Estuarine caridean shrimps ( Crustacea : Decapoda ) from Ilhéus , Bahia , Brazil : Updated checklist and a key for their identification

Materials and Methods Study area The Municipality of Ilhéus, located on the southeastern coast of the state of Bahia (Figure 1), northeastern Brazil, covers an area of 1,712 km2. Its coastline is about 80 km long, is limited to the north by the Sargi River (14°30’06.7”S, 39°02’29.4”W) and to the south by the Acuípe River (15°05’41”S, 38°59’50”W), and includes several estuaries (Andrade 2003; Almeida et al. 2006). The Cachoeira River is the main river of Ilhéus, and together with the Santana and Fundão rivers forms a large estuary in the Ilhéus urban area. The Cachoeira River basin receives inputs from domestic and industrial effluents from Ilhéus and Itabuna, the major urban centers of the region, as well as heavy metals from fungicides used on cacao plantations (Klumpp et al. 2002; Lima et al. 2010).


Introduction
With almost 3500 species described so far, caridean shrimps are the second most diverse decapod infraorder and the most diverse group among the shrimplike decapods (De Grave and Fransen 2011).Caridean shrimps are also remarkable for their ecological diversity, occurring from tropical to polar regions, in intertidal, subtidal and pelagic habitats, on hard and soft bottoms as epi-or infaunal organisms, on algae and seagrass, or in symbiosis with other animals (Bauer 2004).They have also successfully colonized diverse freshwater environments (De Grave et al. 2008), as well as estuaries and mangroves (e.g., Carvacho 1979;Echeverría-Sáez 2003;Neves et al. 2007).Similarly to other decapods, caridean shrimps are permanent inhabitants of estuaries or use them as nursery grounds.As abundant members of the benthic communities in this type of environment, they are also an species from mud and fine-sand bottoms.The sediment obtained with the pump was sieved to reveal the smallsized infaunal shrimp.Salinity, measured using a portable refractometer, ranged from 1 to 32.5 in this study.However, it may reach at least 36.5 at the mouth of the Cachoeira River (A.O.Almeida, pers. obs.).The collections conducted in this study complied with current applicable state and federal laws of Brazil (permanent license for collection of Zoological Material No. 24408-1 MMA/IBAMA/SISBIO for AOA).
The specimens were anesthetized on ice, fixed in 70% ethanol, and all but the specimens of Alpheus brasileiro Anker, 2012 (specimen not collected, identified by means of the color pattern according to Anker 2012, p. 79, fig. 55, and p. 80, fig. 56) were deposited in the collection of crustaceans of the Universidade Estadual de Santa Cruz (UESC), Ilhéus.The classification adopted follows the proposal by De Grave and Fransen (2011).For complete synonymies of the taxa, also refer to De Grave and Fransen (2011).The order of species within families is alphabetical.
The key for identification was developed taking as a starting point an adaptation of the keys proposed by Chace (1972) and Holthuis (1993).Additional distinctive characters were obtained by examining the material and in the original description of the taxa.Abbreviations used: (f) female, (m) male, (nov) non-ovigerous specimen, (ovf) ovigerous female.
Remarks: The material reported from Ilhéus in previous studies by Almeida et al. (2006Almeida et al. ( , 2012) ) as A. heterochaelis is now recognized as a new species of Alpheus Fabricius, 1798, currently in process of description by the first author.
Previous records from Ilhéus: none.
Previous records from Bahia: none.Remarks: Automate dolichognatha, originally described from Indonesia, is a widely distributed, almost pantropical species complex (Anker 2001;Anker and Komai 2004) and is in need of a comprehensive revision.The record of the species from Rio de Janeiro by Christoffersen (1998), in a list of alpheoid shrimps from Brazil, is the only known report from the Brazilian coast.No illustrations or morphological account of this material were provided by Christoffersen (1998).Anker and Komai (2004) divided the genus Automate De Man, 1888 into three informal groups of species: A. dolichognatha, A. evermanni Rathbun, 1901, andA. hayashii Anker andKomai, 2004.The combination of characteristics such as (1) major chela subrectangular (see Figure 2D), ( 2) propodus of pereiopod 3 with row of spiniform setae, (3) dactylus of pereiopod 3-5 simple, subconical and ( 4) diaeresis of uropodal exopodite with two dorsal teeth place our specimens in the A. dolichognatha group.The other species within this group is the little-known eastern-Atlantic A. talismani Coutière, 1902, whose taxonomic status remains unclear (see Chace 1988; Anker and Komai 2004).For this reason our material is referred provisionally as A. cf.dolichognatha.Our material also agrees, in general, with the illustrations provided by Chace (1972) as A. gardineri.The color pattern of the Brazilian material is illustrated for the first time (Figure 2).The record of color pattern of fresh material will aid in mapping the geographic distribution of the taxa, after a taxonomic revision of A. dolichognatha sensu lato can be conducted and our material properly attributed.Dworschak and Coelho, 1999 Material examined: Distribution: Western Atlantic -Mexico (Yucatan), Guadeloupe and Brazil (Paraíba, Pernambuco, Bahia, São Paulo and Paraná) (Anker 2007;2010).
Previous records from Bahia: none.

Discussion
The list of caridean shrimps from estuaries of Ilhéus currently comprises 22 species in four families.It is difficult to compare species richness among estuaries because the number of species recorded in surveys may vary depending on several factors such as the size of the study area, climate and oceanographic conditions, sampling effort, diversity of substrata available, type(s) of substrata sampled, method(s) of sampling, and the experience and taxonomic group of expertise of the collector(s), among others.
The number of caridean species obtained in this study is high compared to the numbers obtained in some quantitative studies carried out in estuaries or other shallow-water coastal areas in both warm and cold temperate areas (e.g., Gore et al. 1981;Able et al. 2002;Neves et al. 2007) (see Table 1).This result was expectable, since there is a general trend toward a decrease in the number of caridean species at higher latitudes (d'Udekem d' Acoz 1999;Boschi 2002;Clarke and Crame 2010), as observed for other marine groups.With a total of 14 species, the alpheids were the most prominent family with respect to species richness.Indeed, alpheid shrimps are highly diverse in tropical regions, where they occupy a wide variety of marine and estuarine habitats, living on various types of bottom and in association with other phyla of invertebrates as well as with fish (Anker et al. 2006b).In contrast, the richness of palaemonids and hippolytids is proportionally higher in shallow-water environments in temperate areas, especially in areas covered with vegetation (Hooks et al. 1976;Gore et al. 1981;López de la Rosa et al. 2002;Glancy et al. 2003).
The number of species recorded in estuaries of Ilhéus is lower than that reported by Carvacho (1979) (n=29) in mangroves from Guadeloupe (Antillean Province, see Boschi 2000) and higher than the numbers reported by Hendrickx (1984) 1).The number of species reported by Carvacho (1979) would be expected to outnumber those in the present study, because the Antillean Province is the richest in number of decapod species among all the zoogeographic marine provinces of the Americas (see Boschi 2000).
The estuarine caridean fauna along the northern and northeastern Brazilian coast has been very little studied.The epibenthic carideans (e.g., most palaemonids and hippolytids) are in general well documented.On the other hand, the (ecologically) cryptic fauna is especially little known, especially the soft-bottom infauna.The difficulties of collection and accurate taxonomic identification partly explain this situation, which is not exclusive to this area.The number of species recorded here is much higher than the numbers found in the vast majority of surveys that have been carried out along the Brazilian coast (e.g., Ramos-Porto 1980, Ilha de Itamaracá, Pernambuco; Coelho-Santos and Coelho 2001, Paripe River, Pernambuco;Calado and Sousa 2003, Alagoas;Ferreira and Sankarankutty 2003, Rio Grande do Norte), most of them general studies on decapod fauna.The sampling effort concentrated on carideans, allied to recent advances in the taxonomy of certain taxa (e.g.Anker 2012;Almeida et al. 2013) are the main factors responsible for this relatively long species list.Systematic surveys in other estuaries along this stretch of the Brazilian coast are likely to reveal local caridean faunas as rich as or richer than that recorded from Ilhéus.Sampling of the infauna is especially likely to result in the discovery of new records and new taxa for science.
Previous records from Ilhéus: estuaries: Almeida et al.