Ektraleptochelia Bamber & Marshall 2015
Creators: name: Gu, Modest
name: Bird, Graham J.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Tanaidacea
Leptocheliidae
Ektraleptochelia

description: Ektraleptochelia Bamber & Marshall, 2015 and Permixtimella Guţu, 2016
Comparing the 2015 series of diagnoses and the descriptions of the type-species of the genera with those described by Guţu (2016) we conclude that the macro- and microfeatures of the type-female of Permixtimella (P. oculifurcillata Guţu, 2016) are similar, but not identical, to those of the type-female of Ektraleptochelia (E. phoxops Bamber & Marshall, 2015). Based on the data presented by Bamber & Marshall (op.cit.: 355–359, figs 8– 9) and Guţu’s diagnosis and comments (op.cit.: 144–152, figs 46–48), the morphological features of the females of the two genera appear to be different from other known leptocheliids.
According to the descriptions and illustrations presented by the above authors, the main similarities between the type-females of Ektraleptochelia and Permixtimella, consist of:
- the length of proximal article of antennule (about five-six times as long as medial width); - the second article of antenna conspicuously longer than third article; - the second article of antenna with two–three setae (no robust spines) on distal extremity; - the third article of antenna with a dorsodistal stout spine;
- maxilliped endite with seta and three flat spines on distal side; - cheliped merus with two ventral setae;
- cheliped carpus with two or three small setae on mid-proximodorsal; - cheliped fixed finger with at least seven setae;
- pereopods 1–3 bases with short proximodorsal seta;
- pereopod-2 merus with ventrodistal long seta;
- pereopod-2 propodus with two distal setae and small ventro-subdistal spine; - pereopods 4–6 meri with two ventrodistal small spines;
- pereopods 4–6 carpi with three small spines on distal extremities; - uropod endopod six-segmented.
In addition, the two females are distinguishable by some characters, suggesting the existence of two different species, although their type-localities are in two close marine areas (the Celebes Sea and off northern Brunei, respectively). We note the following features:
- the shape of ocular lobes (with anterior pointed apophysis, cf. Bamber & Marshall, op.cit.: 356 and fig. 8B, and with bifurcate crochet in top, cf. Guţu, 2016: 147 and fig. 46C);
- the length of chelipedal carpus (three and about 2.5 times as long as wide in E. phoxops and P. oculifurcillata, cf. Bamber & Marshall op.cit.: 356 and fig. 9A, and Guţu 2016: 149 and fig. 47A, respectively);
- the length of pereopod-1 dactylus with its unguis (as long as carpus and propodus together in E. phoxops, cf. Bamber & Marshall op.cit., fig. 9B, but conspicuous shorter in P. oculifurcillata, cf. Guţu 2016, fig. 47C);
- the number of ventral setae on pereopods 2–3 ischia (two in P. oculifurcillata, cf. Guţu 2016: 149 and fig. 47D, E, and only one in E. phoxops, cf. Bamber & Marshall op.cit.: 359 and fig. 9C, D);
- the number of plumose setae on outer margins of endopod and exopod of pleopods (more numerous in P. oculifurcillata, cf. Guţu 2016: 150, and Bamber & Marshall op. cit.: 359);
- the number of segments of the uropodal exopod (two in P. oculifurcillata, cf. Guţu 2016: 151 and fig. 46I, and only one in E. phoxops, cf. Bamber & Marshall op.cit.: 359 and fig. 9H).
In the above listing, the small differences present in the setation of the propodus and merus of pereopod-2 (two distal setae on propodus and the absence of the ventro-distal seta on merus, mentioned by Bamber & Marshall op. cit.: 359 and fig. 9D, in comparison with one seta on the propodus and one on the merus, cf. Guţu 2016: 149 and fig. 47D, E) were not taken into consideration, as we consider them insignificant.
We conclude that Permixtimella is a junior synonym of Ektraleptochelia, which now includes two species: E. phoxops Bamber & Marshall, 2015 and E. oculifurcillata (Guţu, 2016), comb. nov. Furthermore, the elongate chelae of Leptochelia males from Burma (Lang 1973, fig. 10d, e) are very similar to that of E. oculifurcillata comb. nov. (Guţu, 2016, fig. 49G) from the Celebes Sea, and may belong to a third species of the genus Ektraleptochelia.
As for Ektraleptochelia, any complete generic diagnosis (for both sexes) cannot be realised until the male of the type-species, Ektraleptochelia (E. phoxops), is discovered. Therefore, the diagnosis for males presented by Guţu (2016: 144–145) for Permixtimella (now Ektraleptochelia) should be considered a presumptive diagnosis. Otherwise, there is a risk of repeating the mistake made for the earlier diagnosis of Leptochelia, when the morphological features of the females of “ L. dubia / savignyi group” were associated with those of the males of “ L. minuta group” (Lang 1973).
As we have stated above, although the type-females of the two genera Permixtimella and Ektraleptochelia are similar, they are not identical, and the small differences require the completion of the diagnosis of Ektraleptochelia with two amendments, at least: “ pereopod 1 dactylus about as long as unguis, or only slightly longer than that ” and “ uropodal exopod with one or two articles [segments] ”.
A conundrum here is the position of Ektraleptochelia within the systematics of the family Leptocheliidae. Although Bamber & Marshall (op.cit.) classified it in the Catenariinae Bamber, 2013, we consider that it belongs to the Leptocheliinae (Guţu 2016). Guţu emphasised (2016: 19) that the two morphological features of the genus Catenarius Bamber, 2008 (type-genus of the subfamily Catenariinae) are also present in the species of Leptochelia Dana, 1849 (sensu Guţu 2016), the type-genus of the subfamily Leptocheliinae, namely the pointed maxilliped endite spines and five-articled antennule (alternatively “three-articled peduncle and two flagellar segments”). Larsmentia Bamber & Marshall, 2015, whose males are unknown, classified by them in the Catenariinae, has similar morphological features to those of the species of Leptocheliinae. The amended diagnosis of the Catenariinae (Bamber & Marshall op.cit.: 352) did not remove these confusions. We also note that, as the males of the three genera classified by Bamber & Marshall (op.cit.) in the Catenariinae are unknown, extreme caution is required in establishing the status of this subfamily. There are known examples when females in this family, apparently similar and initially classified in the same genus, were reclassified in different genera, according to the morphological features of the males (Bamber 2013: 8, 28; Guţu 2016: 50–52, 129–130).
description: Published as part of Gu, Modest & Bird, Graham J., 2017, The synonymy of the genus Permixtimella Guţu, 2016 (Crustacea: Tanaidacea) with Ektraleptochelia Bamber & Marshall, 2015 and remarks on other leptocheliid taxa, pp. 587-593 in Zootaxa 4263 (3) on pages 588-589, DOI: 10.11646/zootaxa.4263.3.10, http://zenodo.org/record/573701