''Iotrochota birotulata'', commonly known as the green finger sponge, is a
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
sea sponge
Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and are o ...
in the family
Iotrochotidae. It is found in shallow waters in the Caribbean Sea.
Description
The green finger sponge usually has upright or sprawling cylindrical branches that occasionally divide. The branches are about in diameter and can grow to in length. Young individuals and some large specimens have an encrusting habit. They grow over the surface of a rock in a layer a few millimetres thick with occasional short chimney-like outgrowths. Other individuals have a number of vertical tubes, each with a large opening called an
osculum
The osculum (: oscula) is an excretory structure in the living sponge, a large opening to the outside through which the current of water exits after passing through the spongocoel. Wastes diffuse into the water and the water is pumped through ...
at the end. These variations in growth habit led to the belief that several different species of sponge were involved. However, specimens growing in reef caves often have an encrusting base with a central, finger-like cluster of branches, so it is now believed that the different forms are a single species, perhaps differing in structure because of different environmental conditions.
In the branched form, the osculi are found on the upper side of the branches and may be slightly raised above the surrounding tissue. The consistency of the sponge is soft but resilient, and when squeezed, it exudes a purple fluid.
[ The general colour of the sponge is purplish black but there is often a layer of bright green cells on the ]epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...
. These have dendritic
Dendrite derives from the Greek word "dendron" meaning ( "tree-like"), and may refer to:
Biology
*Dendrite, a branched projection of a neuron
*Dendrite (non-neuronal), branching projections of certain skin cells and immune cells
Physical
*Dendri ...
patterns on the surface and cover sub-surface canals which lead to the osculi.
Distribution and habitat
The green finger sponge is found in the Caribbean Sea at depths varying from . Its range includes the West Indies, the Bahamas, southern Florida, Venezuela and northern Brazil, but it is absent from Bermuda.[ It inhabits ]reef
A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...
s, the deeper water outside the reef crests and the underside and surfaces of rocks in shallow bays.[
]
Biology
The golden zoanthid (''Parazoanthus swiftii''), a colonial coral, is often found twined round the sponge in a symbiotic
Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...
relationship. The polyps look like small sea anemone
Sea anemones ( ) are a group of predation, predatory marine invertebrates constituting the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemone ...
s and contain toxins which deter predatory
Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
fish from eating the sponge.[
]
References
{{Taxonbar, from=Q1892902
Poecilosclerida
Sponges described in 1877