Platorchestia monodi ( Mateus, Mateus & Afonso, 1986 )

Serejo, Cristiana S., 2004, Talitridae (Amphipoda, Gammaridea) from the Brazilian coastline, Zootaxa 646, pp. 1-29 : 14-21

Platorchestia monodi ( Mateus, Mateus & Afonso, 1986) ( Figs 7–10 )

Orchestia monodi Mateus, Mateus & Afonso, 1986: 100 : figs. 1–7.

Orchestia platensis — Oliveria, 1953: 329, figs. 10–12; Soares, 1979: 98.

Platorchestia platensis (Kroyer, 1845) forma monodi ( Mateus, Mateus & Afonso, 1986) — Stock & Biernbaum, 1994: 796, fig. 1.

Platorchestia monodi — Morino & Ortal, 1995: 825, figs. 1–3; Stock, 1996: 150, figs. 2–4 (part).

Material examined. Paraíba — Cabedelo Harbor, PB, 9 males and 17 females, I/1964, MNRJ 9762. Pernambuco — Maria Farinha, Paulista, in mangrove, PE, 4 females, 31/ VII/1985, MNRJ 9790. Alagoas ­ Mundaú Lagoon, Maceió, AL, 1 male and 2 females, A. Lemos de Castro col., 2/VIII/1978, MNRJ 10841. Espírito Santo — Santa Cruz, ES, 6 males and 30 females, A. Lemos de Castro col., 19/I/1973, MNRJ 9758; Barra de Itabapoana, ES, 2 males and 3 females, A. Lemos de Castro and B. dos Prazeres col., 7/XI/1973, MNRJ 9768. Rio de Janeiro — Rodrigo de Freitas Lagoon, RJ, 6 males and 9 females, C. Serejo col., 25/V/2002, MNRJ 18448; Guaíba Island, Mangaratiba, RJ, 12 males, 35 females, 24/VII/2002, MNRJ 18443; Mambucaba, RJ, A. Lemos de Castro & B. dos Prazeres col., 16/XII/1974, MNRJ 9759. São Paulo — Cananéia, Arrozal, SP, 13 females, A. S. Tararam col., X/1988 to I/1989, MNRJ 15074; 2 females, MNRJ 15078; 1 female, MNRJ 15081; 2 males, MNRJ 15084; 1 female, MNRJ 19108; Iguape, SP, 5 males and 16 femlaes, Y. Wakabara col, 19/VII/1985, MNRJ 15126. Paraná — Fortaleza beach, Ilha do Mel, PR, 50 males, 65 females, C. Serejo and P. Young col., 04/II/1999, MNRJ 18442; Pontal do Sul beach, PR, 1 male and 17 females, C. Serejo and P. S Young col., 3/II /18445, MNRJ 18445. Santa Catarina — Caieria beach, Florianópolis, SC, 6 males and 45 females, C. Serejo & P. Young col., 16/II/1999, MNRJ 18440; Brava beach, Camboriú, SC (near river estuary), 1 male, C. Serejo and P.S. Young col., 18/II/1999, MNRJ 18441; Porto Belo, SC, 100 specimens, 28/XI/1987, MNRJ 9765.

Comparative type material. " Orchestia platensis Kr. , Montevideo. 13/12 40. Beslemte oj opstill. af Kroyer. Silbert hans Anj. Exemplares". Lectotype, 1 male, 12.3 mm, ZMUC 8221; Paralectotypes, 1 male, 6.8 mm; 1 female, 7.6 mm; 7 damage specimens, ZMUC 7803.

Diagnosis. Male gnathopod 1 subchelate, dactylus cuspidactylate and shorter than palm. Male gnathopod 2 palm with very shallow medial concavity. Posterior lobe of coxa 6, antero­distal corner with or without distinct process. Male pereopod 7 merus and carpus not expanded. Oostegite 5 posterior margin with the same number of setae of anterior margin. Uropod 3, peduncle and ramus subequal in length. Telson emarginated, each side with two pairs of robust setae on lateral margin and 3 distal robust setae.

Description. Male, 12.8 mm. Antenna 1 reaching the end of article 4 of peduncle of antenna 2, flagellum with about 6 articles. Antenna 2 with peduncle incrassate, flagellum with about 14 articles ( Fig. 7 A). Mandible with left lacinia mobilis 5­dentate. Maxilla 1, inner plate with two distal plumose setae; outer plate with 9 dentate robust setae, palp reduced and 1­articulate. Maxilla 2, inner plate with several distal setae and a robust proximal plumose seta; outer plate a little larger than inner plate. Maxilliped palp 3­articulate and densely setose, article 2 with medio­distal inner lobe, medial robust setae absent.

Gnathopod 1 subchelate ( Fig. 7 B, C), carpus and propodus with well­developed postero­distal lobe, dactylus cuspidactylate and shorter than palm. Gnathopod 2 robust ( Fig. 7 D), palm with several robust setae and a very shallow medial concavity, dactylus not attenuated distally. Coxa 2–4 about as wide as deep, with well developed posterior process ( Fig. 7 D–F). Pereopod 4 distinctly shorter than pereopod 3; carpus about 2X longer than wide; dactylus thickened ( Fig. 7 F). Pereopod 5 ( Fig. 7 G) slightly longer than half of pereopod 6, pereopods 6–7 subequal in length ( Fig. 8 A, B). Posterior lobe of coxa 6 with a 90º antero­ventral angle, antero­distal process absent (Brazilian population). Pereopod 6, basis oval ( Fig. 8 A). Pereopod 7 not sexually dimorphic, basis rounded; merus and carpus not expanded ( Fig. 8 B). Coxal gills 2–6 simple or slightly convoluted, gills 2 and 6 larger than gills 3–5.

Pleopods 1–3 similar and not reduced, rami subequal in length and slightly shorter than peduncle. Peduncle of pleopod 1 lacking setae; pleopods 2 peduncle with 4–5 medial robust setae; pleopod 3 peduncle with 4–5 sub­distal robust setae and 2 proximal robust setae. Uropod 1 inner ramus, inner margin with 5 robust setae and outer margin with 4 robust setae; outer ramus lacking marginal setae ( Fig. 8 C). Uropod 2 ( Fig. 8 D) outer ramus with one marginal robust seta. Uropod 3 ( Fig. 8 E), peduncle and ramus subequal in length, peduncle with 3 to 4 sub­distal robust setae, ramus with marginal and distal setae. Telson ( Fig. 8 F) longer than wide, emarginated and with a distinct medial line, each side with two pairs of robust setae on lateral margin and 3 distal robust setae.

Female, 8.5 mm. Peduncle of antenna 2 not incrassate. Gnathopod 1 ( Fig. 9 A) minutely subchelate. Gnathopod 2 ( Fig. 9 B), basis enlarged. Coxal gill 2 as long as gnathopod 2 basis. Oostegites 2–5 oval ( Fig. 9 C–F). Oostegites 2–4 long and slender, about 4 times longer than wide, with 9–11 marginal setae; oostegite 5 shorter, about 2.5 times longer than wide, with 4–5 setae, posterior margin with the same number of setae of the anterior margin.

Variation. The medial concavity present in the palm of male gnathopod 2 is variable according with the development of the specimens. Juveniles observed (7.3 to 10 mm) do not present this concavity.

Type locality. Azores Island, Atlantic Ocean.

Distribution. Mid­Atlatic Islands: Azores, Ascension, Madeira; Western Atlantic: Guadeloupe (West Indies); West Florida and Charleston, USA ( Biernbaum & Stock, 1994; Stock, 1996); Negev Desert, Israel ( Morino & Ortal, 1995). Records from Madeira and Guadeloupe are as P. platensis , although Stock (1996) considered them as possible P. m o n ­ odi. Careful examination of material from these areas is needed for confirmation of the above records.

Ecology. Found on the sea shore of Azores and Brazilian coast. Prefer protected beaches and can be found in estuarine areas and mangroves. Some authors found this species on inland areas on altitudes of 762–792 m ( Stock, 1996) and near springs and wells ( Morino & Ortal (1995).

Remarks. Bousfield (1982) erected the genus Platorchestia , including 5 species from North Pacific, and P. platensis , considered a nearly cosmopolitan species along tropicaltemperate coastlines. Nowadays, the genus includes 13 described species ( Table 2 ), although the generic status of some species has been questioned, especially within the terrestrial taxa ( Jo, 1988; Richardson, 1991). Among these, there are three Atlantic sibling species that needs careful examination for an accurate identification. These are P. platensis originally described from Montevideo, Uruguay, P. monodi from warm­temperate and subtropical zones of the Atlantic Ocean, and P. aschmoleorum Stock, 1996 from low­latitude zones of St. Helena Island ( Stock, 1996). Jo (1988) observed the cuspidactylate male gnathopod 1 to distinguished P. platensis from other similar species within the genus. Only three species within Platorchestia has a cuspidactylate male gnathopod 1, P. platensis , P. monodi , and P munmui Jo (1988) . For distinguishing these three species see key bellow.

As discussed by Stock & Biernbaum (1994) and Stock (1996) the distinction of P. platensis and P. monodi are sometimes quite difficult to observe, mainly because most of the characters used are age dependent. Thus, the syntype series of P. platensis was examined, a lectotype designated and compared with the Brazilian material ( Fig. 10 A–D). The diagnostic character pointed out by Jo (1988) for P. platensis as the cuspidactylate gnathopod 1, and posterior lobe of coxa 6 with antero­distal lobe was confirmed. The sexual dimorphism on male antenna 2 and pereopod 7 was also observed ( Fig. 10 A, E). The presence of one or two notches on the palm of male gnathopod 2 has been used to diagnostic P. platensis ( Jo, 1988; Stock & Biernbaum, 1994). The lectotype (12.3 mm) showed a sinuous palm, without a definite notch, although this character seems to be extremely variable within the development of general talitrids and its use as diagnostic should be carefully applied. The Brazilian material has the palm of gnathopod 2 with a shallow medial notch and also more robust setae when compared with P. platensis lectotype. Also, the former lacks the process on antero­distal corner of coxa 6 (present in P. p l a t e n s i s) and carpus of male pereopod 7 is not expanded. Specimens observed by Oliveira (1953) from Guanabara Bay, RJ also do not have pereopod 7 expanded, suggesting that his material might be P. monodi or a juvenile form of P. p l a t e n s i s.

The Brazilian specimens agrees with the original description of P. monodi Mateus et al. (1986) in general aspects, except that the former has the antero­distal corner of posterior lobe of coxa 6 without process (vs. with process). Distinction from Stocks (1996) material was noticed on the female gnathopod 2 with gill as long as the basis (vs. half size of basis). Comparing with material from Israel ( Morino & Ortal, 1995), they also described coxa 6 posterior lobe without process, although the maxilliped palp article 2 lacks robust setae (vs. present or absent), and male antenna 2 is well­incrassate (vs. slightly incrassate).

This is the first record of P. monodi from the Brazilian coast.

Figures

FIGURE 7. Platorchestia monodi (Mateus et al. 1986), male, 12.8 mm, MNRJ 18442. A, head; B, gnathopod 1; C, detail of gnathopod 1; D, gnathopod 2; E, pereopod 3; F, pereopod 4; G, pereopod 5. Scale bars: A – B, D – G, 0.5 mm; C, 0.1 mm.

FIGURE 8. Platorchestia monodi (Mateus et al. 1986), male, 12.8 mm, MNRJ 18442. A, pereopod 6; B, pereopod 7; C, uropod 1; D, uropod 2; E, uropod 3; F, telson. Scale bars: A – D, 0.5 mm; E – F, 0.2 mm.

FIGURE 9. Platorchestia monodi (Mateus et al. 1986), female, 8.5 mm, MNRJ 18442. A – D, oostegites 2 – 5 respectively; E, gnathopod 1; F, gnathopod 2. Scale bars: A – D, F, 0.5 mm; E, 0.2 mm.

FIGURE 10. Platorchestia platensis (Kroyer, 1845), lectotype, male, 12.3 mm, ZMUC CRU 8221. A, head; B, gnathopod 1; C, detail of gnathopod 1; D, gnathopod 2; E, pereopod 7. Scale bars: A, E, 1 mm; B, D, 0.5 mm; C, 0.1 mm.

Tables

TABLE 2. World species of Platorchestia described with information on type locality, distribution and habitat.

Species	Type locality	Distribution	Habitat
ashmoleorum Stock, 1996	Saint Helena Island	as type locality	sea­shore
bousfieldi Hou & Li, 2003	China or Vietnam, not specified	as type locality	possibly terres­ trial
chathamensis Bousfield, 1982	Chatham Island, near Vic­ toria, BC, Canada	as type locality	sea­shore
japonica (Tattersall, 1922)	Lake Biwa, Japan	Western Pacific	terrestrial
joi Stock & Biernbaum, 1994 (= P. crassicornis (Derzavin, 1937))	Soviet coast, Japan Sea	NW Pacific, including Soviet coasts, Japan and Korea	sea­shore
kaalensis (Barnard, 1955)	Mount Kaala, Oahu, Hawaii (3000 ft. altitude)	as type locality	terrestrial
lanipo Richardson, 1991	Lanipô Trail, Oahu, Hawaii (2520 ft altitude)	Hawaii	terrestrial
monodi Mateus et al. 1986	Azores Island	Mid­Atlantic Islands, Brazilian coast (from PE to SC) and Israel	sea­shore