Hidden Biology of Sponges and Ctenophores

These vocabulary flashcards cover the key biological structures, phylogenetic hypotheses, and glossary terms for sponges and ctenophores based on the provided lecture notes.

Hidden biology

The blind spots to complex traits in non-model species that lead to misconceptions about animal evolution and an underestimation of complexity in group's like Porifera and Ctenophora.

Ctenophora

A clade of marine animals characterized by $8$ longitudinal rows of ciliary paddles called combs, often referred to as comb jellies.

Porifera

A clade of sessile benthic animals known as sponges that filter bacteria and picoplankton through an aquiferous system.

Aboral end

The end of an animal that is opposite its mouth.

Choanoflagellates

Eukaryotic organisms that are the closest known relatives of animals, consisting of collar cells that live singly or in small colonies.

Choanocyte

Collar cells of sponges that form chambers to drive water through the sponge for feeding.

Clade

A monophyletic group of organisms.

Collar cell

A cell with a flagellum surrounded by a collar of microvilli used for feeding or sensory functions; found in sponges, choanoflagellates, and other animals.

Mesenchymal cells

Unpolarized cells dispersed in an extracellular matrix.

Mesoglea

A thick extracellular matrix found in many animals, including ctenophores and cnidarian medusae.

Monophyletic

A group of organisms comprising all descendants of their most recent common ancestor and no other organisms.

Picoplankton

Plankton on the order of $0.2-2 \text{ }\text{mm}$ (as stated in the transcript glossary) including bacteria and small eukaryotes.

Synapomorphy

An evolutionarily derived trait shared by multiple organisms that was present in their most recent common ancestor.

Coelenterata

A phylogenetic hypothesis placing Ctenophora and Cnidaria as sister groups, characterized by radial symmetry and two germ layers.

Acrosomata

A phylogenetic hypothesis placing Ctenophora as the sister group to Bilateria based on sperm and muscle structure.

Parahoxozoa

A clade comprising Placozoa, Cnidaria, and Bilateria.

Colloblasts

Specialized prey-capturing adhesive cells (glue cells) found only in ctenophores.

Apical organ

A domed structure at the aboral end of a ctenophore with bundles of cilia supporting carbonate secretions that serves primarily as a gravity-sensing organ.

Rotational symmetry

A symmetry pattern where any plane through the central oral-aboral axis divides the animal into two halves that match when rotated $180$ degrees.

Porocytes

Pore cells in the surface epithelium of sponges through which water enters the body.

Spicules

Articulated inorganic skeletons found in sponges made of minerals like silica or calcium.

Osculum

The excurrent opening of a sponge, often containing sensory cilia that monitor water flow.

Mesohyl

A middle collagenous layer in sponges containing motile cells.

Hexactinellid sponges

Also known as glass sponges, a group with syncytial tissues that uses calcium/potassium action potentials for rapid arrest of feeding currents.

Homoplasy

An evolutionary situation where a trait, such as the nervous system, has arisen more than once or been lost in one or more lineages.