Necallianassa nosybeensis, Poore, 2023

Poore, Gary C. B., 2023, New records, one new genus and 21 new species of Callianassidae (Crustacea, Axiidea) from the Indo-West Pacific, Memoirs of Museum Victoria 82, pp. 167-255 : 200-203

Necallianassa nosybeensis sp. nov.

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4ADD-8178-0EB02450F14B

Figures 24 , 25

Necallianassa MA-03.— Robles et al., 2020: figs 1, 3, 6.

Material examined. Holotype. Madagascar, Nosy Bé , E of Hellville, at CNRO complex, 13.4069° S, 48.2917° E, intertidal mud to silty sand flat with some rocks (stn MGNW-31), UF 14624 (female, 4.4 mm) . Paratypes. Collected with holotype, UF 14499 # (male, 3.0 mm) ; UF 14500 (male, 3.6 mm)

Description. Female. Rostrum triangular, blunt, flat, situated level with dorsal carapace, about one-third length of eyestalks. Carapace dorsally flat, as long as pleomeres 1–2 combined; orbital margin almost transverse; anterolateral lobes insignificant; subanterolateral margin oblique; anterior margin of branchiostegite with shallow dorsal concavity; cervical groove across 0.75 length of carapace, deep at midpoint, reaching linea thalassinica. Thoracic sternite 7 subpentagonal; ventral surface with obsolete posterior median groove. Pleomere 1 tergite flat dorsally, wider posteriorly. Pleomere 2 about as wide across posterior margin as long. Pleomeres 3–5 each wider than long; pleura each with patch of plumose setae. Pleomere 6 about as long as wide, 1.2 times as long as pleomere 5.

Eyestalk about 1.2 times as long as wide, with dorsal face close to rostrum, anterolateral margin evenly tapering, convex, oblique, anteromedial angle rounded in dorsal view, reaching distal margin of antennular peduncle article 1. Cornea densely pigmented, sitting in distal part of eyestalk.

Antennular peduncle reaching distal margin of antennal peduncle; article 1 visible in dorsal view; article 3 about as long as articles 1 and 2 combined; articles 2 and 3 with longitudinal ventral row of long setae. Antennal peduncle article 5 0.85 length of article 4; scaphocerite semicircular.

Maxilliped 3 coxa with small mesial tooth; ischium dilating distally, 1.1 times as long as wide, crista dentata consisting of row of 11 small, well-spaced teeth; merus half as long as ischium measured along outer margin, about 1.6 times as wide as long, with mesiodistal margin evenly convex; carpus about as long as merus outer margin; propodus oval, 1.3 times as long as wide; dactylus 0.9 times as long as propodus, elongate-oval, with dense row of short setae along flexor (lower) margin.

Pereopods 1 (chelipeds) unequal, dissimilar. Major cheliped carpus-palm upper margin 0.9 carapace length. Ischium expanding distally, upper margin unarmed; lower margin unarmed. Merus shorter than ischium, 2.5 times as long as wide (tooth excluded), subrectangular; upper margin weakly convex; lower margin with small tooth at about third length. Carpus 1.2 times as long as wide; margins carinate. Propodus upper margin 0.8 carpus length; palm almost parallel-sided, as long as wide; upper and lower margins with slight ridge; lateral surface smooth, convex, with concave gape; mesial surface convex; lower margin with row of setae extending onto fixed finger; fixed finger 0.7 length of palm, triangular; cutting edge with row of 5 spaced triangular teeth. Dactylus as long as fixed finger, hooked distally; upper margin with tufts of long setae; cutting edge with 8 rounded teeth, more closely spaced over distal two thirds.

Minor cheliped carpus-palm upper margin as long as carapace length. Ischium lower margin unarmed. Merus 0.9 length of ischium; margins smooth. Carpus parallel-sided over most of length, 1.5 times as long as merus, 2.1 times as long as wide. Palm square, as long as wide; upper margin barely convex; lower margin carinate, with row of long setae extending on to fixed finger. Fixed finger triangular, almost as long as palm, cutting edge with 7 triangular teeth over proximal two thirds. Dactylus as long as palm, curved; cutting edge smooth.

Pereopod 2 merus lower margin slightly sinusoidal, 2.5 times as long as wide; carpus 1.6 times as long as wide; chela subtriangular; palm 1.6 times as wide as upper margin; dactylus twice as long as palm upper margin. Pereopod 3 carpus subtriangular, twice as long as wide; propodus wider than long, with evenly curved lower margin, marginal setae evenly spaced, without gaps, with 1 short spiniform seta; dactylus shorter than propodus upper margin. Pereopod 4 coxa flattened ventrally; carpus shorter than merus; propodus as long as carpus, with dense grooming setae distally on lower margin, scattered stiff setae on outer surface, with long spiniform setae parallel to dactylus; dactylus half as long as propodus. Pereopod 5 slender, chelate.

Pleopod 1 of 2 articles; ramus about as long as peduncle, with 3 distal setae. Pleopod 2 biramous; peduncle slightly bent; endopod 0.7 length of exopod; endopod of 2 articles, second short. Pleopods 3–5 biramous, endopod 1.7 times as long as wide; appendix interna twice as long as wide, projecting well beyond mesial margin of endopod, bearing coupling hooks on apical margin.

Uropod endopod and exopod scarcely overreaching posterior margin of telson. Endopod subcircular, about as long as wide; anterior margin straight, ending in sharp spine about 0.7 length of margin; posterodistal margins setose. Exopod widest at midpoint, about as long as wide; anterior margin straight; posterior margin with about 12 blade-like setae indistinguishably merged with densely setose distal margin; dorsal plate extending about 0.4 distance across exopod, scarcely differentiated from distal margin, comprising short stiff setae merging anteriorly with similar setae on distal margin; proximal plate with minute dorsal tooth.

Telson tapering, 1.3 times as long as wide, widest proximally, narrowing posteriorly to 1 minute and 1 posterolateral prominent curved spines; posterior margin concave, setose.

Male. Pereopods 1 (chelipeds) unequal, dissimilar. Major cheliped carpus-palm upper margin about as long as carapace length. Ischium expanding distally, upper margin unarmed; lower margin with 2 obsolete teeth. Merus about as long as ischium, 3 times as long as wide (tooth excluded), subrectangular; upper margin weakly convex, with 2 proximal teeth; lower margin with triangular tooth occupying proximal third, distally with irregular small teeth. Carpus as long as wide; margins carinate. Propodus upper margin 0.9 times as long as carpus; palm almost parallel-sided, as long as wide; upper and lower margins with slight ridge; lateral surface smooth, convex, with deep concave gape; mesial surface convex; fixed finger 0.7 length of palm, triangular; cutting edge with row of 6 irregular triangular teeth. Dactylus as long as fixed finger, hooked distally; cutting edge with irregular teeth, 2 forming a proximal molar.

Minor cheliped carpus-palm upper margin 0.8 carapace length. Ischium lower margin unarmed. Merus 0.8 length of ischium; margins smooth. Carpus parallel-sided over most of length, 1.5 times as long as merus, 2.3 times as long as wide. Palm square, as long as wide; upper margin barely convex; lower margin carinate. Fixed finger triangular, almost as long as palm, cutting edge with 6 triangular teeth over proximal half. Dactylus as long as palm, curved; cutting edge smooth.

Pleopod 1 small, curved, biarticulate. Pleopod 2 absent.

Etymology. From Nosy Bé, town in Madagascar, the type locality.

Distribution. Western Indian Ocean ( Madagascar, known only from type locality); intertidal.

Remarks. The prominent spine at the base of the uropodal exopod found in Necallianassa acanthura (Caroli, 1946) and N. berylae Heard and Manning, 1998 (see Ngoc-Ho, 2003: fig. 8) is represented in N. nosybeensis by a minute tooth on the articulating proximal sclerite. The cheliped of the male of all previously described species possesses a strong meral hook and deep gape between the fingers; the cheliped of the two males in this collection have a relatively smaller tooth that is still more developed than the small spine of the female. The gape between the fingers is larger than in the female but not as much as in the other two species. Necallianassa nosybeensis differs from previously described species in having a row of triangular teeth along cutting edges of both fingers of the major cheliped and the fixed finger of the minor cheliped in both sexes. Necallianassa nosybeensis has a second minute posterolateral tooth on the telson; N. acanthura has one pair of spines, N. berylae has two similar spines, and N. truncata has none.

The new species was found close to N. acanthura and N. truncata in the molecular phylogram ( Robles et al., 2020).

Figures

Figure 24. Necallianassa nosybeensis sp. nov. Madagascar. UF 14624, holotype female, 4.4 mm: a, carapace, pleon, telson, uropod endopods, dorsal; b, carapace, pleomeres 1, 2, lateral; c, d, anterior carapace, eyestalk, antennular, antennal peduncles; e, thoracic sternum 7, coxa 4; f, major cheliped (right, mesial view); g, major cheliped fingers (lateral view); h, minor cheliped (left, mesial view); i, minor cheliped fingers (lateral view). Paratype male, UF 14500: j, major cheliped (right, mesial view); k, major cheliped fingers (lateral view); l, minor cheliped (left, mesial view). Scale bars = 1 mm.

Figure 25. Necallianassa nosybeensis sp. nov. Madagascar. UF 14624, holotype female, 4.4 mm: a, maxilliped 3; b–e, pereopods 2–5; f–h, pleopods 1–3; i, telson, left uropod. UF 14500, paratype male; j, telson, left uropod. UF 14499, paratype male; k, pleopod 1. Scale bars = 1 mm.