Seasonality and thallus ontogeny of edible seaweed Monostroma latissimum (Kützing) Wittrock (Chlorophyta, Monostromataceae) from Tosa Bay, Kochi, Japan

Abstract

Monostroma latissimum (Kützing) Wittrock is an intertidal rock-dwelling green algal species of commercial importance in Japan. This article reports on the seasonality of its growth and occurrence from three distinct habitats of marine and estuarine regions in Tosa Bay, Japan, for two consecutive growth seasons. Thallus lengths of individuals and environmental parameters were monitored monthly between November 2005 and July 2007. Culture studies were carried out to establish the species-level identity of the specimens. Nuclear encoded ITS 1 (Internal Transcribed Spacer 1) sequences reveal that the naturally occurring strain of M. latissimum has identical nucleotide sequences to those of the commercially cultivated strain from the Shimanto river estuary. We have also found that the two strains are cross-fertilizing. Seasonal fluctuations in thallus length were found to be distinctive to the habitat where the strain grows and re-occur annually. Algal cover was highest during winter months and lowest during the summer. However, we found only a very weak positive correlation between chosen environmental parameters and thallus length. Appearance and decay of thalli occurred earlier in high saline habitats. Therefore, it is likely that salinity influences the maturation of microscopic sporophytes or the growth and survival of germlings in M. latissimum.

Concise review of green algal genus Monostroma Thuret

“…Various life stages are known; sexual forms (dioecious/monoecious, isogamous/anisoganous) and asexual forms without a codiolum/cyst stage or with a codiolum/cyst phase (produced via parthenogenetic female pseudo-gametes). A monomorphic asexual lifecycle in this genus has also been reported from a population in Japan (Bast et al 2009b). In this lifecycle, there is no sexual fusion and the swarmer germinates directly without passing through the sporophyte stage (Fig.…”

“…Three distinct thallus types (inner-bay type, estuary type, and opensea type) of Monostroma have been characterized based on the habitat (Kida 1990). Physico-chemical characteristics such as temperature, irradiance, salinity, nutrient level and biological (presence or absence of grazers) characteristics of the habitat or a combination of these factors could cause these habitat-dependent differences (Bast et al 2009b). Wave action might be a limiting factor as it is shorter in wave-swept habitats than in sheltered ones.…”

Rethinking competence in marine life cycles: ontogenetic changes in the settlement response of sand dollar larvae exposed to turbulence

“…Less attention has been given to a second feature regarding the timing of competence: namely, when the competent period begins, and what controls its onset. The common observation across marine invertebrates (and even marine fish and some algae [66][67][68][69]) is that dispersal stages pass through an obligate precompetent period during which they are incapable of responding to cues and settling to the sea floor. The transition in marine invertebrate larvae from precompetence to competence has been described as being 'pre-programmed' [12][13][14][15], in the sense that there is a certain degree of growth and/or differentiation that must occur before the larva is even capable of undergoing settlement.…”

Taxonomic identification and life cycle comparison of two populations of the monostromatic green algae Monostroma nitidum

“…Members of the genus Monostroma (Chlorophyta, Ulvophyceae) stand out as the most cultivated species of green seaweed with widespread distribution in warm inner bays and estuaries (Bast et al., 2009a , 2009b ; Leliaert et al., 2012 ), and are valued for delicious taste and rich nutritional value (Gupta et al., 2015 ; Nisizawa et al., 1987 ; Pise et al., 2012 ). Monostroma polysaccharide extract is widely used in the production of marine medicines, healthcare products, cosmetics, and various industrial applications (Hoang et al., 2015 ; Karnjanapratum & You, 2011 ; Lee et al., 2010 ; Tako, 2017 ).…”

“…In 2009, Bast et al. reported that the early development of M. latissimum was characterized by a filament‐blade asexual life cycle (Bast et al., 2009a , 2009b ). Analysis of nuclear‐encoded rDNA revealed consistency in the ITS1 sequences of asexual and sexual M. latissimum .…”