Localization of corticotropin-releasing factor-immunoreactive nervous tissue and colocalization with neuropeptide Y-like substance in the optic lobe and peduncle complex of the octopus (<Emphasis Type="Italic">Octopus vulgaris</Emphasis>)

The distribution of corticotropin-releasing factor (CRF)-like immunoreactivity and its colocalization with neuropeptide Y (NPY)-like substances were investigated in the optic lobe and peduncle complex of the octopus (Octopus vulgaris) using immunohistochemical techniques. In the optic lobe cortex, CRF-immunoreactive (CRF-IR) and NPY-immunonegative varicose fibers were observed in the plexiform layer. In the medulla, CRF-IR somata were seen in the cell islands, and CRF-IR varicose fibers were observed in the neuropil. About half of the CRF-IR structures in the medulla showed NPY-like immunoreactivity. In the peduncle lobe, no CRF-IR somata but abundant CRF-IR varicose fibers were observed, and about half of them showed NPY-like immunoreactivity. In the olfactory lobe, CRF-IR somata and abundant CRF-IR varicose fibers were observed. Almost all the CRF-IR somata located in the posterior olfactory lobule showed NPY-like immunoreactivity, whereas those seen in the median olfactory lobule were immunonegative for NPY. About half of the CRF-IR fibers in the anterior lobule neuropil were immunopositive for NPY, but those in the median and posterior lobule neuropils were immunonegative for NPY. In the optic gland, almost all the CRF-IR varicose fibers were immunoreactive for NPY. Western blot analysis of the optic lobe and peduncle complex indicated that anti-CRF antiserum labeled approximate 16.4- and 14.6-kDa bands and that anti-NPY antiserum labeled an approximate 16.2-kDa band. CRF-IR and NPY-immunoreactive neurons in the optic lobe may participate in the modulation of visual information and those in the optic gland may be involved in the regulation of endocrine function.     

Vibrio lentus associated with diseased wild octopus (Octopus vulgaris)

Studies were undertaken to identify the bacteria involved in a disease of wild octopus (Octopus vulgaris). Signs of the disease include round hard lesions in the arms or head mantle, leading, in advanced cases, to the loss of skin and the exposure of the muscle beneath. Bacterial strains isolated from sterile organs have been evaluated taxonomically and by experimental infections. Different phenotypes and ribotypes of Vibrio lentus were identified. Experimental infection by bath challenge demonstrated that V. lentus was able to reproduce the skin lesions, colonize the internal organs and induce mortality in healthy octopuses. V. lentus was re-isolated from the skin lesions and gill heart of dead octopuses, as confirmed by numerical taxonomy analysis. No effects were produced in sea bream or turbot by intraperitoneal injection of the bacterial isolate.     

Receptor-mediated inhibition of octopamine-stimulated adenylate cyclase in the optic lobe of Octopus vulgaris

1. Inhibition of octopamine-stimulated adenylate cyclase was studied in the optic lobe of Octopus vulgaris.2. The octopamine antagonist, mianserin, and the dopamine D₂ agonists, PPHT and metergoline, induced dose-dependent inhibition of octopamine-stimulated adenylate cyclase activity.3. The binding of the tritiated benzazepine neuroleptic YM-09151-2 to octopus membranes and the displacement of [³H]YM-09151-2 by PPHT, metergoline and spiperone were consistent with the presence of a D₂-like dopamine receptor in the octopus optic lobe.4. The conclusion is drawn that octopamine-stimulated adenylate cyclase in the octopus is negatively regulated by a dopamine D₂-like receptor.     

Malabsorption syndrome observed in the common octopus Octopus vulgaris infected with Aggregata octopiana (Protista: Apicomplexa)

Octopus vulgaris infected with Aggregata octopiana were collected from an open-water culture system in the Ría of Aldán (NW Spain). Digestive tract infection values were determined with the use of a Neubauer chamber by counting the number of A. octopiana sporocysts. After determining enzyme activity values by the colorimetric Api-Zym system Biomerieux, one representative enzyme of glycosidases, peptid hydrolases and phosphoric hydrolases showing high activity was spectrophotometrically analysed. The enzymes were maltase and leucine-aminopeptidase (LAP) involved in the absorption process, and acid phosphatase, a lysosomic enzyme, respectively. Enzymatic activity of maltase and LAP decreased significantly, with increased sporocyst counts. However, acid phosphatase activity increased with severity of infection, indicating the presence of degradative enzymes from phagocytic cells in the infected area. A detrimental effect on gastrointestinal function may result from a decrease or malfunction of absorption enzymes. The results suggest a malabsorption syndrome resulting from parasitic infection.     

Environmental assessment of common octopus (Octopus vulgaris) from a small-scale fishery in Algarve (Portugal)

The International Journal of Life Cycle Assessment - Common octopus is the fishing species with highest economic revenue in Portugal, and its consumption per capita is very high. The majority of...     

Extraintestinal gamogony of Aggregata octopiana in the reared common octopus (Octopus vulgaris) (Cephalopoda: Octopodidae)

Aggregata octopiana (Apicomplexa, Aggregatidae) is the most prevalent coccidian in the wild common octopus (Octopus vulgaris), whose heteroxenous life cycle includes gamogony and sporogony undergoing in the octopus digestive tract. In the infected reared octopi, we observed an unusual extraintestinal distribution of the coccidian, with both gamogony and sporogony ongoing in dermal and gill tissue. Oocysts and macrogamonts were embedded in the dermal connective tissue of octopian arms, demarcated by a thin cyst wall or multilayered dark membrane. In gill connective and epithelial tissue all developmental stages were observed, eliciting hemocytic infiltration. Sometimes a complete substitution of the tissue by cysts and developmental stages occurred, resulting in necrosis of gill tissue.     

Developmental and physiological challenges of octopus (Octopus vulgaris) early life stages under ocean warming

The ability to understand and predict the effects of ocean warming (under realistic scenarios) on marine biota is of paramount importance, especially at the most vulnerable early life stages. Here we investigated the impact of predicted environmental warming (+3 °C) on the development, metabolism, heat shock response and antioxidant defense mechanisms of the early stages of the common octopus, Octopus vulgaris. As expected, warming shortened embryonic developmental time by 13 days, from 38 days at 18 °C to 25 days at 21 °C. Concomitantly, survival decreased significantly (~29.9 %). Size at hatching varied inversely with temperature, and the percentage of smaller premature paralarvae increased drastically, from 0 % at 18 °C to 17.8 % at 21 °C. The metabolic costs of the transition from an encapsulated embryo to a free planktonic form increased significantly with warming, and HSP70 concentrations and glutathione S-transferase activity levels were significantly magnified from late embryonic to paralarval stages. Yet, despite the presence of effective antioxidant defense mechanisms, ocean warming led to an augmentation of malondialdehyde levels (an indicative of enhanced ROS action), a process considered to be one of the most frequent cellular injury mechanisms. Thus, the present study provides clues about how the magnitude and rate of ocean warming will challenge the buffering capacities of octopus embryos and hatchlings’ physiology. The prediction and understanding of the biochemical and physiological responses to warmer temperatures (under realistic scenarios) is crucial for the management of highly commercial and ecologically important species, such as O. vulgaris.     

Development of the eye and optic lobe of Octopus

The development of the lens, retina and optic lobes was followed in Octopus australis and O. pallidus , two species that produce benthic larvae and can readily be reared in the laboratory from egg to adult.
The inner part of the lens starts to form at Naef's stage IX, and consists of a central core with overlying layers formed from processes of the lentigenic cells. Microvilli occur on the surface of the lens, and cilia and microvilli are visible in the retina, which at this point, however, is undifferentiated. The optic lobes have not started to form. The outer part of the lens starts to develop from stage XVI.
Cellular differentiation of the retina, through cell nuclei crossing the basement membrane, starts at stage XV, with rhabdome development occurring from stage XVI onwards. The optic lobes are clearly formed at stage XII, but only start to differentiate and show layering from stage XVI.
At hatching all adult structures are clearly visible, although considerable quantitative changes still occur before the final adult form is reached.
The development of the visual system of Octopus is similar to that of several species of decapod previously reported.     

Functional organization of visual responses in the octopus optic lobe

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Antigen-induced secretion in the optic gland of Octopus vulgaris.

The optic gland of the octupus responds to a variety of foreign proteins--1 to 2 days after the injection--by the mass production and release of a particulated material. In the electron microscope the antigen-induced substance shows as a non-membrane bound particle of size about 30 nm. When released into the blood it does not disintegrate instantly. The chemistry of this material, which is probably identical with the optic gland hormone, is not known. However, non-vesicular storage and release as well as the abundance of tubular mitochondria suggest that the hormone is a steroid. The optic gland hormone, which is known to control sexual maturation, feeding and death in Octopus, appears to be involved in a defence mechanism against non-octopus proteins.     

Presence of two neuropeptides in the fusiform ganglion and reproductive ducts of Octopus vulgaris: FMRFamide and gonadotropin-releasing hormone (GnRH)

We have found evidence of FMRFamide-like and cGnRH-I-like immunoreactivity in the central nervous system (CNS) and in the reproductive ducts of both female and male cephalopod Octopus vulgaris. Cell bodies and fibers were immunolocalized in the fusiform ganglion from which the nerves that reach the female and male reproductive ducts arise. FMRFamide-like and cGnRH-I-like immunoreactive nerve endings were present in the oviduct, and in the oviducal gland of the female and in the seminal vesicle of the male. The GnRH-like peptide from the reproductive ducts has been partially characterized by HPLC. The retention time of the Octopus vulgaris GnRH-like peptide was similar to the retention time of cGnRH-I. Based on these observations we suggest that FMRFamide-like and a novel GnRH-like peptide are involved in the control of reproductive ducts of Octopus vulgaris. One possibility is that the peptides affect gamete transport. Another possibility is that they regulate secretory products such as mucus and mucilaginous substances from the oviducal gland and the seminal vesicle. Our data provide further evidence to support the hypothesis of the existence of a central and peripheral peptidergic control of reproduction of Octopus vulgaris.     

Control of GnRH expression in the olfactory lobe of Octopus vulgaris

In the cephalopod mollusk Octopus vulgaris, the gonadotropic hormone released by the optic gland controls sexual maturity. Several lobes of the central nervous system control the activity of this gland. In one of these lobes, the olfactory lobe, a gonadotropin releasing hormone (GnRH) neuronal system has been described. We assume that several inputs converge on the olfactory lobes in order to activate GnRH neurons and that a glutamatergic system mediates the integration of stimuli on these neuropeptidergic neurons. The presence of N-methyl-d-aspartate (NMDA) receptor immunoreactivity in the neuropil of olfactory lobes and in the fibers of the optic gland nerve, along with the GnRH nerve endings strongly supports this hypothesis. A distinctive role in the control of GnRH secretion has also been attributed, in vertebrates, to nitric oxide (NO). The lobes and nerves involved in the nervous control of reproduction in Octopus contain nitric oxide synthase (NOS). Using a set of experiments aimed at manipulate a putative l-glutamate/NMDA/NO signal transduction pathway, we have demonstrated, by quantitative real-time PCR, that NMDA enhances the expression of GnRH mRNA in a dose-response manner. The reverting effect of a selective antagonist of NMDA receptors (NMDARs), 2-amino-5-phosphopentanoic acid (D-APV), confirms that such an enhancing action is a NMDA receptor-mediated response. Nitric oxide and calcium also play a positive role on GnRH mRNA expression. The results suggest that in Octopusl-glutamate could be a key molecule in the nervous control of sexual maturation.     

Relationship between photoreceptor terminations and centrifugal neurons in the optic lobe of octopus

Summary Retinal bundles, connecting the retina of the octopus to the ipsilateral optic lobe, contain both retinal photoreceptor axons that terminate in the optic lobe and centrifugal axons whose cell bodies lie within the lobe. Staining axonal elements in proximal stubs of individual retinal bundles by cobalt diffusion and subsequent sulphide treatment reveals the topographic relationship between afferent terminals and centrifugal cell bodies. At the outer border of the plexiform layer, stained terminal bags (photoreceptor axon enlargements), an indicator of photoreceptor terminal spread within this layer, overlap stained centrifugal cell bodies located within the inner granule layer. The details of this overlap indicate a dorsoventral representation of each retinal bundle within the optic lobe cortex.     

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.