Gecarcinus ruricola
Creators: name: Hartnoll, Richard G.
name: Clark, Paul F.
Publisher: name: Zenodo
Year: 2006
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Gecarcinidae
Gecarcinus
Gecarcinus ruricola

description: GECARCINUS RURICOLA (LINNAEUS, 1758)
Carapace (Fig. 3A): rostral small, sharply directed ventrally and slightly inclining posteriorly; carapace sparsely setosed.
Antennule (Fig. 4A): biramous; peduncle 3-segmented with c. 8,8,3 setae, respectively; endopod 1-segmented with 2 subterminal and 2 terminal setae of unequal length; exopod 3-segmented, segment 1 with 5 aesthetascs, segment 2 with 4 aesthetascs and 2 setae, segment 3 with 3 aesthetascs and 2 unequal setae.
Antenna (Fig. 4B): peduncle 3-segmented with 4,3,4 setae, respectively; 7-segmented endopod flagellum with 0,0,4,0,5,3,4 (terminal) setae, respectively. Exopod and protopod lost.
Mandible (Fig. 4C): palp 3-segmented, basial segment without setae; endopod two segmented, distal segment with c. 16 marginal setae.
Maxillule (Fig. 4D): coxal seta present; coxal endite with c. 25 setae; basial endite with c. 34 setal processes; endopod 2-segmented, proximal segment with 2 setae, distal segment with 4 (3 subterminal +1 terminal) setae; exopod seta present.
Maxilla (Fig. 5A): coxal endite bilobed with c. 22 + 10 setae; basial endite bilobed with c. 16 + 20 setae; endopod simple (not bilobed) with 5 basal setae; exopod (scaphognathite) margin with c. 73 setae and 4 lateral setae.
First maxilliped (Fig. 5B): epipod with c. 18 long setae and 1 small basal plus 3 terminal setae; coxal endite with c. 24 setae; basial endite with c. 27 setae; endopod unsegmented with 2 subterminal setae, 1 long-terminal seta sometimes present; exopod 2-segmented, proximal segment with c. 4 distal setae; distal segment with 4 long-terminal plumose feeding setae.
Second maxilliped (Fig. 6A): epipod present with small podobranch gill bud and c. 8 long setae; coxa and basis not differentiated, with 5 setae; endopod 5-segmented, ischium without setation, merus with 1 seta, carpus with 1 seta, propodus with 8 setae, dactylus with 9 marginal setae; exopod 2-segmented, proximal segment with 5 distal setae; distal segment with 5 long-terminal plumose feeding setae.
Third maxilliped (Fig. 6B): epipod with 29 long setae plus podobranch and arthrobranch gill; coxa and basis not differentiated, with c. 29 setae; endopod 5-segmented, ischium with c. 30 setal processes; merus with c. 26 setae; carpus with c. 15 setae; propodus with c. 11 setae; dactylus with 8 setae; exopod 1-segmented, with 1 seta.
Pereiopods (Fig. 7A–E): gills and setation as figured.
Sternal plates (Fig. 3B): plates 1–4 fused, plate 1 without setae, plates 2–4 with c. 46 setae.
Abdomen (Figs 8A, B, 9A–E): 6 somites present; somite 1 with a row c. 5 pairs of medial setae and a row c. 5 pairs of marginal, plus with 4 lateral setae on each side; somites 2 and 3 each with 1 pair of medial setae and c. 5 pairs of marginal setae plus 3 lateral setae on each side; somite 4 with 2 pairs of medial setae plus c. 5 pairs of marginal setae plus 3 lateral setae on each side; somite 5 with 3 pairs of medial setae and 4 pairs of marginal setae plus 3 lateral setae on each side; somite 6 with 1 pair of marginal setae plus 4 setae on each side; somites 2–5 each with 1 pair of biramous pleopods, endopod unsegmented, with a row of 5 cincinuli on internal margin; exopod unsegmented with c. 31, 32, 30, 27 long marginal plumose natatory setae on pleopods 1–4, respectively; somite 6, uropod uniramous without endopod, proximal segment with 2 setae; exopod segment with c. 17 long marginal plumose natatory setae.
Telson (Fig. 8A, B): telson forks absent; 6 pairs of dorsal and 1 pair of ventral setae plus 3 terminal setae.
Remarks
Six genera have been assigned to Gecarcinidae MacLeay, 1838; Cardisoma Latreille, 1828; Discoplax A. Milne-Edwards, 1867; Epigrapsus Heller, 1862; Gecarcinus Leach, 1814; Gecarcoidea H. Milne Edwards, 1837 and Johngarthia Türkay, 1970. Of these genera the larvae are only known for Cardisoma, Gecarcinus and Gecarcoidea (see Table 1). In the Caribbean the megalops are known for two other gecarcinid land crabs, Gecarcinus lateralis described by Willems (1982), and Cardisoma guanhumi by Costlow & Bookhout (1968). These can be compared with and distinguished from the megalop described in the present study (see Table 2). The absence of a distal exopod segment on the third maxilliped in Gecarcinus lateralis and G. ruricola megalops appears to be a distinguishing character for this genus when compared with Cardisoma (see C. guanhumi by Costlow & Bookhout, 1968: fig. 46; C. carnifex by Kannupandi et al., 1980: fig. 56; C. hirtipes by Shokita & Shikatani, 1999: fig. 7i) in which the segment is present with terminal setae.
description: Published as part of Hartnoll, Richard G. & Clark, Paul F., 2006, A mass recruitment event in the land crab Gecarcinus ruricola (Linnaeus, 1758) (Brachyura: Grapsoidea: Gecarcinidae), and a description of the megalop, pp. 149-164 in Zoological Journal of the Linnean Society 146 (2) on page 153, DOI: 10.1111/j.1096-3642.2006.00195.x, http://zenodo.org/record/5435573