Bathyporeia gladiura, D’Acoz & Vader, 2005

D’Acoz, Cédric D’Udekem & Vader, Wim, 2005, New records of West and South African Bathyporeia, with the description of four new species and a key to all species of the genus (Crustacea, Amphipoda), Journal of Natural History 39 (30), pp. 2759-2794 : 2772-2779

Bathyporeia gladiura sp. nov.

( Figures 11–15 )

Etymology

From the Latin, gladius 5sword and the Greek oúRÁ 5tail, alluding to the large sword-like third uropod. The name is a noun in apposition.

Material examined

Holotype: one female holotype mounted on nine slides, University of Cape Town, Ecological Survey, FBY. 100. P., South Africa, 34 ° 07.59S, 018 ° 299E, 16 m, ‘‘white sand and shell coarser than FBY 98–99’’, grab, 12 October 1967, SAM A45273 . Paratypes: two specimens, University of Cape Town, Ecological Survey , FBY. 90. P., 34 ° 08.49S, 018 ° 309E, 23 m, medium white sand with coarse particles, grab, 12 October 1967, SAM A45271 ; one adult male (U3 removed and mounted on a slide), University of Cape Town, Ecological Survey, FBY. 98. T ., 34 ° 07.59S, 018 ° 299E, 16 m, ‘‘white sand and shell finer than FBY 100–101’’, grab, 12 October 1967, SAM A45272; 10 specimens (one female partly mounted on three slides) , University of Cape Town, Ecological Survey , FBY. 100. P., 34 ° 07.59S, 018 ° 299E, 16 m, ‘‘white sand and shell coarser than FBY 98–99’’, grab, 12 October 1967, SAM A45273 ; one specimen, University of Cape Town, Ecological Survey , FBY. 112. N., 34 ° 169S, 18 ° 38.19E, 58 m, khaki sand, grab, 12 October 1967, SAM A45274 .

Description

Body and appendages extremely stout. Eye small with well-developed ommatidia in adults. Pseudorostrum short and broad, with rounded tip, not overhanging, with two proximoventral setae in adults; development and number of apical spines normal. Major flagellum of A1 with six articles in females, 10 in males; several articles of major flagellum with a spine in male; first article of accessory flagellum with one or two non-apical groups of spines. Flagellum of A 1 in males rather long (combined length of major flagellum and distal two articles of peduncle 1.8 as long as length of pseudorostrum). Anterior border of third article of peduncle of A2 with one group of spinules and setae in apical position only; article 4 with lateral and apical spinules; flagellum with seven to eight articles in females, eight in males; A2 of adult males 0.4 times as long as body length, not longer than in females, with flagellum almost as long as peduncle.

Penultimate article of mandibular palp elongate.

Third article of maxillipedal palp without longitudinal row of setae on dorsal side (two transverse groups of anterior setae only are present); inner plate with four strong setae on dorsal surface; outer plate with five nodular spines.

Coxa 1 with tip narrowly rounded, without ventral tooth, with anteroventral angular discontinuity; a long seta associated with this discontinuity, other setae short, especially those anterior to the anteroventral angular discontinuity, which can be considered as setules.

Coxa 2 without posterior tooth; transition between anterior and ventral border without any angular discontinuity; anterior and ventral borders forming a regular curve; anterior and posterior borders parallel converging downwards (since the anterior border is curved and the posterior nearly straight); ventral border with 10–12 short and narrow irregularsized setae; four to five medial setae.

Coxa 3 without posterior tooth; anterior and posterior border parallel; ventral border with 12 slender irregular-sized setae in adult females, of normal length, four medial setae.

Coxa 4 with 20 irregular-sized setae in adult females, of normal width and length; posterior setae not setulose.

P3 with carpal fang not reaching tip of propodus, distally broad, with accessory setule; propodus extremely robust; outer spines/setae of propodus few in number (six), consisting of two long very strong spines, two short strong spines, one long seta and one rather short seta; dactylus stout, with well-developed unguis, with posterior border convex. Propodus of P3 longer than propodus of P4. Ratio of propodus length and merus length of P 3 in adult female: 0.62. Ratio of dactylus length and propodus length of P 3 in adult female: 0.19. Ratio of length and width of dactylus of P 3 in adult female: 2.5. Ratio of unguis length and total length of dactylus of P 3 in adult female: 0.33. Ratio of unguis length and dactylus width in P3 of adult female: 0.83.

P4 with carpal fang much shorter than propodus, distally broad, with accessory setule; propodus extremely robust; outer spines/setae of propodus few in number (five), consisting of two long very strong spines, two short strong spines, one long seta; dactylus stout, with well-developed unguis, with posterior border convex.

Median part of anterior border of basis of P5 straight. Posterior border of basis of P5 with only four very short setae in holotype. Merus of P5 elliptic but not unusually broad (2.0–2.1 times as long as broad); posteromedian seta group of merus with one long and strong major seta and one minute non-setulose accessory seta; posterodistal seta group with one long and strong straight seta (overreaching tip of carpus in female, almost reaching tip of carpus in male), and zero to two setules (minor sexual dimorphism); anterodistal area with one to two setae that are distally denticulate; longest posterior spine of carpus overreaching tip of propodus or shorter than propodus.

Posterodistal lobe of basis of P6 protruding; anterior border strongly and regularly convex; posterior border distinctly convex; in females, anterior border with narrow setae on proximal 0.7, with spiniform setae on distal 0.3. Posterior border of basis of P6 with only three very short setae in holotype. Merus of P6 with three posterior groups of spines/setae and five anterior groups (one reduced to a single seta); longest seta of each anterior seta group not of significantly increasing size towards distal part of merus; carpus without posterior spines (distal group not considered); propodus with two posterolateral, and two anteromedial groups of spines (terminal crown of spines not considered). Spines of carpus and merus long and of normal robustness.

P7 with anterior and posterior border of basis very convex; posterior border of basis with stout ornamentation (spines); spines regular-sized; four to five spines; medial side without spines in females (with pappose setae only). Ischium very short, reaching 0.34 of outer side of merus; anterodistal border barely concave on outer side, weakly concave on medial side; posterodistal border straight on outer side, scarcely concave on medial side. Spines of carpus and merus stout and normal-sized.

Middle of posterior border of Ep1 weakly angular and of Ep2 scarcely angular (almost straight); neither Ep1 nor Ep2 with middle of posterior border produced as tooth.

Ep3 with posteroventral border regularly rounded, without posteroventral tooth, with zero to two single ventrolateral spines and three to four ventral setules, with two to four setules on posterior border.

Urosomite 1 with one pair of anteriorly directed setae, and no posteriorly directed spines dorsally; ventrolateral border without strong setae arising from outer side.

Peduncle of uropod 1: outer dorsal border with four to five spines consisting of following succession: (1) two to three short robust spines, (2) the usual penultimate short robust spine, (3) very short space followed by very strong distal spine; dorsomedial border with three single strong styliform spines. Inner and outer rami neither especially stout nor slender; inner ramus with border facing outer ramus, with only one long spine in subdistal position. Spines on rami neither especially stout nor slender.

Peduncle of uropod 2 of normal proportions; outer dorsal border with four robust spines; dorsomedial border with two single robust spines. Rami neither especially stout nor especially slender; inner ramus with border facing outer ramus with only one long spine in subdistal position. Spines on rami neither especially stout nor especially slender. Peduncle of uropod 3: longest distal spine may slightly overreach inner ramus (endopodal spines excluded); outer border of peduncle of uropod 3 with one group of two strong setae or without setae. Inner ramus elliptic, with two normal-sized spines. Outer ramus with first article of normal width, second article long and very broad. Second article of outer ramus with one to three medial setae and one to two very short outer setae. Medial side of outer ramus (first and second articles together) in female with six rather short, non-plumose setae (setules); in male with nine rather short plumose setae, sometimes associated with short accessory spiniform non-setulose setae; all plumose setae much longer than longest setae on outer side (in male). Outer side of outer ramus (first and second article together) with four to five groups of one to three spiniform setae, much shorter than outer ramus width. Ratio between length of second article and length of first article: 0.47–0.48. Ratio between length of second article and width of first article: 1.8–1.9.

Telson of typical morphology; lobes without medial setae.

Size. 3 mm.

Ecology. On sand, and sand with coarse particles, between 16 and 58 m. Not found in the same samples as B. cunctator sp. nov., which seems to prefer finer sediments.

Distribution. South-western South Africa.

Discussion

Bathyporeia gladiura sp. nov. shares a number of characters with the north-east Atlantic species B. elkaimi d’Udekem d’Acoz and Menioui, 2004 , B. pilosa Lindström, 1855 and B. sarsi Watkin, 1938 , such as the absence of teeth on coxae 1–3, the morphology of the carpal fang (blunt-tipped with accessory setule), and the absence of posteriorly directed dorsal spines on the first urosomite. However, its pseudorostrum is stouter (actually it is the stoutest in the genus) and it has quite distinctive third uropods with a long and broad second article (this is short and narrow in B. pilosa and B. sarsi ). B. gladiura sp. nov. has slightly stouter dactyli on P3–P4 than in B. pilosa and B. sarsi and therefore differs considerably from B. elkaimi which has slender dactyli with a long unguis. B. gladiura sp. nov. of both sexes have strong spines on the posterior border of the basis of P7 as in female B. sarsi , while B. pilosa , B. elkaimi , and male B. sarsi have setae on this border. The third epimeral plate has zero to two ventrolateral spines in B. gladiura sp. nov. while it has at least four spines (and usually many more) in B. elkaimi , B. pilosa , and B. sarsi . The second article of the outer ramus of U3 is long in B. gladiura sp. nov., just as in B. elkaimi , but it is broader. It differs considerably from the second articles of B. pilosa and B. sarsi which are short and narrow. Adult males of B. gladiura sp. nov. have short second antennae as in females, just like B. elkaimi , B. gracilis , B. microceras d’Udekem d’Acoz and Menioui, 2004 , B. parkeri Bousfield, 1973 , and B. quoddyensis Shoemaker, 1949 . Other Bathyporeia species have long or medium-sized antennae in adult males. In the related more basal genus Amphiporeia , the adult males have short antennae too, as in the even more basal and morphologically similar genus Gammarus . Therefore, the character stage ‘‘short antennae in adult males’’ is possibly the plesiomorphic condition in the genus Bathyporeia and would give an indication of the evolutionary trends in the genus. This problem will be examined in more detail elsewhere.

A single Bathyporeia specimen is identified as Bathyporeia cf. gladiura . This female specimen is exceedingly similar to B. gladiura sp. nov. and is probably identical with it. It has, however, a slightly narrower pseudorostrum (possibly a distortion artefact) and a different third uropod, with much longer outer spines and a narrow second article. This difference in the third uropod is possibly a regeneration anomaly. This specimen has been dissected and mounted on 17 slides. Its coordinates are: University of Cape Town, Ecological Survey, South Africa, FBY. 125. A., 34 ° 06.39’S, 018 ° 299E, fine white sand, 2 m depth, grab, 6 November 1967, SAM A45275.

Figures

Figure 11. Bathyporeia gladiura sp. nov. Adult females, South Africa, FBY. 100: (A–D, F–H, J, K) holotype; (E, I) paratype. (A) Head; (B) left A1; (C) ventral border of first article of peduncle of right A1; (D) left A2; (E) flagellum of right A2; (F) mandibular palp; (G) right Mxp; (H) left coxa 1; (I) right coxa 1; (J) right coxa 2; (K) left coxa 3. Scale bar: 0.21 mm (A, B); 0.10 mm (C, G–I); 0.26 mm (D, E); 0.13 mm (F, J, K).

Figure 12. Bathyporeia gladiura sp. nov. Adult female, holotype, South Africa, FBY. 100: (A) Left P1; (B) right P2; (C) left P3; (D) anterior part of left P3 (medial spines/setae of propodus not shown); (E) right P4; (F) anterior part of right P4 (medial spines/setae of propodus not shown); (G) dactylus of right P4. Scale bar: 0.21 mm (A, C, E); 0.42 mm (B); 0.071 mm (D, F); 0.025 mm (G).

Figure 13. Bathyporeia gladiura sp. nov. Adult females: (A–C, E) holotype, South Africa, FBY. 100; (D) paratype, South Africa, FBY. 112N. (A) Right P5; (B) left P6; (C) left P7; (D) tip of left P7; (E) proximal part of right P7 (medial view). Scale bar: 0.26 mm (A–D); 0.21 mm (E).

Figure 14. Bathyporeia gladiura sp. nov. Adult females, South Africa, FBY. 100: (A–E, G–I) holotype; (F) paratype. (A) Right Ep1; (B) right Ep2; (C) right Ep3; (D) left Ep3; (E) first urosomite and proximoventral part of peduncle of left U1; (F) right U1; (G) right U2; (H) left U3; (I) telson. Scale bar: 0.21 mm (A–E); 0.14 mm (F, G); 0.18 mm (H); 0.10 mm (I).

Figure 15. Bathyporeia gladiura sp. nov. Adult male, paratype, South Africa, FBY. 98T. (A) Head, antennae and mandibular palp; (B) distal part of left P5; (C) basis and ischium of left P7; (D) first urosomite; (E) right U3; (F) accessory spine. Scale bar: 0.21 mm (A–D); 0.18 mm (E); 0.083 mm (F).