Effects of Exposure to Trade Antifouling Paints and Biocides on Larval Settlement and Metamorphosis of the Compound Ascidian Botryllus schlosseri

Abstract

To evaluate the effects of antifouling paints and biocides on larval settlement and metamorphosis, newly hatched swimming larvae of the compound ascidian Botryllus schlosseri, a dominant species of soft-fouling in coastal communities, were exposed to (i) substrata coated with seven antifouling paints on the market containing different biocidal mixtures and types of matrices and (ii) sea water containing various concentrations of eight biocidal constituents. All antifouling paints showed high performance, causing 100% mortality and metamorphic inhibition, with ≥75% not-settled dead larvae. All antifouling biocides prevented the settlement of larvae. The most severe larval malformations, i.e., (i) the formation of a bubble encasing the cephalenteron and (ii) the inhibition of tail resorption, were observed after exposure to metal and organometal compounds, including tributyltin (TBT) at 1 μM (325.5 µg L−1), zinc pyrithione (ZnP) at 1 μM (317.7 µg L−1), and CuCl at 0.1 μM (98.99 µg L−1), and to antimicrobials and fungicides, including Sea-Nine 211 at 1 μM (282.2 µg L−1) and Chlorothalonil at 1 μM (265.9 µg L−1). The herbicides seemed to be less active. Irgarol 1051 was not lethal at any of the concentrations tested. Diuron at 250 μM (58.2 mg L−1) and 2,3,5,6-tetrachloro-4-(methylsulphonyl)pyridine (TCMS pyridine) at 50 μM (14.8 mg L−1) completely inhibited larval metamorphosis. These results may have important implications for the practical use of different antifouling components, highlighting the importance of their testing for negative impacts on native benthic species.

Searching for the Origin and the Differentiation of Haemocytes before and after Larval Settlement of the Colonial Ascidian Botryllus schlosseri: An Ultrastructural Viewpoint

“…Entire embryonic development can be studied within parental individuals after obtaining colonies with embryos at well-determined stages of development [55][56][57]. Moreover, the metamorphosis stages of the hatched tadpole larva can be easily recognised [58]. In particular, the following stages of embryo-larval development have been considered: (i) early tailbud embryo, with the tail forming an initial turn around the cephalenteron; (ii) late tailbud embryo, with the tail at its maximum extension (1.5 turns around the cephalenteron); (iii) newly hatched tadpole larva (early metamorphosis); (iv) late metamorphosis larva; and (v) oozoid.…”

Effects of Tributyltin-Contaminated Aquatic Environments and Remediated Water on Early Development of Sea Urchin (Hemisentrotus pulcherrimus)

“…TBT affects biochemical processes such as the inhibition of mitochondrial oxidative phosphorylation, genotoxicity, DNA damage, ATP synthesis, inhibition of ATPases, and perturbation of calcium homeostasis [36]. Calcium ions play a critical role in TBT-induced apoptosis by disrupting Ca 2+ homeostasis [36,37]. Alterations in calcium signaling cause developmental toxicity in sea urchin embryos and larvae [35,36].…”

Larval Settlement on Marine Surfaces: The Role of Physico-Chemical Interactions

“…Cima and Varello (2022) [9] analyse the effects of various trade antifouling paints commonly used on various submerged surfaces-e.g., ship's hulls, piers, buoys, and marine platforms-on the larval settlement and metamorphosis of the colonial ascidian B. schlosseri. Highlighting the toxic mechanisms of biocides released in the immediate surroundings or acting by contact, the authors remark upon the importance of testing antifouling components before their practical use to avoid potential long-term negative impacts on benthos communities.…”