Subfamily Cyclograpsinae H. Milne Edwards, 1853

Pachygrapsus minutus [from Haswell 1882: pl. 2 fig. 4]

Museums

Regional Maps

• Cyclograpsacea Milne Edwards, H. 1853. Mémoires sur la famille des Ocypodiens, suite. Annales des Sciences Naturelles, Paris Zoology 3 20: 163-228 pls 6-11 [191].
• Helicinae Kossmann, R. 1877. Malacostraca (1. Theil: Brachyura). Chapter Erste Halfte, III. 1-66 pls 1-3 in Kossmann, R. (ed.). Zoologische Ergebnisse einer im Auftrage der Königlichen Academie der Wissenschaften zu Berlin ausgeführten Reise in die Küstengebiete des Rothen Meeres. Leipzig : W. Engelmann. [57].

  Type genus:

   Helice De Haan, 1833.

Introduction

The Cyclograpsacea of H. Milne Edwards has long been treated as synonymous with Dana's Sesarminae. Recent studies of larval morphology and 16S mtDNA by Schubart & Cuesta (1998) and Schubart et al. (2000), however, have cast doubt on a close relationship with other sesarmines of at least two genera, Cyclograpsus and Chasmagnathus. Both studies suggest that these genera are better placed in the Varuninae. Similarly a cladistic study by Sternberg & Cumberlidge (1998) found the Sesarminae to be paraphyletic. This analysis showed that a number of genera (Chasmagnathus, Cyclograpsus, Helice, Helograpsus, Metaplax, and Paragrapsus) fail to conform with other sesarmine genera; these were `reassigned elsewhere within the Grapsoidea'.

None of these studies has resulted in a satifactory solution regarding the placement of this group of genera. Two important character states always have seemed to indicate that these and several other allied genera belong in the Sesarminae, namely the pterygostome, subbranchial and subhepatic regions with a more or less regular reticulation of hooked setae (used to oxygenate water); and secondly, the third maxillipeds possessing an oblique setose crest extending across the merus and outer distal corner of the ischium and used in channelling water flow. These derived, and admittedly linked, character states do at first seem to be compelling evidence of a close relationship between cyclograpsines and the Sesarminae. However, an almost identical pattern of setal reticulation can also be seen on at least one species of Plagusia, P. glabra Dana, 1852, and this is evidence that this adaptation has occurred more than once, and thus can reasonably be considered homoplaseous. However, careful morphological comparisons reveal that a group of genera related to Cyclograpsus all have a different pattern of development of the grooves that direct respiratory water flow across the pterygostome, and in particular, have a more or less clearly defined vertical groove running subparallel with the buccal cavity that is not found in the Sesarminae sensu stricto. In addition, these genera have a strongly developed, typically stridulatory, sub-orbital crest that is relatively straight, and extends some distance across the lateral branchial region. In this latter feature, they are most similar to Varuninae, and this supports a putative sister-group relationship corroborating the results of Schubart et al. (2000). Two names are available for the genera concerned, Cyclograpsacea H. Milne Edwards, 1853, and Helicinae Kossmann, 1877. H. Milne Edwards' name, in its corrected form, Cyclograpsinae, is the oldest, and is here resurrected to include Chasmagnathus De Haan, 1833, Cyclograpsus H. Milne Edwards, 1837, Helicana K. Sakai & Yatsuzuka, 1980, Helice De Haan, 1833, Helograpsus Campbell & Griffin, 1966, Metaplax H. Milne Edwards, 1852, and Paragrapsus H. Milne Edwards, 1853.

Diagnosis

Carapace oval to quadrate or quadrangular with lateral margins convex to subparallel; regions often discernible, although grooves shallow; dorsal surface typically naked, without tufts of setae; body sometimes more-or-less flattened to deeply vaulted; anterolateral margins entire or with one or two epibranchial teeth or notches. Front deflexed; moderately broad, clearly less than half maximum carapace breadth. Orbits open laterally; sub-orbital crest more or less straight, typically long, extending some distance across lateral branchial region, typically stridulatory in conjunction with chelipeds; pterygostomial grooves opening into anterolateral corner of buccal cavity; pterygostome, subbranchial and subhepatic regions with or without a more or less regular reticulation of hooked setae (used to oxygenate water, but apparently sometimes secondarily reduced in more terrestrial groups such as Cyclograpsus); pterygostome with more or less deep vertical groove placed subparallel to buccal cavity. Third maxilliped with oblique setose crest extending across merus and outer distal corner of ischium; leaving medial rhomboidal gape; reaching forward to margin of epistome to completely close buccal cavity anteriorly; exopod normal, narrow; flagella of maxilliped exopods not especially elongate and not noticeably protruding from behind third maxillipeds. Endostome smooth, more or less medially prominent. Male abdomen with seven free segments (six abdominal somites plus telson). Chelipeds usually subequal, massive. Legs oval to circular in cross section, typically more or less narrow and not markedly dorso-ventrally flattened; posterodistal margin of meri not armed with spines; propodi and dactyli not armed with strong black bristles.

General References

Schubart, C.D., Cuesta, J.A., Diesel, R. & Felder, D.L. 2000. Molecular phylogeny, taxonomy, and evolution of nonmarine lineages within the American grapsoid crabs (Crustacea: Brachyura). Molecular Phylogenetics and Evolution 15(2): 179-190

Schubart, C.D. & Cuesta, J.A. 1998. The first zoeal stages of four Sesarma species from Panama, with identification keys and remarks on the American Sesarminae (Crustacea: Brachyura: Grapsidae). Journal of Plankton Research 20: 61-84

Sternberg, R. von & Cumberlidge, N. 1998. Taxic relationships within the Grapsidae MacLeay, 1838 (Crustacea: Decapoda: Eubrachyura). Journal of Comparative Biology 3(2): 115-136

History of changes