INTRODUCTION
The members of the family Caprellidae are considered to constitute a keystone part of shallow-water marine ecosystems as secondary and tertiary producers (Guerra-Garcia & Takeuchi, Reference Guerra-García and Takeuchi2004). They are very abundant members of the marine benthos living as epibionts on a variety of substrata from the littoral zone to a depth of 4790 m (McCain, Reference McCain1968; Arimoto, Reference Arimoto1976; Guerra-Garcia & Takeuchi, Reference Guerra-García and Takeuchi2004). Despite its abundance and role on marine ecology, little is known about the caprellids amphipods on the north-east Brazilian coast. Indeed, only three species have been recorded (Wakabara & Serejo, Reference Wakabara, Serejo and Young1998).
The genus Aciconula was erected by Mayer (Reference Mayer1903) based on two female specimens of A. miranda Mayer, Reference Mayer1903 collected from Singapore, Malaysia and Koh Krau, Thailand. Mayer (Reference Mayer, Michaelsen and Hartmeyer1912) described the male of A. miranda based on material collected from Shark Bay, Australia. Later on, Chess (Reference Chess1989) described the second species of the genus, A. acanthosoma from Santa Catalina Island, Southern California. Recently, a third species, A. australiensis, was described by Guerra-Garcia (Reference Guerra-García2004a) from Lizard Island, Queensland, Australia. Additionally, Guerra-García (Reference Guerra-García2004b) and Guerra-García et al. (Reference Guerra-García, Krapp-Schickel and Müller2006) recorded this genus as undescribed species (Aciconula sp.) from Phuket, Thailand and the Carribean coast of Colombia, respectively. Hence, only three valid species have been described for this genus, with a worldwide and very disjoint biogeographical distribution.
In this paper we describe a new species of Aciconula from an intertidal exposed zone of beach rocks, in association with seaweeds from the Pernambuco State coast, Brazil. Furthermore, this is the first record of this genus from Brazilian waters. Also a key to all species of Aciconula is provided.
MATERIALS AND METHODS
Type material is deposited in the Museu de Oceanografia–Petrônio Alves Coelho/Universidade Federal de Pernambuco (MOUFPE). Appendages and mouthparts were mounted on glass slides and sealed with glycerol gel after staining with Chlorazol Black. The illustrations were drawn under optic microscope with a camera lucida and digitally prepared according to methods described by Coleman (Reference Coleman2003). The crustacean spines and setae classification follows Watling (Reference Watling, Felgenhauer, Watling and Thistle1989). Terminology in describing gnathopodal palm follows Poore & Lowry (Reference Poore and Lowry1997). The following abbreviations are used in the figures: A, antenna; Ab, abdomen; G, gnathopod; Gi, gill; Ha, habitus; Hd, head; LL, lower lip; Md, mandible; Mx, maxilla; Mxp, maxilliped; P, pereopod; m, male; f, female; l, left; r, right.
RESULTS
SYSTEMATICS
Order AMPHIPODA Latreille, Reference Latreille and Cuvier1816
Suborder COROPHIIDEA Leach, Reference Leach and Brewster1814
Family CAPRELLIDAE Leach, Reference Leach and Brewster1814
Genus Aciconula Mayer, Reference Mayer1903
Aciconula tridentata sp. nov.
(Figures 1–5)
Aciconula tridentata sp. nov., holotype male (2.4 mm) Praia de Suape, Pernambuco State, Brazil, July 2009, MOUFPE 15070. Paratype female (2.6 mm) from the same locality of holotype, MOUFPE 15013. Scale bars: 0.2 mm.
Aciconula tridentata sp. nov., holotype male, Praia de Suape, Pernambuco State, Brazil, July 2009, MOUFPE 15070. Paratype female from the same locality of holotype, MOUFPE 15013. Scale bars: 0.1 mm for mA1 and mA2; and 0.05 mm for the remainder.
Aciconula tridentata sp. nov., holotype male, Praia de Suape, Pernambuco State, Brazil, July 2009, MOUFPE 15070. Paratype female from the same locality of holotype, MOUFPE 15013. Scale bars: 0.1 mm.
Aciconula tridentata sp. nov., holotype male, Praia de Suape, Pernambuco State, Brazil, July 2009, MOUFPE 15070. Paratype female from the same locality of holotype, MOUFPE 15013. Scale bars: 0.1 mm.
Aciconula tridentata sp. nov., holotype male, Praia de Suape, Pernambuco State, Brazil, July 2009, MOUFPE 15070. Paratype female from the same locality of holotype, MOUFPE 15013. Scale bars: 0.1 mm.
TYPE MATERIAL
Holotype: male (2.4 mm), Praia de Suape (8°23′03.31″S–34°57′20.64″W), Pernambuco State, Brazil, in intertidal seaweeds' bed on beachrock, July 2009, T.N.V. Reis col., MOUFPE 15070.
Paratypes: 1 female (2.6 mm), dissected and drawn, Praia de Suape (8°23′03.31″S–34°57′20.64″W), Pernambuco State, Brazil, in intertidal seaweeds' bed on beachrock, July 2009, T.N.V. Reis col., MOUFPE 15013. 1 female, Praia de Suape (8°23′03.31″S–34°57′20.64″W), Pernambuco State, Brazil, in intertidal seaweeds bed on beachrock, July 2009, T.N.V. Reis col., MOUFPE 15064. 1 male, Praia de Suape (8°23′03.31″S–34°57′20.64″W), Pernambuco State, Brazil, in intertidal seaweeds' bed on beachrock, July 2009, T.N.V. Reis col., MOUFPE 15065. 1 female, Praia de Suape (8°23′03.31″S–34°57′20.64″W), Pernambuco State, Brazil, in intertidal seaweeds' bed on beachrock, July 2009, T.N.V. Reis col., MOUFPE 15066.
DIAGNOSIS
Head with a small sharp median forward projection. Antenna 1 about 1/3 of body length. Lower lip with inner lobes bilobed. Maxilliped outer plate reaching end of palp article 1. Gnathopod 2 male propodus ovate, palm extremely acute, occupying the entire posterior margin, first half with a 3-dentate projection, followed by a large excavation leading to a projection with two sharp processes and one very robust seta defining the end of palm. Pereopods 3 and 4 of male rudimentary, two-articulate, article 2 shorter than article 1 (0.3×), with three simple setae distally. Female pereopods 3 and 4 more developed than the male; pereopod 3 4-articulate and pereopod 4 3-articulate. Pereonite 5 female bearing a pair of lobes on ventral margin.
DESCRIPTION—BASED ON HOLOTYPE MALE
Head with a small sharp median forward projection. Pereonite 2 with a small sharp median forward projection. Pereonite 3 and 4 subequal, the first with a small hump medially. Pereonites 5–7 decreasing in length, respectively.
Antenna 1 about 1/3 of body length; article 1 longer than article 3 (1.5×); article 2 longer than article 3 (2.3×); flagellum 4-articulate and shorter than peduncle. Antenna 2 reaching end of article 2 of antenna 1; peduncle article 1 with a posterodistal subacute projection; flagellum 2-articulate. Upper lip symmetrically bilobed, not setose apically. Mandibles palp 3-articulate; article 2 with a single distal seta; article 3 dentated distally, with six simple setae; mandibular molar present; left mandible with incisor 6-toothed, lacinia mobilis large and 6-toothed followed by three setae; right mandible incisor 4-toothed, lacinia mobilis large and serrate distally, followed by two setae. Lower lip with inner lobes bilobed, well demarcated. Maxilla 1 outer lobe with five robust setae; palp 2-articulate, article 2 surpassing well inner plate, with a seta medially and three setae distally. Maxilla 2 inner lobe shorter than outer lobe (0.5×), with three and four setae distally, respectively. Maxilliped inner plate short with two setae distally; outer plate reaching end of palp article 1, with a seta medially and three setae apically; palp 4-articulate, scarcely setose; articles subequal in length.
Gnathopod 1 basis as long as ischium, merus and carpus together; propodus triangular, palm acute, poorly setose, with robust setae defining palm. Gnathopod 2 inserted ventrally on the anterior half of pereonite 2; basis long and slender, 3.3× longer than wide; ischium rectangular, 1.25× longer than wide; merus rounded; carpus very short and triangular, 0.13× propodus length; propodus ovate, palm extremely acute, occupying entire posterior margin, first half with a 3-dentate projection, followed by a large excavation leading to a projection with two sharp processes and one very robust seta defining ending of palm.
Gills present on pereonites 3–4, oval, length about 1.2× width. Pereopods 3 and 4 rudimentary, about 1/3 of gill length, 2-articulate, article 1 inflated; article 2 shorter than article 1 (0.3×), with three simple setae distally. Pereopod 5 elongate and 6-articulate, basis short, slightly expanded distally with two plumose setae on anterior margin; merus longer than ischium (1.75×) with two plumose setae on posterior margin; carpus and propodus subequal in length, both with plumose setae medially and distally; dactylus rudimentary and triangular. Pereopod 6 basis subequal to ischium and merus combined; carpus short, 0.4× of propodus length; propodus curved, palm excavated and defined by a subacute process bearing a pair of grasping spines; dactylus falcate, robust and slightly shorter than propodus (0.9×). Pereopod 7 subequal to pereopod 6, basis subequal to ischium and merus combined; carpus short, 0.45× of propodus length; propodus curved, palm excavated and defined by a subacute process bearing a pair of grasping spines; dactylus falcate, robust and slightly shorter than propodus (0.9×).
Penes rounded, as long than wide (2.8×). Abdomen, bearing a pair of lateral lobes, each of one with two groups of three setae, the first one in proximal half and the second in the distal half; a single dorsal lobe present with two short setae distally.
SEXUALLY DIMORPHIC CHARACTERS—BASED ON PARATYPE FEMALE
Pereonites 3 and 4 subequal, both with a small hump medially. Pereopods 3 and 4 more developed than in male. Pereopod 3 4-articulate (instead of 2-articulate); all articles with plumose setae distally; article 1 longer than article 3 (1.25×); article 2 about 1/2 length of article 3; article 4 reduced to a small cone, about 0.2× of article 3 length, with a plumose seta distally. Pereopod 4 3-articulate (instead of 2-articulate), articles 1 and 2 rectangular, subequal in length; article 2 with two plumose setae distally; article 3 reduced to a small cone distal article with a short seta distally. Oostegites present on pereonites 3 and 4. Pereonite 5 bearing a pair of lobes on ventral margin. Abdomen, bearing a pair of lateral lobes each of one with two groups of one seta, the first one in proximal half and the second in the distal half; a single dorsal lobe present with two short setae distally.
TYPE LOCALITY
Praia de Suape (8°23′03.31″S–34°57′20.64″W), Cabo de Santo Agostinho, Pernambuco, Brazil.
ETYMOLOGY
The epithet tridentata refers to the 3-dentate projection on the palm of male gnathopod 2.
REMARKS
As a whole, Aciconula tridentata sp. nov. differs from its congeners in having propodus palm of male gnathopod 2 bearing a 3-dentate projection. Also, it is very different from A. acanthosoma by the body dorsally not spinose, shape of male and female gnathopods 1 and 2 and female pereopods 3 and 4 4- and 3-articulate (instead 2-articulate). However, the new species is closely related to A. miranda and A. australiensis by the general feature of body and appendages, but in the former the inner lobe of lower lip is simple and the female pereopod 3 has the fourth article (distally) tiny and almost not tabicated (Guerra-Garcia, Reference Guerra-García2004a), whereas it is bilobed and clearly 4-articulate in A. australiensis and A. tridentata sp. nov.
Finally, A. tridentata sp. nov. can be distinguished from A. australiensis by the following combination of characters: article 1 of peduncle of antenna 1 lacking a setose hump proximally; outer plate of maxilliped reaching the end of palp article 1 (versus reaching 1/2 palp article 1 length); female pereopod 4 3-articulate (instead of 2-articulate); and, male pereopods 3 and 4 with article 2 about 1/3 of length of article 1, instead of being subequal.
KEY TO SPECIES OF ACICONULA
1. Body dorsally strongly spinose, pereopods 3 and 4 in both male and female 2-articulate, abdominal appendages present.........................Aciconula acanthosoma Chess, 1989Footnote *
— Body dorsally not spinose, pereopods 3 and 4 in male 2-articulate, but in female pereopods +3-articulate, abdominal appendages absent...............................................................2
2. Head lacking a small sharp median forward projection; lower lip inner lobe simple......................................................... .................................................Aciconula miranda Mayer, 1903
— Head with a small sharp median forward projection; lower lip inner lobe bilobed ...............................................................3
3. Antenna 1 article 1 lacking setose hump proximally; outer plate of maxilliped reaching the end of palp article 1; female pereopod 4 3-articulate...........Aciconula tridentata sp. nov.
— Antenna 1 article 1 bearing a setose hump proximally; outer plate of maxilliped reaching 1/2 length of palp article 1 length; female pereopod 4 2-articulate.................. ..................................... A. australiensis Guerra-Garcia, Reference Guerra-García2004a
ACKNOWLEDGEMENTS
The authors are grateful to Dr Thiago Nogueira Vasconcelos Reis who enabled us to study the specimens of Aciconula. The first author thanks CNPq, the Master of Science degree fellowship. The second author is thankful to the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco (FACEPE) for fellowship (Edital 2010/1).
