This longevity may be due to telomerase , an enzyme that repairs long repetitive sections of DNA sequences at the ends of chromosomes, referred to as telomeres. Telomerase is expressed by most vertebrates during embryonic stages, but is generally absent from adult stages of life. They generally live singly in crevices or in burrows under rocks. They scavenge if necessary, and are known to resort to cannibalism in captivity. However, when lobster skin is found in lobster stomachs, this is not necessarily evidence of cannibalism — lobsters eat their shed skin after moulting. However, when they flee, they swim backward quickly by curling and uncurling their abdomens.
|Published (Last):||23 November 2008|
|PDF File Size:||7.83 Mb|
|ePub File Size:||9.49 Mb|
|Price:||Free* [*Free Regsitration Required]|
The genus has been interpreted intuitively to be morphologically primitive and ancestral to some or many modern nephropid genera. One issue is the difficulty in characterizing i. For Hoploparia, and far more than for other lobster genera, many characters show variable character states.
A second issue is that the morphologies of some Recent genera e. Both issues stem from an originally ambiguous diagnosis of Hoploparia that has been variously expanded in de facto fashion to the point that, today, nobody really knows what Hoploparia means.
Cladistic analyses herein indicate that Hoploparia is paraphyletic and, therefore, support the intuitive judgement that Hoploparia is a wastebasket genus. This paper, the first species-level cladistic analysis of Hoploparia, is not intended to be the sole basis for taxonomic revision but is, instead, intended to generate discussion among lobster specialists. Hopefully, this discussion will bring forth additional characters for cladistic analysis and other new insights that may lead to better supported cladograms addressing lobster taxonomy.
Hoploparia McCoy, , is a well-known, clawed lobster genus with a record extending from the Lower Cretaceous Valanginian to the Miocene. Hoploparia is, by far, the best known genus of fossil clawed lobster, and the most diverse lobster genus, fossil or Recent.
The next most diverse nephropid lobster genus is the extant Metanephrops Jenkins, , known by 17 species 14 Recent, 3 fossil. Hoploparia was cosmopolitan in geographic range, extending from Canada and Greenland to the Antarctic Peninsula.
Hoploparia has been interpreted intuitively to possess a morphology that is primitive for the Nephropidae. This, plus its diversity in the Lower Cretaceous, strongly suggests that Hoploparia was ancestral to some or many modern nephropid genera Mertin, ; Secretan, ; Glaessner, ; Tshudy, Essentially, Hoploparia was proposed as a genus of fossil lobsters generally resembling the Recent American lobster Homarus Weber, but having a more sculptured grooved, locally inflated, etc.
Scale bar equals 1 cm. Open in new tab Download slide Schematic line drawing of nephropid lobster cephalothorax, showing postions of grooves, spines, etc. Discussion of these features in Tshudy, — Since , many other fossil lobster species have been discovered. Only a few fossil species, those with very distinctive morphologies, have not been referred to Hoploparia.
Similarly, fossil Metanephrops Jenkins, , bear distinctive ridges and spines that show their obvious relationship to Recent Metanephrops. The inclusion of 50 other fossil species in Hoploparia has, in de facto fashion, variously stretched and expanded the definition of Hoploparia to accommodate this or that spine, this or that carina, etc.
Currently, there is so much variation among lobster species referred to Hoploparia that the genus is difficult to characterize. Tshudy encountered this while attempting to write an updated diagnosis of the genus. His diagnosis pp. Cladistically, apes, both nonhuman and human, form a monophyletic group defined by synapomorphies.
Pongidae is defined not by synaporphies but instead by the lack of synapomorphies that define humans Hominidae. One issue is the aforementioned variability within the genus and the resulting difficulty in characterizing its morphology, e. A second issue is that morphologic comparisons between some recent genera e.
Nephropides, a monospecific genus known from slope depths in the Caribbean Sea, is noteworthy for the rigidity of its carapace and for the uniformly dense coverage of its carapace by large tubercles. However, carapace rigidity is indeterminate in the lobster fossil record, and there is nothing in the definition of Hoploparia that excludes coverage by tubercles. In fact, many Hoploparia are well covered by granules or tubercles.
In fact, there are no consistent differences between the two genera. Unlike most Hoploparia, Eunephrops possess a gastrolateral spine on the cephalothorax. Also, the gastric tubercle a small projection located dorsomedially on the cephalothorax, approximately midway between the orbit and the postcervical groove is present on most Eunephrops but absent on Hoploparia. In the absence of consistent differences, why would anyone not refer a fossil Eunephrops to Hoploparia?
In this study, we test the hypothesis with species-level cladistic analysis of morphology. Materials and Methods The first author has examined all known fossil and Recent nephropid species total; 70 fossil and 52 Recent , directly whenever possible, but otherwise through the literature, in an attempt to understand the nature and range of morphologic variation in nephropid lobsters Tshudy, Emphasized are carapace grooves characters 1—10 and ornamentation 11—25 , but the abdomen 26 , telson 27—29 , claws 30, 31 , other appendages 33—35 , and a fusiform plate in the cephalothorax 32 are also considered.
We used all known characters in the analysis but, nonetheless, express the following opinions and preferences about them. Carapace grooves, being expressions of internal anatomy at least as sites of muscle attachment Albrecht, ; de Saint Laurent, personal communication, but maybe even body segmentation Secretan, , others; Glaessner, , would seem to be more conservative, i.
Ornamentation is still well represented in the data matrix because these features—spines, ridges, etc. The abdomen is less commonly preserved than the cephalothorax Tshudy et al. Claws are relatively well calcified and therefore commonly preserved; however, they are especially subject to homoplasy Tshudy and Sorhannus, Characters 33—35 are rarely, if ever, observable on fossil lobsters.
This was most true for carapace grooves, which sometimes are neither plainly evident nor plainly absent. As a test on the reproduceability of character coding, the first author reexamined the matrix one year after its construction. In the 35 character by 29 taxon matrix character states , eight states 0. Seven of the eight changes concerned fossil taxa.
For the master data matrix, we selected 28 nephropid taxa for cladistic analysis. We used 16 of the better known better preserved Hoploparia species that represented the range of morphologic variation in the genus. We also included genera that resemble Hoploparia—including Homarus the distinction between Hoploparia and Homarus has been much debated Tshudy, , p. The lobster Eryma Von Meyer, , representing the family Erymidae, was selected as the outgroup and used to root the trees.
The first was an unweighted heuristic search using random addition of sequences replicates and tree-bisection-reconnection branch swapping. Through successive weighting, the phylogenetic signal in the original matrix can be enhanced, even when cladistically reliable characters are heavily outnumbered by unreliable ones Farris, In the third analysis, we reduced the number of taxa in the hopes of producing a more resolved cladogram.
Eleven fossil species, including eight Hoploparia and two Homarus, were removed from the master matrix, leaving eight well-preserved species representing the range of morphologic variation in Hoploparia. TreeView Page, was used to draw the phylogenetic trees.
Rescaled weighted and unweighted Bremer support values were calculated following the procedure outlined in Bremer Bremer support values indicate the number of extra evolutionary steps needed to collapse a node in the strict concensus tree; thus, the higher the value, the more stable the node. Bremer support values were computed in the program TreeRot Version 2. Results In the master matrix of 35 characters, three are constant, and five variable characters are autapomorphous.
This leaves 27 characters as parsimony informative. In the taxon-reduced matrix, also of 35 characters, three are constant, and four variable characters are autapomorphous, leaving 28 as parsimony informative. Unweighted analysis of the master matrix the first analysis produced a cladogram that is unresolved with regard to monophyly of Hoploparia Fig.
Unweighted Bremer support values are shown for resolved clades Fig. Hoploparia is shown to be paraphyletic. Rescaled, weighted Bremer support values for the resolved nodes are shown on the cladogram. Cladogram is well resolved but with poorly supported groups. Rescaled, weighted Bremer support values for the resolved nodes are shown on the tree.
Unweighted analysis of the reduced matrix the third analysis produced a cladogram that is resolved sufficiently to show that Hoploparia is paraphyletic Fig. Unweighted Bremer support values are shown on the cladogram. Reduction in the number of taxa improved the support values as compared to those on the cladogram Fig.
Cladistic analysis herein shows that Hoploparia is a paraphyletic group, and, therefore, we failed to reject the hypothesis. Hoploparia is shown to be paraphyletic in both the second and the third analyses showing resolution for Hoploparia; i. Nevertheless, these fossil genera are part of what makes Hoploparia a paraphyletic group.
Monophyletic groups in our cladograms also mix Hoploparia and Recent non-Hoploparia. Note, for example, the positions of the Recent genera Nephropides and Eunephrops Figs. From a traditional, systematic standpoint, this suggests either that both Nephropides and Eunephrops should be made junior synonyms of Hoploparia, or that Hoploparia should be rediagnosed in a more restricted fashion, one congruent with ranges of morphologic variation in Recent genera.
We favor the latter; nevertheless, it should be pointed out that traditional systematic specialists on Recent lobsters have generally ignored fossil taxa. For example, Manning made no mention of fossil taxa when erecting Nephropides, even though Nephropides seems easily accommodated within Hoploparia. If the authors of some Recent genera had considered fossil taxa, then some of these Recent genera might never have been erected. Not all of the cladograms is in opposition to the existing, intuitively derived systematic classification.
Several aspects of the cladograms reconcile well with the existing classification: a. In Figs. On the basis of morphologic similarity and stratigraphic occurrence, the fossil Oncopareia has been confidently considered as ancestral to the Recent Thaumastocheles. Milne-Edwards, , and Homarinus form a monophyletic group. Homarinus was known as Homarus capensis Herbst, , until Kornfield et al.
What is the remedy for the paraphyly of Hoploparia? In acknowledging that Hoploparia is paraphyletic, the traditional systematist might narrow the diagnosis of Hoploparia, creating new genera for species thereby excluded. Ranges of morphologic variation in Recent genera would be used as a guide to drawing generic boundaries in fossils. Also, some Recent genera would become junior synonyms of Hoploparia. Alternatively, a cladistic approach, which we prefer, would abandon the existing taxa and propose new, monophyletic groupings.
We do not, however, believe that proposing a new, formal classification is prudent at this time. Instead, this paper is intended as a first step toward a more meaningful taxonomy. This is the first published species-level cladistic analysis of Hoploparia, or of a data matrix for same. It is hoped that this publication will generate discussion among lobster specialists and bring forth additional characters for cladistic analysis and other new insights that may lead to better support in cladograms addressing lobster taxonomy.
Conclusion While it is true that any genus is merely an opinion about how to group similar species, and that there is no biological basis, or even any standard, objective basis, for the genus concept, the case of Hoploparia is worse, having been variously stretched and expanded through time in de facto fashion by various workers to the point that, today, nobody really knows what Hoploparia means. Hoploparia McCoy, , was erected for a single species and, by modern standards, was ambiguously diagnosed on the basis of just a few characters.
Cladistic analyses herein indicate that Hoploparia is paraphyletic and, therefore, support the intuitive judgement that Hoploparia is a wastebasket genus. In fact, many Hoploparia fossl well covered by granules or tubercles. Food and Drug Administration. Microbiology and Molecular Biology Reviews. Both issues stem from an originally ambiguous diagnosis of Hoploparia that has been variously expanded in de facto fashion to the point that, today, nobody really knows what Hoploparia means. Exopod on maxilliped 2: Abstract Hoploparia McCoy, Lower Cretaceous Valanginian —Miocene is, by far, the most diverse clawed lobster genus fossil or Recent ; 49 species are known. Milne Edwards, Decapoda: Cladogram is well resolved but with poorly supported groups.
FOSSIL NEPHROPIDAE PDF
Murisar Email the author Login required. It is hoped that this publication will generate discussion among lobster specialists and bring forth additional characters for cladistic analysis and other new insights that may lead to better support in nephropisae addressing lobster taxonomy. Morphology-based phylogenetic analysis of the clawed lobsters family Nephropidae and the new family Chilenophoberidae. In fact, many Hoploparia are well covered by granules or tubercles. Lobsters, like many other decapod crustaceans, grow throughout life and are able to add new muscle cells at each moult.