A NEW SPECIES OF THE GENUS CHELORCHESTIA (AMPHIPODA,TALITRIDAE) FROM PALMA ISLAND, MALAGA BAY, PACIFIC COAST

OF COLOMBIA

BY

BELLINETH VALENCIA1,2) and ALAN GIRALDO1)1) Grupo de Investigación en Ecología Animal, Universidad del Valle, Facultad de Ciencias,

Departamento de Biología, A.A. 25360, Cali, Colombia

ABSTRACT

A new species of talitrid amphipod, Chelorchestia colombiensis sp. nov., is described from thecentral zone of the Pacific coast of Colombia. Specimens examined were collected on the intertidalrocky shore associated with encrusting and filamentous algae. This new species of Chelorchestiadiffers from the other four described species, C. costaricana (Stebbing, 1906), C. vaggala (Bowman,1977), C. darwinii (Muller, 1864), and C. forceps Smith & Heard, 2001 principally by the presenceof well developed lobes on the ischium of the second gnathopod in males, as well as by the presenceof two well developed rounded humps on the palm of the second gnathopod in males. Furthermore,variation was found in the length of antenna 2, uropod 1, uropod 2, and telson.

RESUMEN

Se describe una nueva especie de anfípodo talítrido, Chelorchestia colombiensis sp. nov., para laregión central de la costa Pacífica colombiana. Los especimenes fueron colectados en la zona rocosaintermareal asociados a algas filamentosas e incrustantes. Esta nueva especie de Chelorchestia difierede las otras cuatro especies descritas para el género, C. costaricana (Stebbing, 1906), C. vaggala(Bowman, 1977), C. darwinii (Muller, 1864), y C. forceps Smith & Heard, 2001, principalmente porla presencia de un lóbulo bien desarrollado en el isquio del segundo gnatópodo de los machos, y lapresencia de dos tubérculos bien desarrollados en la palma del segundo gnatópodo de los machos.Adicionalmente, se encontraron diferencias en la longitud de la antena 2, urpodo 1, uropodo 2 ytelsón.

INTRODUCTION

The family Talitridae comprises amphipods that have been adapted to semiter-restrial and terrestrial life styles, in their morphology, physiology, behaviour, and

2) Corresponding author; e-mail: bellival@univalle.edu.co

© Koninklijke Brill NV, Leiden, 2009 Crustaceana 82 (1): 1-10Also available online: www.brill.nl/cr DOI:10.1163/156854008X363768

2 BELLINETH VALENCIA & ALAN GIRALDO

ecology. According to Bousfield (1984), the family can be divided into four units,with the genus Chelorchestia classified among the palustral talitrids, which arecharacterized as semiaquatic, living in tropical estuaries (salt marshes, mangroves)and freshwater systems, and which exhibit strong sexual dimorphism.

At present, four species of the genus are recognized in the tropical andsubtropical regions of America: C. costaricana described from Costa Rica byStebbing (1906); C. vaggala, described from the Galapagos Islands by Bowman(1977); C. darwinii, described by Muller (1864) from the Brazilian coast (recentlyredescribed by Serejo (2004)); and C. forceps, described by Smith & Heard (2001)from the coast of Florida. Species of the genus Chelorchestia are characterized bya high habitat plasticity, ranging from terrestrial habitats on the Galapagos Islands(found 1 to 4 km inland), to estuaries and mangrove areas in Costa Rica and alongthe Brazilian coast, and further to salt marshes in Florida.

In this paper, a new species of the genus Chelorchestia, C. colombiensis sp. nov.,is described from Palma Island, off the Pacific coast of Colombia (fig. 1).

MATERIAL AND METHODS

Amphipods were collected during low tide in the littoral fringe zone on thesouthwestern side of Palma Island, associated with encrusting and filamentousalgae. Individuals associated with encrusting algae were collected manually (29June 2007), while in the zone of the filamentous algae a 10 × 10 cm quadrantwas used (8 December 2006). Additionally, some individuals were collected in themouth of some streams that only experience the influence of marine salinity duringhigh tide. Samples were fixed in 70% ethanol. Dissected appendages were mountedon glass slides in glycerin. Drawings were made with a compound microscope(Olympus CH20). The type material is deposited in the amphipod collection of theUniversidad del Valle (CAN-UV), Cali, Colombia.

SYSTEMATICS

Chelorchestia colombiensis sp. nov. (figs. 2-6)

Material examined. — Holotype: male (8.6 mm, CAN-UV 092), Acantilado Verde (3◦54′09.4′′N77◦21′37.0′′W), Palma Island, Malaga Bay, Colombia, 29 June 2007, collected manually by AlanGiraldo and Bellineth Valencia. Paratypes: two females (4.5 mm, 4.6 mm, ethanol, CAN-UV093), Punta Brava (3◦53′48.95′′N 77◦21′22.50′′W), Palma Island, Malaga Bay, 9 December 2006;four males (4.7 mm, 4.2 mm, 5.4 mm, 5.5 mm, ethanol, CAN-UV 093) data same as paratypefemales; two males (2.4 mm, 2.5 mm, ethanol, CAN-UV 094), Morro Escondido (3◦54′4.05′′N

CHELORCHESTIA COLOMBIENSIS NOV. 3

Fig. 1. Location of Isla Palma on the Pacific coast of Colombia.

77◦21′19.95′′W) Palma Island, Malaga Bay, 8 December 2006. All specimens were collected by theauthors.

Description. — Holotype male: body length 8.6 mm. Antenna 1 reaching 2/3 offourth peduncular article of antenna 2, flagellum with 4 articles. Antenna 2, 60%of body length, peduncle consisting of 5 articles, fifth article longer than fourth,flagellum with 12 articles. Eyes rounded and small, 7% of head area (fig. 2).

Upper lip elliptical, apex with minute setae (fig. 3A). Lower lip bilobed, apicaland inner margin with set of setules (fig. 3B). Incisor of left mandible with 5denticles, lacinia mobilis 4-dentate, with plumose setae between lacinia mobilisand molar (fig. 3C, 3D). Maxilla 1, inner plate with 2 apical, plumose setae, outer

4 BELLINETH VALENCIA & ALAN GIRALDO

Fig. 2. Chelorchestia colombiensis sp. nov., male 8.6 mm, Isla Palma. Scale 2.0 mm.

plate with 9 spines, the first 6-dentate (fig. 3E). Maxilla 2, inner plate with 1proximal, large plumose seta and several (15-17) distal spines, outer plate withmost spines curved (approximately 15) (fig. 3F). Maxilliped, inner plate withseveral plumose setae on lateral and apical margin, and 3 apical, tooth-like spines.Outer plate with 4 spines on lateral margin and approximately 11 spines on apicalmargin. Maxillipedal palp 4-articulate (fig. 3G).

Gnathopod 1, with merus, carpus, and propodus with well developed posteriorlobes. The propodus is subchelate and the posterior lobe has several spines(fig. 4A). Gnathopod 2, basis with 1 tubercle on the anterior margin, provided witha spine; ischium with well developed lobe on its anterior margin, carpus fusedto propodus, propodus chelate, palm with two well developed, rounded humps,the first one with 6, the second with 4 spines. Dactylus robust, with broad medialexpansion (fig. 4B). Pereopods 3 to 5 shorter than pereopods 6 and 7. Dactyli ofpereopods 3 to 7 simple (fig. 4C–G).

Uropod 1, peduncle with four pairs of spines and with interramal spine, innerramus with 4 marginal spines, outer ramus without marginal spines (fig. 5A).Uropod 2, peduncle with 3 pairs of spines, inner ramus with 2, outer ramus with3 marginal spines (fig. 5B). Uropod 3, peduncle with large spine distally, ramusshorter than peduncle and with 1 terminal spine (fig. 5C). Telson with shallowapical notch and a group of 3 spines followed by one spine on both lateral margins,as well as one robust terminal spine (fig. 5D).

Female (paratype, CAN-UV093). — Similar to male, except for: gnathopod 1,subchelate, without posterior lobes (fig. 5F). Gnathopod 2, subchelate, with merus,carpus, and propodus with posterior lobes, propodus with small dactylus (fig. 5G).Oostegites oval-shaped, with long setae (fig. 5E).

Variation in male gnathopod 2. — Within the genus Chelorchestia, it is verycommon that the males exhibit variation in the second gnathopod during develop-

CHELORCHESTIA COLOMBIENSIS NOV. 5

Fig. 3. Chelorchestia colombiensis sp. nov., male 7.5 mm, Isla Palma. A, upper lip; B, lower lip; C,mandible; D, detail of incisor and lacinia mobilis; E, maxilla 1; F, maxilla 2; G, maxilliped. Scales

equal 0.1 mm except in fig. 3G, in which the scale equals 0.05 mm.

6 BELLINETH VALENCIA & ALAN GIRALDO

Fig. 4. Chelorchestia colombiensis sp. nov., male 7.5 mm, Isla Palma. A, gnathopod 1; B, gnathopod2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6; G, pereopod 7. Scales equal 0.5 mm.

ment. Two male gnathopod variations were found in this study. In individuals of2.36-2.54 mm in size, the tubercle on the anterior margin of the basis is absent.Furthermore, these individuals do not have a lobe on the anterior margin of theischium. Moreover, the propodus has only a tiny rounded hump with two spines inthe proximal zone of the palm (fig. 6A). In individuals of 4.18-4.68 mm in size, onthe anterior margin of the basis one tubercle with a spine is present. The palm ispoorly developed, and the rounded humps on the propodus are closer to each other.

CHELORCHESTIA COLOMBIENSIS NOV. 7

Fig. 5. Chelorchestia colombiensis sp. nov., male 7.5 mm, Isla Palma. A, uropod 1; B, uropod 2; C,uropod 3; D, telson; female 4.5 mm, E, oostegite 2; F, gnathopod 1; G, gnathopod 2. Scales equal

0.5 mm.

Furthermore, the first tubercle has 2 spines, and the second has 7 spines (fig. 6B).Finally, males of 7.5-8.6 mm have gnathopods like those of the holotype (fig. 4B).

8 BELLINETH VALENCIA & ALAN GIRALDO

Fig. 6. Chelorchestia colombiensis sp. nov., Isla Palma. Variations in the second gnathopod of malesduring development. A, males 2.36-2.54 mm in size; B, males 4.18-4.68 mm. Scales equal 0.5 mm.

Etymology. — The specific name “colombiensis” refers to the place of capture;it is a geographical adjective agreeing in gender with the (feminine) generic name.

Habitat. — Palma Island is a rocky island located 1.8 km off the coast in frontof Malaga Bay. Around the island, sea surface temperatures vary from 26.6 to29.7◦C, salinity varies between 1.4 and 30.0, the average annual precipitation isnear 6000 mm, and the tidal range is semidiurnal (Cantera et al., 1998).

Remarks. — The most evident characters to distinguish Chelorchestia colom-biensis from C. vaggala, C. costaricana, C. darwinii, and C. forceps are the pres-ence of well developed lobes on the ischium of the second gnathopod in males, andtwo well developed rounded humps on the palm of the second gnathopod in adultmales. Another difference between C. colombiensis and C. forceps is found in thelength of antenna 1 and antenna 2, as in the former species antenna 1 extends tothe distal margin of the peduncular article 4 of antenna 2, and antenna 2 is 40% ofthe body length. Moreover, in C. forceps 2 or 3 tubercles on the basis of the secondgnathopod of the males are present, and three pairs of setae on the lateral marginof the telson. A difference between C. colombiensis and C. darwinii is the pres-ence in the former species of three marginal setae on the inner ramus of uropod 1,and two or three pairs of setae on the lateral margin of the telson. C. colombiensisand C. costaricana can be distinguished by the number of articles in the flagellumof antenna 2. The former species has 20 articles, and it also has two tubercles onthe anterior margin of the basis. Finally, a difference between C. colombiensis andC. vaggala is the presence in the former species of a subchelate gnathopod 2 witha transverse palm.

CHELORCHESTIA COLOMBIENSIS NOV. 9

Fig. 7. Principal characters that difference species of the genus Chelorchestia. A, C. vaggala(Bowman, 1977) gnathopod 2; B, C. costaricana (Stebbing, 1906) gnathopod 2; C, C. forceps Smith& Heard, 2001 gnathopod 2; D, C. forceps propodus of pereopod 4; E, C. darwinii (Muller, 1864)gnathopod 2; F, C. darwinii propodus of pereopod 4. [C. vaggala (his fig. 3C) was reproducedfrom Bowman (1977) in Proceedings of the Biological Society of Washington, 90(3): 658-668with permission from the Biological Society of Washington. C. forceps (their fig. 14 and fig. 22)and C. costaricana (their fig. 49) were reproduced from Smith & Heard (2001) in Journal ofCrustacean Biology, 21(4): 1031-1041 with permission from Allen Press. C. darwinii (her fig. 1Iand fig. 3H) alignment reproduced from Serejo (2004) in Zootaxa, 646: 1-29 with permission from

Magnolia Press.]

KEY TO THE KNOWN SPECIES OF THE GENUS CHELORCHESTIA

1. Gnathopod 2 subchelate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. vaggala (fig. 7A)– Gnathopod 2 chelate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Antenna 2 reaching about 60% of body length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3– Antenna 2 reaching about 40% of body length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3. Palm of gnathopod 2 with two well developed rounded humps . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. colombiensis sp. nov. (fig. 4B)

– Palm of gnathopod 2 without rounded humps. . . . . . . . . . . . . . . . . . . . . .C. costaricana (fig. 7B)

4. Propodus of pereopods 3 and 4 with two stout hinge spines at articulation with dactylus, onedorsal and one ventral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. forceps (fig. 7C–D)

– Propodus of pereopods 3 and 4 with a stout hinge spine in ventral margin and two long setaedorsally . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. darwinii (fig. 7E–F)

ACKNOWLEDGEMENTS

We would like to thank Dra. Yusbelly Díaz and Dr. Alberto Martín (UnversidadSimón Bolivar, Caracas, Venezuela) for their introduction to amphipod taxonomy.

10 BELLINETH VALENCIA & ALAN GIRALDO

Furthermore, we want to express our gratitude to Dra. Cristiana Serejo (NationalMuseum of Federal University of Rio de Janeiro, Brazil) who confirmed our initialtaxonomic identification, and who allowed us to compare our C. colombiensis sp.nov. material with specimens of C. darwinii. Additionally, we would like to thankDr. John Carr (University of Louisiana) for revision of the English in an early stageof the draft. Harrison López made the drawings of the specimens. Two anonymousreviewers made outstanding contributions to improve this paper.

REFERENCES

BOUSFIELD, E. L., 1984. Recent advances in the systematics and biogeography of landhoppers(Amphipoda: Talitridae) of the Indo-Pacific region. In: F. J. RADOVSKY, P. H. RAVEN, S. H.SOHMER (eds.), Proceedings of the symposium on biogeography of the tropical Pacific. BishopMuseum Special Publication, 72: 171-210.

BOWMAN, T. E., 1977. Orchestia vaggala, a new land-hopper from the Galapagos Islands (Crus-tacea: Amphipoda: Talitridae). Proceedings of the Biological Society of Washington, 90(3):658-668.

CANTERA, J. R., R. NEIRA & C. RICAURTE, 1998. Bioerosión en la costa pacífica colombiana. Unestudio sobre la biodiversidad, la ecología y el impacto humano de los animales destructores delos acantilados rocosos. (Universidad del Valle, Departamento de Biología, Sección de BiologíaMarina, Fondo FEN Colombia).

MULLER, F., 1864. Für Darwin. (Wilhelm Engelmann, Leipzig).SEREJO, C. S., 2004. Talitridae (Amphipoda, Gammaridea) from the Brazilian coastline. Zootaxa,

646: 1-29.SMITH, D. G. & R. W. HEARD, 2001. A new species of Chelorchestia (Amphipoda: Talitridae)

from southwest Florida, with comments on other species within the genus. Journal of Crus-tacean Biology, 21(4): 1031-1041.

STEBBING, T. R. R., 1906. A new Costa Rican amphipod. Proceedings of the United States NationalMuseum, 31: 501-504.

First received 6 August 2007.Final version accepted 12 February 2008.