Bruno Dore

Adaptation of the reproductive cycle in Triturus alpestris apuanus to an unpredictable habitat

The annual reproductive cycle was studied in a Triturus alpestris apuanus population from northwestern Italy. Adult and larval newts were captured and measured monthly. By using histological techniques, the status and evolution of male gonads were examined. T. a. apuanus shows a post-nuptial gametogenesis, and testes reach their smallest size and weight in spring, when there are mainly mature sperm ampullae and yellow glandular tissue. Secondary sexual characters reach their maximum development during this period, decreasing during gametogenesis and increasing again in early autumn. Breeding activity begins at the same time, and is interrupted by the winter. Reproduction starts again in spring, lasting until summer. Eggs are laid at least twice a year, and the two larval cohorts live together. It is suggested that all these biological features are adaptations to unpredictable aquatic environments in a Mediterranean dry climate. These results suggest high levels of flexibility and variability in newt seasonal cycles.

Photomechanical adaptation in the eyes of Squilla mantis (Crustacea, Stomatopoda)

Abstract In the eye of Squilla mantis adapted to the dark the layer of the crystalline cones shortens and the retina becomes longer; the opposite occurs in light adaptation. With dark adaptation the acceptance angle becomes more than twice as large as in light adaptation. With this also the visual field of the ommatidium and the gaussian sensitivity function increase. Myofibrils between the crystalline cones are immersed in veils which are attached to the cornea. At the widest part of the cone a reinforced cone membrane folds inside; the fold contains a ring to which the veils are attached. This unique structure serves possibly as a harness to transfer the mechanical traction of the contractile structures to the cone. Around the distal, tapering part of the cone, the corneage‐nous cells could act as hydraulic shock‐absorbing cushions. Six accessory pigment cells stretch between the distal retina and the basement membrane and contain myofibrils. The shortening of the cones during dark adaptation is presumably due to the contraction of the myofibrils in the veils and the simultaneous relaxation of those in the accessory pigment cells. In light adaptation the latter contract and the fibers in the veils relax.

Morphology of adaptation and morphogenesis in stomatopod eyes

Ommatidia of eyes of stomatopods change with adaptation to light or dark. With dark adaptation the crystalline cones shorten and the retina becomes longer. This is due to contractions of myofibrils in veils surrounding the cones, while microtubules within the accessory pigment cells maintain the cytoarchitecture of the ommatidia. Here we describe the changes in Lysiosquillina maculata, a stomatopod living in an extremely bright habitat, which is compared to stomatopods from other ambient light conditions. The postlarval eye of stomatopods grows over the larval eye, gradually substituting it. Growth starts from a morphogenetic furrow at the inner border with the stalk. Similarly, in the adult eye as well at the inner margin between the stalk and the cornea, a morphogenetic furrow is inserted, which at its interior contains a proliferation tissue with clusters of developing ommatidia. At its distal side the proliferation tissue appears to generate the dioptric apparatus, i.e. veils, corneagenous cells and cones, and at its more proximal part the basement membrane, accessory pigment cells and retinular cells. The ommatidial components grow at different speeds.

Renal Alkaline Phosphatase and osmoregulatory adaptations in Amphibians. I. Seasonal variations and action of an antidiuretic hormone (AVT).

Abstract 1. 1. The biochemical assay of alkaline phosphatase (EC 3.1.3.1) activity was achieved in the kidney of Triturus cristatus adult specimens treated with arginine vasotocin (AVT) and prolactin (PRL). 2. 2. In normal animals the activity of alkaline phosphatase in the terrestrial phase is almost half that in the aquatic phase. 3. 3. AVT treatment consistently elicited a marked reduction in the enzyme activity. 4. 4. No change in renal alkaline phosphatase activity was induced by PRL treatment in terrestrial animals.

A mantis shrimp wearing sun‐glasses

Abstract Lysiosquillina maculata and L. sulcata have an exceptional mechanism, never observed in any other eye, for adaptation to the extreme light condition in their habitat. The eyes of L. maculata and L. sulcata are similar to, and here compared with those of other stomatopods. But a peculiar, complex system of muscles and veils surrounds the cones. Tight linkages attach this system to the cones and wedges, presumably adapting the eye (or different regions of the eye) to the intensities and angles of incident light. The muscles are also attached to a unique system of sunglasses. Viewing the frontal part of the living eye within a small solid angle, a large part appears black but, with a slight change in the viewing direction, it becomes white, i.e., totally reflecting the light. Corresponding to the reflecting part of the eye, the cornea thickens with two additional layers with varying stratification of alternating refractive indices. In this part, a thin layer of a particular tissue is inserted into the cornea and attached to the muscles containing transparent veils that surround the cones. Here the cones are not attached directly to the cornea, but to this tissue, which is composed of an outer lining underlying the cornea, containing many nuclei and many branching strands at the proximal side. The interior is composed of fibrous structures approximately parallel to each other and to the cornea, presenting aligned granules or crystals and cytoplasmic strands connected to the veils. In bright light, the additional cornea layers and the peculiar tissue likely reflect the light with total internal or external (depending on the angle of incident light) reflection. The muscles subserve light‐ and dark‐adaptation. During the day, within a small solid angle, a large part of the frontal ommatidia are screened off from the bright light. During the night, presumably also the frontal ommatidia become operant, due to the contraction of the muscles which alter the optics of the eye.

Skin morphology and function in Xenopus laevis exposed to a saline environment for up to one week.

This study evaluated the skin adaptation response in Xenopus laevis to short- and medium-term stays (24 h, 48 h, 7 days) in brackish water. Morphological, histochemical, histoenzymological (alkaline phosphatase, carbonic anhydrase) and electrophysiological (short-circuit current, resistance) characteristics were examined. The results show that animals adapt to brackish water, implementing a variety of short and medium-term morphofunctional modifications of the epidermis and skin glands. These modifications form part of the defence mechanisms needed to protect the animal from an excess increase in the saline concentration of internal fluids.

Ion transport processes and alkaline phosphatase activity in the skin of the crested newt

Abstract The supposed relationship linking alkaline phosphatase (???) activity and selective transepithelial transport processes was investigated in the skin of the crested newt under various experimental conditions of ion transport stimulation and inhibition. The effects of rearing animals in deionized water and of treatment with aldosterone were analysed in the cold (10° C, winter) and warm seasons (22° C, summer); the effect of treatment with prolactin and prolactin plus aldosterone was analysed in the warm season. ??? activity was detected histochemically using Burstones method, ion transport processes were revealed electrophysiologically by determination of the transepithelial potential difference (PD), short‐circuit current (SCC), and electrical resistance (Rm). ??? activity in keratinocytes markedly increases during the transition from the winter to summer condition. In summer aldosterone significantly increases enzyme activity in keratinocytes compared to controls. In the same condition, prolacti...

Active ion transport and morphofunctional organization in the skin of the alpine newt, Triturus alpestris during the life cycle

Electrophysiological techniques were used to study active ion transport across the skin in larval, pedomorphic and metamorphosed alpine newts (Triturus alpestris apuanus). Data were compared with morphological and histoenzymological studies (alkaline phosphatase - APH -) in the skin of the same animals. A short circuit current, which presumably corresponds to active sodium transport, apparently absent in larvae, develops in pedomorphic specimens during the adult epidermis differentiation process and appears to be sensitive to some extent to temperature changes. Flask cells appear early in pedomorphic forms and reveal intense APH activity, a characteristic which is also found in adult animals. Circumstantial evidence correlates APH activity with transport phenomena. These findings support the hypothesis that morphological and physiological differentiation form part of a single process occurring during metamorphosis.

Abundance of short-chain (C8–C14) fatty acids in the neutral lipids of Tubifex tubifex

1. 1. Column, thin-layer and gas-liquid chromatography were used to determine the neutral lipid fatty acid and sterol composition of an organic Tubifex tubifex extract. 2. 2. Cholesterol (21% of the neutral lipids) was the most abundant sterol. 3. 3. Short-chain fatty acids were particularly abundant, whereas C16–C18 forms were relatively scarce. 4. 4. There was a notable percentage (5%) of branched-chain and/or odd C-number fatty acids. 5. 5. Of the total fatty acids, 47% consisted of mono- and polyunsaturated fatty acids.

Enzyme activities in the integument of amphibia: Biochemical, histochemical and electrophysiological data on Rana kl. esculenta and Xenopus laevis

Abstract The enzymatic activities related to Rana kl. esculenta and Xenopus laevis skin, and in particular to an unstirred layer in the epidermis surface (subcorneal space) where mitochondria‐rich cells (MR cells) and principal cells (PC cells) expose their apical membrane, are studied; histochemical, biochemical and electro‐physiological data are compared. The organization of PAS (Periodic Acid Schiff)/PASM (Periodic Acid, Silver Methenamine) positive material and some ectoenzymes in the subcorneal space and in the apical surface of living and active cells, both MR and PC are described. Subcorneal space appears to be a specialized structure, forming an unstirred layer at the limiting surface of amphibians living in water. This layer may function as an efficient barrier to capture ions and small molecules diffusing from living cells in the skin, so forming the space where active reuptake of ions and small diffusible organic molecules may take place, but in thermo‐dynamically favourable conditions.