Conspicuous Sea Cucumbers

Description:

Dark red-black thin-walled sea cucumbers, with prominent feeding tentacles, ~ 1 inch (2-3 cm) diameter and of length up to two feet (60 cm).

Habitat:

Near shore, shallow, tidal tropical harbor water ecosystem, with bottom of sand, shells, silty estuarine sediment, small rocks, coral rubble and undifferentiated detritus.

Notes:

Spotted in about six inches of water off the west shore of the Pearl City Peninsula, 10 - 30 feet south of the foot of the old PanAm Clipper Pier in Pearl Harbor. I’ve observed these creatures in that locale for decades. I observed them many times as a teenager in the 1950s when I went out onto the pier with my brothers. (In our ignorance, we referred to these creatures, because of their seeming blood-red color, as “bloodsuckers”. In conversation with a man who lives in the area, I discovered they are still so-called.) I observed some when I went fishing off the pier with my son in the 1980s. Although the pier is still standing, access to it has been blocked for many years–it's structurally unsound--but access the shoreline at its foot is not. And just off of that shore is where, as I expected, this species may still be found. Obtaining the spotting was the easy part. Obtaining a species ID which I believe is correct has been difficult Initially, I thought they were Conspicuous Sea Cucumbers, Opheodesoma spectabilis, which are reportedly common in Pearl Harbor (and Kaneohe Bay). See: Hoover, John P., Hawaii’s Sea Creatures, A guide to Hawaii’s Marine Invertebrates. Honolulu, Mutual Publishing, 1999, p.335. This spotting has the same general appearance as the image in Hoover, but the wrong color. Hoover reports it as “bright pinkish orange” (at its darkest) to almost white. Some pictures I’ve seen online show a darker coloration, but the significant factor is the variation in color across those images. http://hbs.bishopmuseum.org/good-bad/sea... http://eol.org/pages/2984384/overview http://www.marinelifephotography.com/mar... I have never seen variation in color in the creatures found at the spotting location. There, all the individuals I’ve observed have had a uniform dark red-black color, darker than what I’ve seen online. Finally, although O. spectabilis was reported as collected in Pearl Harbor in a Bishop Museum study, it wasn’t reported as collected at the location of this spotting, and one of the study’s collection sites was at exactly the same place. How (rhetorical question), could something so commonplace not be collected? http://hbs.bishopmuseum.org/pdf/PHReport... I considered Keferstein’s Sea Cucumber, Polyplectana kefersteinii as well. It is also described in Hoover, also on p. 335. Additionally, other sources reported it as occurring in Hawaii. http://www.marinespecies.org/aphia.php?p... http://eol.org/pages/2988098/overview http://eol.org/pages/2988098/maps Its color in Hoover matched the color of this spotting, as did its color in images found online from Réunion Island and Australia. https://commons.wikimedia.org/wiki/File:... http://species-identification.org/specie... But there were problems also: The Bishop Museum study did not list P. kefersteinii as having been collected in Pearl Harbor, at any of the 15 collection sites. Hoover reported it as occurring at depths > 6 m, and that it hides during daylight. Sealifebase.org describes it as “demersal”, which I’ve found defined as deeper than 20 m. http://www.sealifebase.org/summary/Polyp... The Encyclopedia of Life describes it as a benthic species that hides in crevices during the day and emerges at night to forage. At the spotting site it is neither benthic nor nocturnal, and never has been. http://eol.org/pages/2988098/details I may be too picky, but I found enough information about the appearance, behavior and distribution of both species that “didn’t jive” (never mind that some information I found contradicted other information at the same website), either with my memories across 60 years or with my spotting last week, to prevent me from deciding on Opheodesoma spectabilis for nearly a month. In the end, although my decision wasn't scientifically rigorous, relying as it did on negative evidence, I decided, because everything about this spotting, except color, "fits" the available descriptions of O. spectabilis, and because all other candidate species have been eliminated, to go with that ID. In other words, I decided to ignore the (for me) problematic fact that, given the presence over many decades of so many easily observable individuals at the spotting site, all of which are dark red black, none of the resources I've consulted report that the color range of O. spectabilis includes dark red black.