Heterocuma ambrizetensis, Bochert, Ralf & Zettler, Michael L., 2011

Bochert, Ralf & Zettler, Michael L., 2011, Cumacea from the continental shelf of Angola and Namibia with descriptions of new species, Zootaxa 2978, pp. 1-33 : 24-31

Heterocuma ambrizetensis sp. nov.

Figs. 18–22

Type material. Holotype: adult female 13.9 mm (St. 2: dredge sampling; 7°14.186´S, 12°46.025´E (partially dissected in five slides) [ ZMB 27921; 5018; 5019; 5020; 5021; 5022]; Paratypes: adult male, 13.3 mm (same data as holotype) (partially dissected in four slides) [ ZMB 27921; 5023; 5024; 5025, 5026]; 4 males, 19 females (same data as holotype) [ ZMB 27921]; 11 males; 1 preadult male; 1 ovigerous female; 36 females (St. 1: grab and dredge sampling; 7°14.090´S, 12°41.010´E) [authors collection]; 85 males and females (same data as holotype) [own collection]; 1 ovigerous female (St. 1: grab and dredge sampling; 7°14.090´S, 12°41.010´E) [own collection]; 1 ovigerous female (St. 4: dredge sampling; 9°04.894´S, 12°56.063´E) [own collection]; 1 female (St. 5: grab sampling; 9°20.717´S, 13°01.549´E); 1 male (St. 6: grab sampling; 9°26.000´S, 12°59.974´E) [own collection]; 5 females (St. 7: dredge sampling; 9°33.703´S, 13°06.020´E) [own collection];

Diagnosis. Telsonic somite not produced. Eye present. Basis and merus of maxilliped 3 distally produced. Pereopod 2 and 3 with rudimentary exopods in both sexes, exopods biarticulate. Male with five pairs of pleopods. Uropod endopod article 1 shorter than article 2, endopod very slightly shorter than exopod.

Description. Female, length 13.9 mm. Integument soft. Carapace ( Fig. 18 A) about two times as long as high; anterolateral angle acute and the lower margin smooth; antennal notch deep; with middorsal carina formed as single carina in anterior one-third of carapace and open up towards the posterior end as paired carinae; with a faintly shallow anterolateral depression behind the antennal notch forming a oblique ridge; eye lobe rounded; eye prominent, with several lenses.

Antenna 1 ( Fig. 18 B), peduncle triarticulate, basal segment expanded, second segment slightly shorter and slightly broader than third segment; main flagellum biarticulate, first segment three times as long as second, with two aesthetascs proximally; accessory flagellum minute, 1-segmented.

Mouthparts: mandible ( Fig. 18 C) with 11 serrated setae and one multifurcate seta; maxillule ( Fig. 18 D), inner endite with one simple seta, with two serrated setae and five dentate setae, outer endite with five pair of serrated setae, one single serrated seta and two simple setae; maxilla ( Fig. 18 E), endites exceeding the protopod, with simple, seratted and plumose setae; maxilliped 1 ( Fig. 18 F), basis produced distally with ten long plumose setae and seven short spines on inner margin, carpus inner margin with nine plumose setae, five short acuminate spines and three flaggelate spines; maxilliped 2 ( Fig. 18 G), basis nearly 1.5 times as long as the following segments combined length, straight; ischium not differentiable, probably fused with merus; merus dilated distally, short; carpus long and straight; carpus and propodus strongly setose; maxilliped 3 ( Fig. 18 H), basis nearly 2.5 times as long as the following five segments combined length, with its distal extension reaching nearly to the end of merus, arcuate; ischium short, broader than long; merus dilated distally; carpus slightly shorter than merus, widened distally; dactylus and propodus subequal; propodus with a brush of setae on inner distal margin.

Pereopods: pereopod 1 ( Fig. 18 K), basis 1.3 times longer than the following five segments combined length, arcuate, with short distal prolongation on inner margin reaching half length of ischium; ischium and merus short, merus slightly longer than ischium; carpus straight, slender, about 1.5 times longer than ischium and merus together, propodus straight, slender, three-quarter as long as carpus, with brush of very long setae on distal inner margin, dactylus short, about one-third length of carpus. Pereopod 2 ( Fig. 19 A, 22 A), 6-segmented, basis short and strong, about 2,5 times longer than broad, about 0.7 times as long as the remaining segments, with biarticulate exopod of same length as basis, with five long setae on posterior margin; ischium fused; merus short and strong, as long as broad, with one very cuspidate seta on posterior distal margin, this seta about 1.5 times as long as merus and with microsetulae distally, accompanied by one slender simple seta, with one short, strong and microsetulated seta on distal anterior margin; carpus about one-third length merus, smaller than merus, excavated anteriorly, with one short and microsetulated seta on distal anterior margin; propodus short, distal broader than proximal, nearly fully enwrapped by excavation of carpus, with two strong setae on posterior distal margin, its lengths not reaching the tip of merus seta, dactylus as long as merus and carpus together, with rows of flagellate setae. Pereopod 3 ( Fig. 19 B) basis long and slender, subequal to length of remaining segments; with about 7 simple setae on posterior and anterior margin, with biarticulate exopod, its length about half length of basis; ischium short with brush of simple setae on distal margin; merus slightly longer than carpus, merus with one acuminate and furrowed seta on inner margin; carpus with one row of about six acuminate and furrowed setae anterodistal; propodus and dactylus short, subequal. Pereopod 4 ( Fig. 19 C) basis shorter than the remaining segments, with rows of acuminate setae; carpus longest; merus shorter than carpus, with two pairs of acuminate setae proximal, with one row of about six acuminate and furrowed setae anterodistal, three of them very strong; propodus shorter and broad, about half length of merus, with one acuminate and furrowed seta distally; dactylus subequal to propodus, with one short terminal cuspidate seta. Pereopod 5 ( Fig. 19 D) similar to pereopod 4. Pereopods 3–5 bases with broom setae ( Fig. 22 B–D).

Pleonit 6 strongly excavates posterior-dorsal ( Fig. 19 E).

Uropod ( Fig. 19 F) peduncle slightly longer than rami, 24 short spines, posterior half-dozen of them of increasing length; exopod biarticulate, distal article about 1.5 times as long as proximal article, proximal article with four plumose setae on inner margin, distal article with about 12–15 short plumose setae on inner margin and four stump terminal setae of increasing length, each weakly plumose and with one microsetula on the tip; endopod very slightly shorter than exopod; biarticulate, both articles subequal, proximal article with eleven short cuspidate setae of increasing length towards distal end and with one strong seta of median size distally on inner margin and three plumose setae on distal part of outer margin, distal article with 11–13 slender setae on inner margin and 8 plumose setae on outer margin, with three terminal setae, differing in length, each weakly plumose and flagellate.

Adult male: 13.3 mm total length; as the female, except as follows: carapace with weak middorsal carina, antennal notch depressed, anterolateral angle bluntly rounded, with a faintly slender shallow anterolateral depression at the anterolateral corner forming a oblique ridge ( Fig. 20 A, C); pedigerous somite 3 with lateral carina, pedigerous somites 4 and 5 with short weak lateral carinae; thoracic sideplate of pedigerous somite 4 with prominent linguiform anterior projection, sideplate retracted lateral forming a hole to thoracic sideplate of pedigerous somite 3 which gives cavity for the strong dorsal directed plumose seta of the bulb of pereopod 3; the sideplates from thoracic somite 3 until abdominal somite 5 each median midventrally with one row of 3–7 short spines rectangular directed interiorly to hold the second antenna; antenna 1 ( Fig. 20 B), article 3 of peduncle with ten aesthetascs distally; flagellum 1-segmented, with two strong setae and two acuminate setae; antennae 2 reaching rami of uropod; maxilliped 3 basis straight, with short rows of fine setae; pereopod 1 ( Fig. 20 E) basis straight, without prolongation distally, with one row of fine setae distally, with seven slender setae of different length proximal; pereopod 3 ( Fig. 21 A) basis posterio-proximal with strong bulb which carries one strong plumose seta dorsally directed and one row of eleven setae median-ventrally and on posterior margin

Uropod peduncle 1.2 times as long as rami; peduncle with up to 100 short setae arranged as follows: with one row of 4–7 serrated setae proximally and one row of 7–12 serrated setae distally, interrupted on middle inner margin by about five rows serrated setae and about three rows slightly slender and longer setae; exopod of uropod article 2 about 1.6 times as long as article 1.

With five pair of pleopods, basal segment of pleopod on inner margin with one row of eight acuminate plumose setae and eight stump plumose setae ( Fig. 21 D), later with few short rows of microsetulae on tip, endopod without external process.

Etymology. The new species is named after the coastal region Ambrizete near the town N’zeto in northern Angola, close to the sampling are of most of the specimens.

Remarks. Because of the strong molecular similarity and lack of morphological differentiation, the two genera Cumopsis Sars, 1878 and Heterocuma Miers, 1879 were merged, with priority for the name Cumopsis by Haye (2007). In contrast, the following morphological features clearly distinguish both groups: pleonite 6 dorsally truncate/excavate posteriorly, endopod of pleopod in male with/without external process and basis of maxilliped 3 without/ with distal prolongation ( Kurian, 1954). The existing morphological differences suggest that these are two distinct genera. Therefore we maintain the validity of Heterocuma and assign the new species to this genus.

The new species is very similar to Heterocuma africanum africanum Zimmer, 1920 and Heterocuma africana intermedia ( Fage, 1924) in having the endopod of uropod shorter than peduncle; and it shares only with the latter species the 2-segmented exopods on pereopod 2 and 3. It differs from this species in the longer article 1 of flagellum of antenna 1 in females, in the pereopod 1 ratio of carpus and propodus and the subequal length of uropod exopod and endopod. In H. africana intermedia the pereopod 1 carpus is subequal to propodus, and the uropod endopod is four-fifths of exopod length. The strong bulb of pereopod 3 in male is a sexual character of adult males ( Fig. 21 A), which was never been described before. It is also present in Heterocuma inerme ( Corbera et. al., 2005, fig. 11; Corbera, pers. comm.) and in Iphinoe africana (own observations), I. armata , I. douniae (from the Mediterranean) and I. senegalensis (from southwest Africa) (Corbera, pers. comm.).

Broom setae are figured by SEM micrographs for the first time. The shape is very complex in having a short basal article, a longer flat stem and up to 100 fine long cilia distally ( Fig. 22 C–D). Broom setae were mainly found on the bases of pereopods 2 to 5, exceptionally they were situated on the propodus of pereopod 5 and on peduncles of antennae 1. The lengths of the stem reaches about 70 µm. Different size classes with increasing lengths were observed. The flat basal article is about 10 µm in length, widened distally and forms a hinge which always longitudinal to the body directed and opens anteriorly. The cuticular derivation of the special setae corresponds to that of neighbouring setae. The function of these setae remains unclear. Sensory setae similar in appearance were found also in other cumacean species ( Petrescu, 1998, Haye, 2004). Day (1975) remarks the occurrence of distinctive knobbed setae on the bases of pereopods 3 to 5 for H. africana intermedia , but these setae differ considerably from special setae of H. ambrizetensis .

Records. Known from shelf coast of northern Angola between 7,235 and 9,562 °S, 20– 46 m.

Figures

FIGURE 18. Heterocuma ambrizetensis sp. nov. Holotype female. A, carapace lateral view; B, antenna 1; C, mandible; D, maxillule, E, maxilla; F, maxilliped 1; G, maxilliped 2; H, maxilliped 3; K, pereopod 1.

FIGURE 19. Heterocuma ambrizetensis sp. nov. Holotype female. A, pereopod 2; B, pereopod 3; C, pereopod 4; C, pereopod 5; E, pleonit 6 dorsal view; F, uropod.

FIGURE 20. Heterocuma ambrizetensis sp. nov. Paratype male. A, lateral view; B, antenna 1; C, carapace lateral view; D, maxilliped 3; E, pereopod 1; F, pereopod 2.

FIGURE 21. Heterocuma ambrizetensis sp. nov. Paratype male. A, pereopod 3; B, pereopod 4; C, pereopod 5; D, pleopod 1; E, uropod; F, adult male, uropod.

FIGURE 22. Heterocuma ambrizetensis sp. nov. scanning electron micrographs of a female. A, left pereopods (P) 2 – 3 ventral view; B, right pereopod 3 – 5 ventral view; C, left pereopod 4 basis medial view; D, left pereopod 4 basis posterolateral view; arrows: special sensory setae.