphological analysis, we concluded that this is a new species of the genus Maera. This species is characterized by gnathopod 1 propodus with an anterodistal robust seta, gnathopod 2 palm with two triangular humps, and telson with three simple dorsal setae on each lobe. We provide a detailed description of the species along with its illustrations.

Abstract Several approaches have been adopted to assess the evolutionary patterns and life history of different animal and plant species worldwide. Quantitative analysis application to assess genome size (GS) or nuclear DNA content, based on flow cytometry, is a new tool used to investigate evolutionary patterns in several animal species. However, it remains relatively poorly explored when it comes to invertebrates. The “c-value” enigma requires building an effective and robust DNA picogram database about as many species as possible, since conclusive hypotheses are only possible when accurate data are available in the literature. Therefore, the current study aims to provide new information about both the genome size and the biology of the sponge-dwelling shrimp species Typton distinctus Chace, 1972, which is a symbiotic/parasite to sea sponges and provides the accuracy of flow cytometry technique in registering DNA and cell cycle division. All GS estimates were based on analyses of more than 1k propidium iodide-stained nuclei per sample. The mean genome size (c-value) of the herein investigated species reached 10.79 ± 0.008 pg DNA. We were able to estimate the G2 phase information in cell division visually. This GS value is acknowledged as the mean value of all other Caribbean shrimp in tropical regions. The current study has suggested and addressed the hypothesis that caridean shrimp’s genome size can directly correlate to species’ latitudinal distribution and life history adaptation to each location. Thus, registering these new findings about this typical tropical Palaemonidae species is essential.

Abstract Gammarus odettae was first identified in 1990 by Mateus & Mateus, using specimens collected from the provinces of Ankara, Bursa and Balıkesir in Turkey. Since then, there have been no taxonomic studies on G. odettae, nor any records from other regions. In this study, specimens of G. odettae were collected from decaying plant debris in slow-flowing streams in the provinces of Ordu and Samsun in Turkey. The records in this study represent the second recorded sighting of this species. G. odettae specimens were detected in locations different from their type locality and provided a detailed morphological redescription along with drawings of the species.

Abstract The phylogenetic relationships among species of Brachyura, particularly within the subsection Heterotremata, have yet to be fully elucidated. We sequenced the complete mitochondrial genome of Paradorippe granulata to gain further insight into the internal composition and phylogeny of Heterotremata. The results revealed that the complete mitochondrial genome of P. granulata spans 15 084 bp, encoding 37 genes. These genes are composed of 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The nucleotide composition of the genome is as follows: A (36.90%), T (37.92%), C (16.27%) and G (8.91%), demonstrating a pronounced AT bias (74.82%). All tRNA genes, with the exception of trnF (lacking the acceptor arm), trnS1 (lacking the DHU arm), and trnP, trnY, and trnM (lacking the TψC loop), were predicted to form the typical cloverleaf secondary structure. Significant rearrangements were observed in the mitochondrial genome of P. granulata when compared to the ancestral mitochondrial gene arrangement within the Brachyura infraorder. Notably, the relative positions of nad1, nad2, nad3, nad6 and 14 tRNA genes (, K, D, G, A, R, N, S1, E, P, , I, W, Y) were found to differ from those reported in the currently recognized mitochondrial gene orders of Brachyura, indicating a novel gene arrangement. Bayesian Inference and Maximum Likelihood trees of Heterotremata, constructed based on the nucleotide sequences of the 13 PCGs, indicated that P. granulata and Heikeopsis japonica cluster together to form Dorippoidea. This clade was found to share the closest phylogenetic relationship with Leucosioidea. At the family level, most families were determined to be monophyletic, whereas Majidae and Xanthidae were not. With regard to superfamilies, Trapezioidea was identified as non-monophyletic and was divided into two distinct clades. Trapezioidea1 was recovered as the sister group to Pilumnoidea, whereas Trapezioidea2 was positioned more distantly from Trapezioidea1.

Abstract Antarctic krill (Euphausia superba Dana, 1850), a dominant psychrophilic species in the cold Antarctic and sub-Antarctic marine environments, relies on specialized enzymatic mechanisms for survival in low temperatures. Trypsin, a key enzyme in food digestion and zymogen activation, plays a crucial role in cold adaptation. However, the molecular mechanisms underlying this adaptation remain poorly understood. This study characterized trypsin genes from E. superba and warm-adapted crustaceans, revealing differences in structure and sequence. Activated trypsin from E. superba was expressed and purified using the E. coli BL21 (DE3) system. The enzyme exhibited optimal catalytic efficiency at 40°C, a lower temperature compared to trypsin from warm-adapted species like Penaeus vannamei. Multiple sequence alignments revealed conserved active and substrate-binding sites, alongside distinct residue proportions in E. superba trypsin relative to warm-adapted counterparts. Structural predictions showed a higher proportion of random coils and increased flexibility in the E. superba trypsin protein, supporting its cold-adaptive functionality. PAML analysis identified potential selection sites within the E. superba trypsin gene. Site-directed mutagenesis further suggested that strong selection pressure at these sites contributes to its adaptive evolution in cold environments. This research provides insights into the cold-adaptation mechanisms of E. superba trypsin, advancing our understanding of enzymatic functionality in extreme environments. These findings may also support the development of recombinant cold-adapted enzymes for biotechnological applications.

Abstract A recent survey of benthic biota at 80 m depth off Israel collected a specimen of Pisa armata (Latreille, 1803) bearing a single externa of Sacculina carcini Thompson, 1836, and a specimen of Pagurus cuanensis Bell, 1845 bearing four externae of Peltogasterella sulcata (Lilljeborg, 1859). The identification of the rhizocephalans was confirmed based on phylogenetic analyses using the mitochondrial genes cytochrome c oxidase subunit I (COI) and the large ribosomal RNA subunit (16S). These are the first records of S. carcini and P. sulcata in the Levantine Sea and the first published sequences of S. carcini and P. sulcata from the Mediterranean Sea.

Abstract Four new species of Lernaeopodidae, i.e., Clavellotis helicoleni sp. nov., Maxiclavella scombropi sp. nov., Parabrachiella coryphaenoidis sp. nov. and Praeclavella neobythitesi sp. nov., are described, in addition to redescriptions of Clavellotis sargi (Kurz, 1877), Parabrachiella hugu (Yamaguti, 1939), P. regia (Lewis, 1967), and Praeclavella scombropis (Yamaguti, 1939).

Abstract A total of 743 zoea I and II snow crab (Chionoecetes opilio (O. Fabricius 1788)) were collected in the northwest Atlantic, Canada, in 2012 and 2013. Nine larval appendages were measured for both zoeal stages (410 zoeae I and 333 zoeae II). Snow crab larval morphometric information in the current literature was examined from the Sea of Japan, the northern Pacific, the Northwestern Atlantic, the Barents Sea, and the Kara Sea. Larval size measurements from the present study, conducted at the southernmost sampling location, were compared with those of seven different geographic locations worldwide. Results suggested an increasing trend in the rostro-dorsal spine length with latitude.