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7 recordsLinked to original sources
PubMed1978

The eyes of mesopelagic crustaceans. II. Streetsia challengeri (amphipoda).

In Streetsia challengeri left and right eyes have fused and become a single cylindrical photoreceptor, which occupies the basal half of a forward directed head projection. This unusual compound eye consists of approximately 2500 ommatidia, which are arranged in such a way that the animal has almost circumferential vision, but cannot look ahead or behind. It is thought that the eye operates on light-guide principles, and that the crystalline cones are the major dioptric component. Ommatidia in anterior-posterior rows show a greater overlap of visual fields than dorso-ventrally arranged ommatidia. Cone layer and retinula are separated by a 4 micrometer thick screen-membrane, which contains tiny pigment granules of 0.15 micrometer diameter. Cells of unknown function and origin, containing unusual multitubular organelles, are regularly found near the proximal ends of the crystalline cone threads. The twisted rhabdoms measure 18--20 micrometer in diameter, and consist of microvilli 0.05 micrometer in width, which belong to five retinula cells and which show no trace of disintegration. The position of interommatidial screening pigment, the density of retinula cell vesicles and inclusions, and the narrowness of the perirhabdomal space all suggest that the eyes have been light-adapted at the time of fixation for electron microscopy. The retinula cell nuclei lie on the proximal side of the heavily pigmented basement membrane. A tapetum or basal retinula cells are not developed. It is concluded that the eye optimally combines acuity with sensitivity, and that for distance estimation parallax may be important.

Animals↗
PubMed1976

Some histochemical reactions on the neurosecretory cells of Rivulogammarus syriacus chevreux (Crustacea, Amphipoda).

The histochemistry of neurosecretory material in neurosecretory cells of Rivulo-gammarus syriacus has been investigated. Histochemically, these cells contain different neurosecretory substances. The material in A and C cells consists of mucopolysaccharides and lipids, that in B, B' and D cells there are a protein containing cystine S-S group, mucopolysaccharides and lipids, and that in E cell contains a weak protein with cystine S-S group, a substance showing beta metachromasia and lipids. The lipids are found in all the cells.

Crustacea↗
PubMed1977

[Determination of the molecular weight of vitellogenin and of lipovitellins of Orchestia gammarella, Crustacea, Amphipoda].

Vitellogenin and lipovitellins of Orchestia gammarella, tested by electrophoresis on gels of different acrylamide concentrations, following the procedure of Hedrick and Smith (1968), displays a migration pattern identical to that of proteins of respectively congruent to 4 x 10(5) (vitellogenin), congruent to 3,5 x 10(5) (lipovitellins I and I') and congruent to 5 x 10(5) (lipovitellin II) molecular weights.

Animals↗
PubMed2026

Fine-Scale Population Genomics Reveals Genetic Differentiation in the Brooding Amphipod Cheirimedon femoratus Across the South Shetland Islands, Antarctica.

Antarctic marine ecosystems are sensitive to environmental change, and impacts on processes such as population connectivity will play a fundamental role in future population dynamics and persistence, affecting short-term demography and long-term evolution. We investigated the population genomics of the common benthic brooding Antarctic amphipod Cheirimedon femoratus (Pfeffer, 1888), using 8837 high-quality single-nucleotide polymorphisms (SNPs) from 87 individuals collected at 4 sites in the South Shetland Islands, separated by up to 200 km: Deception Island, King George Island, Livingston Island, and Snow Island. While Admixture, F ST, principal component analysis (PCA), and demographic (Ne) analyses revealed a generally weak population genetic structure, Livingston Island emerged as a distinct population, especially compared to King George Island. All populations showed a heterozygote deficit with positive inbreeding coefficients (F IS), particularly high in the Snow Island population (~0.55). Tajima's D test suggested overall neutral evolution, although slight variation was observed among sites. Despite the limited dispersal potential of this brooding species, the observed connectivity may be maintained through passive dispersal, likely via floating macroalgae or ice-rafted debris, facilitated by prevailing regional ocean currents. This may enhance the population resilience of Antarctic benthic communities under environmental change, including regional warming and shifts in ocean circulation, compared to more isolated populations. Our findings underscore the complex interplay between passive connectivity and fine-scale differentiation in shaping Antarctic benthic invertebrate diversity.

Amphipoda↗
PubMed2026

Psychrobacter sp. XL111, a novel bacterial species from hadal amphipods: genomic insights into environmental adaptation and biotechnological potential.

The hadal zone presents one of the most extreme environments on Earth. While amphipods dominate this realm, the adaptive mechanisms of their resident gut microbiota are not fully understood, which is essential both for understanding the limits of life and for unlocking novel microbial resources. This study investigates Psychrobacter sp. XL111, a novel bacterial species isolated from the gut of hadal amphipods, to elucidate its survival strategies and biotechnological potential. Pan-genome analysis confirms the high genomic plasticity of this genus and highlights the genomic innovations in genes related to environmental adaptation. Genomic analysis revealed specialized adaptations to the deep-sea niche, including expansions in signal transduction systems, pathways for degrading complex organics and the capacity to synthesize stress-resistant compounds. A notable loss of oligosaccharide transporters alongside an enrichment of glycosyltransferases suggests a distinctive evolutionary reconfiguration of carbohydrate metabolism. Functional characterization confirmed that the strain produces an exopolysaccharide with potent radical-scavenging activity, underscoring a key mechanism for mitigating oxidative stress. Our results position hadal micro-organisms as a valuable source of novel enzymes and bioactive molecules for industrial and biomedical applications.

Animals↗