Eye-independent, light-activated chromatophore expansion (LACE) and expression of phototransduction genes in the skin of Octopus bimaculoides.

Cephalopods are renowned for changing the color and pattern of their skin for both camouflage and communication. Yet, we do not fully understand how cephalopods control the pigmented chromatophore organs in their skin and change their body pattern. Although these changes primarily rely on eyesight, we found that light causes chromatophores to expand in excised pieces of Octopus bimaculoides skin. We call this behavior light-activated chromatophore expansion (or LACE). To uncover how octopus skin senses light, we used antibodies against r-opsin phototransduction proteins to identify sensory neurons that express r-opsin in the skin. We hypothesized that octopus LACE relies on the same r-opsin phototransduction cascade found in octopus eyes. By creating an action spectrum for the latency to LACE, we found that LACE occurred most quickly in response to blue light. We fit our action spectrum data to a standard opsin curve template and estimated the λmax of LACE to be 480 nm. Consistent with our hypothesis, the maximum sensitivity of the light sensors underlying LACE closely matches the known spectral sensitivity of opsin from octopus eyes. LACE in isolated preparations suggests that octopus skin is intrinsically light sensitive and that this dispersed light sense might contribute to their unique and novel patterning abilities. Finally, our data suggest that a common molecular mechanism for light detection in eyes may have been co-opted for light sensing in octopus skin and then used for LACE.

Analysis of the 3' untranslated regions of alpha-tubulin and S-crystallin mRNA and the identification of CPEB in dark- and light-adapted octopus retinas.

PURPOSE: We previously reported the differential expression and translation of mRNA and protein in dark- and light-adapted octopus retinas, which may result from cytoplasmic polyadenylation element (CPE)-dependent mRNA masking and unmasking. Here we investigate the presence of CPEs in alpha-tubulin and S-crystallin mRNA and report the identification of cytoplasmic polyadenylation element binding protein (CPEB) in light- and dark-adapted octopus retinas. METHODS: 3'-RACE and sequencing were used to isolate and analyze the 3'-UTRs of alpha-tubulin and S-crystallin mRNA. Total retinal protein isolated from light- and dark-adapted octopus retinas was subjected to western blot analysis followed by CPEB antibody detection, PEP-171 inhibition of CPEB, and dephosphorylation of CPEB. RESULTS: The following CPE-like sequence was detected in the 3'-UTR of isolated long S-crystallin mRNA variants: UUUAACA. No CPE or CPE-like sequences were detected in the 3'-UTRs of alpha-tubulin mRNA or of the short S-crystallin mRNA variants. Western blot analysis detected CPEB as two putative bands migrating between 60-80 kDa, while a third band migrated below 30 kDa in dark- and light-adapted retinas. CONCLUSIONS: The detection of CPEB and the identification of the putative CPE-like sequences in the S-crystallin 3'-UTR suggest that CPEB may be involved in the activation of masked S-crystallin mRNA, but not in the regulation of alpha-tubulin mRNA, resulting in increased S-crystallin protein synthesis in dark-adapted octopus retinas.

Role of FMRFamide in the reproduction of Octopus vulgaris: molecular analysis and effect on visual input.

As a part of continuous research on the neurobiology of the cephalopods in general, and the neuroendocrine control of reproduction in Octopus vulgaris in particular, the presence, the molecular analysis and the effect of FMRFamide on the screening-pigment migration in the visual system have been analysed. FMRFamide immunoreactive fibres are present in the outer plexiform layer of the retina as well as in the plexiform zone of the deep retina. These fibres presumably come from optic and olfactory lobes. We isolated an incomplete Octopus FMRFamide cDNA which encodes an amino terminal truncated precursor containing several FMRFamide-related peptides (FaRPs) showing a high degree of identity with the FaRPs encoded in the precursor of Sepia officinalis, except for the presence of an Rpamide related peptide, present only in cnidarians. Finally, stimulation of isolated retina demonstrated that the effect of this tetrapeptide, coupled with dopamine, is the induction of an extreme adaptation of the retina to the light condition. This situation de facto inhibits sexual maturation. Our results on the effect of FMRFamide on the retina confirm the suggested hypothesis that this peptide plays an inhibitory role on the activity of optic gland.

Long-term decline of radiocesium concentration in seafood from the Ligurian sea (northern Italy) after Chernobyl.

The activity of 137Cs, 134Cs and 40K in tissues from fish, molluse and shellfish of the Ligurian sea was measured during 1987-1988. The mean annual concentrations in 1987 were 5.92 +/- 4.1 Bq/kg (wet tissue) for 137Cs and 2.7 +/- 1.5 Bq/kg for 134Cs and 2.46 +/- 1.82 and 0.33 +/- 0.57 Bq/kg respectively in 1988. The mean value of 40K activity was 138.6 +/- 22.1 Bq/kg. Contamination was significantly higher in the littoral area up to 1000 m from the coast (8.39 +/- 7.6 and 1.74 +/- 2.08 Bq/kg respectively versus 2.91 +/- 1.87 and 0.58 +/- 0.59 Bq/kg respectively in the open sea). The common octopus (Octopus vulgaris) had the highest radioactivity values and could be utilized as an indicator of radioactivity pollution. There were no significant differences regarding the trophic level, the seafood phylum, or the east and west Ligurian sea areas. Long-term reduction in the sea habitat was estimated at about 200 days for 137Cs and 110 days for 134Cs, reflecting differences in the physical half-life of these radionuclides. These values were lower than those found in terrestrial foodstuff and could have reflected dilution of the contaminants in the open sea. The effective dose equivalent for the Ligurian population of radiocesium originating from seafood was estimated at 1.3 microSv in 1987 and 0.5 microSv in 1988. These va ues represent 0.8 and 0.3% respectively of the annual dose (180 microSv/year) due to 40K intake with the diet.