Aplanospore

Japanese: aplanospore

...When the hybrid between species is sterile, the resulting spores are usually abnormal and amorphous in shape and have a very low ability to germinate.
[Various spores]
There are two types of spores: planospores, which are motile zoospores with flagella, and aplanospores, which are non-motile spores without flagella. Zoospores are usually called zoospores and are found in green algae, brown algae, and phycomycetes.

From [Souco]

…the spores of algae and fungi are motile and have flagella. They are distinguished from immobile spores by the presence or absence of motility, but there is no difference between the two in terms of their position in the life cycle. Also, spores of land plants are not called immobile spores.

*Some of the terminology that mentions "aplanospore" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…種間の交雑によってできた雑種が不稔の場合は，それからできる胞子はふつう形は異常かつ不定形で，発芽能力も著しく低い。
［さまざまな胞子］
　胞子には鞭毛をもった運動性の動胞子planosporeと，鞭毛をもたない非運動性の不動胞子aplanosporeがある。動胞子はふつう遊走子とよばれ，緑藻，褐藻，藻菌類などにみられる。…