Morphological variability of recent species of the order Cassiduloida (Echinodermata: Echinoidea) of Mexico (original) (raw)
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Zoosystema, 2006
Test morphologies were examined for both living and denuded specimens of all established species of Diadema Gray, 1825 and Echinothrix Peters, 1853, including two colour morphs of Echinothrix calamaris (Pallas, 1774). Twentyeight morphological characters were measured and analysed using ordination by multi-dimensional scaling (MDS) and cluster analysis. Specific test features were found which differentiated the species. Of these the apical systems, markings on the genital plates, features of the median areas of the interambulacra and distribution of iridophores were particularly useful forms of taxa distinction. Well defined associations in test morphologies were found between Diadema antillarum Philippi, 1845, D. ascensionis Mortensen, 1909, D. mexicanum A. Agassiz, 1863, D. savignyi Michelin, 1845 and D. paucispinum A. Agassiz, 1863. Diadema setosum (Leske, 1778) and particularly D. palmeri Baker, 1967 appeared to be outlying species within the genus; D. palmeri being the only species within the genus Diadema to have a monocyclic apical system. Test morphologies of Echinothrix diadema (Linnaeus, 1758) and E. calamaris were distinctly different, with marked differences in test size and shape, plate arrangements, features of the apical system and structures of the median areas of the interambulacra. The different colour morphs of E. calamaris demonstrated similar test features; however, differences were found which suggest that the brown colour morph may be a separate species or subspecies.
Analysis on a sample of Echinodiscus cf. auritus Leske, 1778 (Echinoidea Clypeasteroida)
2014
In order to ascertain the extent of the natural intraspecific variability of living and fossil echinoids belonging to the family Astriclypeidae Stefanini, 1912, morphometric and structural aspects were examined in a number of specimens of extant Echinodiscus cf. auritus Leske, 1778, from Madagascar and Philippines. The data obtained will be compared, in a following work, with those of other echinoids belonging to the same family. The analysis of the results indicates, for the sample studied, a great variability in the length of the posterior ambulacral notches, in the petaloid length and in the position of the periproct respect to the posterior margin, while the study of the complete scheme of the plates has clarified the stability and constancy of some parts of this scheme and the variability of other. On the basis of these observations, it has been claimed that the variability of these measures is not so extensive as to affect or determine specific distinctions, if used without ca...
Marine Biology, 2004
Cassidulus mitis Krau, 1954 is an endemic species from Rio de Janeiro, Brazil. To study the reproductive cycle of this species, samples were collected at Praia Vermelha, in Guanabara Bay, from October 1998 to April 2000. The sex ratio for C. mitis was 1:1, and reproduction occurred throughout the year. The gonadal index of males was greater than that of females. Five gametogenic stages were identified in males: early growth, premature, mature, partially spawned and early growth with a partially spawned stage. There were no spent or recovery stages such as those seen in females. Females had six gametogenic stages: recovery, early growth, premature, mature, partially spawned and spent stage; there was no early growth with a partially spawned stage as there was in males. The mean oocyte diameter was 382 μm (SD=49 μm), and the mean number of juveniles per female was 100 individuals (SD=108). The anterior gonads were frequently smaller than the posterior ones, and there were differences in the gametogenic stages between the anterior and posterior gonads. First sexual maturation occurred in individuals with a diameter of 17 mm. The intestinal wet weight was two- to threefold higher than the test wet weight. This may indicate that C. mitis uses its intestine as a “weight belt” to avoid displacement from the substratum.
Echinoderm research perspectives: A Central American bibliometric review
UNED Research Journal
Introduction: Central America, a narrow strip of land dividing the Atlantic and Pacific oceans, has a high diversity of marine and terrestrial species. Echinoderms are one of the most diverse marine groups with 420 reported species. Objective: To summarize echinoderm research in Central America. Methods: We compiled the literature from SCOPUS, Web of Science, SciELO, Google Scholar, Biodiversity Heritage Library, the Internet Archive and the Smithsonian Library. Results: We found 324 publications dating from 1840 to 2020; the early studies had a strong taxonomic focus, but after the 1970s, ecology, evolution and reproduction gained prominence. Echinoidea is the most studied class (38% of publications) due to its use in evolutionary studies as well as the importance of the genus Diadema in reef ecology and dynamics. Conclusion: We recommend more research on fisheries management, conservation and environmental education; and greater integration of local and international research.
Taxonomic significance of spine morphology in the echinoid genera Diadema and Echinothrix
Invertebrate Biology, 2005
The spine morphology of all established species of Diadema and Echinothrix, including 2 color morphs of E. calamaris, were examined externally and internally via transverse sectioning to identify diagnostic species features and to assess the morphological relationship between species. Forty-nine different morphological characters were measured and analysed using ordination by multi-dimensional scaling (MDS) and cluster analysis. Specimens of Dia- &ma paucispinum and D. setosum had very distinct spine structures. In D. paucispinum, the spines were more robust than those of other species of Diadema. This was evident in the spine’s internal structure, with large, closely packed solid wedges, a small axial cavity, and rings of trdbeculae throughout the spine’s length. The spines in D. setosum were distinctive because of their length in relation to test size and the reduced flaring of their verticillations. The spines of other members of this genus were very similar to each other. Without careful sectioning, the spines from specimens of D. antillarurn, D. ascensionis, D. mexicanurn and D. savignyi were difficult to differentiate. The internal structures of spines for each species did, however, possess a combination of features that differentiated the species. Such features included the shape, orientation, and number of solid wedges, the presence or absence of spokes and rings of trabeculae between the solid wedges, and the presence or absence of tissue within the axial cavity. Individuals of Diadema palmeri also had spines morphologically similar to other species, however, the red pigmentation of these spines (in life and when preserved) made them easily distinguishable. The spine structures of the 2 species of Echinothrix were starkly different, while the white and brown color morphs of E. calamaris had morphologically distinctive ambulacral and interambulacral spines. The blunt, open-tipped interambulacral spines, with reticular tissue present in the axial cavity of the white color morph, were easily distinguished from the pointed, closed-tipped spines, with a hollow axial cavity found in the brown color morph. Such differences indicate that the brown color morph is either a subspecies or a separate species. Taken together the data show that each species has significant morphological differences in the structure of the spines. It is evident from our data that spine morphology is a useful tool to differentiate these commonly confused species.