Rafael Lemaitre

HERMIT CRAB PHYLOGENY: A REAPPRAISAL AND ITS “FALL-OUT”

Abstract The hypothesis of monophyly in Paguroidea and the relationship of this superfamily to the other three superfamilies of Anomura have been reassessed using current cladistic methods and computer generated analysis. In the analysis, 79 external morphological characters were examined for an in-group consisting of the seven paguroid families, Pylochelidae, Coenobitidae, Diogenidae, Pylojacquesidae, Paguridae, Parapaguridae, and Lithodidae (divided into the subfamilies Lithodinae and Hapalogastrinae), three hippoid families, Blepharipodidae, Albuneidae, and Hippidae, five galatheoid families, Galatheidae, Chirostylidae, Kiwaidae, Aeglidae, and Porcellanidae, and the Lomisoideas monotypic Lomisidae. The out-group was comprised of Neoglyphea inopinata, representing Fractosternalia, and the families Dromiidae and Dynomenidae representing Brachyura. This analysis has shown that Anomura indeed is a monophyletic infraorder, as is Hippoidea a monophyletic superfamily. However, while six of the paguroid families form a cohesive clade, the two subfamilies of Lithodidae form a distinct clade more closely related to the superfamily Hippoidea than to the other paguroids. Galatheoidea, as presently constituted, is polyphyletic. Aeglidae, like Lithodidae, is more closely related to Hippoidea than to the galatheoid clade formed by the families Galatheidae, Chirostylidae, and Porcellanidae. Kiwaidae is also distinct from Galatheoidea sensu stricto, but its relationship, and that of Lomisoidea, to the remainder of the anomuran taxa are unresolved in the present analysis. As a result of this reappraisal, we propose that Lithodidae be removed from Paguroidea sensu lato and elevated to superfamily rank with families Lithodidae and Hapalogastridae. Similarly, we propose that Galatheoidea be restricted to the families Galatheidae, Chirostylidae, and Porcellanidae, whereas Kiwaidae and Aeglidae are each to be elevated to superfamily rank. Anomura will then consist of seven superfamilies, Hippoidea, Lithodoidea, Aegloidea, Lomisoidea, Kiwaoidea, Galatheoidea sensu stricto, and Paguroidea sensu stricto.

Preliminary Phylogenetic Analysis of Generic Relationships Within the Callianassidae and Ctenochelidae (Decapoda: Thalassinidea: Callianassoidea)

A phylogenetic analysis of 106 representatives in the thalassinidean families Ctenochelidae and Callianassidae, based on 93 adult morphological characters, was performed to investigate the interrelationships between the 25 currently recognized genera. The callianideid, Callianidea typa H. Milne Edwards, was used as the out-group. The two in-group families, Ctenochelidae and Callianassidae, were both shown to be monophyletic. Monophyly of the four ctenochelid subfamilies (Anacalliacinae, Callianopsinae, Ctenochelinae, and the recently suggested Gourretinae) was not supported. Three callianassid subfamilies (Callianassinae, Cheraminae, and Eucalliacinae) were found to be monophyletic but with species compositions different from those presently understood. The fourth callianassid subfamily (Callichirinae) is paraphyletic and ancestral to the other subfamilies. Several species described as species of Callianassa s.l. were found to belong to other genera. Recent diagnosis of several small genera from the Americas and Japan has left larger traditional genera such as Callianassa s.l. and Cheramus paraphyletic. Glypturus is apparently paraphyletic as presently diagnosed. The taxonomic position of some species remains enigmatic largely because of missing data. A listing of all valid genera and species of Ctenochelidae and Callianassidae at the time of publication is provided.

A comprehensive and integrative reconstruction of evolutionary history for Anomura (Crustacea: Decapoda).

BackgroundThe infraorder Anomura has long captivated the attention of evolutionary biologists due to its impressive morphological diversity and ecological adaptations. To date, 2500 extant species have been described but phylogenetic relationships at high taxonomic levels remain unresolved. Here, we reconstruct the evolutionary history—phylogeny, divergence times, character evolution and diversification—of this speciose clade. For this purpose, we sequenced two mitochondrial (16S and 12S) and three nuclear (H3, 18S and 28S) markers for 19 of the 20 extant families, using traditional Sanger and next-generation 454 sequencing methods. Molecular data were combined with 156 morphological characters in order to estimate the largest anomuran phylogeny to date. The anomuran fossil record allowed us to incorporate 31 fossils for divergence time analyses.ResultsOur best phylogenetic hypothesis (morphological + molecular data) supports most anomuran superfamilies and families as monophyletic. However, three families and eleven genera are recovered as para- and polyphyletic. Divergence time analysis dates the origin of Anomura to the Late Permian ~259 (224–296) MYA with many of the present day families radiating during the Jurassic and Early Cretaceous. Ancestral state reconstruction suggests that carcinization occurred independently 3 times within the group. The invasion of freshwater and terrestrial environments both occurred between the Late Cretaceous and Tertiary. Diversification analyses found the speciation rate to be low across Anomura, and we identify 2 major changes in the tempo of diversification; the most significant at the base of a clade that includes the squat-lobster family Chirostylidae.ConclusionsOur findings are compared against current classifications and previous hypotheses of anomuran relationships. Many families and genera appear to be poly- or paraphyletic suggesting a need for further taxonomic revisions at these levels. A divergence time analysis provides key insights into the origins of major lineages and events and the timing of morphological (body form) and ecological (habitat) transitions. Living anomuran biodiversity is the product of 2 major changes in the tempo of diversification; our initial insights suggest that the acquisition of a crab-like form did not act as a key innovation.

Comparative larval development in two species of the burrowing ghost shrimp genus Lepidophthalmus (Decapoda: Callianassidae)

ABSTRACT The early life history is described and compared in the estuarine callianassid shrimp species Lepidophthalmus sinuensis from the Caribbean coast of Colombia and L. louisianensis from the northern Gulf of Mexico, on the basis of laboratory larval cultures and wild plankton collections. Both species have an abbreviated larval development of 2 zoeal stages usually transcended within 3-4 days, with that of L. sinuensis being the shorter and exhibiting greater advancement in the zoeal stages. Development in both species is markedly shorter and morphologically more advanced than in comparable callianassid species for which stages have been described, including most of those known to have only 2 zoeal stages. Larval duration in Lepidophthalmus is nearest that of the ecologically comparable Callianassa s.l. kraussi from southern Africa and suggests possible convergence in early developmental strategies. On the basis of presently known larval histories, genera allied to Lepidophthalmus within the Callichirinae appear to either have long larval histories of 5 zoeal stages, or, if of 2 stages, to bear a morphological resemblance as zoeae to comparable stages in some of the non-Callichirinae. The decapodid (first postlarval) stage is imaginal in form and exhibits burrowing behavior, though appendage development is far short of adult form. Successive early postlarval development and behavior beyond this stage remains unknown. Detailed illustrations of zoeal and decapodid stages are provided to support comparative discussions and for use in larval identifications.

A NEW FAMILY FOR A NEW GENUS AND NEW SPECIES OF HERMIT CRAB OF THE SUPERFAMILY PAGUROIDEA (DECAPODA: ANOMURA) AND ITS PHYLOGENETIC IMPLICATIONS

Abstract A new family, Pylojacquesidae, is proposed for Pylojacquesia colemani, new genus and species. Although the new family, with its monotypic genus, exhibits characters of both superfamilies of the Section Paguridea, it is tentatively assigned to the Paguroidea until additional material becomes available that would permit a more detailed study. The new family Pylojacquesidae is diagnosed, and its type genus and species are described and illustrated. The possible phylogenetic relationships of the new genus are discussed. A key to all the families of hermit crabs is presented.

Aspects of evolution in the anomuran superfamily Paguroidea: one larval prospective

Summary McLaughlin and Lemaitre (1997), in their examination of carcinization in the Anomura, rejected the traditional concept of paguroid evolution, which had consistently maintained that the lithodid crab-like body form evolved from a typical shell-dwelling hermit crab. Their hypothesis proposed just the reverse, i.e., the lithodid crab-like body form gave rise to the simple hermit crab body form through calcium loss, habitat change and consequential morphological adaptations. Their original hypothesis was based on characters derived from adult morphology, but they suggested that larval data would support their view. The megalopal and first or first- and second-crab stages of representatives of both subfamilies of the Lithodidae provide the first of such larval information. Ten species in eight genera have been examined specifically for development of abdominal tergites. These data, although preliminary in scope, unequivocally disprove the Bouvierian concept of lithodid abdominal plate development, and in so doing, lend substantial support to McLaughlin and Lemaitres hypothesis.

Descriptions of megalopa and juveniles of Sympagurus dimorphus (Studer, 1883), with an account of the Parapaguridae (Crustacea: Anomura: Paguroidea) from Antarctic and Subantarctic waters

Four species and a megalopa of the hermit crab family Parapaguridae were obtained during cruises of the USNS Eltanin (1962–8) and Hero (1971) to Antarctic and Subantarctic waters. Adults, numerous juveniles, and the presumed megalopal larvae of Sympagurus dimorphus (Studer, 1883), are reported. Morphological variations and pleopod development in juveniles, and the megalopa of this species, are described and illustrated. Sympagurus haigae (De Saint Laurent, 1972), and Parapagurus latimanus Henderson, 1888, previously were either poorly defined or known from only a few localities; they are diagnosed or their descriptions amended, and illustrated. Parapagurus bouvieri Stebbing, 1910, was found off the coast of New Zealand, extending its range across the Indian Ocean. It is postulated that, at least in some species of Sympagurus, megalopal development is more variable than previously assumed.

Western Atlantic Species of the Parapagurus pilosimanus Complex (Anomura, Paguroidea, Parapaguridae): Description of a New Species and Morphological Variations

ABSTRACT A review of the deep-water hermit crabs of the genus Parapagurus has shown that 10 of the taxa assigned to this genus, and an additional new species, represent a group of closely related species defined herein as the P. pilosimanus complex. Four species of the complex occur in the western Atlantic: P. pilosimanus, P. nudus, P. scaber, and P. alaminos, new species. These species are diagnosed or described and morphological variations evaluated and illustrated. Results of this study provide an indication of the range of variations that could be expected in species of the complex in general. Diagnostic characters at the specific level have been found in the branchiostegite, antennal acicle, left cheliped, propodal rasp of the fourth pereiopod, uropods, and telson. SEM micrographs of the scales constituting the propodal rasp are included. The right cheliped is shown to be affected by size and sexual dimorphism, and is not useful in distinguishing the species.

ON STABILISING THE NAMES OF THE INFRAORDERS OF THALASSINIDEAN SHRIMPS, AXIIDEA DE SAINT LAURENT, 1979 AND GEBIIDEA DE SAINT LAURENT, 1979 (DECAPODA)

The names Gebiidea and Axiidea, erected by de Saint Laurent (1979), have priority over others for the two infraorders of shrimps previously included in Thalassinidea. Importantly, Thalassinidea are not monophyletic and the name should be replaced. Gebiidea and Axiidea, besides having priority and describing two monophyletic taxa, are now in common use (130 citations) and are more stable than alternative schemes proposed by Sakai (2005 and later). The history of the names of higher taxa applied to these groups is reviewed, and all family-group taxa listed.

A review of eastern Atlantic species of the family Parapaguridae (Decapoda, Anomura, Paguroidea)

Fifteen hermit crab species of Parapagurus Smith, 1879, Sympagurus Smith, 1883, or Strobopagurus Lemaitre, 1989, have been found to occur in the eastern Atlantic. Of these, eight are also found in the western Atlantic and have been sufficiently described previously. The remaining seven species are reviewed and for each, a complete synonymy, a diagnosis or amended description, and illustrations, are presented. Keys to aid in the identification of all eastern Atlantic species are included.