First record of an adult Galapagos slipper lobster, Scyllarides astori, (Decapoda, Scyllaridae) from Isla del Coco, Eastern Tropical Pacific

Abstract

The Galapagos Slipper lobster, Scyllarides astori, has been reported from rocky reefs along the Eastern Tropical Pacific: the Gulf of California, the Galapagos Archipelago and mainland Ecuador. Although larval stage S. astori has been found in other localities throughout this range, there are no records of adults inhabiting waters between these three locations. Here we present the first record of an adult S. astori from Isla del Coco and Costa Rican Pacific waters. The single specimen, a male, was hand-collected within a coral reef in Pájara islet. This finding increases the reported lobster species richness of Costa Rican Pacific waters to six species and expands the adult geographic range of S. astori to Isla del Coco.

Introduction

Marine lobsters are a highly diverse group that includes six families, 55 genera, and 248 species that occupy a wide range of habitats and are distributed worldwide (Chan 2014; Briones-Fourzán and Lozano-Álvarez 2015). The slipper lobsters (Scyllaridae) can be distinguished from other lobster families in the infraorder Achelata by having the antennal peduncle segments wide and flat, and the antennal flagellum as a single broad and flat segment without noticeable articulations (Holthuis 1985, 1991). Slipper lobsters are bottom-dwelling decapods commonly inhabiting mud, mud-sand, sand or rocky subtidal zones (Holthuis 1985; Hearn 2006). They are known to prey on several invertebrates (Martínez 2000). Although some scyllarid species are economically important, most of them remain poorly studied (Briones-Fourzán and Lozano-Álvarez 2015).

Only two scyllarid species are registered for the Eastern Tropical Pacific (ETP): Evibacus princeps Smith, 1869 and Scyllarides astori Holthuis 1960 (Johnson 1975b; Hendrickx 1995). The Shield Fan Lobster (E. princeps) is distributed along the Pacific coast from the Gulf of California to Peru (Johnson 1975b; Holthuis 1985; Hendrickx 1995), while S. astori has been reported in the Gulf of California, the Galapagos Archipelago, nearby Clipperton atoll and mainland Ecuador (Holthuis and Loesch 1967; Holthuis 1991; Hendrickx 1995; Béarez and Hendrickx 2006; Butler et al. 2013). These two species are caught incidentally in spiny lobster fisheries. Although they are not exploited for exportation, they are commercially important to local fisheries (Holthuis 1991).

Isla del Coco is an offshore Pacific island, located approximately 500 km away from the coast of Costa Rica. The remarkable biodiversity of this island has been studied since 1888 (see Cortés 2008), and studies of crustaceans from this remote island started in the middle of the 20th century (see Vargas and Wehrtmann 2008). A phyllosoma larva of S. astori was collected in the surrounding water column off the island (Johnson 1970). However, no adult scyllarid lobsters have been previously recorded for Isla del Coco (Vargas and Wehrtmann 2008; Vargas and Wehrtmann 2009; Cortés 2012). Here we present the first record of an adult S. astori from Isla del Coco and extend its geographic distribution to this oceanic island.

Material and methods

Isla del Coco is one of five islands in the ETP and belongs biogeographically to the Panamic Province (sensu Boschi 2000). The island is the only protruding seamount on the Coco’s Range (Lizano 2012; Rojas and Alvarado 2012). The Isla del Coco National Park was declared in 1978 and comprises the principal island, several islets and its surrounding waters that cover nearly 2000 km² (Cortés 2008; Lizano 2012). The island and surrounding waters are affected by the seasonal movement of the Inter-Tropical Convergence Zone (Broenkow 1965; Alfaro 2008), El Niño-Southern Oscillation (Fiedler and Talley 2006), and the seasonal upwelling in the Gulf of Papagayo, Costa Rica (Lizano 2008). The neighboring waters are also chemically influenced by coastal and oceanic water bodies (Acuña et al. 2008).

The specimen was collected on October 14th 2015 during a scuba diving survey of macro-invertebrates at Isla del Coco. The single specimen was hand-collected at the western side of the Pájara islet (5.5535°N; −87.0545°W) (Fig. 1) during twilight, at 18 m depth over a sandy patch within a coral reef. The specimen was stored at 0 °C before being transported to the crustacean collection of the Museum of Zoology, Universidad de Costa Rica (MZUCR), where it was preserved in 70 % ethanol. The identification was carried out following Holthuis (1991). The geographic range of the species was verified based on the scientific literature (Holthuis 1960; Holthuis and Loesch 1967; Johnson 1970; Holthuis 1991; Hendrickx 1995; Hickmann and Zimmerman 2000; Béarez and Hendrickx 2006; Butler et al. 2013). After the identification, the specimen was deposited at MZUCR (3383–01). The specimen was collected under the Isla del Coco Marine Conservation Area permission: 2015-1-ACMIC-018.

Fig. 1

Distribution of Scyllarides astori Holthuis 1960 in the Eastern Tropical Pacific. Striped area: extant distribution of S. astori obtained from IUCN Red List, circle: new record of S. astori; star: sample site at Isla del Coco

Results

SYSTEMATICS

Order DECAPODA Latreille, 1803

Suborder PLEOCYEMATA Burkenroad, 1963

Family SCYLLARIDAE Latreille, 1825

Genus Scyllarides Gill, 1898

Scyllarides astori Holthuis 1960

(Figure 2)

Fig. 2

Male of Scyllarides astori Holthuis 1960: a) dorsal view, b) ventral view. Scale = 10 cm. Catalog number MZUCR 3383–01 of the Museum of Zoology, Universidad de Costa Rica

Description

The male specimen measured 26 cm total length, and 13 cm carapace length (Fig. 2a, b). Dorsal surface of carapace faintly arched, without conspicuous elevations or teeth, with wide and shallow grooves; no cervical incision of lateral margin. Median carina absent from second to fifth abdominal somites. Basal part of posterior margin of pleura of second abdominal somite concave. Carpus of first pereiopod without dorsal carinae and not swollen. Ocular peduncles bear longitudinal color stripes. First abdominal somite with smooth dorsal surface and two large nearly circular lateral dark-red spots (Fig. 2a). Between these spots, surface is yellowish with many smaller red spots placed near together, which look like another big median spot.

Remarks

The other scyllarid species reported for ETP waters, E. princeps, shows a deep cervical incision in the anterior part of the lateral margin of the carapace, and the final segment of the antennae is conspicuously crenulated (Holthuis 1991). In contrast, these characteristics are not observed in S. astori.

Previous records

Adults have been reported from the Gulf of California (Mexico), the Galapagos Archipelago and mainland Ecuador (Holthuis 1960, 1991; Hendrickx 1995; Béarez and Hendrickx 2006). A postlarva, probably of S. astori, was found 200 miles north of Clipperton atoll (Holthuis and Loesch 1967). A phyllosoma larva of S. astori was found off Isla del Coco in 1958 (Johnson 1968, 1970). Holthuis (1991) and Butler et al. (2013) stated that this species is likely to be distributed from the Gulf of California to the Galapagos Archipelago, including the ETP oceanic islands. In contrast, Hickmann and Zimmerman (2000) suggested that this species is endemic to the Galapagos Archipelago.

Discussion

There are no scientific reports of adult S. astori from inshore waters of Costa Rica nor Isla del Coco (Vargas and Wehrtmann 2008; Vargas and Wehrtmann 2009; Cortés 2012). Only a phyllosoma larva of S. astori has been recorded off Isla del Coco at 5°16′N; 87°57′W (Johnson 1970). This is not surprising considering that scyllarid larvae could be transported thousands of kilometers by the ocean currents (Johnson 1968, 1970, 1975a, 1975b; Béarez and Hendrickx 2006). Therefore, the occurrence of the phyllosoma larvae in a given area does not necessarily mean that adults can inhabit and reproduce in the same area. In this paper we present the first record of an adult S. astori at Isla del Coco. It should be noted that dive masters visiting Isla del Coco have mentioned that this lobster has been observed a few times during night dives. Moreover, a picture of a Galapagos Slipper Lobster was taken at Isla del Coco by Franco Banfi in 2009 and is posted in the web (www.banfi.ch). This implies that there is probably an established population of S. astori in Isla del Coco. The presence of adult specimens of S. astori in scattered sites in the Gulf of California, and Ecuador, suggests that settlement of juveniles and survival of adults might be more likely in colder temperate/subtropical waters (Béarez and Hendrickx 2006). However, the new record found in Isla del Coco shows that adult S. astori could also inhabit warm tropical waters.

Although the biology of S. astori has been well studied in the Galapagos Archipelago (Holthuis and Loesch 1967; Martínez 2000; Hearn 2006; Hearn and Toral-Granada 2007), there is no information about population dynamics nor trophic ecology of this species in locations outside the Galapagos. Moreover, it is important to note that this species is reported as data deficient by the IUCN (Butler et al. 2013), and its commercial interest in Galapagos lobster fisheries has recently increased due to the depletion of spiny lobsters (Martínez et al. 2002; Hearn 2004; Murillo et al. 2004). Therefore, the population of Isla del Coco could represent an opportunity to evaluate growth models and reproductive aspects of S. astori in a protected area without fisheries impacts.

Reporting the presence of new species in Isla del Coco, even after many scientific expeditions have been carried out, reemphasizes the importance and necessity of continued research at this island. Finally, the finding increases the reported diversity of Costa Rican Pacific lobster from five to six species (Vargas and Wehrtmann 2009).