No. 63–The Enigmatic Porifera Part II

Make sure you check out the first part of this discussion, The Enigmatic Porifera, Part 1.

The enigmas surrounding the natural history of the sponge family are rivaled by the tremendous diversity and variety of species found within it. We are presented with an astounding kaleidoscope of shapes and colors guaranteed to intrigue even the casual observer.

Sponges follow one of three basic anatomical designs. The most primitive and simplest of these is called asconoid. Species of this design may be cylindrical or tubular with some having multiple tubes and others with a network of tubes. All are tiny, 1mm in diameter; because the aquiferous system of this design does not scale up efficiently regarding water volume and movement.

The syconoid design is a step the structural efficiency ladder allowing for somewhat larger species, one to a few cm, but they retain the radial symmetry of the asconoids that preceded them. The primary difference is in the structure of the lining of the central cavity known as the spongocoel. Whereas it is smooth in the asconoid design, it is crinkled, so to speak, in synconids. The advantage is a greater surface area supporting larger numbers of choanocytes* responsible for water movement and feeding.

The third and most highly developed structural design is found in leuconoid sponges. These evolved from the syconoid line transforming the spongocoel from a single chamber into a network of smaller chambers containing sets of choanocytes. This reconfiguration provided the ability to pump life giving water in higher volumes at greater efficiency. Radial symmetry and the restrictions it placed on growth was abandoned giving rise to the remarkable variety of shapes and sizes known today.

The vast majority, 90 to 95%, of extant sponges are leuconoid. Some grow quite large like the massive loggerhead sponge at up to six feet across and half as deep. A few of the wide variety of shapes that have evolved include multiple finger-like projections, bowls, tubes joined together, vases, balls, amorphous globs – and the list could go on. There are encrusting sponges and sponges with chemical defense mechanisms. Their variety in color rivals the most chromatically ostentatious painter’s pallet. If you ever want to get lost in a strange world for a few minute to a few hours, type in porifera and hit search and see where it takes you.

While it’s true the more spectacular of the species of porifera inhabit reef environments in tropical seas, there are a few rather interesting species that may be observed locally.

The yellow boring sponge (Cliona celata) may be seen, if you look closely enough, around oyster beds on low tide. They are the small, 1 to 5mm, bright yellow bumps on oyster shells. They have specialized cells that excavate and expel the calcium carbonate one tiny chip at a time creating a fox hole home in the shell. I’ve found no record of their being a problem locally but they and another closely related species have had a devastating effect on oyster fisheries in the Chesapeake and elsewhere. If you find a shell that looks like it’s been riddled with buckshot, you’re observing the handiwork of the boring sponge.

Often, in my intertidal wanderings, I come across red beard sponges (Microciona prolifera) that have been broken lose from their subtidal holdfast and left stranded. Their bright orange-red color makes them easy to spot even from a distance. Structurally they are a dense grouping of intertwining branches that can reach 8″ in length and have an overall mass the size of a large cabbage. They provide relatively safe habitat for small and juvenile fish and many small shrimp and other crustacean species. They may be most easily observed growing on dock floats and pilings.

The red beard was the first species laboratory tested for its regenerative powers. Specimens were pressed through a fine mesh screen into containers of sea water where over time individual cells moved about attaching to each to eventually reconstitute a complete structure. Scientific studies continue to explore the implications this amazing property demonstrated by a lower life form may have for medical science.

The brown finger sponge occasionally washes ashore on our beaches. It has a single holdfast attachment base with multiple finger-like pliable projections of varied length reaching up to several inches. I’ve had no success trying to determine its genus and species and learn more about the apparently common creature after a long and frustrating search of the web. Deadlines are deadlines. I’ll continue the search, however, and hopefully include it in a future Potpourri column.

With much of my attention devoted to other duties, it’s taken two months for me to even partially understand how truly complicated these supposedly simple creatures are and then find the words to share what I have learned with those of you, who like myself, lack the scientific background to easily comprehend the cumulative esoteric knowledge available. I am ever humbled by the task of trying to interpret and translate the observations and writings of minds far greater than mine and who often find themselves in dispute. In the end I have come to understand that the origin, meaning and future of life on earth is a puzzle to even the most knowledgeable. I take some margin of comfort in that – so should we all.

*Choanocytes – structures with flagella that help to swish water through the sponge to deliver food and oxygen to its body cells and carry away wastes. Courtesy of Wikipedia.