Massimiliano Bottaro

Observations of crypt neuron-like cells in the olfactory epithelium of a cartilaginous fish

A new receptor neuron (RN) type was recently described in bony fish olfactory epithelium (OE): the crypt receptor neuron. This name is due to its main feature: the presence, at the apical part, of a deep invagination into which cilia protrude. The presence of this receptor neuron type is well documented in different species of bony fishes but it has never been described in cartilaginous fishes. In this study we demonstrate that crypt neuron-like cells are present in the olfactory epithelium of the elasmobranch Scyliorhinus canicula (Linnaeus, 1758). Histological observations allowed us to detect the presence of a few egg-shaped cells, characterized by a crypt like zone; alpha-tubulin immunoreactivity suggested the presence of cilia in the same area; fluorocrome conjugated lectin bindings suggested a distinctive mucus composition inside the presumptive crypt. The possible presence of crypt neuron-like cells in chondrichthyes would represent an interesting common feature between bony and cartilaginous fishes.

Appearance of Crypt Neurons in the Olfactory Epithelium of the Skate Raja clavata During Development

Crypt neurons are olfactory receptor cells located in the olfactory epithelium of fishes. They exhibit a peculiar and well‐recognizable morphology, although their odorant specificity is still unknown. Data on their appearance during development are few and far between. This study set out to identify the time at which crypt neurons appeared in the skate, Raja clavata, using histological and immunohistochemical methods. For this purpose, embryos and juveniles at different stages of development, from 13 weeks after laying (11 weeks before hatching) to 24 weeks after hatching, were examined. The crypt neurons were identified on a morphological basis. An anti–α‐tubulin antibody and two lectins (wheat germ agglutinin and peanut agglutinin) were used to highlight morphological details. The olfactory marker protein was detected by immunohistochemistry, because this protein is a marker of neuronal maturity in vertebrates. The crypt neurons could be detected by their morphology at 15 weeks after laying and became strongly olfactory marker protein immunoreactive 22 weeks after laying. Although involvement of crypt neurons in reproductive behavior has been inferred in various studies on bony fishes, their early presence in skate embryos and juveniles may suggest that they are not exclusively involved in sexual behavior. Anat Rec, 290:1268‐1272, 2007.

New records of the lessepsian fish Fistularia commersonii (Osteichthyes: Fistulariidae) from the central Tyrrhenian Sea: signs of an incoming colonization?

A total of fifteen adult specimens of the so-called ‘lessepsian sprinter’ Fistularia commersonii were captured by bottom trawlers and gill-netters operating along the Latium coasts, Italy, in October–November 2007. This non-native species is established in the eastern Mediterranean but it has been sporadically reported beyond the Strait of Sicily. Never before has the species been recorded in such large numbers from a single locality in the western Mediterranean. These records may suggest an incoming establishment of a self-sustained population of the species also in the western Mediterranean and they document for the first time the presence of a lessepsian fish in Latium waters. Biometry and meristics of the available specimens of F. commersonii and data on their diet and reproductive condition are given.

First detection of olfactory marker protein (OMP) immunoreactivity in the olfactory epithelium of a cartilaginous fish.

Olfactory marker protein (OMP) is a protein expressed in the mature olfactory and vomeronasal neurons of many vertebrates, such as mammals, amphibians and bony fishes. Aim of this work was to investigate the OMP expression in the olfactory epithelium of the shark Scyliorhinus canicula (Linnaeus, 1758), by immunohistochemistry (IHC). Immunoreactivity was detected in the olfactory receptor neurons, in the crypt neurons and in the nerve fibers below the epithelium. Although very little is known about the OMPs function, its involvement in synaptogenesis, transduction cascade, neurogenesis and development of olfactory system has been suggested. The present work shows for the first time OMPs presence in a cartilaginous fish.

The compensatory growth in juveniles of sea bass: gastric distributive pattern of molecules regulating metabolism.

The aim of this work was to investigate the distribution of regulative molecules in the stomach of juvenile Dicentrarchus labrax during compensatory growth, using immunohistochemical methods. Antisera against galanin, neuropeptide Y, ghrelin, leptin, and serotonin were used on fasted and refed D. labrax. The results show a characteristic distributive pattern for the sought molecules in fish refed after 35 days of fasting, with a high increased presence of both ghrelin and leptin.

Born among the ice: first morphological observations on two developmental stages of the Antarctic silverfish Pleuragramma antarcticum, a key species of the Southern Ocean

The Antarctic silverfish Pleuragramma antarcticum is a keystone species in the Southern Ocean ecosystem, providing one of the major links between lower and higher trophic levels. Despite the importance of this species, surprisingly little is known of its early development. The first spawning area for the silverfish has been recently identified in the near-shore of Terra Nova Bay (Ross Sea). Evidence indicates that spawning and embryo development occurs in the cryopelagic environment, below the seasonal pack-ice. In order to contribute to the knowledge of the life cycle of this very important Antarctic species, we carried out the first histological characterization on pre-hatching embryos and newly hatched larvae. Embryonated eggs and larvae of P. antarcticum were collected between late October and November 2005 at TNB through holes drilled into the sea ice. Embryonic stage just before hatching and the first post-hatching stage were the most abundant within our samples and thus were analysed using both macroscopic and histological approaches. Early life stages of the Antarctic silverfish revealed interesting features: the sensory system, foraging apparatus and heart appeared well developed, whereas the liver and gills were underdeveloped. Morphological details of the organogenesis were performed, providing the first substantial information on the development of P. antarcticum and representing a further steps towards the knowledge of the life cycle of this important Antarctic key species.

Ampullary pore distribution of Galeus melastomus and Etmopterus spinax : possible relations with predatory lifestyle and habitat

The number and distribution of ampullary pores present on the blackmouth catshark, Galeus melastomus and the velvet belly dogfish, Etmopterus spinax do not differ with the size/maturity or gender of the specimen and were found to be related to prey preference.

Presence and distribution of FMRFamide‐like immunoreactivity in the cyprid of the barnacle Balanus amphitrite (Cirripedia, crustacea)

The presence and distribution of FMRFamide‐like peptides (FLPs) in the cyprid larvae of the barnacle Balanus amphitrite were investigated using immunohistochemical methods. Barnacles are considered to be one of the most important constituents of animal fouling communities, and the cyprid stage is specialized for settlement and metamorphosis in to the sessile adult condition. FLPs immunoreactive (IR) neuronal cell bodies were detected in both the central and the peripheral nervous system. One bilateral group of neurons somata was immunodetected in the brain, and IR nerve fibers were observed in the neuropil area and optic lobes. Intense immunostaining was also observed in the frontal filament complex: frontal filament tracts leaving the optic lobes and projecting towards the compound eyes, swollen nerve endings in the frontal filament vesicles, and thin nerve endings in the external frontal filament. Thin IR nerve fibers were also present in the cement glands. Two pairs of neuronal cell bodies were immunodetected in the posterior ganglion; some of their axons appear to project to the cirri. FLPs IR neuronal cell bodies were also localized in the wall of the dilated midgut and in the narrow hindgut; their processes surround the gut wall and allow gut neurons to synapse with one another. Our data demonstrated the presence of FLPs IR substances in the barnacle cyprid. We hypothesize that these peptides act as integrators in the central nervous system, perform neuromuscular functions for thoracic limbs, trigger intestinal movements and, at the level of the frontal filament, play a neurosecretory role. Microsc. Res. Tech., 2009.

Distribution of choline acetyltransferase immunoreactivity in the alimentary tract of the barnacle Balanus amphitrite (Cirripedia, Crustacea).

To date only peptidergic innervation has been described in the alimentary tract of barnacles. In the present work the presence and distribution of choline acetyltransferase (ChAT), the acetylcholine (ACh) synthesizing enzyme, was investigated by immunohistochemistry in the alimentary tract of the adult barnacle Balanus amphitrite. Numerous ChAT-immunoreactive (IR) cells and a net of ChAT-IR cytoplasmic processes were localized inside the epithelium of the posterior midgut, close to the basement membrane; no IR nerve endings were detected in the midgut longitudinal and circular muscle bundles. Epithelial neurons or endocrine cells in the gut epithelium have been described in some invertebrate species belonging to different taxa and their peptidergic features are reported in the literature. Our results point out the presence of neuroepithelial cells also in the gut epithelium of barnacles; moreover, for the first time, a cholinergic feature is suggested for this cell type. These data seem to indicate the involvement of ACh in the gut functions of barnacle and suggest that the barnacle alimentary tract is more complex than previously thought and requires further study.

The occurrence of lead in the bone tissues of Trematomus bernacchii , Terra Nova Bay, Ross Sea

The occurrence of lead in various bone tissues of Trematomus bernacchii was investigated in order to identify the optimal target tissue and to examine potential relationships between bone lead concentration and fish size and age. Lead concentration values found in vertebrae and jaws (0.44 ± 0.13 and 0.41 ± 0.09 μg g−1 of dry weight tissue, respectively) were significantly higher than those in the other bones examined (otoliths, branchiostegal rays and pectoral girdles), indicating a preferential accumulation of lead in these tissues. Hence, vertebrae and jaws were selected as suitable target organs. The significance of T. bernacchii as a marker of lead bio-availability for the marine environment was tested by comparing data with the ones obtained for the Scorpaena notata, a benthic fish living in the more polluted coasts of the Mediterranean Sea, and by correlating the lead content found in the fish bones with the concentration of bio-available lead in the marine sediments on which the two fishes live. Bio-availability was evaluated by solid speciation and size fractionation techniques. All data clearly indicated that the difference in bone lead content between S. notata and T. bernacchii (0.83 ± 0.17 μg g−1 and 0.42 ± 0.08 μg g−1, significant at the 99.9% confidence level) can be ascribed to the concentration of bio-available lead in their respective environment. Finally, no correlation between the lead accumulation in bone tissues and fish size and age was found for either fish species.