21 Histopathological Alterations of the Mantle of Mytilus galloprovincialis. . .
241
Results
Although macroscopically anomalies were not found, from comparative histological
study, multiple cellular and tissular abnormalities were observed which can be
considered as neoplastic disorders, affecting mainly germ cells.
The gonadal lesions observed were mainly found close to the gills and exhibited
different degrees of malignancy. Histologically we observed a loss of tissue
organization and of the gonadal follicles architecture (Fig. 21.1a, f). At cellular level
we found larger hyperchromatic spermatocytes in males and pleomorphic oocytes in
females (Fig. 21.1a, c, h); multinucleated germinal cells of great size, with clumped
chromatin and irregularly shapes; pyknotic nuclei, karyorrhexis and karyolysis;
vacuolizated cytoplasm; hyperchromatic nucleolus of large size; mitotic figures that
suggest a high rate of cell division and enucleated cells with thin cytoplasm (ghost
cells) (Fig. 21.1b, c, g–i). In many cases, the basal membrane surrounding follicles
was breached and tumour cells invaded the adjacent connective tissue, sinusoids
and haemolymphatic vessels. Intra- and extra-follicular fibrosis was present in the
affected areas (Fig. 21.1d, i).
Along with these alterations an immune response is likely to take place, showing
a proliferation of haemocytes and phagocytes around the affected follicles. Often,
such haemocytes and phagocytes also show neoplastic features: numerous and
atypical mitotic figures; a considerable increase of the nucleus/cytoplasm ratio;
large haemocytes, with hyperchromatic, multiple or fragmented nuclei, prominent
nucleolus, and often cytoplasmatic inclusions of lipofucsin or degradation products
(Fig. 21.1e, j).
The prevalence of these histopathological alterations was 18 %, being higher in
males (62.5 %) than in females (37.5 %). Moreover, it was during periods of active
gametogenesis when the neoplastic incidence was highest: 61.5 % during spawn
and gonadal restoration periods and 23.4 % during early stages of gametogenesis
(Fig. 21.2).
The analyzed pollutants accumulated in Mytilus (PAHs, organochlorine compounds and trace metals) showed a statistically significant seasonal variation
(p < 0.01). Total PAHs concentration (
P
13PAHs) ranged from 52.26 to 739 g
kg
1 dw. Among them, the most toxic and carcinogenic species (Chry, BkF, BaA,
BbF, BaP, DBA, IP) ranged between 8.86 and 310.70 g kg
1 dw, showing also
a significant seasonal variation (p < 0.01). Accumulation of organochlorines was
between 3 and 11 times lower than hydrocarbon concentrations. PCBs (
P
10
congeners PCBs) ranged between 12.25 and 58 g kg
1 dw, and penta- and hexachlorinated congeners including some dioxin-like, varied from 10.12 to 53.01 g
kg
1 dw. Among OCPs analyzed, DDTs and HCHs showed significant seasonal
variations (p < 0.01) but within a narrow range of values between 2.21 and 10.80 g
kg
1 dw and 0.50 and 2.69 g kg
1 dw, respectively. Finally, the total trace elements
accumulated varied between 99.25 and 375.73 mg kg
1 dw (Fig. 21.3).
241
Results
Although macroscopically anomalies were not found, from comparative histological
study, multiple cellular and tissular abnormalities were observed which can be
considered as neoplastic disorders, affecting mainly germ cells.
The gonadal lesions observed were mainly found close to the gills and exhibited
different degrees of malignancy. Histologically we observed a loss of tissue
organization and of the gonadal follicles architecture (Fig. 21.1a, f). At cellular level
we found larger hyperchromatic spermatocytes in males and pleomorphic oocytes in
females (Fig. 21.1a, c, h); multinucleated germinal cells of great size, with clumped
chromatin and irregularly shapes; pyknotic nuclei, karyorrhexis and karyolysis;
vacuolizated cytoplasm; hyperchromatic nucleolus of large size; mitotic figures that
suggest a high rate of cell division and enucleated cells with thin cytoplasm (ghost
cells) (Fig. 21.1b, c, g–i). In many cases, the basal membrane surrounding follicles
was breached and tumour cells invaded the adjacent connective tissue, sinusoids
and haemolymphatic vessels. Intra- and extra-follicular fibrosis was present in the
affected areas (Fig. 21.1d, i).
Along with these alterations an immune response is likely to take place, showing
a proliferation of haemocytes and phagocytes around the affected follicles. Often,
such haemocytes and phagocytes also show neoplastic features: numerous and
atypical mitotic figures; a considerable increase of the nucleus/cytoplasm ratio;
large haemocytes, with hyperchromatic, multiple or fragmented nuclei, prominent
nucleolus, and often cytoplasmatic inclusions of lipofucsin or degradation products
(Fig. 21.1e, j).
The prevalence of these histopathological alterations was 18 %, being higher in
males (62.5 %) than in females (37.5 %). Moreover, it was during periods of active
gametogenesis when the neoplastic incidence was highest: 61.5 % during spawn
and gonadal restoration periods and 23.4 % during early stages of gametogenesis
(Fig. 21.2).
The analyzed pollutants accumulated in Mytilus (PAHs, organochlorine compounds and trace metals) showed a statistically significant seasonal variation
(p < 0.01). Total PAHs concentration (
P
13PAHs) ranged from 52.26 to 739 g
kg
1 dw. Among them, the most toxic and carcinogenic species (Chry, BkF, BaA,
BbF, BaP, DBA, IP) ranged between 8.86 and 310.70 g kg
1 dw, showing also
a significant seasonal variation (p < 0.01). Accumulation of organochlorines was
between 3 and 11 times lower than hydrocarbon concentrations. PCBs (
P
10
congeners PCBs) ranged between 12.25 and 58 g kg
1 dw, and penta- and hexachlorinated congeners including some dioxin-like, varied from 10.12 to 53.01 g
kg
1 dw. Among OCPs analyzed, DDTs and HCHs showed significant seasonal
variations (p < 0.01) but within a narrow range of values between 2.21 and 10.80 g
kg
1 dw and 0.50 and 2.69 g kg
1 dw, respectively. Finally, the total trace elements
accumulated varied between 99.25 and 375.73 mg kg
1 dw (Fig. 21.3).