Alpheus christofferseni Anker, Hurt and Knowlton, 2007

Bochini, Gabriel Lucas, Guéron, Rodrigo, Terossi, Mariana & Almeida, Alexandre Oliveira, 2023, Extension of the known range of the snapping shrimp Alpheus christofferseni Anker, Hurt and Knowlton, 2007 (Caridea: Alpheidae), Nauplius (e 2023001) 31, pp. 1-7 : 4

Alpheus christofferseni Anker, Hurt and Knowlton, 2007

( Fig. 2 )

Alpheus christofferseni Anker, Hurt and Knowlton, 2007: 3 , figs. 1–6, 11a–c, 12b, c; De Grave and Fransen, 2011: 380; Soledade and Almeida, 2013: 97; De Grave and Anker, 2017: 4.

Material examined. Brazil, Pernambuco: 1 female (CL: 3.8mm), MOUFPE 20210 , of Recife , associated with a biogenic substrate such as calcareous algae, dead coral, and sponges, depth: 51 m, 27.ii.2018, colls. G.L. Bochini, G.O. Soldade and R. Gueron ; 1 male (CL: 3.3 mm), DZ/ UFRGS 6934 (genetic voucher, GenBank access ON746697), Praia dos Carneiros, Tamandaré , ARS, depth: 3–6 m, 20.viii.2019, colls. G.L. Bochini and G.O. Soledade .

Distribution. The species is found in the Western Atlantic: Panama (Bocas del Toro) and Brazil [Atol das Rocas and Pernambuco (off Recife and Tamandaré)] ( Anker et al., 2007; this study).

Habitat. The species is mainly found in burrows on intertidal or shallow seagrass flats (0–1.5 m), associated with echiurans ( Anker et al., 2007); reef areas (beach rock) 3–6 m; and substrate of biogenic origin such as calcareous algae, and dead coral, 51 m (this study).

Genetic data. The topology obtained ( Fig. 1B ) showed a clade formed by the two sequences of A. christofferseni and a clear separation of these from the other species. The intraspecific genetic distance of A. christofferseni was 0.9%, much smaller than the divergence of this species from other species of the brevirostris group (9.9% - 14.4%).

Remarks. The distribution range of A.christofferseni is extended by approximately five degrees south from the type locality (Atol das Rocas, ~3°51”S, Fig. 1A ). The current southernmost record of the species is Praia dos Carneiros, Tamandaré, Pernambuco (~ 8°41’S). Furthermore, the bathymetric distribution increased significantly considering the collection of a specimen at 51 m depth. The specimens from Pernambuco (female and male) resemble the holotype. However, some morphological variations between the two specimens from Pernambuco and the holotype were observed, such as the exopod of the third maxilliped ( Fig. 2B, C ) reaches the penultimate segment of the endopod (vs. not reaching the penultimate segment of the third maxilliped in the holotype); telson ( Fig. 2H, I ) with mesial spiniform setae 4.5 times longer than the lateral spiniform setae (vs. mesial spiniform setae twice the size of the lateral spiniform setae in the holotype); third and fourth pereiopods ( Fig. 2F, G ) armed with four spiniform setae along the ventral margin and a pair of distal spiniform setae (vs. five spiniform setae and a pair of distal spiniform setae in the holotype).

Figures

Figure 1. Alpheus christofferseni Anker, Hurt and Knowlton, 2007. A, Presently known distribution, star represents the type locality, blue and red circles represent the new occurrences, and green circle represents specimen previously reported from Panama. B, Phylogram of A. christofferseni (bold) and some congeners morphologically similar, using the Maximum Likelihood analysis of the 16S ribosomal subunit gene. Numbers are support values for 960 bootstraps; values <75% were not included. Atl: Atlantic; PE: Pernambuco; SP: São Paulo. References: A, Chow et al. (2021); B, This study; C, Roura et al. (2018); D, Wang et al. (2020); E, Liao et al. (2019); F, Bracken-Grisson et al. (2014); G, Almeida et al. (2018).

Figure 2. Alpheus christofferseni Anker, Hurt and Knowlton, 2007, male from Praia dos Carneiros, Tamandaré, Pernambuco, Brazil (DZ/UFRGS6934):A, Frontal region and cephalic appendages,dorsal view;B, third maxilliped,lateral view;C, detail of the exopod of the third maxilliped, lateral view; D, left major cheliped, lateral view; E, right minor cheliped, lateral view; F, third pereiopod, lateral view; G, fourth pereiopod, lateral view; H, telson and uropod, dorsal view; I, same, detail of posterior margin. Scale bars: A, D, F, H, I = 1 mm; B, C, E, G = 0.5 mm.