Material examined.

MHNCI 2844 One female from the phytal of red alga Spyridia aculeata, 7 m deep, Araras Island (26°27'S, 48°34'W), Tamboretes Archipelago, Santa Catarina, Brazil, 16^th May, 2009.

MHNCI 2845 One male and two females from the phytal of the calcareous red alga Amphiroa beauvoisii, 4 m deep.

MHNCI 2846 Three males and two females from the phytal of Amphiroa beauvoisii, 1.5 m deep, Pássaros Island (26°22'S, 48°31'W), Tamboretes Archipelago, Santa Catarina, Brazil, 16th May, 2009.

MHNCI 2847 Four males and two females from the phytal of brown alga Sargassum cymosum, Bombinhas (27°08'28"S, 48°28'42"W), Santa Catarina, Brazil, 30^th June, 2011.

CEZ 968 Holotype male from of Sargassum, Itamaracá, Pernambuco, Brazil 5^th August, 1968. Collector: Dr. Pierre Montouchet.

CEZ 971 Two paratypes males and three paratypes females from of Sargassum, Mar Grande, Bahia, Brazil, 22th January, 1968. Collector: Dr. Pierre Montouchet.

CEZ 972 12 paratypes males and eight paratypes females from of Sargassum, Itamaracá, Pernambuco, Brazil 5^th August, 1968. Collector: Dr. Pierre Montouchet.

CEZ 973 Seven paratypes males and four paratypes females from of Sargassum, Mar Grande, Bahia, Brazil, 22th January, 1968. Collector: Dr. Pierre Montouchet.

CEZ 974 One paratype male and one paratype female from of Sargassum, Guarapari, Espírito Santo, Brazil, 6^th September, 1968. Collector: Dr. Pierre Montouchet.

Male (Fig. 1A). Body length 3.0 mm. Pereonites 3 and 4 the longest, followed by pereonites 2 and 5. Head and pereonite 1 (suture clearly present) concave along dorsal margin, head with an anteriorly curved mid-dorsal projection, pereonite 1 with a small postero-dorsal projection. Pereonite 2with paired mid-dorsal projections, 1 postero-dorsal projection, paired antero-lateral projections and paired mid-lateral projections. Pereonite 3 with paired mid-dorsal projections, 1 postero-dorsal projection and paired mid-lateral projections. Pereonite 4 with paired mid-dorsal projections, 1 weak postero-dorsal projection, paired antero-lateral projections and paired mid-lateral projections. Pereonite 5 withpaired mid-dorsal projections, paired antero-lateral projections and paired mid-lateral projection near the swollen basal part of pereopod 5. Pereonite 6 with paired postero-lateral projections near the basal part of pereopod 6.

Antennae (Figs. 2A, 2B). Antenna 1 about half body length. Peduncular articles with ca. 10 to 20 simple setae of varied length; peduncular article 2 the longest followed by article 1. Flagellum 6-articulate with 4/5 of peduncular length. Antenna 2 about 4/5 of antenna 1 length, without swimming setae; peduncular setose in varied length; flagellum with 8 and 6 simple setae in the proximal and distal articles.

Mouthparts (Figs. 3A–G). Upper lip notched, forming rounded projections. Right mandiblewith incisor with 5 teeth and followed by lacinia mobilis with 5 teeth and 3 trapezoid plates; palp article 2 with 1 lateral seta; palp article 3 setal formula 1–6–1 with a distal knob. Left mandible incisor with 5 teeth followed by 3 trapezoid plates; palp article 2 with 1 lateral seta; palp article 3 setal formula 1–6–1 with a distal knob. Lower inner lips round and fused each other, outer lobes round with 1 apical seta. Maxilla 1outer plate with 6 stout apical setal-teeth; palp distal margin with 4 setae. Maxilla 2inner plate triangular with 4 apical setae; outer plate elongate with about 4 apical setae. Maxilliped basal endite (inner plate) with 2 setae on outer margin; ischial endite (outer plate) oval, 2 times longer than inner plate, with 4 or 5 setae on inner margin; palp article 2 with 2 or 3 setae on inner margin; palp article 3 with 5 distal setae; palp article 4 (dactylus) weakly falcate.

Gnathopod 1 basis as long as ischium, merus and carpus combined, covered by sparse setae of varied length; propodus subtriangular, palm with a pair of proximal stout setae (grasping spines) and a row of 8 simple setae; dactylus with sparse and short setae, inner margin smooth with a teeth subdistally (Fig. 2C).

Gnathopod 2 inserted in the pereonite 2 at 2/5 from anterior margin (Fig. 1A); coxa vestigial; basis 1.3 times of pereonite 2 length, with a spiny projection near antero-distal corner; ischium rectangular; merus rounded; carpus triangular and provided with scarce simple setae; propodus oval, ratio between width: length = 0.57, inner margin provided with 1 stout setae proximally, 3 triangular projections medially and distally and numerous setae: few simple setae on the outer margin; dactylus shorter than palm and slightly curved with a row of setulae alongside the inner margin (Fig. 2D).

Gill 3length 2/5 of corresponding pereonite, elliptical (Fig. 1A), pereopod 3 tiny with 2 simple setae apically (Fig. 4A). Gill 4length 1/3 of corresponding pereonite, elliptical (Fig. 1A), pereopod 4 similar to pereopod 3 (Fig. 4B).

Pereopod 5 basis to carpus furnished with 3–10 setae of varied length; palm of propodus very slightly concave with 2 setae proximally and a row of 7 robust setae alongside; dactylus slightly curved (Fig. 4C). Pereopods 6 and 7 similar to pereopod 5 in feature but increasing in size (Figs. 4D, 4E).

Penes length about 2 times width (Fig. 4F).

Abdomen with a pair of lateral lobes and dorsal lobe with a pair of dorsal setae (Fig. 4F).

Female. Body length 3.1 mm (Fig. 1B). Pereonites 3 and 4 subequal and the longest, followed by pereonite 2. Clear suture between head and pereonite 1, head with 1 anteriorly curved mid-dorsal projection. Antenna 1 flagellum 7-articulate. Pereonite 1with 1 postero-dorsal projection. Pereonite 2with paired mid-dorsal projections, 1 postero-dorsal projection and paired antero-lateral projections. Pereonite 3with paired mid-dorsal projections, 1 postero-dorsal projection, paired mid-lateral projections and paired postero-lateral projections. Pereonite 4with paired mid-dorsal projections and paired mid-lateral projections. Pereonite 5with paired mid-dorsal projections. Gnathopod 2 propodus length 1.5 times width (Fig. 2E), with grasping spine proximally followed by a serrated margin; two smooth triangular projections medially.

Intraspecific variation.

In adult males and females including those collected by Quitete (Quitete, 1971a) in Pernambuco State, the number of articles in the flagellum of antenna 1 varies from 5 to 7 during growth. The size reduction of the mid-dorsal projections on pereonites 3 and 5 mentioned by this author was only found among specimens studied by her. Setal formula for terminal article of mandibular palp can be 1–5-1 or 1–6-1. The body spination is rather constant among individuals summing up 30 spines in males.

Type locality.

Itamaracá, Pernambuco State, Brazil.

Distribution.

Western South Atlantic. Brazil. Itamaracá, Pernambuco State; Olivença, Ilhéus, Bahia State; Vitória and Guarapari, Espírito Santo State (Quitete 1971a). Ubatuba, São Paulo State (23°32'S, 45°10'W – 23°30'S, 45°08'W) (Jacobucci et al. 2002, 2009). Paranaguá Bay, Paraná State (25°31'S, 48 °30'W) (Neves 2006). Tamboretes Archipelago: Pássaros Island (26°22'S, 48°31'W) and Araras Island (26°27'S, 48°34'W), Balneário Barra do Sul and Bombinhas Beach, Bombinhas, Santa Catarina State (present study).

Habitats.

Amongst thallii of the brown seaweed Sargassum sp. (Quitete 1971a and present paper), Sargassum cymosum (Jacobucci et al. 2002) and Sargassum filipendula (Jacobucci et al. 2009); on boat hulls and floating piers (Neves 2006); amongst thallii of the red algae Amphiroa beauvoisii and Spyridia aculeata and tubular branches of polychaete colony (present paper).

Remarks.

Takeuchi (1993) proposed a classification with four families, Caprellidae, Caprogammaridae, Paracercopidae, and Phtisicidae for the Amphipoda Caprellidea (Cyamidae excluded) based on the cladistic analysis. Fallotritella and Pseudaeginella were set under the Caprellidae. At the same time, Laubitz (1993) proposed a classification with eight families, Caprellidae, Caprellinoididae, Caprogammaridae, Cyamidae, Paracercopidae, Pariambidae, Phtisicidae and Protellidae. In her classification system, Fallotritella and Pseudaeginella were included in Caprellinoididae which is considered to be more related to Paracercopidae and Phtisicidae than to Caprellidae.

The above treatment of Fallotritella and Pseudaeginella performed by Takeuchi (1993) was followed by Myers and Lowry (2003) and Vassilenko (2006). In the higher classification system of Myers and Lowry (2003) based on cladistic analysis of corophiid amphipods, Caprellidae, Caprogammaridae and Cyamidae are included among the Caprelloidea. The Caprellidaeof Myers and Lowry (2003) is composed of two subfamilies, Caprellinae and Phtisicidae. Fallotritella and Pseudaeginella with ca. 50 genera constitute the Caprellinae under the Caprellidae (Myers and Lowry 2003). Vassilenko (2006) reviewed the recent studies dealing her support to Takeuchi's (1993) treatment more than to Laubitz (1993) concerning to the phylogeny of the Caprellidea.

The genus Fallotritella was established based on Fallotritella biscaynensis McCain, 1968 collected from Florida, U.S.A, Antigua & Barbuda and St. Lucia (McCain 1968), just prior to Quitete (1971a). The suggestion of synonymy of these two genus, i.e., Pseudaeginella and Fallotritella was mentioned under remarks of Pseudaeginella by McCain (1968). The lack of reference materials of Pseudaeginella tristanensis (Stebbing, 1888), the type species of Pseudaeginella, has been led to the presumption towards absence of pereopods 3 and 4 in Pseudaeginella. At the same time, Fallotritella biscaynensis was recorded to possess 1-articulate pereopods 3 and 4 in the generic description for Fallotritella. He also noted that, in case of presence of pereopods 3 and 4 in the two known species of Pseudaeginella, Fallotritella would fall as junior synonym of Pseudaeginella (see McCain 1968, p. 100). Almost 30 years later, Laubitz (1995) examined individuals of Pseudaeginella tristanensis collected from Amsterdam Islands in the southern Indian Ocean and reported the synonymy of these two genera based on the presence of minute pereopods 3 and 4 on these specimens.

Pseudaeginella montoucheti (Quitete, 1971) is a tiny caprellidean that measures less than 3.5 mm in body length (see Fig. 1). Within this genus, Pseudaeginella montoucheti is the second spiniest species (total of 30 spines on the head and pereonites 1–7 of males) and only surpassed by Pseudaeginella sanctipauli that has a total of 33 spines on body surface. In the drawing of Pseudaeginella montoucheti from Pernambuco State performed by Quitete (1971a) the following body projections are missing in male: a pair of dorsal projections instead of one dorsal spine medially on pereonite 5 and ventro-lateral projections over the insertion of pereopod 5 and 6 on pereonite 5 and 6, respectively. In spite of the wide distribution, Pseudaeginella montoucheti showed a relatively low intraspecific variation in its external morphology.

Although restricted to the Atlantic coast of Brazil, the present study showed that Pseudaeginella montoucheti is distributed along more than 2, 600 km, from tropical (Itamaracá Island, Pernambuco State, 7°44'S, 34°49'W) to subtropical (municipalities of Barra do Sul, 26°27'S, 48°34'W and Bombinhas, 27°08'S, 48°28'W, Santa Catarina State) latitudes. Recently, Caprella dilatata Krøyer, 1843 was also reported showing wide distribution from Sao Paulo State, Brazil (Jacobucci et al. 2002) to Mar del Cobo and Mar del Plata Harbour, Argentina along the south Atlantic coast of South America (Masunari and Takeuchi 2006).

Pseudaeginella Mayer, 1890 is currently composed of 10 species: Pseudaeginella antiguae Barnard, 1932 from Antigua and Barbuda, Pseudaeginella biscaynensis (McCain, 1968) from Florida, U.S.A., Pseudaeginella campbellensis Guerra-García, 2003b from subantarctic islands of New Zealand, Pseudaeginella colombiensis Guerra-García, Krapp-Schickel & Müller, 2006 from Colombia, Pseudaeginella inae Krapp-Schickel & Guerra-García, 2005 from Indonesia, Pseudaeginella montoucheti (Quitete, 1971) from Brazil, Pseudaeginella polynesica (Müller, 1990) from Bora Bora and Moorea, French Polynesia, Pseudaeginella sanctipauli Laubitz, 1995 from St. Paul and Amsterdam Islands, France, Pseudaeginella tristanensis (Stebbing, 1888) from Tristan da Cunha, and Pseudaeginella vaderi Guerra-García, 2004 from Australia.

Of 10 species of Pseudaeginella, the closest species to Pseudaeginella montoucheti can be considered Pseudaeginella sanctipauli that wasdescribed from St. Paul and Amsterdam Islands, South Indian Ocean (Laubitz 1995), since both are the spiniest species within the genus. On the other hand, Pseudaeginella montoucheti can be distinguished from Pseudaeginella sanctipauli by the spinier body, antenna 1 length equals half body in males, and presence of ventro-lateral spines over gills on pereonites 3 and 4.

A key to the species of Pseudaeginella is presented below; it was mainly based on the characteristics of body somites because these can be observed without dissections of mouthparts.

Key to species of the genus Pseudaeginella