What have I learned about Rowedota shepherdi since writing New Noodle Bar At Ardrossan?
As explained in New Noodle Bar At Ardrossan, Rowedota shepherdi was first named Trochodota shepherdi by (FWE) Rowe in 1976. According to “Marine Invertebrates of Southern Australia” Part I, edited by SA Shepherd & IM Thomas, FWE Rowe was from the Australian Museum in Sydney at the time (1982). They wrote the chapter on sea cucumbers in “Marine Invertebrates of Southern Australia” Part I.
(Photo taken by Brian Saunders)
It appears that the 1976 paper by FWE Rowe about the then Trochodota shepherdi, was titled Restriction of the chirodotid genus Trochodota Ludwig (1891) (Holothurioidea: Apodida), with the description of a new species from South Australia (Trans.R. Soc. S. Aust. 100, 203-6.
This, and three other papers by FWE Rowe are listed in the Selected Bibliography for sea cucumbers in “Marine Invertebrates of Southern Australia” Part I, one of them as co-author with DL Pawson in 1967, plus another one co-authored with AM Clark in 1971.
In the introduction to the chapter on sea cucumbers in “Marine Invertebrates of Southern Australia” Part I, Rowe said that tubefeet are absent in apodids (Order Apodida) such as Trochodota and “The food-catching tentacles surrounding the mouth are modified tube feet.”
According to the Key to Orders in “Marine Invertebrates of Southern Australia” Part I, in the Orders Apodida & Molpadiida, “Body wall thin, translucent; no tube-feet but papillae (not modified from tube-feet) may be present; twelve pinnately divided tentacles surrounding the mouth (Fig. 10.27c”.
Trochodota shepherdi is the last species listed in the Key to Species in “Marine Invertebrates of Southern Australia” Part I. The comment in that key read, “Larger forms, black/olive-green in life; sigmoid (curved) hooks with small spines”.
“Marine Invertebrates of Southern Australia” Part I, describes Trochodota shepherdi as “A black species reaching a length of about 60mm and closely related to (Trochodota allani). It occurs in Spencer Gulf and Gulf St Vincent, SA to a depth of 10m.”
Fig. 10.37(b) illustrates the wheel (spicules) and sigmoid rod of (then) Trochodota shepherdi
(Source: “Marine Invertebrates of Southern Australia” Part I
Sea cucumber chapter by FWE Rowe)
As Trochodota shepherdi in “A field guide to the marine invertebrates of South Australia”, the species is described as ‘90mm long’, ‘delicate’, ‘very dark brown to black’, ‘lacks tube feet on body surface’, ‘uses tentacles for feeding and to move the animal along’, ‘found in sand, on sheltered to moderately exposed coats; 0-12m depth’.
The species, as Trochodota shepherdi, belongs to the family Chiridotidae, and was described by Rowe in 1976. I’m guessing that the species was named after/for Dr Scoresby Shepherd. Its CAAB code is given as 25 432012.
If I follow the two keys in “Marine Invertebrates of Southern Australia” Part I for Trochodota (Rowedota) shepherdi correctly, I find:
“Body wall thin, translucent; no tube-feet but papillae (not modified from tube-feet) may be present; twelve pinnately divided tentacles surrounding the mouth = Orders Apodida & Molpadiida.
10-12 tentacles, with two but usually more pairs of lateral digits; spicules include anchors, wheels and/or sigmoid hooks.
Body wall with wheels and curved (C-shaped) rods or sigmoid hooks.
Spicules include wheels.
Spicules include wheels and sigmoid rods.
Wheels with teeth in groups around the inner rim.
Larger forms, black/olive-green in life; sigmoid (curved) hooks with small spines.
Twelve pinnately divided tentacles surrounding the mouth
(Source: “Marine Invertebrates of Southern Australia” Part I
Sea cucumber chapter by FWE Rowe)
(Photo taken by Fiona McQueen)
Comments made against a posting of Rowedota shepherdi on iNaturalist include:
“Interesting that it’s considered critically rare in Victoria, ….. I’m not too familiar with the genus, but FWIW there’s an interesting short article on the MLSSA website about a localised high density of R. shepherdi (presumed, but the article images support the ID) found recently by 2 freedivers at Ardrossan SA.”
“Agreed. I mentioned the peculiar critically rare status of R shepherdi in Victoria to Lauren and Fi (on Facebook) when they found hundreds of these at Ardrossan recently, because I don’t think it is critically rare. Probably ended up with that status in Victoria in the 1990s / early 2000s when a lot of species were listed, because it hadn’t been found in abundance during widespread searches for echinoderm. The O’Hara report comes to mind. But we know abundances change over time! It seems to thrive in areas with short seagrass and lots of sediment (being a detritivore). Note the interesting recorded distribution so far in SA.”
(Photo taken by Fiona McQueen)
Comments added to the article on the MLSSA website include:
“I’m tempted to speculate that this Ardrossan population explosion, which is probably a short-term phenomenon, is a relatively new event and may be anthropogenic for a number of potential reasons including climate change, anthropogenic disruption of predator prey balance, habitat disturbance, etc.. Jetties, wharves and piers anecdotally are often places where such population explosions are observed. One example is those unusual anemones and, to a lesser extent, a somewhat more warm temperate to tropical holothurian I wrote about several decades ago under Port Lincoln’s town (public) jetty (All the Way with Port Lincoln Jetty ).
(Header photo taken by Fiona McQueen)
My thanks go to FWE Rowe, Fiona McQueen & Brian Saunders for the use of their photos & drawings.)