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The <3% dissimilar Amplicon Sequence Variant (ASV) clusters of the 18S‐V4 barcode were used as species‐proxies for the evaluation of ASV composition and ASV diversity indices characterizing the hitherto poorly investigated meiofaunal communities of the south‐eastern part of the Levantine basin. Accompanied by abundance measurements, the relationships of these characteristics with sedimentary and bottom terrain parameters were interpreted. The construction of community composition profiles, namely ASVs' list and their estimated abundances, was done using our previously established procedure (Harbuzov et al., 2022, Marine Genomics 65, 100980), combining metabarcoding with sample reads normalization by the abundance of hard‐bodied meiofaunal taxa. The study province included the 54–1418 m depth range, across vertical sub‐bottom horizons ranging 0–17 cm. Oxygen, hydrogen sulfide and methane concentrations in the pore water, as well as sediment grain size spectra and sedimentary protein and carbohydrate levels, were measured, followed by an evaluation of their involvement in the shaping of the meiofaunal communities' characteristics. Community composition was generally site‐and‐horizon dependent and its abundance decreased with increasing bottom depth and across sub‐bottom horizons, typical to benthic habitats which are nourished by organic carbon from the euphotic zone. The relatively sharply inclined continental slope bottom located in the northern part of the Israeli coast was an exception. Its meiofaunal community characteristics were speculated to be affected by intensive sediment mixing and lateral transport of food from the shelf, in addition to the effect of the euphotic zone‐originated food sources. [ABSTRACT FROM AUTHOR]

The red swamp crayfish ( Procambarus clarkii , Girard 1852) is among the most economically important freshwater crustacean species, and it is also considered one of the most aggressive invasive species worldwide. Despite its commercial importance and being one of the most studied crayfish species, its genomic and transcriptomic layout has only been partially studied. Illumina RNA-sequencing was applied to characterize the eyestalk transcriptome and identify its most characterizing genes. A collection of 83,170,732 reads from eyestalks was obtained using Illumina paired-end sequencing technology. A de novo assembly was performed with the Trinity assembly software generating 119,255 contigs (average length of 1007 bp) and identifying the first sequenced transcriptome in this species. The eyestalk is a major site for the production of neurohormones and controls a variety of physiological functions such as osmotic regulation, molting, epidermal color patterns and reproduction. Hence, its transcriptomic characterization is interesting and potentially instrumental to the elucidation of genes which have not been comprehensively described yet. Moreover, the availability of such a large amount of information supported the characterization of molecular families which have never been described before. The P. clarkii eyestalk transcriptome reported here provides a resource for improving the knowledge of the still incompletely defined neuroendocrinology of this species and represents an important source of data for all the interested carcinologists. [ABSTRACT FROM AUTHOR]

Conversion of one or more amino acids in eukaryotic peptides to the D-enantiomer configuration is catalyzed by specific L/D-peptide isomerases and it is a poorly investigated post-translational modification. No common modified amino acid or specific modified position has been recognized, and mechanisms underlying changes in the peptide function provided by this conversion are not widely studied. The 72 amino acid crustacean hyperglycemic hormone (CHH) in Astacidea crustaceans exhibits a co-existence of two peptide enantiomers with either D- or L-phenylalanine as their third residue. It is a pleiotropic hormone regulating several physiological processes in different target tissues and along different time scales. CHH enantiomers differently affect time courses and intensities of examined processes. The short-term effects of the two isomers on gene expression were examined in the hepatopancreas, gills, hemocytes and muscles of the astacid Pontastacus leptodactylus. Gene expression in muscles and hemocytes was not affected by either of the isomers. Two modes of action for CHH were elucidated in the hepatopancreas and the gills: specific gene induction in both organs by D-CHH, and targeted attenuation caused by both enantiomers in the gills. Consequently, a two-receptor system is proposed for conveying the effect of the two CHH isomers. [ABSTRACT FROM AUTHOR]

The rigid crustacean exoskeleton, the cuticle, Is composed of the polysaccharide chitin, structural proteins and mineral deposits. It is periodically replaced to enable growth and its construction is an energy-demanding process. Ecdysis, the shedding event of the old cuticle, is preceded by a preparatory phase, termed premolt, in which the present cuticle Is partially degraded and a new one is formed underneath it. Procambarus clarkii (Girard 1852), an astacid crustacean, was used here to comprehensively examine the changing patterns of gene expression In the hypodermis underlying the cuticle of the carapace at seven time points along - 1 4 premolt days. Next generation sequencing was used to construct a multitissue P. clarkii transcript sequence assembly for general use in a variety of transcriptomic studies. A reference transcriptome was created here in order to perform digital transcript expression analysis, determining the gene expression profiles in each of the examined premolt stages. The analysisrevealed a cascade of sequential expression events of molt-related genes involved in chitin degradation, synthesis and modification, as well as synthesis of collagen and four groups of cuticular structural genes. The new description of major transcriptional events during premolt and the determination of their timing provide temporal markers for future studies of molt progress and regulation. The peaks of the expression of the molt-related genes were preceded by expression peaks of cytoskeletal genes that are hypothesized to be essential for premolt progress through regulating protein synthesis and/or transport, probably by remodeling the cytoskeletal structure. [ABSTRACT FROM AUTHOR]

The major component of the animal egg yolk is the lipoglycoprotein vitellin, derived from its precursor vitellogenin (VTG), which is produced species-specifically in decapod crustaceans in the hepatopancreas and/or in the ovary of reproductive females. Previous studies on Procambarus clarkii vitellogenesis report the existence of two single VTGs. Here, from a multiple tissue transcriptome including ovaries and hepatopancreas of P. clarkii, we characterized four different VTG and two VTG-like transcriptomes encoding for the discoidal lipoprotein-high density lipoprotein/β-glucan binding protein (dLp/HDL-BGBP). The relative expression of the various genes was evaluated by quantitative Real-Time PCR in both the ovary and hepatopancreas of females at different reproductive stages (from immature until fully mature oocytes). These studies revealed tissue-specificity and a reproductive stage related expression for the VTGs and a constitutive expression in the hepatopancreas of dLp/HDL-BGBP independent from the reproductive stage. This study may lead to more detailed study of the vitellogenins, their transcription regulation, and to the determination of broader patterns of expression present in the female hepatopancreas and ovary during the vitellogenesis. These findings provide a starting point useful for two different practical aims. The first is related to studies on P. clarkii reproduction, since this species is highly appreciated on the market worldwide. The second is related to the study of new potential interference in P. clarkii reproduction to delay or inhibit the worldwide spread of this aggressively invasive species. [ABSTRACT FROM AUTHOR]

The present study sought to quantitatively characterize the live and dead benthic foraminifera communities of the deep southeastern Levantine basin of the Mediterranean Sea (33.4º–31.7 ºN, 31.3º–34.9 ºE; 100–1900 m water depth) and their relationships to environmental conditions. Box corer samples were collected at 50 sites between June and July 2013. The foraminiferal macrofauna (> 250 µm) were enumerated and identified (76% to the species level). Six live foraminiferal assemblages were identified, inhabiting six biotopes, the shelf margin (SM), two upper continental slopes (UCS1 and UCS2), the lower continental slope (LCS), the eastern bathyal plain (EBP) and the western bathyal plain (WBP). The dead communities were divided into four biotopes, generally compatible with the live ones, excluding the UCS2 and the EBP. The foraminiferal density in the various live biotopes was relatively stable across the studied area, excluding the UCS2 and EBP, unlike the density of the dead shells, which increased with depth. The number of taxa per biotope was estimated by rarefaction curves and compared to the observed numbers, with a decreasing number of live taxa with water depth. The alpha-diversity, which was evaluated in relation to the number of sampled individuals, reached an asymptote in all biotopes, with very low values in the WBP. The within-biotope heterogeneity was evaluated by the average Chao-Sørensen similarity index and by a beta-diversity index (exp(gamma diversity) - exp(alpha diversity)), revealing variable heterogeneities in both assemblages. Water depth, sediment grain size mode, CaCO 3 (wt%), and clay fraction (wt%) were jointly but feebly correlated with live faunal composition. [ABSTRACT FROM AUTHOR]

The present study sought to quantify the infauna and environmental characteristics of the deep SE Levantine Basin, Mediterranean Sea (33.4-31.7 N, 31.3-34.9E; 100-1900 m water depth). Box corer samples were collected at 50 sites in June-July 2013. The infauna (>250 μm) were enumerated and identified to the lowest possible taxonomic level (~37 % to the species level). Three faunal assemblages were identified, inhabiting three biotopes, the shelf margin (SM), the continental slope (CS) and the bathyal plain (BP). The within-biotope heterogeneity was evaluated by the average Chao-Sørensen similarity index and the beta diversity (exp(gamma diversity)-exp(alpha diversity)), revealing values of 0.64-0.7 and 1.73-2.77, respectively, upon applying the pooled bathyal plain samples. The corresponding non-pooled samples revealed higher heterogeneity, with values of 0.26 and 6.27, respectively, likely due to insufficient sampling. The infaunal density in the various biotopes (geometric mean 59-2220 ind m) exhibited a logarithmic decline with water depth. The estimated number of taxa per biotope was calculated by rarefaction analysis in relation to the sampled area and the number of sampled individuals, resulting in 203 (sampled area)−206 (number of individuals) (SM), 170-163 (CS) and 144-130 (BP) taxa. The rarified alpha diversity in relation to the sampled area revealed decreasing values toward the deeper biotopes. However, similar rarified alpha diversities were found in all the biotopes in relation to the number of sampled individuals. Water depth, sediment grain size mode, CaCO%, and clay% were jointly correlated with faunal composition; water depth provided the single strongest correlate. [ABSTRACT FROM AUTHOR]

Some crustaceans possess exoskeletons that are reinforced with calcium carbonate. In the crayfish Cherax quadricarinatus, the molar tooth, which is part of the mandibular exoskeleton, contains an unusual crystalline enamel-like apatite layer. As this layer resembles vertebrate enamel in composition and function, it offers an interesting example of convergent evolution. Unlike other parts of the crayfish exoskeleton, which is periodically shed and regenerated during the molt cycle, molar mineral deposition takes place during the pre-molt stage. The molar mineral composition transforms continuously from fluorapatite through amorphous calcium phosphate to amorphous calcium carbonate and is mounted on chitin. The process of crayfish molar formation is entirely extracellular and presumably controlled by proteins, lipids, polysaccharides, low-molecular weight molecules and calcium salts. We have identified a novel molar protein termed Cq-M15 from C. quadricarinatus and cloned its transcript from the molar-forming epithelium. Its transcript and differential expression were confirmed by a next-generation sequencing library. The predicted acidic pI of Cq-M15 suggests its possible involvement in mineral arrangement. Cq-M15 is expressed in several exoskeletal tissues at pre-molt and its silencing is lethal. Like other arthropod cuticular proteins, Cq-M15 possesses a chitin-binding Rebers- Riddiford domain, with a recombinant version of the protein found to bind chitin. Cq-M15 was alsofound to interact with calcium ions in a concentration-dependent manner. This latter property might make Cq-M15 useful for bone and dental regenerative efforts. We suggest that, in the molar tooth, this protein might be involved in calcium phosphate and/or carbonate precipitation. [ABSTRACT FROM AUTHOR]