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Table 1 Fate of some larval structures during metamorphosis in studied phoronid species

From: Metamorphic remodeling of morphology and the body cavity in Phoronopsis harmeri (Lophotrochozoa, Phoronida): the evolution of the phoronid body plan and life cycle

Name of studied species and author of study

Fate of larval organs

Preoral lobe

Tentacles

Telotroch

Protocoel

“Actinotrocha A” (probably larva of Phoronopsis harmeri) [22]

transforms into small unpaired remnant that gives rise to the adult epistome

completely turns into definitive tentacle

retained for at least 4 days and then degenerates

? “…the existence of a coelomic epithelium in the juvenile epistome is impossible confirm or deny…”

Phoronopsis harmeri [15, 26, 27, herein]

is partly retained as two lateral remnants, which contribute to the future formation of the epistome

undergo partial reduction: the postroral ciliated band degenerates. Larval tentacles change neither in length nor number

retained for 9 days and then disappears

retained, but greatly reduces in size

Phoronis muelleri [23, 35]

retained as fold of the larval episphaere near the mouth and then turns into epistome

completely destroyed; adult tentacles arise from anlagen of definitive tentacles, which are located under the larval

is drawn into the digestive tract and becomes hindgut

cells, which form the lining of the preoral lobe are completely retained and give rise to the definitive protocoel

Phoronis muelleri [39]

?

completely destroyed; adult tentacles arise from anlagen of definitive tentacles, which are located under the larval

is drawn into the digestive tract and becomes hindgut

protocoel is present neither in larva nor adult

Phoronis psammophilla [24]

retained as fold of the larval episphaere near the mouth and then turns into epistome

completely destroyed; adult tentacles arise from anlagen of definitive tentacles, which are located under the larval

retained for several days and then disappears

?

Phoronis pallida [25]

completely destroyed

undergo great cellular death. Accordingly to figures, the length and number of larval tentacle greatly reduce. Definitive tentacles apparently arise from proximal portions of larval tentacles.

? can not be observed by SEM in juvenile just after the completion of metamorphosis. Apparently, the telotroch is drawn into the digestive tract

?

“Actinotrocha C” [38]

completely destroyed

thickened proximal portions are retained through metamorphosis and give rise to definitive tentacles

is drawn into the digestive tract

?

  1. ?” – the fate of larval organs unknown or not described in detail