The structure and mechanical characteristics of silk fibers are influenced by metal ions, which have an impact on the conformational alteration of silk fibroin.
The rearing of silkworms for the production of raw silk is called sericulture. The silkworms of the Bombyx mori moths, which consume the green leaves of the mulberry Morus indica, produce this silk. The stages of the mulberry silkworm’s life cycle—egg, larva, pupa, and moth—complete in about 45–55 days. The egg stage lasts for 9–10 days, the larval stage for 24–28 days, the pupal stage for 8–10 days, and the moth stage for 3–4 days.
In this article, we study the effects of different metals like Potassium, Magnesium, Calcium, Zinc, and Iron (fed with mulberry Leaves) on larvae, pupa, adults, and the life cycle of silkworms under Laboratory conditions.”
Conditions for Rearing
Silkworm eggs must be incubated in a dark environment with a relative humidity of 65% at room temperature. First and second instar larvae need conditions of 27–28 °C and 80–85% RH, whereas third, fourth, and fifth instar larvae need conditions of 24–25 °C and 60–65% RH.
Effect of Metals on Silk Formation
The structure and mechanical characteristics of silk fibers are influenced by metal ions, which have an impact on the conformational alteration of silk fibroin. Except for Ca, whose quantity dramatically dropped in the anterior region of the silk gland, all other metal element quantities increased from the posterior to the anterior section of the gland.
(i) The effects of Ca2+ on establishing a stable protein network (gel)
(ii) The capacity of Na+ and K+ to destabilise the protein network
(iii) The ability of Mg2+, Cu2+, and Zn2+ to trigger the conformation change of silk fibroin to a sheet
The two main sources of heavy metal discharge into the environment are anthropogenic and natural. High quantities of these metals, which are very poisonous and reactive, are predicted to penetrate soils and groundwater, bioaccumulate in food webs, and negatively impact biota.
The most significant natural product is the silkworm. The purpose of the recently published study is to determine if the buildup of heavy metals in plants’ harvestable components, such as their leaves, contributes to the tropic levels of the silkworm food chain. (Bombyx mori).
The biological parameters were evaluated to demonstrate how heavy metal contamination affected the life cycle and production of silkworms. The study of soil and plant leaf samples using X-rays revealed that the amounts of heavy metals in various soils varied significantly.
Higher amounts of Zn, Cr, Cu, Pb, Cd, and Sr were observed in sites I and II; this may be because these soils were irrigated with heavy metal-contaminated water, whereas lower quantities were found in the control soil, which was irrigated with treated water. (tap water).
Zn, Cu, Pb, Cr, and Cd were the heavy metals with the highest quantities in the leaves from sites I and II. The control leaf sample, however, contained lower quantities.
Additionally, the weight of the cocoon, the percentage of cocooning, the Effective Rate of Rearing, and the silk output all saw overall declines as a result of pollution in the silkworm food chain. Additionally, it causes the larval mortality rate to rise. It is advised that the presence of heavy metals in the feeding chain of silkworms be closely checked.
Effects of Zinc Metal on Silkworm
The introduction of Zn (II) from mulberry trees that were watered with synthetic Zn (II)-containing effluents into the Bombyx mori (silkworm) food chain
The pH of the synthetic effluent enhanced the quantity of Zn (II) that was deposited on the soil. However, when the effluent pH was in the acidic range, there was significant bioaccumulation of Zn (II) in Morus alba leaves and B. mori larvae.
Even though B. mori expelled a sizable amount of Zn (II), the majority of the metal remained inside its body. The toxicity of Zn (II) was particularly severe in the first instar of B. mori. B. mori’s body length and weight dropped as the amount of bioaccumulated Zn (II) in the larval body increased. Significantly more Zn (II) was present in the larval body, which raised the mortality rate of B. mori.
Effects of Potassium Metal on Silkworm
Oral intake of potassium chloride at concentrations of 50, 100, and 150 g/ml and its beneficial effects on the hemolymph trehalose and protein of fifth-instar larvae of Bombyx mori L. (Lepidoptera: Bombycidae) when compared to the comparable characteristics of the carrier control dramatically increased all of the treatment groups’ observed parameters.
These findings could indicate that minerals might increase the activity of an enzyme that affects metabolism, boosting the biochemical content of the silkworm, B. mori L.’s fat body, and hemolymph.
Effects of Magnesium Metal on Silkworm
Magnesium has both positive and negative effects, depending on concentration and method of application.
Positive effects:
Magnesium is an essential mineral for various physiological functions, including immune system regulation. Magnesium is involved in many enzymatic reactions related to protein synthesis and energy metabolism. Magnesium plays a role in maintaining electrolyte balance within a silkworm’s body. Proper electrolyte balance is essential for normal physiological functions, including nerve and muscle activity.
Negative effects:
Magnesium imbalance might affect the reproductive capabilities of silkworms, potentially leading to decreased fertility and abnormalities in egg production. Excessive magnesium levels disrupt the balance of other essential minerals. Magnesium imbalances could interfere with the silkworm’s digestive system, causing issues such as poor nutrient absorption, digestive disorders, or even mortality.
Effects of Metal Zinc (Zn) on Silkworm
After being fed to silkworms, zinc-fortified mulberry leaves increase silkmoth reproductive capacity as well as cocoon quality indicators like higher shell-to-body ratios, raw silk percentages, denier, and renditta. In addition, it lowers the floss-shell ratio by reducing the protein synthesis in the floss.
Effects of Metal Iron on Silkworm
According to research, modified silk is resistant to stress and has more toughness than ordinary silk. A rather high proportion of -sheet in the modified silk is shown by the integration of the amide I band intensities.
Summary
Silkworms require certain metals, such as magnesium, potassium, and zinc, in small quantities to promote their growth and development. High concentrations of several metals, such as magnesium, calcium, potassium, and iron, can have harmful effects on silkworms and cause stunted growth, aberrant developmental patterns, or even death.