Functional disposition of the lophophore in living Brachiopoda

Abstract

Emig, C. C. 1992 07 15: Functional disposition of the lophophore in living Brachiopoda. The shape and disposition of adult brachiopod lophophores relate to in‐ and excurrent apertures. to the internal water irrigation system, to shell orientation at substratum and to near‐bottom currents. The arrangement of the mantle canals and gonads of different lophophores are induccd by water circulation. The trocholophe (2% of living species) is considered as a plesiomorphic character which represents the basic plan of the lophophore, shared by all Lophophorata. Three different types of schizolophe (10%) are represented in terebratuloids, thecidioids and discinids. The spirolophe (19%), characteristic of rhynchonellides and most inarticulate brachiopods, except the schizolophe Pelagodiscus, has evolved divergently into specific arrangements of the mantle canals and gonads. The zygo‐plectolophe (67%) is characteristic of most Terebratulida. The ptycholophe (2%) probably evolved independently in Megathlris and the thecidioids. The mesolophe, known in the fossil chonetdceans, is considered to be a primitive zygo‐plectolophe. The median brachiopod sulcus increases the efficiency of the excurrent system and is considered as an evolved character but a homoplasy within the brachiopods. The characteristics of Recent lophophore types have to be taken into account when reconstructing the lophophore in fossil forms. Brachiopoda, Lophophorata, lophophore, water system, orientation, evolution.

Brachiopodes actuels : historique et révision de la collection D.-P. Œhlert (Laval) ; brachiopodes des côtes françaises métropolitaines

“…Le lophophore est une extension formée de tentacules, qui entoure la bouche, pas l'anus (voir Emig, 1992) ; ses fonctions sont dans la capture des particules alimentaires et dans la respiration grâce aux courants engendrés dans la coquille par les battements des cils des tentacules (figure 23). La forme du lophophore des brachiopodes varie en complexité selon les espèces et au cours de la croissance (voir Emig, 1992) : trocholophe (2% des espèces vivantes) est un caractère primitif ; schizolophe (10 %) présent chez des téréb ratuloidés, thécidioidés et discinidés ; spirolophe (19%) chez des rhynchonellidés et chez la plupart des linguliformes et craniiformes ; zygo-plectolophe (67%) est caractéristique des térébratulidés ; ptycholophe (2%) chez Megathiris et des thécidioidés.…”

Brachiopoda

“…Beyond differences in their mineralized parts, there are also morphological and functional differences in brachiopods' main feeding and respiratory structure, the lophophore, which can be composed of looped, spiraled, or U-shaped fi elds of ciliated tentacles (Emig 1992 ). Only rhynchonelliform brachiopods support the lophophore with calcifi ed support structures called brachidia, whereas all other brachiopods use only musculature and connective tissue.…”

Evolutionary Developmental Biology of Invertebrates 2

“…Craniiform brachiopods (e.g., Novocrania ) also have calcitic shells, but the shells of linguliform brachiopods (such as the lingulid Glottidia and the discinid Discinisca ) are composed of apatite, a phosphatic mineral, with an outer layer of chitin (Williams et al 1997 ). Beyond differences in their mineralized parts, there are also morphological and functional differences in brachiopods' main feeding and respiratory structure, the lophophore, which can be composed of looped, spiraled, or U-shaped fi elds of ciliated tentacles (Emig 1992 ). Rhynchonelliform brachiopods are often attached to hard substrata by the rigid pedicle with their ventral valves oriented upward (Richardson 1997 ).…”