Identification and characterisation of hemocyanin of the fish louse Argulus (Crustacea: Branchiura).

Hemocyanin transports oxygen in the hemolymph of many arthropod species. Within the crustaceans, this copper-containing protein was thought to be restricted to Malacostraca, while other crustacean classes were assumed to employ hemoglobin or lack any respiratory protein. Only recently it has become evident that hemocyanins also occur in Remipedia and Ostracoda. Here we report for the first time the identification and characterisation of hemocyanin in the fish louse Argulus, which belongs to the class of Branchiura. This finding indicates that hemocyanin was the principal oxygen carrier in the stem lineage of the pancrustaceans, but has been lost independently multiple times in crustacean taxa. We obtained the full-length cDNA sequences of two hemocyanin subunits of Argulus foliaceus by a combination of RT-PCR, RACE and Illumina sequencing of the transcriptome. In addition, one full-length and one partial cDNA sequence were derived from the transcriptome data of Argulus siamensis. Western blot analysis confirmed the presence of at least two hemocyanin subunits in A. foliaceus, which are expressed at the mRNA level at a 1:3.5 ratio. The addition to the branchiuran hemocyanin subunits to a multiple sequence alignment of arthropod, hemocyanins improved the phylogenetic resolution within the pancrustacean hemocyanins. Malacostracan, ostracod and branchiuran hemocyanins are distinct from the hexapod and remipede hemocyanins, reinforcing the hypothesis of a close relationship of Remipedia and Hexapoda. Notably, the ostracod hemocyanins are paraphyletic with respect to the branchiuran hemocyanins, indicating ancient divergence and differential loss of distinct subunit types.

Peptide discovery in the ectoparasitic crustacean Argulus siamensis: identification of the first neuropeptides from a member of the Branchiura.

Recent advances in high-throughput sequencing have facilitated the generation of large transcriptomic datasets for an ever-growing number of crustaceans, one being the carp louse Argulus siamensis. This and other members of the subclass Branchiura are obligate fish ectoparasites, and as such, are a major concern for commercial aquaculture. Using the extant transcriptome shotgun assembly (TSA) sequences for A. siamensis, 27 transcripts encoding putative neuropeptide precursors were identified, and their pre/preprohormones deduced and characterized using a well-established bioinformatics workflow. The structures of 105 distinct peptides were predicted from the deduced proteins, including isoforms of adipokinetic hormone (AKH), allatostatin A, allatostatin B, allatostatin C, allatotropin, bursicon α, bursicon ß, crustacean cardioactive peptide (CCAP), diuretic hormone 31, diuretic hormone 44, eclosion hormone, myosuppressin, neuroparsin, neuropeptide Y, orcokinin, pigment dispersing hormone, proctolin, short neuropeptide F, SIFamide, sulfakinin and tachykinin-related peptide. While several of the predicted peptides are known from other crustacean and/or insect species, e.g. RYLPT, a broadly conserved arthropod proctolin isoform, and PFCNAFTGCamide (disulfide bridging between the two cysteines), the stereotypical crustacean CCAP, the vast majority of them are described here for the first time, e.g. pQVNFSTKWamide, a new AKH/red pigment concentrating hormone superfamily member, pQEGLDHMFMRFamide, a novel myosuppressin, and SYKSKPPFNGSIFamide, a new member of the SIFamide family. As the peptides presented here are the only ones thus far described from A. siamensis, or for that matter, any branchiuran, they represent a new resource to begin investigations of peptidergic control of physiology and behavior in this and other related aquacultural pests.

Ecotoxicological effects of jute retting on the survival of two freshwater fish and two invertebrates.

Severe deterioration of water quality occurs during jute retting in ponds, canals, floodplain lakes, and other inland water bodies in the rural areas of West Bengal in India. Attempts were made to evaluate changes in the physicochemical parameters of water caused by jute retting, and their impact on the survival of two species of freshwater fish (Labeo rohita and Hypophthalmicthys molitrix) and two species of freshwater invertebrate (Daphnia magna, a Cladocera, and Branchiura sowerbyi, an Oligochaeta). Results showed that jute retting in a pond for 30 days resulted in a sharp increase in the BOD (>1,000 times) and COD (>25 times) of the water, along with a sharp decrease in dissolved oxygen (DO). Free CO(2), total ammonia, and nitrate nitrogen also increased (three to five times) in water as a result of jute retting. Ninety-six-hour static bioassays performed in the laboratory with different dilutions of jute-retting water (JRW) revealed that D. magna and B. sowerbyi were not susceptible to even the raw JRW whereas fingerlings of both species of fish were highly susceptible, L. rohita being more sensitive (96 h LC(50) 37.55% JRW) than H. molitrix (96 h LC(50) 57.54% JRW). Mortality of fish was significantly correlated with the percentage of JRW.