Posted: May 8 2015
Harpa harpa Linnaeus, 1758
Background on species presentations and a comparison of species features
The contemporary seminal work on world-wide Harpa is Harold Rehder’s monograph The Family Harpidae of the World (1973). Rehder presented 11 species of living Harps. There have been many new taxa proposed since 1973. All but one are now generally accepted as forms of one or the other of the 11 species addressed by Rehder. Only Harpa goodwini Rehder, 1993 is mostly accepted as a valid addition to his 1973 list. Whether or not all 11 of the taxa addressed by Rehder (plus H. goodwini) are truly separate species or if the many localized forms given species/subspecies names actually represent separate species will have to await a comprehensive DNA analysis.
I intend to present all 12 of Rehder’s taxa, plus two synonyms of H. major (H. conoidalis and H. kawamurai) and H. amouretta form crassa because of their popularity. Although Rehder argued that H. davidis was distinct from H. major, principally due to a comparison of the dark parietal blotches (three for H. davidis and two for H. major), I have found that too many H. davidis from the Bay of Bengal display the blotch pattern of H. major (two or one blotch) to be able to accept his argument. I would also note that the characters described for H. kawamurai Habe, 1970 from the Philippines (swollen, widely spaced thin ribs) closely coincide with other features Rehder noted to distinguish H. davidis from H. major (“body whorl … more broadly ovate and rounded,” “ribs tend to be narrower and more distant”). My own opinion is that H. davidis should be treated as a regional variation of H. major until a comprehensive DNA analysis demonstrates otherwise.
Here is a list of the Harpa species addressed by Rehder and the "accepted" species addressed 31 and 42 years later.
Okon, Moshe E. 2004. The genus Harpa revisited. American Conchologist. Vol. 32 (3), 4-13.
Rehder, Harold A. 1973. The Family Harpidae of the World. Indo-Pacific Mollusca, Volume 3, No. 16. Delaware Museum of Natural History.
WoRMS Editorial Board (2015). World Register of Marine Species. Accessed 2015-01-22.
My opinion is that most of the gross characters of Harpa are quite variable within populations and across geographic range. So variable that they occur readily across taxa, especially those that share common geographic distributions and influences, and most often cannot be relied upon to distinguish between species when confronted with a particular specimen. In my presentations I have limited the features discussed to those that should be relied upon to distinguish among taxa. I have presented the protoconchs for all, but did not find this feature to be helpful (too variable, too often missing or incomplete, and too similar) in distinguishing among taxa, except in a few cases (H. gracilis and H. goodwini). I did not find color to be helpful for taxa that are otherwise close and from the same locales. I did not find reliance on “blotching” to be more than partially helpful without linkage to other confirming features. I have addressed the distribution of parietal glazing and found it to be quite helpful and distinctive for many taxa (especially when linked to other features), but not decidedly so for the most problematic taxa (H. major and H. davidis). I do not present a general description of each taxa, which is available many places elsewhere (see Rehder 1973). Rather, for some I present some background information and then start my descriptions with the parietal glazing and follow with those features that I found can best be used to distinguish among taxa.
The following table presents the features I found best allow identifying and distinguishing the 12 taxa. The green cells describe key features that should be identified first (and in some taxa, alone or linked to other “greens,” are sufficient to identify a taxon). The pink cells describe features very helpful in narrowing the possibilities for otherwise similar taxa. The yellow cells describe features that I found very consistently separate taxa within the geographic range of H. major from H. major. I apologize for the tiny text in the table, but I wanted to get it all on one page.
My presentations and conclusions are principally based upon observation of my personal collection, which includes one specimen of H. goodwini, six of H. gacilis, four of H. costatus, and from a dozen to several dozen for the others, limited examination of shells displayed at shell shows by exhibitors and dealers, some images from the web (usually too poor to be helpful), and images in literature (also usually also too poor to be helpful). Obviously, my sample is limited in terms of actual material for close examination, and my conclusions should be tempered accordingly. I would be happy to hear from those with specimens in any of these taxa that question or confirm my observations (email@example.com). However, I would also hope that you can provide good quality photos or would be willing to loan the specimens for a photo session. I will continue to add to these presentations with comments or more photos/material contributed by other fans of Harpa.
I have made some specialized use of terminology in describing Harpa. Three terms (subsutural plateau, shoulder and T) should be understood. Normally, “shoulder” refers to the area from the suture to an inflection point (a pronounced downward angle) or, when absent, the periphery. All Harpa have inflection points rather than smoothly curving profiles. So, for Harpa, the shoulder would normally be the area from suture to the inflection point (where spines are located). I have defined the area from the suture to the inflection point as the subsutural plateau. And, when I refer to the shoulder, I am referring narrowly to the spiral line representing the inflection where the subsutural plateau turns downward (and is where the rib spines normally occur). I have observed that all mature Harpa, except H. gracilis, have essentially four teleoconch whorls. H. gracilis has three. As a matter of shorthand I may use T1, T2, T3 or T4 to refer to the teleoconch whorls. So,
T1 = the first teleoconch whorl after the protoconch
T2 = the second teleoconch whorl (antepenultimate whorl)
T3 = the third teleoconch whorl (penultimate whorl)
T4 = the body (adult) whorl.