*3.1. Morphologic Identification*

A total of 26 crabs were sexed and identified taxonomically based on coloration patterns, the shape of the cephalothorax and the size and shape of the chelipeds. Taxonomic characteristics based on Castro [16,24] determined that the crabs belonged to three *Trapezia* species, and a mix of males, females and juveniles were obtained and described as follows (Figure 2): The crabs identified as *T. formosa* (3 females, 4 males) were all characterized as small adults, with cephalothoracic widths ranging from 4 to 7 mm (Table 1). They usually presented a reddish-orange color, with the lower margin of the propodus (chelipeds) yellowish and with chelipeds lengths 3-fold greater than widths (Table 1). Their carapaces were globose, with the anterolateral sides strongly curved (up to 45◦; Figure 2A). The crabs identified as *T. bidentata* (7 females, 5 males and 1 juvenile) showed most of the morphologic characteristics of *T. formosa* with the key difference being that the specimens identified as *T. bidentata* showed a darker red coloration and presented less curved anterolateral sides of the carapace (Figure 2B); for this species the specimens examined presented higher carapace and cheliped sizes than *T. formosa* (Table 1). Finally, the crabs identified as *T. corallina* (5 males and 1 juvenile) presented a dark orange-brown color, brown reticulations on the propodus, and, in general, thick and bulky chelipeds; they were also characterized by a complete suture between the (i) second and third thoracic sternites and (ii) the ischium of the endognath of the third pair of maxillipeds; also, this species showed a rough appearance in the middle portion of the inner margin (Figure 2C). Finally, *T. corallina* presented both the largest cheliped and largest carapace of the species collected (Table 1).

**Table 1.** *Trapezia* carapace and cheliped measurements per species and sex. Values reported as means ± SD. N/A corresponds to no available data.


**Figure 2.** *Trapezia* crabs of the Tropical Eastern Pacific. (**A**) *Trapezia formosa*; (**B**) *T*. *bidentata*; (**C**) *T. corallina*. CW—carapace width; CL—carapace length; RC—right cheliped.
