No abstract

The ontogenetic development of IgM-containing cells is described as demonstrated by immunoperoxidase staining with a mouse anti-trout IgM monoclonal antibody and the differentiation of enzyme-histochemical markers in the non-lymphoid cells forming the stroma of the thymus, spleen and kidney of the rainbow trout. The first lymphoid cells staining with the monoclonal antibody occurred at day4-5 after hatching in the renal lympho-haemopoietic tissue. By I month after hatching IgM-positive cells also appeared in the spleen and thymus. Enzyme-histochemical demonstration of the alkaline and acid phosphatase and non-specific a-naphthyl acetate esterase enzymatic activities in the non-lymphoid cells indicated that a certain degree of maturation of the cellular stroma of the developing lymphoid organs of trout was reached before or at the time when IgM-expressing cells could be observed. The relationships of the stromal components of the various lymphoid organs to the development of IgM-positive cells, and the possible role of the renal lympho-haemopoietic tissue as a primary lymphoid organ for B-cell differentiation in the trout are discussed.

Dinophysis acuta and D. acuminata are associated with lipophilic toxins in Southern Chile. Blooms of the two species coincided during summer 2019 in a highly stratified fjord system (Puyuhuapi, Chilean Patagonia). High vertical resolution measurements of physical parameters were carried out during 48 h sampling to i) explore physiological status (e.g., division rates, toxin content) and ii) illustrate the fine scale distribution of D. acuta and D. acuminata populations with a focus on water column structure and cooccurring plastid-bearing ciliates. The species-specific resources and regulators defining the realized niches (sensu Hutchinson) of the two species were identified. Differences in vertical distribution, daily vertical migration and in situ division rates (with record values, 0.76 d−1, in D. acuta), in response to the environmental conditions and potential prey availability, revealed their niche differences. The Outlying Mean Index (OMI) analysis showed that the realized niche of D. acuta (cell maximum 7 × 103 cells L−1 within the pycnocline) was characterized by sub-surface estuarine waters (salinity 23 -25), lower values of turbulence and PAR, and a narrow niche breath. In contrast, the realized niche of D. acuminata (cell maximum 6.8 × 103 cells L−1 just above the pycnocline) was characterized by fresher (salinity 17 -20) outflowing surface waters, with higher turbulence and light intensity and a wider niche breadth. Results from OMI and PERMANOVA analyses of co-occurring microplanktonic ciliates were compatible with the hypothesis of species such as those from genera Pseudotontonia and Strombidium constituting an alternative ciliate prey to Mesodinium. The D. acuta cell maximum was associated with DSP (OA and Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.DTX-1) toxins and pectenotoxins; that of D. acuminata only with pectenotoxins. Results presented here contribute to a better understanding of the environmental drivers of species-specific blooms of Dinophysis and management of their distinct effects in Southern Chile. Previous article Highlights► 48 h of high frequency physical data for co-occurring blooms of 2 Dinophysis species. ► D. acuta (exceptional µ) thin layer briefly disrupted by an increase in turbulence. ► Co-occurring D. acuminata and D. acuta blooms showed a clear niche differentiation. ► Niche analysis results compatible with putative ciliate prey other than Mesodinium. ► D. acuta maximum associated with DSP toxins (OA, DTX1), D. acuminata with PTX2 only.

In late February 2016, a harmful algal bloom (HAB) of Alexandrium catenella was detected in southern Chiloé, leading to the banning of shellfish harvesting in an extended geographical area (~500 km). On April 24, 2016, this bloom produced a massive beaching (an accumulation on the beach surface of dead or impaired organisms which were drifted ashore) of surf clams Mesodesma donacium in Cucao Bay, Chiloé. To determine the effect of paralytic shellfish poisoning (PSP) toxins in M. donacium, samples were taken from Cucao during the third massive beaching detected on May 3, 2016. Whole tissue toxicity evidence a high interindividual variability with values which ranged from 1008 to 8763 μg STX eq 100 g−1 and with a toxin profile dominated by GTX3, GTX1, GTX2, GTX4, and neoSTX. Individuals were dissected into digestive gland (DG), foot (FT), adductor muscle (MU), and other body fractions (OBF), and histopathological and toxin analyses were carried out on the obtained fractions. Some pathological conditions were observed in gill and digestive gland of 40–50% of the individuals that correspond to hemocyte aggregation and haemocytic infiltration, respectively. The most toxic tissue was DG (2221 μg STX eq 100 g−1), followed by OBF (710 μg STX eq 100 g−1), FT (297 μg STX eq 100 g−1), and MU (314 μg STX eq 100 g−1). The observed surf clam mortality seems to have been mainly due to the desiccation caused by the incapability of the clams to burrow. Considering the available information of the monitoring program and taking into account that this episode was the first detected along the open coast of the Pacific Ocean in southern Chiloé, it is very likely that the M. donacium population from Cucao Bay has not had a recurrent exposition to A. catenella and, consequently, that it has not been subjected to high selective pressure for PSP resistance. However, more research is needed to determine the effects of PSP toxins on behavioral and physiological responses, nerve sensitivity, and genetic/molecular basis for the resistance or sensitivity of M. donacium.

No abstract

No abstract

No abstract

We present an enzyme-and immuno-cytochemical, and ultrastructural characterization of trout thymic nurse cells (TNCs). Our data suggest that isolated trout thymic multicellular complexes are epithelial cells with acidic compartments that may be involved in the processing of antigens and in the generation of the MHC-II proteins that these cell express, and also that isolated (Gerdes et al., 1983;Manconi et al., 1984;Wick and Oberhuber, 1986;Tsunoda and Kojima, 1987). The epithelial nature of TNCs was established by the presence of keratin bundles (Vakharia, 1983;de Waal Malefijt et al., 1986;Toussaint-Demylle et al., 1993), whereas thymocytes within TNCs are mainly immature double-positive CD4 CD8 cells (Ritter et al., 1981;Kyewski and Kaplan, 1982;Van Vliet et al., 1984;Kyewski et al., 1987), although some authors have reported more mature cells in the complexes *Corresponding author. (Vakharia, 1983;Hugo et al., 1988) and others also include double-negative CD4-CD8-cells (Singer et al., 1986;Kyewski, 1986;Wood et al., 1988).Although TNCs have repeatedly been claimed to play a decisive role in T-cell maturation, their true functional significance is a matter of discussion. They have been involved in the establishment of positive (Farr and Anderson, 1985;Kyewski, 1986;Owen et al., 1986;Ron et al., 1986) and negative selection (Wick and Oberhuber, 1986;Lorenz and Allen, 1989;Speiser et al., 1992), although their formation is not dependent on TCR-MHC interaction (Boyd et al., 1993;Aguilar et al., 1994 between the epithelial cells and thymocytes (Pulsford et al., 1991;lvarez, 1993), whereas thymocyte-macrophage complexes have been reported in both elasmobranches (Pulsford et al., 1984;Navarro, 1987) and teleosts (Finge and Pulsford, 1985).In this paper, we report for the first time the in vitro isolation of TNCs from the adult trout thymus, analyzing their cytochemical and ultrastructural characteristics and their presumptive relationships with thymocyte-epithelial-cell complexes observed in situ. RESULTS Light MicroscopyIsolated lymphoid-epithelial-cell complexes appeared as large round cells with a regular outline containing I to 11 (average 3 to 4) round lymphocytic nuclei. The nuclei of the epithelial cells were irregular in shape, eccentric, and poorly stained (Fig. 1). Enzyme-and Immuno-Cytochemical AnalysisEnzyme-Cytochemical Analysis The lymphoid-epithelial-cell complexes showed ACPH (Fig. 2), AKPH (Fig. 3), and ANAE (Fig. 4 (Fig. 11). Their cytoplasm contained microfilaments, elements of the Golgi apparatus, profiles of rough endoplasmic reticulum, a few electron-dense vesicles, as well as numerous vesicles with a heterogeneous electron-pale content (Fig. 11). The nucleus, irregular in shape, was moderately heterochromatic, with a prominent nucleolus. Engulfed thymocytes frequently appeared in the epithelial cytoplasm in close contact with pale vesicles (Fig. 11). On the other hand, pale epithelial cells had euchromatic nuclei and ovoid electron-lucent cytoplasm. They contained free ribosomes, mitochon...