# Laminar _Ulva_ Species: A Multi-Tool for Humankind?
## 2 The Biology of _Ulva_ sp.
### Reproduction  
Reproduction can occur both sexually and asexually (Figure 2). The life cycle is isomorphic and biphasic, where the multicellular adult sporophyte and gametophytic phases are morphologically similar but genetically different, as sporophytes contain twice the level of nuclear DNA (2C) and number of chromosomes (2N) per cell as gametophytes (1C or 1N) [2; 4].  
Figure 2: Typical life cycle of _Ulva_ sp.  
Sexual reproduction involves the production of haploid biflagellate gametes that fuse during copulation, resulting in the formation of a diploid zygote. This zygote then develops into a diploid multicellular adult sporophyte thallus. As these typical vegetative cells mature, they transition into zoospore mother cells, which undergo meiosis to produce haploid quadriflagellate zoospores. These zoospores germinate and give rise to haploid male and female isomorphic adult gametophytic thalli through mitosis. At maturity, these thalli once again produce their respective gametes through mitosis. This reproductive process is termed a \"haploidinotic\" life cycle (Figure 2). Both zoospores and gametes have no cell walls and are described as naked and are produced mainly in cells at the end of the thallus [2; 4].  
A difference in the duration of the division stages was reported; for example, the 4-cell and 8-cell states last longer in the gametophyte than in the sporophyte, which is evident from the greater DNA synthesis during this period in the gametophyte [13]. Ca-metophytes' multicellularity allows them to create significant quantities of photosynthesis and so produce a bigger number of gametes (potential sporophytes) than unicellular haploids. Ulvaleans' widespread ecological success is most likely aided by the alternation of multicellular generations [2].  
Algae of the genus _Ulwa_ are opportunistic and have similar reproductive characteristics compared to \"selected\" species: many spores released by the reproductive cycle, small spores (approximately 10 \(\upmu\)m), a wide range of dispersive potential (flagellates), and fast growth and short life cycles.  
[PERSON] et al., in 2022 [14], conducting research on gene expression during the various stages of gamete formation in _Ulwa_ sp., found that 8296 distinct genes (62.2% of annotated genes) were expressed during gametogenesis, with relatively low variation in the total number of expressed genes between time points, ranging from 7146 (0 h) to 7949 expressed genes (72 h). They also identified 6056 differentially expressed genes (DEGs) between any two of the five time periods (0 h, 6 h, 24 h, 48 h, 72 h) during gametogenesis, accounting for 45% of the annotated genome. They also obtained consistency with results from [PERSON] et al. [15], where the analysis of DNA synthesis carried out during gametogenesis observed that DNA replication begins 25 h after induction.  
In 2018, [PERSON] et al. [16] documented a haploid genome of 98.5 Mbp (comprising 12,924 protein-coding genes) in _Ulwa compresa_, previously known as _Ul. mutabilis_. Through the construction of a phylogenetic tree using a concatenated alignment of 58 nuclear protein-coding genes (totaling 42,401 amino acids), _Ulwa_ was determined to be closely related to Chlorophyta. The identification of specific features such as ecotypic genetic variation in bloom-forming organisms will aid in our comprehension of the molecular pathways involved in growth and reproduction in response to environmental conditions [13; 16].