Madeirasquilla, Ďuriš, 2018

Ďuriš, Zdeněk, 2018, Madeirasquilla tuerkayi, a new genus and species of mantis shrimps from Madeira Island, eastern Atlantic (Crustacea: Stomatopoda: Nannosquillidae), Zootaxa 4399 (4), pp. 553-562 : 555-556

Genus Madeirasquilla gen. nov.

Diagnosis. Cornea subglobular. Rostral plate anteriorly tridentate. Antennal protopod with 2 mesial and 1 ventral papillae. Mandibular palp absent. Five epipods present. Raptorial claw dactylus with 11or 12 teeth, and with acute proximoventral tooth; ischiomeral articulation terminal; ischium unarmed. Pereiopods 1–3 with first protopod segment unarmed. Pleonite 6 with strong posterolateral spines, and with pair of teeth posteriorly on sternum. Telson dorsally with broad shield-like field forming ‘false eave’ with slender median tooth posteriorly; marginal armature either side with movable submedian tooth, 4or 5 submedian denticles, and 4 fixed primary teeth with 1 denticle between each. Uropodal protopod with 2 primary spines, outer longer; endopod elliptical, proximolateral margin folded over dorsally.

Etymology. Derived from the name of the type locality, Madeira Island, and the generic name Squilla; gender feminine.

Type-species. Madeirasquilla tuerkayi sp. nov., by present designation.

Included species. One – Madeirasquilla tuerkayi gen. et sp. nov.

Systematic position. Madeirasquilla gen. nov. belongs to the family Nannosquillidae for which the following main characters are diagnostic: cornea subglobular; raptorial claw dactylus uninflated basally, ischium usually exceeding 0.5 of merus length, propodus with 4 proximal movable spines; pereiopods 1 and 2 with subcircular distal segment of endopod, that of pereiopod 3 elongate; pleonite loosely articulated; telson with primary teeth and denticles distinct, slender; and proximal margin of uropodal endopod with strong dorsal fold ( Manning 1980; Ahyong 2001). Up to now, this pantropical family has comprised 14 genera.

Based on external morphology, Madeirasquilla gen. n. ( Figs 1–3A, B ) shows affinity to the ‘ Platysquilla -like’ genera of the nannosquillids, i.e., Platysquilla Manning, 1967 , Platysquilloides Manning & Camp, 1981 , and Mexisquilla Manning & Camp, 1981 , whose species possess a subglobular cornea, lack the ‘fan-shaped’ row of dorsal spines on the telson, and the hook process of the petasma is relatively elongate (Ahyong 2001). From the above taxa, Madeirasquilla is most similar to Platysquilla , another monotypic eastern Atlantic genus. With P. eusebia ( Fig. 3C–E ), Madeirasquilla shares the broad ‘false eave’ dorsally on the telson, four pairs of fixed primary teeth posteriorly on the telson with 1 denticle between each, an epipod on maxillipeds 1–5, at least 11 teeth on the raptorial claw dactylus, and the pleonite 6 sternum with two posteriorly directed spines. The new genus differs from Platysquilla by the following main characters: (1) rostral plate with three sharp anterior projections (versus anterolateral corners rounded); (2) antennal protopod with two mesial and one ventral papillae (versus two and two papillae, respectively); (3) raptorial claw dactylus with acute proximal spine on outer margin (versus faint rounded lobe); (4) walking legs with first protopod segment unarmed (versus with ventrally directed lateral and medial spiniform teeth); (5) pleonite 6 with strong posterolateral spine (versus rounded posterolateral angle); (6) telson with posterior median tooth acute, spiniform (versus posteriorly obtuse), anus situated distinctly posterior to midlength of telson (versus anterior); (7) uropodal protopod with outer primary spine longer (versus inner spine longer) ( Manning 1969, 1977; Camp 1971, 1973; Manning & Camp 1981). Besides Madeira Island, P. eusebia is known also from Portugal, France, west coast of Ireland, the North Sea, and the Mediterranean Sea ( García Raso et al. 2010; Lewis & Gittenberer 2013).

Another Atlantic genus, Platysquilloides , differs from all other nannosquillids by the presence of a strong dorsal spine on the antennal protopod ( Manning 1969, 1977). The single representative of the following western Atlantic genus Mexisquilla , M. horologii ( Camp, 1971) , has a cordiform rostral plate and broad depressed eyes (versus more slender, longer than broad in the new genus), maxillipeds 1–4 with epipods (versus 1–5), first protopod segment of each walking leg with two spines (versus unarmed), a small obtuse median projection dorsally on the telson (versus broad ‘false eave’ with acute median tooth posteriorly), straight series of the submedian telson denticles (versus arranged in a convex line either side of the midline), and reduced outer spine of the uropodal protopod (versus well developed, longer than inner spine) ( Camp 1971; Manning & Camp 19081).

Madeirasquilla is remarkable, among others, also by the tridentate rostral plate. A more or less similar rostrum is present also in the Indo-West Pacific Hadrosquilla perpasta (Hale, 1924) and Keppelius hystricotelson (Barnard, 1958) , in the pantropical Alachosquilla , and in some species of the cosmopolitan Nannosquilla . All those but Keppelius have pleonite 6 with posterolateral spines as in Madeirasquilla , but lack the pair of the posterior sternal spines, which, on the other hand, are present in Keppelius (cf. Manning 1969, 1977, 1978; Ahyong 2001) and Madeirasquilla .

Based on the present molecular analysis of 16S rRNA sequence ( Fig. 4 ), the single available specimen of Madeirasquilla is well separated from representatives of all five other analysed nannosquillid genera, namely Alachosquilla Schotte & Manning, 1993 , Austrosquilla Manning, 1963 , Coronis Desmarest, 1823, Platysquilla Manning , and Pullosquilla Manning, 1978 ( Tab. 1). In the present molecular study, the new species shows a close relationship with Austrosquilla (represented here by A. tsangi Ahyong, 2001 ) from temperate waters of eastern Australia. The genus Austrosquilla actually consists of six species sharing with the new genus the posterolateral spine on the pleonite 6, the smooth dorsal surface of the telson with a posterior median projection, and the posterior armament of the telson; one species of Austrosquilla also has the same number and position of the antennal papillae. Both latter genera, Madeirasquilla and Austrosquilla , are sister-positioned to Platysquilla eusebia in the present analysis. The geographic range of P. eusebia encompasses the type locality of the present new species, Madeira Island ( Biscoito 1985; García Raso et al. 2010). Based on closer morphological similarities especially in the telsonal dorsum and marginal armature, or in the pleonite 6 sternum, and regarding their geographic affinities, Platysquila seems to be closer to the new genus than Austrosquilla . Although Madeirasquilla , Platysquilla and Austrosquilla form a quite well supported clade (BP 87%), the bootstrap proportion for the Madeirasquilla + Austrosquilla clade is only 44%, so a closer relationship between Madeirasquilla and Platysquilla is still statistically plausible based on the 16S marker.

Figures

FIGURE 1. Madeirasquilla tuerkayi gen. et sp. nov., holotype, male. A, anterior part of body, dorsal. B, posterior part of pleon, telson and uropod, dorsal. C, posterior part of pleonite 6and telson, dorsal. D, pleonite 6, telson, and uropod, ventral. E, anterior region of ophthalmic somite, ventral. F, eye, dorsolateral. G, right antenna, dorsal. H, same, lateral. I, right uropod, dorsal.J, left uropodal protopod, ventral.Scale bars, 1 mm; E – unscaled..

FIGURE 2. Madeirasquilla tuerkayi gen. et sp. nov., holotype, male. A, telson, lateral aspect (right side). B, left raptorial appendage, outer side, C–E, left pereiopods 1–3 (resp.), posterior view. F, right male pleopod 1 endopod, anterior view. G, same, apical processes.Scale bars, 1 mm.

FIGURE 3. Colour patterns of Madeirasquilla tuerkayi gen. et sp. nov. (A, B), and Platysquilla eusebia (Risso, 1816) (C–E) from Madeira Island. A, B, male holotype TL 24.2 mm, habitus and posterior pleon with tail fan (resp.), dorsal. C, ovigerous female, MNHN-IU-2015-1650, TL 42 mm, habitus, dorsal. D, E, pre-ovigerous female, MMF 46567 (TL 43 mm), habitus and posterior pleon with tail fan (resp.), dorsal; orange colour indicates extension of female gonads.Photos, author.

FIGURE 4. Phylogenetic tree for 6 selected stomatopod species of the family Nannosquillidae, with Squilla mantis (Squillidae) used as outgroup, obtained by Maximum Likelihood analysis of 16S rRNA sequences (GTR+I+Γ substitution model); bootstrap probability values shown in nodes.