BARGMANN1A REVISION 



53 



Bargmannia elongata Totton, 1954 



(Figures 1-5) 



Bargmannia elongata Totton 1954 (Text-Figure 28 A-D only); 

 Totton 1965 (Figure 45, A-D only); Kirkpatrick & Pugh, 1984: 

 Figure 11. 



HOLOTYPE. BMNH 1952.1 1.19.7, designated by Totton (1954): 

 one nectophore from Discovery II St. 699; 14° 27.3'N, 30° 02.3'W; 

 14 — v— 193 1 ; 0-370m. The specimen was figured by Totton (1954, 

 text-Figure 28 C, D; 1965, Figure 45 C, D). 



Paratypes. As designated by Totton ( 1 954): eighteen nectophores 

 from the same sample as the holotype. BMNH 1952.1 1.19.8-25. 



Material examined. The holotype and paratype material have 

 been re-examined in order to establish to which of the presently 

 recognised Bargmannia spp. the name elongata should be applied. 

 Totton's (1954) other material also has been re-examined and, 

 although all the material is in poor condition, it appears that only the 

 nectophores from two other Discovery stations belong to this spe- 

 cies. These are St. 681 (21°13'S, 29°55.25'W; l-v-1931) where a 

 TYFV net was fished over a depth range 1500-lOOOm; and St. 107 

 (43°03'S, 17°03'E; 4-xi-1926) where the net used was a N450 and 

 the depth range was 850-950m. The nectophore from the former of 

 these stations was figured by Totton (1954, text-Figure 28 A, B; 

 1965, Figure 45 A, B). The other nectophore, from Discovery St. 

 1769, also illustrated in the same figures (E, F) does not belong to B. 

 elongata, but to B. lata. 



Several nectophores of this species have been found in more 

 recent Discovery collections, as is discussed below. However, the 

 major part of the redescription will be based on two specimens 

 collected by DSRV Atvin off San Diego, California. U.S.A. in 1979, 

 during Dives 961 (32°14'N 117°22'W; 5-ix-1979; water depth 

 833m) and 966 (33°04'N 1 1 8° 1 6'W; 8-ix- 1 979; water depth 747m). 

 The Alvin Dive 96 1 specimen, preserved in Steedman's solution, has 

 been deposited in The Natural History Museum London (BMNH 

 1 998.2 1 63). The exact depths of collection for both Alvin specimens 

 were not recorded. 



Diagnosis. Nectophores with central thrust block broadly rounded 

 or obliquely truncate apically. Pair of short ridges, directed toward 

 mid-line, branch from apico-laterals where latter bend out sharply at 

 a right angle. Outer branches of apico-laterals end, basally, on, or 

 just apical to, enlarged processes lateral to ostium. In preserved 

 specimens ostium opens dorso-basally and nectosac. with appar- 

 ently dense musculature, has distinct dorso- ventral undulations. The 

 ratio of the overall length of the nectophore to the length of the 

 nectosac averaged 1.31. Delicate, foliaceous bracts; typically with 

 patches of ectodermal cells on distal half of dorsal surface. 



DESCRIPTION. A photograph of the living specimen collected 

 during Alvin dive 961 is shown in Figure 1A. By the time it was 

 taken, in a tank on board the mother ship, several nectophores had 

 become detached and the siphosomal stem had contracted. A second 

 living specimen, collected during Johnson-Sea-Link (JSL) I Dive 

 2673 (27°02.7'N, 85°01.5'W, depth 780m), is shown in Figure IB. 



PNEUMATOPHORE. The pneumatophore measured c. 2.2 mm in 

 length and 1 mm in width, but was distorted and ruptured. No 

 pigmentation was apparent. In the Alvin dive 961 specimen, the main 

 gas cavity, the pneumatosaccus (height 1 .8 mm), was separated from 

 the small gas secreting region, the pneumadenia, by a narrow collar. 

 Below the pneumatophore was a long stalk, up to 7.6 mm in length. 

 Immediately above the nectosome, this stalk narrowed and was 

 flattened to form a hinge-like structure, which could facilitate the 



use of the pneumatophore as a means of orientating the animal. 



Nectophore (Figures 2-3). The nectophores had a biserial, stag- 

 gered arrangement down the nectosome (Figure 1). Forty two 

 nectophores were found with the Alvin dive 961 specimen, though 

 many were small or immature; and 26, mostly mature ones, were 

 found with the Alvin dive 966 specimen. The mean dimensions, for 

 the fully developed nectophores of each specimen, were:- length: 

 21.29 ± 0.93 mm and 16.49 ± 0.75 mm; width: 9.58 ± 0.56 mm and 

 7.40 ± 0.32 mm; and the ratios of total length of the nectophore to the 

 length of the nectosac were 1.29 ±0.02 and 1.34 ±0.04, respectively. 

 For net collected nectophores, damage and distortion by preserva- 

 tion, particularly to their basal halves, made it difficult to assess this 

 ratio accurately. 



The nectophores of the dive 966 specimen were noticeably smaller 

 than those from dive 961 but, as will be seen in the description of the 

 following species, the size range of the nectophores can vary greatly 

 between individual specimens. In general, the thrust block was 

 roundly, and often slightly asymmetrically, truncate (Figure 2A, tb\ 

 2B). although for a few of the nectophores of the smaller specimen 

 it was distinctly tapered. The latter was also apparent on several net 



collected nectophores where the apex of the thrust block was 

 drawn out to form a small digitiform process that could be folded 

 over ventrally. 



Fig. 2 Bargmannia elongata. A. Upper, B. lower, and C. lateral views of 

 mature nectophore. Scale bar = 5 mm. bi, bo: inner and outer branches 

 of apico-lateral ridge; mp: mouth-plate; n: nectosac; o: ostium; pc: 

 pallial canal; pedc: pedicular canal; ral, hi, mil: apico-, infra- and meso- 

 lateral ridges; sb: side branch; tb: thrust block. 



