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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Kathrynella

Kathrynella Omodeo, 1996 (ref. ID; 6533 original paper)

Family Alluroididiae Michaelsen, 1900, emendavit Jamieson, 1968 (ref. ID; 6533)

ref. ID; 6533

Diagnosis

Alluroidid megadriles with a cylindrical muscular atrium (euprostate); male pores paired, intraclitellar, opening ventrally and in equatorial position in XIV. Spermathecal pores paired, opening in intersegmental furrow 6/7. Modified setae a and b in VII; grooved penial setae ventral in XIV. Circulatory apparatus strongly developed, showing in the anterior segments long lateral commissures between dorsal and ventral vessels rolled into a ball.

Notes

The allocation of the new genus Kathyrnella to the Alluroididae requires the following changes in Jamieson's (1968) diagnosis of the family: Male pores intraclitellar one pair, either at the anterior border of XIII, in XIII, or in XIV; holoandric, proandric, or metandric male apparatus. The new genus differs from other genera of Alluroididae because of the metandric condition of the male apparatus. Also the presence of sperm sacs and the absence of glandular lining of the atria may be diagnostic.

Etymology

The genus is affectionately dedicated to Dr. Kathryn A. Coates, distinguished student of oligochaetes. (ref. ID; 6533)
  1. Kathrynella guyanae Omodeo, 1996 (ref. ID; 6533 original paper)

Kathrynella guyanae Omodeo, 1996 (ref. ID; 6533 original paper)

Descriptions

  • External characters: Body thread-like, flattened in clitellar and caudal regions, with deep intersegmental furrows conferring a monifiorm appearance to the posterior half of worms. Longitudinal, latero-muscular grooves of body wall not observed. Length of entire specimens 85-89 mm; diameter 600 µm at X, 520 µm at mid-body. Segment number 282, 259 (three specimens were amputated). No cutaneous pigmentation, integument transparent. Prostmium zygolobous, conical; peristomium short. Setae paired with lumbricine arrangement. Pygidium small, anus as a vertical cleft; in one specimen a growth blastema was visible immediately anterior to the pygidium, as is common in limicolous worms. Clitellum cylindrical, extending from the posterior part of XI to XVII; the ventral side of XIV bears two large, circular papillae with swollen borders and a very thick, whitish, central part crossed by 4-5 transverse furrows; behind and beside these papillae two crescent-shaped fields are visible, each bearing a single, large, grooved, penial seta. In all specimens examined, penial setae were broken but their length may be estimated longer than 300 µm. No other ventral setae were visible in XIV. Dorsal setal couples of midclitellar segments do not appear perpendicular to the long body axis but slanting, in that setae c are located more posteriorly than setae d. Male pore as a slit on hinder portion of each crescent-shaped field in XIV; paired female pores on anterior border of XIV, near midventral line. No dorsal coelomic pores. Nephridiopores inconspicuous. Spermathecal pores in furrow 6/7 on setal line a. Setal ratio aa:ab:bc:cd: dd = 5.6:1.1:5.6:1:10 at segment X; 2.5:1:1.5:1:12 in posterior segments (where all setae are displaced ventrad). The length of setae increases from II, where it is 37 µm, to VII where setae a and b measure 92 µm and setae c and d are 43 µm. Further posteriorly, the setal length decreases gradually (penical setae of XIV excepted), to become constant (ca. 50 µm) behind the clitellum. Only caudal setae show distal ornamentation. (ref. ID; 6533)
  • Internal organization: Body wall rather thin; cuticle approximately 0.5 µm thick; layer of circular muscles very thin. Septa 5/6-10/11 thickened, funnel-shaped. No pharyngeal pad distinguishable. Neither a gizzard, nor any apparent distinction between oesophagus and intestine are present. Ciliated epithelium of intestine ending in clitellar region. Perintestinal blood sinus occuring from XII backwards. The holonephridia, apparently avesiculate, begin in XII or XIII; they are initially poorly developed and acquire normal size only behind clitellum. The circulatory apparatus shows an exceptionally great development. Dorsal and ventral vessels run the whole length of the worm and have very large diameter, only slightly less than that of the intestine. Seven pairs of long commissural vessels occur in V-XI, wound in balls whose size increases backwards; each ball is covered with chloragocytes (in one specimen the two vascular balls of XI completely fill the coelomic cavity, representing perhaps a pathological condition). A pair of large vessels originates in VII from the perintestinal blood sinus, and from XII to XVI run along the sperm sacs. Many lesser vessels are to be seen everywhere, but no capillaries. Testes are located in the anterior part of XI and face the large seminiferous funnels, which are covered with sperm and bulge into segment XII. Sperm ducts are coiled in XII in their proximal course, then seem to run laterally within the body wall till XVII; here they emerge again in the coelomic cavity, become thicker, and run frontwards till XIV, where they form the atria. Atria possess thick muscular walls and appear as shining, bent, spindles which open in the middle of XIV, behind the penial setae; atria (which correspond to the 'euprostates' of Eudrilidae) have a thin external coating of non-glandular cells. Other structures of the male apparatus are two long sperm sacs, which begin from septum 11/12 and run till XX, parallel to the egg sacs and to the posterior course of vasa deferentia. Ovaries are located in the ventral forepart of XIII; two long cylindrical egg sacs, apparently beginning in XVII, extend as far back as XXXV; they possess thick glandular walls and contain up to a dozen large ripe eggs (ca. 530 µm wide) between XXV-XXXV. Two large, convoluted spermathecae occur in VII and consist of a short, partly ciliated duct and elongate ampulla; the ectal section of the latter contains the bulk of spermatozoa, whereas the ental section is filled with a hyaline secretion. The spermathecal length exceeds the body diameter and possibly the length of penial setae. It can be inferred that during copulation the sucker-shaped genital papillae in XIV help to fasten the two partners together, while at the same time the penial grooved setae are introduced into the spermathecae for sperm transfer. (ref. ID; 6533)

    Systematic position

    Kathrynella guyanae sp. n. shows traits which are reminiscent of various microdrile taxa. The body thinness and the large blood vessels are typical of microdriles living in anoxic mud; the long egg sacs and sperm sacs, as well as the absence of capillaries, resemble those of some Haplotaxidae. Penial setae and the complex structure of vasa deferentia are similiar to those of the megadriles Brinkhurstia (Brinkhurst 1964; Righi et al. 1978) and Standeria (Jamieson, 1968), and so is the anatomy of nephridia. There are, however, two main differences (autapomorphies) from the Alluroididae hitherto described i.e. the location of male pores in XIV and the metandric condition of the male apparatus which contrasts with the proandric condition of the Alluroidinae and the holoandric, supposedly plesiomorphic (cf. Jamieson 1980), condition of the Syngenodrilinae. Yet, if we consider that parallel modifications of male apparatus, spermathecae and male pores have appeared in several genera (Benhamia, Dichogaster, Microscolex, Parachilota), then the differences observed within the Alluroididae, as here considered, seem to be less relevant. As stated by Pickford (1937: 27): 'A variability of the intensity of meristic suppression [of prostates and spermathecae] is probably associated with the loss of the anterior or posterior pair of testes'. That seems to be the present case. Lastly, there is a noteworthy resemblance of the 'atria' of the new species to the typical 'euprostates' of the Eudrilidae, an African family of unknown kinship. (ref. ID; 6533)

    Type locality

    Kurupukari, Guyana, adjacent to Essequibo River, in sediment of a small pool, between roots and twigs. Donald F. Stacey coll., October 8, 1990. (ref. ID; 6533)

    Type materials

    Type material is deposited at Invertebrate Zoology, Royal Ontario Museum, Tronto (ROMIZ). (ref. ID; 6533)
  • Holotype: ROMIZ13234 (longitudinally sectioned specimen; unsectioned caudal portion in alcohol). (ref. ID; 6533)
  • Paratypes: ROMIZ13235 (transversely sectioned specimen; unsectioned caudal portion in alcohol); ROMIZ13236 (two specimens in alcohol and a whole mounted specimen in Canada balsam). (ref. ID; 6533)