First record of Alpheus platycheirus Boone, 1927 (Crustacea, Alpheidae) on the northwest coast of Venezuela

Abstract

Alpheus platycheirus Boone, 1927 (Decapoda, Alpheidae) is a snapping shrimp widely distributed in the western Atlantic, from the Gulf of Mexico to eastern Brazil. This shrimp usually inhabits muddy marine bottoms; however, here we record for the first time A. platycheirus in association with Thalassia testudinum and Halodule wrightii meadows at an unusually shallow depth in northwest Venezuela. This record extends the known habitat and distribution of A. platycheirus in the Caribbean. Moreover, it represents an additional alpheid species for Venezuela, bringing the known total to 34 species.

Keywords:
Caridean shrimp; distribution range; new record; Paraguaná Peninsula; shallow seagrass meadows

INTRODUCTION

The genus AlpheusFabricius, 1798, is one of the most diverse shrimp taxa worldwide, with 286 described species (De Grave and Fransen, 2011). In the western Atlantic, Alpheus is represented by more than 40 species that are associated with a diversity of seabed habitats (Chace, 1972; Christoffersen, 1979; Knowlton and Keller, 1985; Martínez-Iglesias et al., 1996). However, this richness of species may significantly increase because it is likely that many form species complexes (i.e., groups of species that are morphologically similar but genetically different), which require revision (Anker, 2007; Bracken-Grissom et al., 2014).

In Venezuela, 33 species of Alpheus have been recorded (Rodríguez, 1980; Marcano, 1997; Hernández-Ávila et al., 2007; Vera-Caripe et al., 2012), including unpublished records from one of the authors. However, it is essential to continue surveying the Venezuelan marine carcinofauna because there are still information gaps in the species diversity. For example, species listed for the Caribbean show a discontinuous distribution, since they have not yet been registered on the Venezuelan coast (Mariño et al., 2018). Here, we report Alpheus platycheirusBoone, 1927 for the first time in Venezuelan waters. We also present a morphological description of the coloration, ecology, habitat, and distribution for this species.

MATERIAL AND METHODS

We conducted sampling in the Venezuelan Paraguaná Peninsula on May 19th and 20th, 2013, during the predominant dry season. The sampling site El Supí (12°00’51.2”N 69°49’59.9”W) is located outside of protected areas and close to tourist attractions. El Supí is composed of sandy beaches with a low profile and muddy waters, with intermixed Thalassia testudinum Banks ex König 1805 and Halodule wrigthiiAscherson 1868 seagrass beds (Mariño et al., 2018). We conducted intensive nocturnal samplings using a manual push net with an opening of 1 m (width) x 0.5 m (height), and a mesh size of 1 mm (modified from Manning, 1975). We fixed the collected organisms in situ using ethanol (70%) with glycerin (1%) and photographed them (Cannon Power Shot SX20 IS, zoom lens 20X IS 5.0−100.0 mm 1:2.8−5.7 USM). We measured the specimens (CL = carapace length) and deposited them in the Centro Museo de Biología de la Universidad Central de Venezuela (Centro MBUCV).

TAXONOMY

Phylum Arthropoda von Siebold, 1848

Class Malacostraca Latreille, 1802

Order Decapoda Latreille, 1802

Infraorder Caridea Dana, 1852

Family Alpheidae Rafinesque, 1815

Genus Alpheus Fabricius, 1798

Alpheus platycheirus Boone, 1927

(Figs. 1, 2)

Figure 1.
Alpheus platycheirusBoone, 1927, female. A, Frontal region, lateral; B, frontal region, dorsal; C, major cheliped, lateral; D, minor cheliped, lateral; E, fourth pereopod, lateral.

Figure 2.
Alpheus platycheirusBoone, 1927, ovigerous female. A, Dorsal view; B, lateral view. CL: 7.6 mm.

Alpheus platycheirus. - Boone, 1927: 131-135, figs. 29, 30. - Bracken-Grissom and Felder, 2014: 474-482, figs. 15-18. - De Grave and Anker, 2017: 8.

Alpheus floridanus. - Chace, 1972: 65 (in part, figs. 20a-f). - Christoffersen, 1979: 312. - Felder et al., 2009: 1057, 1091 (in part).

Material examined. MBUCV-XI-5543 (1 ovigerous female, CL: 7.6 mm; 1 male, CL: 10.0 mm), Venezuela, Falcón State, Paraguaná Peninsula, El Supí beach (12°00’51.2”N 69°49’59.9”W), 19 May 2013.

Diagnosis. Carapace smooth, not setose; rostrum acute, not exceeding first article of antennular peduncle; rostral carina delimited between orbital hoods, extending half of the dorsal surface of the carapace; adrostral furrows deep, reaching posteriorly to base of eyes; ocular hoods inflated, rounded, extending beyond eye, unarmed. Cardiac notch deep.

First article of antennular peduncle with ventromesial carina ending in acute tooth, first article about 1.4 times as long as wide, second article about 3 times as long as wide, third article almost as wide as long. Stylocerite broad, lamellate, with acute tip, not exceeding distal margin of first article. Antenna with a robust and sharp ventrolateral tooth on basicerite; scaphocerite broad, lateral margin slightly concave, reaching distal margin of antennular peduncle.

Mouthparts (mandible, maxillule, maxilla, first and second maxillipeds) typical for genus Alpheus. Exopod of third maxilliped long, slender, setose, not extending beyond antepenultimate article of endopod.

Major cheliped of male and female very asymmetrical in shape and unequal in size, massive and large in the male, with ischium short and unarmed (in female weakly serrated on the lateral margin); merus rectangular, with mesial surface with row of 6 teeth (only 4 in the female specimen) and scattered setae, smooth lateral surface (in female, mesiodistal portion armed with a small curved spine); carpus small and cup-shaped, with triangular projection on ventral margin; chela compressed, with abundant and scattered setae; palm without dorsal or ventral notch, 0.5 times (0.6 in female) longer than fingers; – of dorsal surface of mobile finger rounded and with line of short setae, cutting edge almost straight, reaching slightly beyond fixed finger; fixed finger with almost straight cutting edge. Minor cheliped balaeniceps-shaped in male (minor cheliped of female lost), with short ischium; merus subrectangular, ventral surface flattened, with six movable spines and fringe of setae along ventromesial margin; carpus stout, cup-shaped and unarmed; chela slender, compressed, lacking depressions or grooves; fingers elongate, slender, straight, longer than palm, densely setose, with apices crossed.

Second pair of pereopods with ischium and merus elongate and subequal; carpus five-articled, first (proximal) article slightly shorter than second, second almost twice as long as third; third, fourth and fifth, subequal. Third pair of pereopods robust, ischium armed with movable spine on ventrolateral surface; merus about twice as long as carpus; propodus slightly longer than carpus, with four movable spines along ventrolateral surface, dactylus simple, subspatulate, slightly curved. Fourth pair of pereopods similar to third, propodus with five movable spines along ventrolateral surface. Fifth pair of pereopods more slender than third and fourth, ischium lacking movable spine; merus slightly longer than carpus; carpus and propodus similar in length; propodus lacking movable spines, dactylus simple, curved, narrowing to acute tip.

Telson slightly tapering, longer than wide (2 times or more), with two pairs of dorsal movable spines; posterolateral margin broadly rounded, each posterolateral angle with two small movable spines, mesial larger than lateral. Uropodal exopod subequal in length to telson, lateral margin produced with subacute tooth adjacent to strong movable lateral spine; endopod broadly subovate, slightly overreaching length of exopod and telson.

Color. Body greenish, speckled with numerous light yellow and green dots, most of them isolated and not interconnecting. Carapace darker than rest of body. Major and minor chelae mesially without speckled pattern, beige or light brown; major chelae with dark spots of medium size on dorsal surface of fingers and anterior region of palm; pereopods 3-5 with diffuse reddish band on distal third of merus, and broader, less defined reddish band on carpus, more intense on extensor margin. First and second abdominal somites with minute dark dorsolateral spot (Fig. 2).

Remarks. The color pattern of A. platycheirus reported by Bracken-Grissom and Felder (2014) is very different from the two examples collected at the Paraguaná Peninsula, Venezuela. The material described in 2014 exhibits colors such as red, pink, brown, and orange, which differ from the specimens that we collected in Venezuela. Most likely, the shrimps from the study of Bracken-Grissom and Felder (2014) were dying or recently dead, and therefore had lost their natural pattern of coloration, as is the case with most caridean shrimp and other crustaceans.

According to the description of Bracken-Grissom and Felder (2014), the specimens found in this study coincide with the species A. platycheirus. However, in their key and description, they mention that there are 1-4 spines on the propodus of the fourth pair of pereopods, while the specimens in this study have 5 spines on the propodus. Another trait that does not match is the length and width of the first article of the antennular peduncle, which is 2 times longer than wide (Bracken-Grissom and Felder, 2014) while about 1.4 times longer than wide in the material from Venezuela. Additionally, the second article of the antennular peduncle is 4 times as long as wide (Bracken-Grissom and Felder, 2014), while in the specimens collected in Venezuela it is approximately 3 times as long as wide. Nevertheless, these differences are not regarded as substantial enough to indicate that the specimens correspond to another species.

Geographical distribution. Western Atlantic: Gulf of Mexico (Louisiana/Mississippi, USA?; off Veracruz, Mexico), Caribbean Sea (Cuba, Panama, Haiti, Colombia and Guadeloupe) and Eastern Brazil (Alagoas, Espírito Santo, Rio de Janeiro, São Paulo) (Bracken-Grissom and Felder, 2014; Bracken-Grissom et al., 2014; Almeida et al., 2018) (Fig. 3).

Figure 3.
Distribution map of Alpheus platycheirusBoone, 1927. The red stars correspond to localities of previous records (Bracken-Grissom and Felder, 2014; Bracken-Grissom et al., 2014; Almeida et al., 2018). The yellow star indicates the new record observed in the Paraguaná Peninsula, Venezuela (this study).

Ecology and habitat. Alpheus platycheirus inhabits muddy bottoms at depths between 12 to 122 m (Bracken-Grissom et al., 2014). However, in the Caribbean this species typically inhabits shallow depths: 21.9 m in Cuba (Boone, 1927), from 29 to 40 m in Colombia (Bracken-Grissom et al., 2014), from 0.2 to 1.5 m in Panama (De Grave and Anker, 2017), and between 0.17 and 0.6 m in Venezuela (this study). In Haiti, a specimen was collected from a fish stomach (Boone, 1930); two specimens were found inside a loggerhead sponge (Boone, 1930), a symbiotic relationship that does not appear to have been recorded since and is considered unusual (Bracken-Grissom et al., 2014). In our study, we found this species associated with Thalassia testudinum and Halodule wrightii seagrass meadows, which were established on a sandy calcareous substrate with remains of the green algae Halimeda sp. (Mariño et al., 2018).

DISCUSSION

Alpheus platycheirus is part of the A. floridanus Kingsley, 1878 species complex, which is supported by morphological characters and color patterns. The A. floridanus complex consists of five species and one subspecies in the eastern Pacific and tropical Atlantic (Bracken-Grissom and Felder, 2014). The two western Atlantic species, A. floridanus s.s. and A. platycheirus, were recently redescribed. Alpheus floridanus s.s. was redescribed based upon a lectotype selected from the former syntypic pair. The mutilated second specimen of the syntypic pair was identified as A. platycheirus (cf.Bracken-Grissom and Felder, 2014).

Thirty-three species of Alpheus have been previously recorded from the coast of Venezuela, including A. floridanus (cf.Rodríguez, 1980; Marcano, 1997; Hernández-Ávila et al., 2007; Vera-Caripe et al., 2012; plus unpublished data from one of the authors). We report A. platycheirus for the first time in Venezuela, from the Paraguaná Peninsula (Falcón State). In this study, A. platycheirus was found at a remarkably shallow depth (between 0.17 and 0.6 m) in association with well-developed seagrass beds that were delimited by fringing coral reefs (Mariño et al., 2018). This shallow habitat is unusual for a species that mainly inhabits muddy bottoms. At least two species of the A. floridanus complex occur in Venezuela: A. floridanus s.s. and A. platycheirus (cf.Bracken-Grissom and Felder, 2014). Previous records of A. floridanus from the Venezuelan coast may correspond to any of these species and must be treated with caution.

It has been shown that A. platycheirus from the Gulf of Mexico, Cuba, Colombia, and Brazil constitute a monophyletic clade (Bracken-Grissom et al., 2014). Moreover, 16S sequences suggest there is gene flow occurring between these populations (Bracken-Grissom et al., 2014), which is also likely to link populations of this species in northwest Venezuela. Gene flow may be facilitated by the Loop Current (Bracken-Grissom et al., 2014), which plays a significant role in the circulation and transport of water throughout the southeastern Gulf of Mexico and has been suggested to influence the distribution of other species in the region (Williams and Williams, 1981; Bangma and Haedrich, 2008).

ACKNOWLEDGEMENTS

This research was supported by the Venezuelan Institute for Scientific Research (IVIC) project #467. We express our gratitude to Dr. Arthur Anker (Universidade Federal do Ceará), for the valuable help in confirming the color pattern of the species. The authors also thank the anonymous reviewers for their comments.

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Publication Dates

• Publication in this collection
  13 July 2020
• Date of issue
  2020

History

• Received
  22 Jan 2020
• Accepted
  23 Apr 2020