DESCRIPTION OF THREE NYBEL1N1A SPECIES 

 2a 



2b 



2c 



iii 



Fig. 2a-c Nybelinia southwelli sp. nov. a. homeomorphous basal 

 tentacular armature, external surface, b. metabasal tentacular armature, 

 external surface, c. basal (i), metabasal (ii) and apical (iii) tentacular 

 hooks. Scale bar=20 urn. 



are wider than long and have distinct convex margins (Fig. 3a). The 

 size of the proglottids is similar along a large part of the strobila 

 (around 1 30th proglottid: 800-870 x 260-300, last proglottids: 900- 

 970 x 300-370). The genital atrium is ventrosubmarginal in about 

 the middle of the proglottids and alternates irregularly. The cirrus 

 sac is elongate, large, directed anteromedially from the genital 

 atrium and the sac is thin-walled (Figs 3b-c). The cirrus is unarmed, 

 coiled within the sac and an internal seminal vesicle was not seen; 

 external seminal vesicle absent. Testes arranged in double layer, 

 number 70-80, ovoid, 25^4-2 in diameter, encircle the female genital 

 complex, and some testes are present anterior to the cirrus sac. 

 Vagina not seen. Ovary bilobed, 130-160 wide x 80-105 long 

 (BMNH 1977.11.4.8-9). Gravid segments with vitelline follicles of 

 15-20 in diameter, uterus extending over most of the proglottids. 

 Other details of the female genital complex not seen. 



ETYMOLOGY. The new species was named after T. Southwell, in 

 whose collection the present specimens were found. 



Remarks. 



Southwell (1924, 1929a, 1930) gave a first description of N. 

 southwelli sp. nov. but identified the specimens as N. perideraeus 

 Shipley & Hornell, 1906. His scolex measurements lie within the 

 same range (Southwell, 1929a, p. 257-258; 1930, p. 84-86), and the 

 illustrations of the tentacular armature are similar to Figs 2a-c. Fig. 

 28d in Southwell (1929a) as well as Fig. 16d in Southwell (1930) 

 illustrate the slender, strongly recurved hooks of the basal tentacular 



125 



armature (Fig. 2a), and Southwell's Figs (28c and 16c) illustrate the 

 metabasal armature with the rose-thorn shaped hooks (Fig. 2b). 

 However, in contrast to his drawings, Southwell wrongly interpreted 

 the tentacular hooks as being uniform in size, between 1 and 1 2 um, 

 and shape. 



The present material illustrates that the material belongs to 

 Nybelinia subgroup IIBa of Palm et al. (1997), which includes 

 species having an homeoacanthous heteromorphous metabasal ar- 

 mature, a characteristic basal armature and basal hooks smaller than 

 or equal to the metabasal hooks. The species can be easily distin- 

 guished from N. nipponica Yamaguti, 1952, N. rougetcampanae 

 Dollfus, 1960 and N. yamagutii Dollfus, 1960 by the lack of bill 

 hooks and the presence of a homeomorphous basal armature. N. 

 herdmani can be considered synonymous with Kotorella pronosoma 

 (see following), and has a different scolex as well as a different 

 tentacular armature. Nybelinia southwelli sp. nov. is similar to N. 

 beveridgei Palm, Walter, Schwerdtfeger & Reimer, 1997, the only 

 other species having a homeomorphous basal and heteromorphous 

 metabasal armature. It can be distinguished by a much smaller 

 scolex size, smaller tentacular hooks, 13-14 rows of basal hooks in 

 contrast to 6-7 in N. beveridgei, and the absence of a muscular ring 

 around the tentacle sheaths. 



It has to be pointed out that though the form and characteristic 

 arrangement of the tentacular armature was the same, N. southwelli 

 from the two different elasmobranch species differs slightly in hook 

 sizes along the tentacle. The holotype obtained from Rhina 

 ancylostoma had basal hooks with a maximal length of 20, while 3 

 scolices taken from Nebrius ferrugineus had basal hooks with a 

 maximal length of 1 6. Similarly, the metabasal hooks of the holotype 

 were larger. This observation can be interpreted as a record of 

 morphological variability for N. southwelli depending on two differ- 

 ent elasmobranch hosts. 



Nybelinia perideraeus (Shipley & Hornell, 1906) Dollfus, 

 1930 (Figs 4-6) 



Synonymy. 



Tetrarhynchus perideraeus Shipley & Hornell, 1906 



Stenobothrium perideraeum (Shipley & Hornell, 1906) Pintner, 



1913 

 Nybelinia dakari Dollfus, 1960 (new synonymy) 



Material examined. Co-types VNHM 2 1 09 and 2 1 1 1 ; 3 adults 

 from the small intestine of Glyphis gangeticus (Miiller & Henle, 

 1839) (=Carcharhinus gangeticus) (collection of T. Southwell). 



Description. The scolex is craspedote (Fig. 4) with a total length 

 (with velum) of 1222, 1092/co-type VNHM 2109 (1352/ co-type 

 VNHM 2111); SW 767, 770 (715), pbo=546, 533 (637), pv=520, 

 390 (540), pb=408, 461 (429), ppb=59, 16 (69), vel=195, 299 (276), 

 BL=390, 430 (445), BW=103, 114 (115), BR=3.8:1, 3.8:1 (3.9:1), 

 SP=1.3:1.3:1, 1.2:0.8:1 (1.5:1.3:1). A basal tentacular swelling is 

 absent, TW basal=39, 33 (42), TW metabasal=30, 33 (35), TW 

 apical=20, TL=500-570; prebulbular organs and muscular rings 

 around the tentacle sheaths are absent; the retractor muscle inserts in 

 the basal part of the bulbs; TSW=35^10. 



The armature is homeoacanthous, heteromorphous, and the hooks 

 of the basal armature are similar to those of the metabasal armature 

 (Figs 5a-b). hsr=6-7. The hooks of the metabasal armature are 

 different in shape and size on bothridial and antibothridial tentacle 

 surfaces (Figs 5a). On the bothridial surface, the tentacular armature 

 consists of strongly recurved, solid hooks with a large base; L= 10.5- 

 13.0, B=10.5— 1 1.5. On the antibothridial surface, the hooks are 



