OBELIIDAE, Haeckel, 1879
|
publication ID |
https://doi.org/10.1093/zoolinnean/zlz166 |
|
persistent identifier |
https://treatment.plazi.org/id/03AD87EB-FFB9-5733-0824-FA523899FD10 |
|
treatment provided by |
Plazi |
|
scientific name |
OBELIIDAE |
| status |
|
FAMILY OBELIIDAE
Patterns of morphological variation in Obeliidae are mostly congruent among the different datasets examined ( Fig. 7 View Figure 7 ). Considering all species, perisarc thickness (PHMA, PHMe, PHB, PPMe, TD) explains most of the data variation, separating Obelia geniculata ( Linnaeus, 1758) by its thicker perisarc ( Fig. 7A, B View Figure 7 ). This character also set apart O. geniculata from the remaining species when only the genus Obelia is considered ( Fig. 7C View Figure 7 ). In addition, Obelia geniculata has the widest range of variation of perisarc thickness, when Laomedea and Obelia are compared ( Fig. 8A View Figure 8 ). For the remaining genera, perisarc thickness does not notably contribute to the differentiation of the species, because of its extensive overlap ( Fig. 8A View Figure 8 ). Measurements of diameter (DHMa, DHMe, DHB, DBC, DP) explain another direction of variation of the data, and mainly differentiate L. flexuosa Alder, 1857 from the remaining Obeliidae by its broader hydrothecae ( Figs 7A, B, D View Figure 7 , 8B View Figure 8 ). Species of Laomedea also show a wide range of variation and overlap in pedicel length (LP; Fig. 8C View Figure 8 ), but their pedicels are on average longer than in Obelia .
Obelia longissima (Pallas, 1766) is distinguished from the remaining Obeliidae by its larger measurements of first- and second-order branches (LIS, DIS, NIS, LIB, DIB, NIB; Fig. 7A–C View Figure 7 ). It also has a wider range of variation in the hydrothecal length compared to the remaining species, and it cannot be distinguished based on this character because of the extensive overlap with other species ( Fig. 8D View Figure 8 ). Erect and branched colonies also differentiate Gonothyraea loveni (Allman, 1859) and Hartlaubella gelatinosa (Pallas, 1766) , although to a lesser extent; this pattern is clearly observed when Obelia is excluded from the analysis ( Fig. 7D View Figure 7 ). These species, together with O. bidentata Clark, 1875 and Obelia sp.1 , also differ from the remaining Obeliidae in their more cylindrical hydrothecae (higher values of HRatio) and taller hydrothecal cusps ( Figs 7B–D View Figure 7 , 8E, F View Figure 8 ). The exception is Obeliida indet., which has the tallest hydrothecal cusps compared to all other species ( Fig. 8F View Figure 8 ). In general, Obeliida indet. has similar morphometric patterns to O. longissima , mostly related to the presence of erect colonies and hydrothecal length ( Fig. 7B, D View Figure 7 ). The hydrotheca is typically longer in Obeliida indet., but morphological variation attenuates this difference ( Fig. 8D View Figure 8 ).
It is evident from most of the analyses that lineages of Obelia cf. dichotoma ( Linnaeus, 1758) are not distinguished from each other by any of the measurements, showing intermediate values for all characters evaluated ( Fig. 7A–C, E View Figure 7 ). Many specimens of O. longissima cannot be distinguished from the lineages of O. cf. dichotoma , and although some are differentiated by their larger erect and branched colonies, variations in these characters prevent a clear separation of these species ( Fig. 9A View Figure 9 ). Obelia longissima also has longer hydrothecae and taller hydrothecal cusps on average, but their range of variation overlap among species ( Fig. 9B, D View Figure 9 ). Obelia cf. dichotoma sp.3 and O. cf. dichotoma sp.4 are grouped together and slightly separated from the remaining species of Obelia , probably because of their smaller and less branched colonies, but no further patterns of differentiation are seen among these lineages ( Fig. 7E View Figure 7 ). Indeed, when compared to literature descriptions, the size and branching of colonies seem to be among the few characters that could fairly differentiate some of the lineages of O. cf. dichotoma , which are similar to the descriptions of other nominal species (Supporting Information, Table S6).
Characters related to the gonothecae do not differentiate the species of Obelia , but species of Laomedea can be distinguished by their larger gonothecae (LG, DGD, DGMe, DGB, DGP; Fig. 7F View Figure 7 ). Additional PCAs do not show further patterns of differentiation among Obeliidae (Supporting Information, Fig. S4 View Figure 4 ).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.