Munnogonium quequensis, Doti, Brenda L. & Roccatagliata, Daniel, 2013

Doti, Brenda L. & Roccatagliata, Daniel, 2013, Two new species of the genus Munnogonium (Isopoda: Asellota: Paramunnidae) from Argentina, Zootaxa 3717 (3), pp. 301-319 : 302-310

Munnogonium quequensis n. sp.

Figures 1–7

Etymology. The specific epithet is a toponym referring to Quequén, the locality where the type material was collected.

Type locality. Quequén (Buenos Aires Province), 15 Dec 2005. Sta. 4, 38º42.83'S, 58º41.90'W, 45 m. All specimens were found clinging tightly on the aboral surface of the sea star Astropecten brasiliensis Müller & Troschel, 1842 .

Material examined. Holotype. Brooding ♀, 1.93 mm (MACN-In 39184), here designated.

Paratypes. Same data as holotype: 20 brooding ♀, 9 non brooding ♀, 50 ♂ (MACN-In 39185).

Other material examined. Quequén (Buenos Aires Province), 15 Dec 2005: Sta. 2, 38º41.45'S, 58º42.10'W, 39 m: 1 ♂ (MACN-In 39186). Sta. 5, 38º43.65'S, 58º41.85'W, 47 m: 4 ♂, 4 brooding ♀, 1 non brooding ♀ (MACN-In 39187). Sta. 6, 38º46.58'S, 58º41.80'W, 54 m: 1 ♂ (MACN-In 39188). Sta. 12, 38º50.56'S, 58º41.08'W, 57 m: 1 brooding ♀ (MACN-In 39189).

Description. Body width 0.46 length in female (0.38 in male), widest at pereonite 3 in both sexes. Head length 0.48 width; length posterior to eyestalks 0.46 anterior length (0.7 in male). Frontal margin broadly rounded with tuft of setae medially (at low resolution this tuft of setae looks like a short blunt median projection), without angular lateral margins adjacent to antennae. Eyestalks vestigial, length 1.0 width in female (1.5 in male), long axis angling forward at approximately 25° in female (30° in male), with 4 ocelli.

Pereonites 1–4 lateral margins not projecting, coxae not visible in dorsal view; pereonite 1, in female greatest sagittal length 1.87 midline length, in male 2.0 midline length. All pereonites lateral margins rounded.

Pleon length 2.06 width in female (2.01 in male). Pleonite 1 width 0.86 distance between uropods, length 0.68 width. Pleotelson lateral margin rounded and smooth with short proximal neck, lacking inflection between proximal and lateral margins; ventral length proximal to pleopods 0.17 total pleotelson length (see Fig. 1 A); posterior margin apex pointed, evenly curving into lateral margin.

Antennula article 1 extending beyond eyestalk apex and pereonite 1 lateral margin; article 1 tubular, length and width subequal to article 2; article 3 twice longer than article 5, articles 4 and 6 shorter than articles 3 and 5.

Antenna article 3 in ventral view tubular, width 0.33 length; article 5 1.25 longer than article 4; flagellum with 4 articles, proximal article subequal to distal ones.

Mandible molar process distally flared, triturative surface oval-shaped. Maxilliped palp article 1 with small lateral tooth.

Pereopod I basis dorsal margin smooth, length 3 width; merus ventral margin with 1 robust seta distally; carpus triangular, distal width 0.75 ventral margin length, ventral margin with 3 robust setae and crenate ridges; propodus narrowing distally, with 1 robust seta and 1 crenate ridge on ventral margin. Pereopods II–IV carpus and propodus ventral margins with row of elongate stiff robust setae; dactylus dorsal and ventral claws thin, elongate, dorsal claw longer than dactylus, ventral claw nearly as long as dactylus in pereopods II and III, but much shorter than dactylus in pereopod IV. Pereopods V–VII carpus and propodus ventral margins with short robust setae; dactylus dorsal claw thick and robust, subequal in length to dactylus; ventral claw minute, seta-like. Pereopods II and III of male with distoventral bulge on basis and proximoventral bulge on ischium ( Fig. 6 A, B).

Female operculum width 0.78 length, distal part tapering with concave distolateral margins. Male pleopod I lateral lobes distinctly projecting from midlateral margin, width 0.4 distance to midline, apex with tuft of simple setae and 1 thick seta with distal pore; distal projection length 0.33 pleopod total length, forming acute angle, with rounded apices.

Uropods dorsal and adjacent to lateral margins of pleotelson.

Size. Largest female 1.93 mm, largest male 2.05 mm.

Distribution. Known only from its type locality. The type specimens of M. quequensis n. sp. were found clinging tightly on the aboral surface of the sea star Astropecten brasiliensis Müller & Troschel, 1842 . Both the asellotes and the sea stars were covered by mucus.

Remarks. In the male of M. quequensis n. sp., pereopods II and III are sexually dimorphic. The large adult males have a distoventral bulge on the basis and a proximoventral bulge on the ischium of these two pereopods ( Fig. 6 A, B). In small adult males only the pereopod II is sexually dimorphic, while in the juvenile males neither the pereopods II nor III show such bulges on the basis and ischium.

The material examined of M. quequensis n. sp. contained some specimens that were more elongated than others, i.e. their segments were greatly separated and the articular membranes everted. This is especially noticeable between the pleonite 1 and pleotelson (compare Fig. 1 B and 1C), but is probably an artefact caused by fixation.

Figures

FIGURE 1. Munnogonium quequensis n. sp. Holotype female (MACN-In 39184). A, B, habitus in lateral and dorsal views, respectively. Paratype female (MACN-In 39185 - a). C, habitus, dorsal view. Paratype male (MACN-In 39185 - b). D, habitus, dorsal view. Scale bars: 0.5 mm (A, B and C, D share scale).

FIGURE 2. Munnogonium quequensis n. sp. Holotype female (MACN-In 39184). A, head, ventral view. Paratype female (MACN-In 39185 - c). B, antennula. C, antenna. D, E, left mandible in different views. F, right mandible with details of incisor and molar processes. Scale bars: A, 0.2 mm; B, C, 0.1 mm; D, F, 0.05 mm (D, E share the same scale).

FIGURE 3. Munnogonium quequensis n. sp. Paratype female (MACN-In 39185 - c). A, maxillula. B, maxilla. C, maxilliped with detail of the endite. D, pereopod I. Scale bars: A – C, 0.05 mm; D, 0.1 mm.

FIGURE 4. Munnogonium quequensis n. sp. Paratype female (MACN-In 39185 - c). A – D, pereopods II – V, respectively. Detail of the dactylus is shown for pereopods II and V. Scale bars: 0.1 mm.

FIGURE 5. Munnogonium quequensis n. sp. Paratype female (MACN-In 39185 - c). A, B, pereopods VI and VII, respectively. C, Operculum. D – F, pleopods III – V, respectively. G, uropod. Scale bars: A – F, 0.1 mm; G, 0.05 mm.

FIGURE 6. Munnogonium quequensis n. sp. Paratype male (MACN-In 39185 - d). A, B, pereopods II and III, respectively. C, pleopod I with details of lateral lobe and thick seta. D, pleopod II. Scale bars: 0.1 mm.

FIGURE 7. Munnogonium quequensis n. sp. SEM photos. Paratype male (MACN-In 39185 - e). A, B, habitus in dorsal and ventral views, respectively. D, head in dorsal view. E, detail of anterior margin of head (square shown in D). F, head in frontal view. Paratype female (MACN-In 39185 - f). C, habitus in dorsal view. Scale bars: A – C, 0.5 mm; D, F, 0.1 mm.