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INTRODUCTION
Geryonidae Colosi is a family of deep-sea portunoid marine crabs widely distributed on continental slopes and deep waters, between 100 and 3,500 m deep (Manning, 1990; Poupin and Buat, 1992). It currently includes eight genera and 50 recent species, and also has a good fossil record (DecaNet, 2025). Among the geryonids, the genus Chaceon Manning and Holthuis contains the greatest richness, with 34 species, characterized by five teeth on the anterolateral margin of the carapace, well-developed frontal teeth, rounded orbits, and not markedly inflated gill regions (Manning and Holthuis, 1989).
Species in this genus are highly commercially important and are subject to strong fishing pressure worldwide (Pezzuto et al., 2006; Tallack, 2007; Robinson, 2008; Wahle et al., 2008; Pezzuto and Sant’Ana 2009; Mzungu et al., 2024). However, life-history characteristics such as slow growth, late reproduction (Hastie, 1995), and apparently restricted spatial distribution of stocks (Pezzuto et al., 2006) make them highly vulnerable to overexploitation (Groeneveld et al., 2013).
According to Tavares and Pinheiro (2011), nine species of the genus Chaceon are present in the western Atlantic: C. atopus Manning and Holthuis (Saint Helena Island), C. eldorado Manning and Holthuis (Colombia, Venezuela, Lesser Antilles, and French Guiana), C. fenneri (Manning and Holthuis) (east Florida to the Gulf of Mexico), C. inghami (Manning and Holthuis) (Bermuda), C. linsi Tavares and Pinheiro (northeast Brazil), C. notialis Manning and Holthuis (southwest Brazil, Uruguay, and Argentina), C. quinquedens (Smith) (northwest Atlantic to the Gulf of Mexico), C. ramosae Manning, Tavares, and Albuquerque (southern Brazil) and C. sanctaehelenae Manning and Holthuis (Saint Helena Island, also known from the off-shore of São Tomé Island, West Africa).
Since its description in 1989, based on material collected partly in Venezuela, C. eldorado has not been the subject of new findings in the country, possibly due to limited sampling efforts in deep waters. This research reports new encounters of this species in Venezuelan waters and discusses some taxonomic and ecological aspects.
The material analyzed comes from the first three samplings of an annual scientific fishing project in the mesopelagic zone of the central Venezuelan coast. The purpose is to explore the benthic zone between 400 and 600 m depth to identify new fishing areas, assess potential fishery resources, and potentially undescribed species. The study area is located 5.6 to 7.4 km north of Chichiriviche de la Costa, La Guaira state (Figure 1).
Figure 1 Geographic locations of the records of Chaceon eldorado Manning and Holthuis from Venezuela, or referred so: Taissoun (1988): red diamond; Manning and Holthuis (1989): red hexagon (type locality) and black X; present study: yellow circles. Bathymetry layer: modified from GEBCO (2024).
The sex of the specimens was determined by the presence of gonopods in the pleon of males, the shape of the pleon (slender in males, rounded in females), and the location of the genital pore in females. The carapace width (CW) was measured, considered the greatest transverse distance from the longitudinal axis of the carapace in dorsal view. The specimens were photographed and subsequently deposited in the reference collections of the Grupo de Investigación en Carcinología (GIC) of the Universidad de Oriente and the Margarita Marine Museum (MMM), Margarita Island, Venezuela.
Chaceon eldoradoManning and Holthuis, 1989
Fig. 2 - 3
Geryon quinquedens non Smith, 1879, Taissoun (1988): 173; Taissoun (2022): 111, fig. 37.
Chaceon eldoradoManning and Holthuis, 1989: 61, fig. 7-8; Campos et al. (2005) : 228, fig. 191; Tavares and Pinheiro (2011): 65, fig. 5D; Poupin and Corbari (2016): 84, fig. 18D; Poupin (2018): 292.
Material examined: 01/30/2025, 17 males (unmeasured), 2 females (unmeasured), 5.9 km north of Chichiriviche de La Costa, 570 m depth, collector: Fariña, A. 02/26/2025, 6 males (152 - 169 mm CW), 6.1 km north of Chichiriviche de La Costa, 574 m depth, collector: Fariña, A., GIC-944. 03/19/2025, 20 males (133 - 176 mm CW), 42 non-ovigerous females (103 - 151 mm CW), 1 ovigerous female (126 mm CW), 7.4 km north of Chichiriviche de La Costa, between 462 - 574 m depth, collector: Fariña, A., MMM-crust-447 to 449.
General description: Manning and Holthuis (1989) .
Description of male pleopods: First pair relatively short, robust, coriaceous, wider in the proximal half, inner margin rounded, finely setose, apex acute, tubular, curved outwards (Fig. 3A-B). Second pair slender, almost as long as the first pair, with a curved spine on the inner margin of the distal quarter, perpendicular to the longitudinal axis of the pleopod, with setae on its inner edge; From this spine, the pleopod becomes thinner and more sinuous (Fig. 3A-C), the apex does not exceed the 6/7 sternal suture.
Records from Venezuela: Falcón state (641 m depth) and northeast of the Los Testigos archipelago (531 m depth) (Manning and Holthuis, 1989).
General distribution: Colombia to French Guiana; Guadeloupe and Martinique (Poupin and Corbari, 2016).
Comments: Taissoun (1988) was the first to report the presence of the family Geryonidae in Venezuela, based on two females collected “south of Aruba” and wrongly identified as Geryon quinquedens; however, the geographic coordinates he provided actually corresponded to the north of Aruba, outside Venezuelan jurisdictional waters. A year later, Manning and Holthuis (1989) described Chaceon eldorado based on a specimen (selected as the holotype) from Venezuela, 42.6 km east of the Paraguaná Peninsula, Falcón State (11°53‵N - 69°25‵W) (Fig. 1). Additionally, these same authors selected two paratypes, also from Venezuela; however, one of them actually came from Aruba, like the Taissoun material.
The species of this genus are morphologically similar (Poupin and Corbari, 2016), in this sense, C. eldorado can be easily confused with C. notialis and C. ramosae, since they share dorsoventrally depressed dactyls of the pereiopods, poorly developed anterolateral teeth of the carapace and the merus of the fifth pair of pereiopods without a distodorsal spine (Manning and Holthuis, 1989; Manning et al., 1989; Tavares and Pinheiro, 2011). Chaceon eldorado can be differentiated from C. notialis by the length of the merus of the fifth pair of pereiopods, which does not exceed the last anterolateral tooth of the carapace in the latter species, while in C. eldorado the merus exceeds the last anterolateral tooth of the carapace. On the other hand, C. eldorado can be differentiated from C. ramosae by having a short gonopod 2, which does not reach the 6/7 thoracic suture (gonopod 2 extends beyond the 6/7 suture in C. ramosae); furthermore, the merus of fifth pair of pereiopods is more than twice the length of the dactyl in C. eldorado (twice the length of the dactyl in C. ramosae) (Tavares and Pinheiro, 2011).
Male pleopods have proven very useful for separating morphologically very similar species of portunidae (Williams, 1974), pseudotelfusids (Rodríguez, 1982), xanthoids (Martin and Abele, 1986), and grapsoids (Abele, 1992), among others; however, they have received little attention in gerionids, so their potential as a taxonomic tool is uncertain. The material examined fits the species descriptions by Manning and Holthuis (1989) ; however, it presents slight differences, such as the relative length of the merus in relation to the carapace width in a female, which was 0.47, which is considerably smaller than the registered ratio (0.56). These differences, however, appear to be due to morphological variations within the species.
Several specimens showed strong epibiosis by Poecilasmatidae barnacles, being particularly abundant in the pereiopods and thoracic sternites (Figure 3A); chitinolytic lesions were also observed (identifiable as blackened areas of the carapace) (Figure 2A - 3B). This type of lesions is very common among geryonids (Poupin and Buat, 1992; Cartes, 1993), and can affect up to 90% of crabs in certain populations (Pinho et al., 2001). If the lesions are extensive, the crabs may appear unappealing and their commercial value in the market may be affected, requiring processing to sell only the meat, raising production costs (Shields, 2012).
Figure 2 Chaceon eldorado Manning and Holthuis, male, A) dorsal view; B) ventral view; ovigerous female, C) dorsal view; D) ventral view. Scale bars: 100 mm.
Figure 3 Chaceon eldorado, first (right) and second male pleopod (left) A) dorsal view; B) ventral view; C) second pleopod apex. D) infested by Poecilasmatidae barnacles on the pereiopods. E) male specimen with chitinolytic lesions (white arrows) on the dorsal region. Scale bars: 1 mm. D and E Photographs by Martha Montes.
Many ecological and life cycle aspects of Geryonidae remain unknown, including their reproductive periods, sex ratio, and geographic distribution (Wahle et al., 2008; Groeneveld et al., 2013; Mzungu et al., 2024). Such is the case of C. eldorado, whose presence in the scientific literature is based on scattered records (Campos et al., 2005; Poupin and Corbari, 2016; Poupin, 2018). Understanding these aspects is especially relevant due to the economic interest that this family represents from a fisheries perspective. Several biological traits of Geryonidae, such as their high longevity, slow growth, late sexual maturity (Armstrong, 1990), large body size (Fernández-Vergaz et al., 2000), long incubation periods and irregular recruitment (Hastie, 1995), together with spatial patterns of sexual segregation according to depth (Masello and Defeo, 2016) and spatial aggregation related to sexual maturity (Martínez-Rivera et al., 2020) make them highly vulnerable to overexploitation.
Therefore, it is essential to implement rigorous management measures including, among other elements, preliminary stock assessments, the establishment of harvest quotas, determination of the size at first sexual maturity and the minimum catch size, as well as the definition of closed periods and areas. Furthermore, constant monitoring of the fishery is required to allow for timely corrective action when necessary.
