Representatives of Ligophorus Euzet et Suriano, 1977 were found on the gills of Mugil liza Valenciennes caught in southern Brazil. They were identified as Ligophorus uruguayense Failla Siquier et Ostrowski de Núñez, 2009 and Ligophorus saladensis Marcotegui et Martorelli, 2009, even though specific identification proved to be difficult due to inconsistencies in some diagnostic features reported for these two species. Therefore, a combined morphological and molecular approach was used to critically review the validity of these species, by means of phase contrast and confocal fluorescence microscopical examination of sclerotised hard parts, and assessing the genetic divergence between L. saladensis, L. uruguayense and their congeners using rDNA sequences. The main morphological differences between the two species relate to the shape of the accessory piece of the penis and the median process of the ventral bar. The accessory piece in L. uruguayense is shorter than in L. saladensis, has a cylindrical, convex upper lobe and straight lower lobe (vs with the distal tip of the lower lobe turning away from the upper lobe in the latter species). The ventral bar has a V-shaped anterior median part in L. uruguayense (vs U-shaped in L. saladensis). The two species are suggested to be part of a species complex together with L. mediterraneus Sarabeev, Balbuena et Euzet, 2005. We recommend to generalise such comparative assessment of species of Ligophorus for a reliable picture of the diversity and diversification mechanisms within the genus, and to make full use of its potential as an additional marker for mullet taxonomy and systematics.
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Online searches for relevant scientific references using keywords have become common practice. Several multidisciplinary scientific online databases are available, of which Web of Science, Scopus (both payable) and Google Scholar (free of charge) are the most commonly used. We test the hypothesis that results of highly similar searches in these three databases do not necessarily give comparable results. We set out to query the three databases with a real example on “diapause in microcrustaceans” (Cladocera, Copepoda and Ostracoda), using the same time period (2012–2021), the same keywords with the same syntaxis and the same sorting criterion (“relevance”), and compared the first 100 hits provided by each database. There were several references provided which were irrelevant to the search, especially in the Web of Science, and of the remaining relevant references, only 9.84% were provided by all three databases. Our survey showed significant differences amongst the results provided by the databases, especially for “hydroperiod” and “type of environment”. These differences can be the result of different coverage of the scientific literature by the databases, but also of the different ways by which the criterion “relevance” is calculated by the three algorithms. We, therefore, recommend that literature surveys must be based on several databases; otherwise, the results might become biased.
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RBINS Staff Publications 2022
