A trab is a structural element within a

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

formed by the fusion of dendroclones. In the Anthaspidellidae, when

spicules Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

(usually dendroclones) connect at their tips to form a ladder-like structure, trabs may be formed. Oxeas are sometimes employed in the central rod. Trabs have a feather-like structure, or may form rods. Trabs are usually regularly spaced, usually at sub-millimetric intervals. Further dendroclones may interconnect adjacent trabs, forming ladder-like structures. The presence and alignment of trabs is often related to the internal structure of canals within sponges.

References

Sponge anatomy {{sponge-stub