Occurrence of Anthalona neotropica Sousa, Elmoor-Loureiro and Debastiani-Júnior, 2015 (Crustacea: Cladocera: Chydoridae) in Bahia State, Brazil

Abstract

Although the cladoceran Anthalona neotropica Sousa, Elmoor-Loureiro and Debastiani-Júnior, 2015 has a wide geographic range in Brazil, until now, it has only been reported in a few localities. The present study reports the occurrence of this species in the estuaries of the Jequitinhonha River and Una River, representing the first records of An. neotropica in Bahia State, Brazil.

Keywords
Aloninae; delta estuary; estuarine zooplankton; hyporheic habitat; salinity

INTRODUCTION

During the last two decades, knowledge on the taxonomy and phylogenetic position of Alona verrucosaSars, 1901 (Crustacea: Cladocera: Chydoridae) has increased. Initially, it became clear that it was not a single species, but a set of closely related ones (Sinev and Hollwedel, 2002; Van Damme et al., 2011; Sinev and Kotov, 2012; Sousa et al., 2015).

First described as Alona verrucosa by Sars (1901), it was transferred to the genus BiaperturaSmirnov, 1971 and then again later considered as a member of AlonaBaird, 1843 (Sinev and Hollwedel, 2002). The better delimitation of the genus Alona (see Van Damme and Dumont, 2008) showed the need for revision of the so-called Alona-like species, including the Alona verrucosa group (Van Damme et al., 2010), which was, finally, allocated to a new genus AnthalonaVan Damme, Sinev and Dumont, 2011.

Sousa et al. (2015) have synthesized the knowledge on Anthalona species occurring in Brazil, with An. verrucosa presenting the majority of the records and the widest geographic range. These authors also showed the occurrence of Anthalona brandorffi (Sinev and Hollwedel, 2002), Anthalona acutaVan Damme, Sinev and Dumont, 2011, and the new species Anthalona neotropicaSousa, Elmoor-Loureiro and Debastiani-Júnior, 2015 within the distribution range of An. verrucosa.

In contrast to other Anthalona species occurring in Brazil, which possess chitinized spines on setae of inner distal lobe (IDL) of the trunk limb I, An. neotropica presents just fine spinules on this limb. This is a typical feature of the simplex-branch of Anthalona (Van Damme et al., 2011).

So far, An. neotropica has been reported in only a few Brazilian localities (Sousa et al., 2015; Sousa and Elmoor-Loureiro, 2018), and none of them in Bahia State. The present paper aims to report the occurrence of An. neotropica in southern Bahia, as a result of an investigation on zooplankton of two estuarine regions.

MATERIAL AND METHODS

The study was conducted in two estuarine areas in southern Bahia State, Brazil, namely the Jequitinhonha River and the Una River (Fig. 1). For zooplankton sampling, 10 sites were defined along each estuary. Sampling was carried out in October 2012, at low tide, moving in the direction of the river mouth. The specimens were collected using a zooplankton net (68 μm mesh) and preserved in neutralized formaldehyde at 4 % for 48 hours. In the laboratory, the samples were transferred to 70 % alcohol for manipulation under a stereomicroscope and identification with an optical microscope. A subsample of 10 mL of each field sample was analyzed and the cladoceran specimens were separated for identification. Within the scope of the present study, only specimens of Anthalona are considered.

Figure 1.
Occurrence records of Anthalona neotropicaSousa, Elmoor-Loureiro and Debastiani-Júnior, 2015 in southern Bahia State.

The voucher specimens are deposited in the personal collection of Lourdes M. A. Elmoor-Loureiro, under accession numbers EL02515 and EL02559.

In order to verify if the environment could be considered as freshwater, salinity (‰) was obtained with a multiparameter Horiba U50.

SYSTEMATICS

Anthalona neotropica Sousa, Elmoor-Loureiro and Debastiani-Júnior, 2015

(Fig. 2)

Figure 2.
Anthalona neotropicaSousa, Elmoor-Loureiro and Debastiani-Júnior, 2015. A, Habitus, specimen from Jequitinhonha River. B, Habitus, specimen from Una River. C-E, Post-abdomen (arrow indicating the lateral fascicles). F, Labral keel and antenna. G, Spine on the first segment of endopod of antenna. H, First trunk limb, arrows showing the IDL setae. I, Head pores. mp: main pores, lp: lateral pore. Scale bars = 100 µm (A, B) or 10 µm (C-I).

Material examined. 1♀ (EL02515), Brazil, Bahia State, municipality of Belmonte, Jequitinhonha River, 15°51’47”S 38°54’13”W, October 2012, coll. S.B. Jesus; 1♀ (EL02559), Brazil, Bahia State, municipality of Una, Una River, 15°17’57”S 39°00’28”W, October 2012, coll. S.B. Jesus.

Remarks. The observed specimens (Fig. 2) match the main diagnostic characters of An. neotropica. Like all Anthalona members, they possess two main connected head pores and lateral head pores with cosmaria-like sacs below them (Fig 2I); post-abdomen S-shaped with deep concave anal margin, unmerged marginal denticles, lateral fascicles with long distal setulae (Fig. 2C-E); IDL with two setae. The specimens were identified as An. neotropica based on: labrum keel convex and without denticles (Fig. 2F); IDL setae of similar size and presenting fine setulae (Fig. 2H); spine on the first segment of endopod of antenna II very long and almost reaching the end of the third segment (Fig. 2G); pecten of post-abdominal claw organized in two groups; long spinulae on the base of terminal claw.

It should be mentioned that the sites where An. neotropica was found were characterized by the absence of floating macrophytes and by low salinity (< 0.5 ‰), typical of freshwaters. In the samples in which An. neotropica was present, no other Anthalona species was found. In fact, in the sample from Una estuary, An. neotropica was the single species observed. The sample from Jequitinhonha estuary was dominated by typically planktonic species - such as Bosmina freyi De Melo and Hebert, 1994, Ceriodaphnia cornuta Sars, 1885, and Daphnia gessneri Herbst, 1967 - with a few specimens of Ilyocryptus spinifer Herrick, 1882 and An. neotropica.

DISCUSSION

The specimens reported here were first identified as Anthalona cf. simplex (Jesus, 2015). At that time, it was clear that they belonged to the simplex-branch since they presented IDL setae with fine setules. Nevertheless, the Neotropical member of this group of species was then still under the process of description (Sousa et al., 2015). Therefore, it was only after the formal publication of An. neotropica that our specimens could be correctly identified.

So far, An. neotropica was reported only in San Pedro, Argentina, and in a few Brazilian localities in Rio Grande do Sul, Rio de Janeiro, Goiás, Mato Grosso, and the Federal District (Sousa et al., 2015; 2018; Sousa and Elmoor-Loureiro, 2018). Although not frequently reported, An. neotropica has a wide geographic range and it is expected that, as time passes, new records in other Brazilian states will be added. The present study confirms this prospect, presenting the first records of An. neotropica from Bahia State. Moreover, our data also represents the first occurrence in the Brazilian Northeast Region and in the East Atlantic Hydrographic Region.

Of the nine previous records of An. neotropica, only two came from lentic water bodies (Sousa et al., 2015; Sousa and Elmoor-Loureiro, 2018), indicating that this species is easily found in a lotic environment, which is supported by the data presented here. However, it should not be simply assumed that An. neotropica has a preference for lotic waterbodies. Instead, this fact seems to result from living in the sediment and the resuspension action caused by water flow. Indeed, Sousa et al. (2015) discussed some features of An. neotropica that are typical of benthic cladocerans, as well as observing higher densities of this species in hyporheic habitats. The low number of specimens observed in our study - just two individuals in 20 analyzed samples - could be related to the benthic habit of An. neotropica.

It should also be considered that, in general habitus, An. neotropica is remarkably similar to the common An. verrucosa and to the less frequent An. brandorffi and An. acuta. The correct identification of these species demands observation of fine characters, such as the armature of the IDL setae (Sousa et al., 2015). Because of that, it is possible that the presence of An. neotropica may not have been previously noticed in zooplankton studies.

ACKNOWLEDGEMENTS

We are grateful to the Post-Graduate Program in Geochemistry: Oil and Environment (UFBA - Federal University of Bahia) for financial support by means of a partnership with the Queiroz Galvão Company, during the “PETROTECMANGUEBASUL” Project. FAPESB (Fundação de Amparo à Pesquisa do Estado da Bahia) provided a fellowship for SBJ. Thanks to Ms. Susan Casement for the English text revision.

REFERENCES

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• Zoobank:

  http://zoobank.org/urn:lsid:zoobank.org:pub:6E5B8793-CAA6-4989-B6ED-55E6628341DC

Publication Dates

• Publication in this collection
  31 Mar 2021
• Date of issue
  2021

History

• Received
  22 July 2020
• Accepted
  10 Nov 2020