Amynthas diffringens (Baird, 1869)

Blakemore, Robert J., 2013, Megascolex (Perichaeta) diffringens Baird, 1869 and Pheretima pingi Stephenson, 1925 types compared to the Amynthas corticis (Kinberg, 1867) and A. carnosus (Goto & Hatai, 1899) species-groups (Oligochaeta: Megadrilacea: Megascolecidae), Journal of Species Research 2 (2), pp. 99-126 : 109-112

Amynthas diffringens (Baird, 1869)

( Figs. 8-10 )

Megascolex (Perichaeta) diffringens Baird, 1869a: 40 , fig. 1. [Type locality and habitat: a hothouse nursery at Plas Machynlleth (house), North Wales. Types in British Museum: BMNH 1869 :1:2:1 inspected as described below].

Perichaeta diffringens : Vaillant, 1872: 322. [Described with caeca present, prostates absent, four pairs of spermathecae but he miscounted segments (5/6/7/8/9?) as “3/4/5/6/7”].

Pheretima diffringens : Kobayashi, 1938: 158; Gates, 1939: 430 (syns. divergens var. yunnanensis , divergens (part. inc. Japanese types?), heterochaeta , mirabilis ); Gates, 1943: 102 [with genital markings on 7-9 midway between furrows and setal arcs, hearts of 10 lacking, prostate glands absent but gential marking glands in 18 just median to prostatic ducts cf description below]; Chen, 1959: 9, text-fig.; Gates, 1972: 149, footnote 2: [?syns. (some in part) californica, campestris , cingulata, clerica , corticis , divergens , heterochaeta , heteropoda , indica , mirabilis , molokaiensis , nipponica , peregrina ,

27rhs

perkinsi , sanctae -helenae, silvestrii , tajiroensis , torii, ? carnosa , ? directa , ? homoseta ,? kyamikia, ? morii , ? oyamai , ? pingi ]; Gates, 1972: 177 (syn. heterochaeta , divergens yunnanensis, mirabilis ); Gates, 1972: 217 (?syn sheni ); Gates, 1972: 18, 27 (syn. divergens , heterochaeta , heteropoda , indica , nipponica , oyamai , tajiroensis , ? toriii ); 1982: 44.

Amynthas diffringens : Easton, 1979: 119 (syn. ? subquadrangula ); Hong & James, 2001: 92 (i.e. more than 20 years after it was shown to be a synonym of A. corticis !).

Megascolex (Perichaeta) Sanctae -Helenae Baird, 1873: 96. [From high ground at St Helena, I. or J.C. Melliss, Esq. Type in British Museum: BMNH 1869 :6:16:5 - inspected by RJB 24.IV.2012 and 17.VI.2013 found to be juvenile, 40 mm long with 104 segments, damag- ed by dissection with spermathecae and prostates absent or removed, status: incertae sedis]. Baird gives the impression that more than one specimen was found, only one now remains. His description in full :

“ Body consisting of about 86 rings, which are more distinct at the two extremities than in the centre. The 11 or 12 rings at each end, have an acute ridge or keel in the centre; those of the middle portion of the body have the keel flattened. The body of the rings is finely striated. Setae short, of a dark colour at the posterior extremity, rather distant from each other. In the centre of the body and at the anterior extremity they appear (in the specimen from which this description was drawn up) retracted, leaving only a mark where they are situated. The first 7 or 8 rings, at the anterior extremity, are strongly rugose or wrinkled. Length from 1 inch and 9 lines to 3 inches. Hab. High ground at St. Helena, J.C. Melliss, Esq.”]. [Type locality St Helena. Type in British Museum: BMNH 1869 : 6:16:5. Held incertae sedis by Michaelsen (1900: 518) with which I now concur] .

Pheretima divergens var. yunnanensis Stephenson, 1912: 274 . [Type locality: Tengyueh, Yunnan; type in Indian Museum according to Gates (1939: 430-431) and “quite clearly” a synonym of P. diffringens hence its inclusion here, now questionable].

Note. Gates (1939: 340) also inspected Pheretima barbadensis BMNH 1904 :10.5.1219.1228 from Hong Kong that he later (1939: 446, 454) said also contained specimens of P. hawayana and P. morrisi ; Pheretima morrisi 1904:10.5.453 also from Hong Kong that he also later listed (1939: 446, 454) as containing P. hawayana !; from US National Museum Pheretima corrugata Chen, 1931 (part. - a paratype from Szechuan inspected by Gates, 1939: 340, not holotype). Therefore the name is debatably a junior synonym, although the paratype was “rather obviously to be referred to P. diffringens ”.

Material examined. Types in Natural History Museum, London: BMNH 1869:1:2:1, inspected by RJB 24.IV.2012 and 17-20. VI.2013 compared to Baird (1869a) “Description of a new species of earth-worm ( Megascolex diffringens ) found in North Wales ”. Syntypes labeled: “1869. 1.2.1 TYPE Plas Machynlleth Montgomeryshire, N. Wales ”. The jar (not original) contained nine mature specimens (four previously dissected dorsally), one juvenile and three portions; all were in good condition, flexible but rather macerated. The largest specimen was figured and is redescribed in detail here. Baird (1869b: 387) in “Additonal remarks on the Megascolex diffringens ” had specimens sent from Lady Cullum’s hothouse at Hardwick House near Bury St. Edmunds, Suffolk where the gardener says it resided for about 14 years although for 20 years he knew it from Glevering Hall near Woodbridge, Suffolk - these latter two localities unconfirmed and material not located.

Also Megascolex sanctae -helenae (sic) Baird “1869.6. 16.5 TYPE Island of St Helena I.C. Melliss Esq.” a single brittle subadult (inspected) .

Distribution. From hothouses in Wales and possibly England from original descriptions, and from Japan and probably Korea from subsequent descriptions of a (partial?) synonym A. heteropodus ( Goto & Hatai, 1899) .

Original description (in full). Length 4-5 inches (100- 125 mm) and “3 lines in circumference” [secondary annulations], with 104-105 segments. Lives in compost, nocturnal wanderer, very active when disturbed and readily breaks into fragments (hence its name). Clitellum from 14. Setae about 60 per segment. Darkly pigmented dorsum and pale ventrum.

Redescription of Syntypes. Longest complete specimen 120 mm (others smaller). Prostomium open epilobous. First dorsal pore in 11/12 (a non-funtional dot in 10/11). Setae fewer in anterior ventrum but more numerous posteriorly, numbering approximately 40 on 10 and ca. 56 on 20. Spermathecal pores in 5/6/7/8/9. Often with smaller ancilliary markings in 6-8 just prior (anterio-median) to spermathecal pores as seen in several specimens. Other GMs mostly widely paired papillae, presetal in 7-9 (in five of nine specimens), in 7 & 8 in two (one with other markings behind the male pores, the other without these), just in 8 in another, and indeterminate in the final specimen. Some variability manifest, with some markings missing. Male pores superficial with approximately 14 setae intervening (GMs present behind male pores as noted in one specimen).

Internally septa to 7/8 are thin, 8/9 is thick but incomplete to base of gizzard, or absent in some specimens; 8/9 is aborted. Spermathecae as figured in 6-9. Glands associated with GMs. Holandric with seminal vesicles in 11 & 12. Ovaries in 13; ovisacs not seen. Last hearts in 13. Intestine commences in 14 in some, but wider in 15 or 16 in other specimens; intestinal caeca are simple from 27. Prostates with racemose glands on 18lhs in two specimens but mostly the glands absent and only duct present.

Remarks. Amynthas diffringens (Baird, 1869) was first put under A. corticis (Kinberg, 1876) (misspelt as “corticus ”) by Easton (1981: 49) for which he has synonymy of: “ diffringens Baird, 1869: 40 ; (syn. divergens , heterochaeta , heteropoda , indica , nipponica , oyamai , tajaroensis [sic, lapsus tajiroensis ],? torii) Gates, 1972 c: 18”; several other synonyms now probable (see Blakemore, 2012d). Also claimed as “syn. nov.” of corticis by Easton (1982: 726) and by Sims & Gerard (1985). Amynthas corticis is a widely distributed cosmopolitan species-complex (eg by Blakemore, 2003: 14, 2012d) having accrued a large number of synonyms. The problem is that the extant type of A. corticis from Hawaii is an immature form. Thus the definition is somewhat vague and, in its broadest definitions at least, it encompassed earlier A. diffringens definitions. Here the redescription of the syntypes allows a more precise characterization of A. diffringens and its resurrection is proposed based mainly on its greater number of genital markings anteriorly, especially those in front of spermathecal pores (and fewer, or none, near the male pores) compared to what is most often found in a A. corticis that is seemingly now restricted in its definition to exclude these markings anteriorly of spermathecal pores (although they may occur posteriorly to spermathecal pores as in specimen NIBRIV249906 providing DNA WO4).

It should be noted that A. corticis often has markings near the male pores and that the male pores may be entirely missing with only the marking remaining. Related to this is the usual absence of the glandular portion of the prostate, if not deletion of the entire organ. Specimens that are degraded or immature require DNA to determine their identity.

Since no specimens were retrieved from the UK type-locality, the task now is to find live specimens from the unknown original Asian homeland agreeing with A. diffringens and to extract DNA to unambiguously define boundaries of this taxon. Those from Fukuura, Japan described by Ohfuchi (1937: 45) are perhaps closest thus far known.

Ohfuchi (1937) did not consider and was probably unaware of P. diffringens when he produced his detailed accounts - although his associate Kobayashi (1938) knew of diffringens and included Ohfuchi’s nipponica in synonymy (see its synonymy above). However, Ofushi’s description of P. heteropoda ( Goto & Hatai, 1899) seems to overlap the current redescription of the types since he showed ( Ohfuchi, 1937: text-fig. 4B; 5A’-F’) GMs preceding some or all the spermathecal pores as well as the presence or absence of prostate glands ( Ohfuchi, 1937: text-fig 7A). Thus his concept of Amynthas heteropodus should go partly under A. corticis and partly under A. diffringens as currently defined herein. The present description of A. diffringens also compares to those of other earlier workers, especially Kobayashi (1938: 158), Gates (1972, 1982) and Chen (1959: 9) that similarly overlap somewhat what has since been accepted as A. corticis s. lato.

Figures

Fig. 8. Amynthas diffringens copy of Baird’s original fig. 1 (habitus and a seta).

Fig. 9. Amynthas diffringens - A the previously dissected syntype showing prostomium, ventral habitus with spermathecae and prostates in situ and caecum 27rhs; X2 enlargements are of a 9lhs spermathea, 5/6/7/8/9rhs spemathecal pores and 18rhs male pore; B A. sanctaehelenae prostomium of previously dissected subadult type.

Fig. 10. A. corticis - Ohfuchi’s(1937: fig. 4) three representative forms of his ‘P. heteropoda’ from Japan that is now a synonym of A. corticis. However, the central figure agrees almost exactly with A. diffringens types (as described herein) having markings just above spermathecal pores (Fig. 9) while the outer two specimens seem to agree with those A. corticis Korean specimens figured that provided DNA sample WO4- WO5 (Figs. 1, 5).