In the skin of Salmo irideus the production of mucus is due to one type of cell specialized as a mucus cell. The histochemical research presented in this paper describes the mucous cells of Salmo irideus and demonstrates observable variation in such cells during the fish's development

Massari, S.

Porcelli, F.

English

Aquatic Commons

FBA Translation (New Series) No. 128. 
PORCELLI, F. & MASSARI, S. 
Histochemical data on the skin mucous cells during the development 
of the trout. 
Boll.Soc.ital.Biol.sper. 45, 1273-1276. (1969) 
Translated by K. DICKSON. 
In the skin of Salmo irideus the production of mucus is due to one 
type of cell specialized as a mucus cell. 
Massari (1) has observed the presence of such cells in the immature 
prehatching stages and Porcelli (2) has seen them in the ectodermic 
portion of the yolk sac of the same stage. In the literature (3-5) skin 
mucous cells with mucus and a truly complete structure have been described 
only in the adult of those species of teleosts with naked skin or in those 
where scales appear relatively late. The histochemical research presented 
in this paper describes the mucous cells of Salmo irideus and demonstrates 
observable variation in such cells during the fish's development. 
We examined the skin of successive stages of Salmo irideus using 
Prakash's (6) classification: 
Stage 1: immature prehatching, length of the embryo 6.5-8 mm., 
eyes faintly pigmented. 
Stage 2: late prehatching, length of the embryo 8.1-11 mm., 
eyes intensely pigmented. 
Stage 3: immature post hatching; length of the embryo 12.5-l8 mm. 
Stage 4: late post hatching; length variable, yolk sac still of 
moderate dimensions with respect to the fry. 
Stage 5: young trout, juvenile characteristics, yolk sac 
completely disappeared. 
Stage 6: Trout, length 15 cms. 
Stage 7: Trout, length 30 cms. 
- 1 -
Where possible, and it was possible in the first 4 stages, we examined 
both the somatic skin and the ectodermal portion of the wall of the yolk 
sac. We refer you to a paper by one of us (2) in which the development 
and the absorption of the yolk sac was examined in more detail and the 
correspondence between the two locations described. 
The material was fixed in 10% formalin or in Carnoy's liquid then 
routinely dehydrated and embedded, or if lipids were to be looked at they 
were fixed in Ca - formalin and the frozen block was sectioned on a 
freezing microtome. It was then subjected to the following histochemical 
reactions besides the normal histological dyes. 
a) To demonstrate the presence of mucopoly saccharides: 
1) Reaction to periodic acid - Schiff according to 
McManus - Hotchkiss. 
b) To demonstrate the presence of glycogen: 
1) Reaction of McManus - Hotchkiss with previous digestion 
with α - amylase. 
2) Iodine-reaction of Langhans also according to Mancini's 
version. 
3) Reaction of McManus - Hotchkiss previous treatment with 
agitation (see Li son). 
c) To demonstrate the occurrence of acid mucopoly saccharides. 
1) Reaction to colloidal iron according to Hale with 
Muller's modifications. 
2) Alcian blue 8 G.N. according to Stedman. 
3) Alcian blue at several pH's see Spicer. 
4) Alcian blue prior to the blocking of alcianophilia with 
Mg Cl2 according to Scott's method. 
5) Alcian blue with prior methylation see McManus and 
Mowry. 
6) Alcian blue with prior methylation followed by demethylation. 
7) Acridine-orange see Hicks & Matthaei. 
8) Acriflavine - see Takenchi. 
9) Alcian blue with prior enzymatic digestion with bacterial 
hyaluronidase in a concentration of 1mg./ml. in distilled water 
for 1 Hr. at 37°C. 
- 2 -
The following conclusions can be drawn from an examination of the table. 
In the adult stages where the epidermis is very stratified, the ventral 
and dorsal locations of the skin, and the superficial and deep mucous cells 
are shown separately. 
It seems evident that the mucous cells of the trout contain mucopoly 
saccharide material with a complex constitution. Close to a fraction of 
neutral mucopoly saccharide a relatively acid fraction is present with a 
variable amount of sialic acid. The presence of a proteinaceous component 
could not be demonstrated and the reactions for lipid gave practically negative 
results even after the unmasking treatments. The fraction responsible for 
the positive response to the reactions for the sulphated mucopolysaccharides 
were not always present and one can observe a difference in mucous production 
between adjacent cells. One can therefore identify 
10) Alcian blue with prior enzymatic digestion with 
sialidase see Spicer. 
11) Alcian blue with prior enzymatic digestion with 
sialidase (see Spicer) preceded by treatment with 
alcoholic KOH (see Gerard). 
d) To demonstrate the presence of both a neutral and an acidic 
fraction in the polysaccharide material. Double reaction using 
Alcian blue simultaneously with Hotchkiss's reaction see 
Vialli. 
e) To demonstrate of mucopoly saccharides at different acidities. 
1) Alcian blue - alcian yellow see Ravetto. 
f) To demonstrate proteinaceous material: 
1) Staining with bromophenol-blue see Mazia, Bravert and Alfert. 
2) Morel - Sisley's reaction for demonstrating the presence 
of protein containing the amino acid tyrosine. 
g) To demonstrate the presence of neutral lipids. 
1) Sudan black B on frozen material freshly cut with a 
freezing microtome. 
h) To demonstrate the presence of heterophasic lipids: Sudan 
black B on material fixed in 10% formalin and prior treatment 
with unmasking agents: 1% phenol 37°C, acetone t° ambient, 
ethyl alcohol 90° C, distilled water 37°C. 
- 3 -
two types of mucus producing cells on the basis of differences in content 
of sulphated mucopolysaccharides and the coexistence of these two types 
of cells occurs in all developmental stages examined as well as in the adult. 
All the characteristics of the mucus are demonstrable as early as the 
endovular stages. The principal transformation observed during the development 
are considered in the following by comparing the various developmental stages 
and the adult: 
a) The relative increase of glycogen in the adult as opposed to the 
fry. (The digestion removes from the preparation, granular 
material which in general gives a positive reaction to Hotchkiss' 
reaction. This material is very distinctive in the undifferentiated 
cytoplasm which in the mucous cells gives a characteristic foamy 
appearance to the mucus present in the cytoplasm. The difference 
between the zones is not clear). 
b) The increase in the reactivity of sialic acid, which is very clear 
in the stages following hatching increases even further in the adult. 
(In the pictures of the strongly stratified adult skin it is 
possible to identify more signs of sialic acid in the superficial 
mucous cells as opposed to those deeper, and in the ventral 
as opposed to the dorsal portions). 
From the functional point of view it seems evident that, at least in 
the strict sense, there does not exist a correlation between the described 
histochemical transformations and the surrounding changes in connection with 
hatching. The presence of sialic acid is inseparable from the other epithelial 
mucous secretions with which it is described, and not alone as in other skin 
mucous cells of teleosts described in the literature. The presence of glycogen 
in the skin mucous cells is above all due to its persistence in the adult 
stages, this is a piece of information which hints at several interpretations. 
Peyrot (8) has interpreted the presence of glycogen in the duodenal epithelia 
of immature stages of higher vertebrates as a precursor of the glycoprotein 
of the adult and a function of this sort may be attributable to the glycogen 
of the mucus-producing cells in the adult tissues (this would allow a complete 
functional cycle inside a single cell.) On the other hand we can be criticized 
because we have not considered adult trout of 30 cms length (2 yrs. old), 
and it must be noted that trout retains its growth for a long time. 
- 4 -
In some sense the glycogen demonstrated by us in the last stages can be 
considered a transitional condition in the development. On the other hand 
it seems opportune to record that since the skin of the trout is considered 
deprived of specialized types of cells (eg. the clavate cells)(9) and, like 
the majority of teleost, lacks Keratin (10) an essential turgor due to 
glycogen could be called the support mechanism, (see the functional 
interpretations proposed for the clavate cells). Whether this information 
could extend to other skins deprived of clavate cells or not is debatable. 
- 5 -
Fig. 1. Mucous skin of the ventral region of the adult trout (length 30 cms) 
Hotchkiss' reaction. Scale 1000x. 
Fig. 2. Mucous skin of the ventral region of the adult trout (length 30 cms) 
Hotchkiss' reaction with prior digestion using α-amylase. 
Scale x1000. 
- 6 -
Fig. 3. Mucous skin of trout at the early post hatching stage. Stained 
with Alcian blue 8GN. Scale 1000x. 
Fig. 4. Mucous skin of trout at the miniature post hatching stage. 
Stained with Alcian blue 8GN with prior digestion using sialidases 
preceded by treatment with KOH. Scale 1000x. 
- 7 -
- 8 -
Fig. 5. Mucous skin of the ventral region of the adult trout (30 cms long). 
Stained with Alcian blue 8GN. 
Fig. 6. Mucous skin of the ventral region of the adult trout (length 30 cms) 
Stained with Alcian blue 8GN and with prior digestion using sialidases 
preceded by treatment with alcoholic KOH. 
(1) The demonstration of glycogen was obtained by comparing the slides 
from Hotchkiss' reaction and those after digestion with α-amylase. 
The histochemical diagnosis of glycogen was confirmed by the fact 
that in the examined locations Hotchkiss' reaction exists after 
pretreatment with dimedone. Langhams' reaction to iodine gives 
positive results only after 24 hrs of staining following Mancini's 
technique. 
(2) For the sulphated mucopolysaccharides various grades of reactivity 
were observed between adjacent raucous cells (see text). 
(•) There is no data on glycogen in the within-egg stages due to the 
extreme difficulty in cutting material fixed with Carnoy's liquid. 
- 9 -
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Notice 
 
 
Please note that these translations were produced to assist the scientific staff of the 
FBA (Freshwater Biological Association) in their research. These translations were 
done by scientific staff with relevant language skills and not by professional 
translators. 
 
 
 


Histochemical data on the skin mucous cells during the development of the trout [Translation from: Bollettino della Societa Italiana di Biologia Sperimentale 45, 1273-1276, 1969]

http://aquaticcommons.org/4912/1/128_1969_porc_hist.pdf

Histochemical data on the skin mucous cells during the development of the trout [Translation from: Bollettino della Societa Italiana di Biologia Sperimentale 45, 1273-1276, 1969]

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