gastrula

noun

gas·​tru·​la ˈga-strə-lə 

plural gastrulas or gastrulae ˈga-strə-ˌlē  -ˌlī 

: an early metazoan embryo in which the ectoderm, mesoderm, and endoderm are established either by invagination of the blastula (as in fish and amphibians) to form a multilayered cellular cup with a blastopore opening into the archenteron or by differentiation of the blastodisc (as in reptiles, birds, and mammals) and inward cellular migration compare blastula, morula

gastrular

ˈga-strə-lər 

adjective

Word History

Etymology

borrowed from New Latin (originally in a German context), from Greek gastr-, gastḗr "belly, stomach" + New Latin -ula (as in planula) — more at gastro-

Note: Word introduced by Ernst haeckel in Die Kalkschwämme, Band 1 (Berlin, 1872): "Mit dem Namen Gastrula oder Magenlarve belege ich denjenigen Entwickelungs-Zustand, welcher bei den Kalkschwämmen zunächst aus der Planula hervorgeht, und welcher meiner Meinung nach wegen seiner weiten Verbreitung bei den verschiedensten Thieren eine ausserordentlich grosse Bedeutung für die generelle Phylogenie des Thierreichs besitzt. Ich verstehe unter Gastrula eine kugeligen oder sphäroidalen, eiförmigen oder länglich runden Körper, welcher eine innere Höhle mit einer äusseren Oeffnung (primordialen Magenhöhle mit Mundöffnung) enthält …" (pp. 332-33). ("I designate by gastrula or stomach larva that developmental state which among calcareous sponges emerges at first from the planula, and which in my opinion possesses an extraordinarily great significance for the general phylogeny of the animal kingdom on account of its wide distribution among the most diverse animals. I understand by gastrula a globular or spheroidal, ovate or oblong body, which contains an inner cavity with an outer opening (primordial stomach cavity with mouth opening)…") Haeckel clearly modeled the word on planula—here used more or less with the meaning of the later term blastula—and thought of -ula as a suffix denoting a larval or developmental stage.

First Known Use

1876, in the meaning defined above

Kids Definition

gastrula

noun

gas·​tru·​la ˈgas-trə-lə 

plural gastrulas or gastrulae -ˌlē 

-ˌlī

: a cup-shaped three-layered early embryo formed from the blastula by the movement of layers of cells to establish the ectoderm, mesoderm, and endoderm

Medical Definition

gastrula

noun

gas·​tru·​la ˈgas-trə-lə 

plural gastrulas or gastrulae -ˌlē  -ˌlī 

: an early metazoan embryo in which the ectoderm, mesoderm, and endoderm are established either by invagination of the blastula (as in fish and amphibians) to form a multilayered cellular cup with a blastopore opening into the archenteron or (as in reptiles, birds, and mammals) by differentiation of the upper layer of the blastodisc into the ectoderm and the lower layer into the endoderm and by the inward migration of cells through the primitive streak to form the mesoderm compare morula

gastrular

-lər 

adjective