Temperature requirements for the growth and maturation of the gametophytes of Undaria pinnatifida and U. undarioides (Laminariales, Phaeophyceae)

Abstract

Gametophytes of two Undaria species, U. pinnatifida and U. undarioides (Laminariales, Phaeophyceae), were studied to determine their water temperature requirements in order to understand their different distributions in Mie Prefecture, Japan. The optimal temperature for growth was 20 ° C for gametophytes of both species, and the upper critical temperature for growth was also the same for both species at 28 ° C. Therefore, the optimal and critical temperatures for growth of the gametophytes are not the main factors determining distribution. The optimal temperature for maturation of U. pinnatifida was approximately 10-15 ° C, whereas it was closer to 20-21 ° C for U. undarioides , a difference between these species of at least 5 ° C. In autumn and early winter, the seawater temperature at the mouth of Ise Bay, where U. pinnatifida is distributed, ranges from 21.6 ° C (October) to 12.7 ° C (December), and off Hamajima, where U. undarioides is found, the range is from 22.7 ° C (October) to 19.1 ° C (December). The seawater temperatures from October to December, which is the maturation season for the gametophytes, agreed well with the optimal temperature requirements for maturation of the gametophytes of both species. Thus the difference in the maturation temperature range of the gametophytes is a major factor determining distribution of these Undaria species along the Japanese coast.

Macro-environmental modelling of the current distribution of Undaria pinnatifida (Laminariales, Ochrophyta) in northern Iberia

“…The gametophyte stage of this species persists over the summer, and can survive long periods while waiting for optimal conditions in order to mature. Gametophyte development occurs once water temperatures drop below 20°C, with an optimum range between 10 and 15°C (Morita et al 2003a). Mature gametophytes undergo sexual reproduction to produce embryonic sporophytes that subsequently develop into macroscopic individuals.…”

Effects of daylength, irradiance and settlement density on the growth and reproduction of Undaria pinnatifida gametophytes

“…After settlement, gametophytes still grow in the daylength of 12-15 h (June-September) and may mature in October (a daylength of 12 h) because young sporophytes appear between October and November in the field. It is well known that seawater temperature is the most important factor determining the growth and reproduction of U. pinnatifida gametophytes (Morita et al, 2003). In the present study, the culture temperature (16 • C) was optimal for the growth and maturation of U. pinnatifida gametophytes (Akiyama, 1965;Fang et al, 1982), but the fertility of the females was quite low under the long-day condition of 16 h light per day, as reported by Akiyama (1965).…”

“…The optimal temperature for the growth and maturation of U. pinnatifida gametophytes is approximately 15-20 • C and they are positively correlated with the irradiance within 10-80 µmol photons m −2 s −1 (Akiyama, 1965;Morita et al, 2003). The daylength responses on the growth and maturation of U. pinnatifida gametophytes have also been observed (Akiyama, 1965).…”

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“…Por otro lado, está más que demostrado que estos gametófitos se ven estimulados tanto en crecimiento como en maduración sexual por las variaciones estacionales de temperatura e irradiancia lumínica (Morita & al., 2003;Choi & al., 2005), lo que hace pensar que, según dónde se encuentren, su cronología del desarrollo y maduración sea distinta. Esto podría dar una explicación a la distinta intensidad nu- mérica observada en las dos fases principales de reclutamiento.…”