Phenotypic plasticity and morphological adaptation of Halimeda opuntia (Bryopsidales, Chlorophyta) to light intensity

Abstract

Plasticity gives plants the ability to adapt their morphology and growth to various environments. Environmental factors can lead to changes in the growth forms of algae. Halimeda opuntia was used as a model organism to determine the effects of highly irradiated and shade conditions in the field and its responses to low light conditions in the laboratory, which are known to be some of the main factors driving its morphological plasticity. To investigate the morphological and anatomical characteristics of the species, a total of 61 characteristics and 54 samples from Thailand, Japan and Indonesia were examined. In addition, we also tested the response under different light conditions in the laboratory. A phylogenetic tree was constructed using the tufA marker to confirm the species identification. We found that the thallus forms, branching patterns and segment shapes and sizes responded to the different light conditions. A brittle thallus network was found under shade conditions with low light intensity, while a compact thallus form was found under highly irradiated conditions. The H. opuntia segment shape was reniform under highly irradiated conditions, but its segments were adapted to be deeply trilobed in the lower thallus and tripartite shape in the upper thallus under shade conditions. The segment size also adapted; the segments in shaded areas were longer than those in sunny areas, which might have helped them increase their thallus height to ensure exposure to the high light habitat. This morphological variation and plasticity expanded our understanding of the range of H. opuntia plasticity present in the field and could help explain why this species is common and successfully colonizes various habitats worldwide.

Morphometric Analysis of Surface Utricles in Halimeda tuna (Bryopsidales, Ulvophyceae) Reveals Variation in Their Size and Symmetry within Individual Segments

“…The segments themselves are usually also highly variable within and among individuals of the same species. This variation is related to their position on the thallus [7], which may also be caused by environmental heterogeneity [8][9][10]. Recently, it has been shown that morphological variation of H. tuna segments is tightly constrained by the allometric size-to-shape relation [11].…”

Halimeda tuna (Bryopsidales, Ulvophyceae) calcification on the depth transect in the northern Adriatic Sea; carbonate production on the microscale of individual segments

“…These are apical, non-calcified segments and those from the basal part of the thallus that deviate from the species-typical shape. Plasticity of segment shape in response to environmental factors such as light availability ( Neustupa & Nemcova, 2018 ; Pongparadon, Nooek & Prathep, 2020 ) or wave exposure ( Littler & Littler, 2000 ; Kooistra & Verbruggen, 2005 ; Pongparadon, Nooek & Prathep, 2020 ) has also been described.…”

“…In general, calcification rate in Halimeda spp. is influenced by rate of photosynthesis, light, and nutrient availability ( Vroom et al, 2003 ; Yniguez, McManus & Collado-Vides, 2010 ; Pongparadon, Nooek & Prathep, 2020 ).…”

“…The shape of the segments can be a relatively plastic feature ( Vroom et al, 2003 ; Pongparadon, Nooek & Prathep, 2020 ). Verbruggen et al (2005) evaluated the utility of segment size and shape, assessed by geometric morphometrics and elliptic Fourier analysis, as diagnostic features in Halimeda specimens representing the five lineages of the genus delimited by molecular data.…”

Marine Benthic Algal Composition after 45 Years in an Urbanized Bay in Cebu, Philippines

“…Both species, however, have photosynthetic segments that are protected with a calcium carbonate layer, which might confer better resilience under environmental stress(Wei et al 2020). In addition, H. opuntia has been shown to survive in stressful conditions through the development of segment plasticity(Pongparadon et al 2020).Information on oceanographic conditions within Silot Bay is limited. Nonetheless, the impact of changes in oceanographic conditions over the years on algal flora within the bay may be inferred from observations made in other studies around the world.…”