Research Article |
Corresponding author: Martha Angélica Gutiérrez-Aguirre ( marguta71@gmail.com ) Academic editor: Kai Horst George
© 2023 Martha Angélica Gutiérrez-Aguirre, Adrián Cervantes-Martínez.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Gutiérrez-Aguirre MA, Cervantes-Martínez A (2023) Redescription of two species of Microcyclops (Copepoda, Cyclopoida) and use of ordination models to classify American species. ZooKeys 1173: 111-130. https://doi.org/10.3897/zookeys.1173.97827
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Two species of the freshwater copepod genus Microcyclops are redescribed, M. finitimus Dussart, 1984, and M. minor Dussart, 1984 from type specimens. Redescription includes the microstructure of intercoxal sclerites and the basipodites of thoracic appendages, as well as the urosomal microstructure. According to the cluster (UPGMA and Euclidean distance) and PCA analyses performed, it was possible to improve the resolution between the American Microcyclops species by considering characters such as the distal region of antennal basis, the maxillary ornamentation, and the thoracic appendages, especially the intercoxal sclerites and medial margin of the basipodite of the first to fourth trunk limbs. Considering a set of 28 morphological characters in adult females, traditional features such as the length ratio of caudal rami, the length: width ratio of the third endopod of the fourth leg, or the length ratios between apical setae of the same segment, appear to be less important for defining differences between very similar species of American Microcyclops. In these analyses, the redescription of the Palearctic M. varicans was considered, and this species was clearly separated from the American M. dubitabilis Kiefer, 1934 and M. inarmatus Gutiérrez-Aguirre and Cervantes-Martínez, 2016.
Classification, diversity, freshwater, species richness, taxonomy
Deep taxonomic revisions of some freshwater zooplankton Neotropical groups have been carried out in recent decades. These revisions supported that the species richness is still underestimated and the geographic distribution is poorly understood in freshwater zooplankton taxa. For instance, several species considered cosmopolitan, with high phenotypic plasticity and genetic variability, are in fact species complex (usually grouping, five or more species) based upon deep, long-term and wide scale geographical studies (see
Even though a high level of resolution has been reached with some taxonomically problematic groups, incomplete descriptions and lack of designated type (type series) hamper a systematic revision in many Neotropical freshwater zooplankton species, which limits the improvement of the systematic of many taxonomic groups. This kind of taxonomical problem is magnified because of the gaps in knowledge related to taxonomic studies of zooplankton. Either gaps in time, or the interest in faunistic studies are focused on a few groups (
Some examples of Nearctic, Neotropical, or Pantropical freshwater genera that have recently been reviewed are Mastigodiaptomus (
In addition, these reviews reveal morphological characters never previously considered or the re-evaluation of refuted characters that facilitate the systematic and faunistic studies of the high diversity in tropical freshwater (
In this work, we explore the possibilities of several morphological characters both used and not used in identification keys of Microcyclops under the assumption that through classification and ordering models, it is possible to define the species diagnostic characters verifiable by light microscopy observations (in adult females). In addition, the exploration of these characters helped with the redescription of M. finitimus Dussart, 1984, and M. minor Dussart, 1984, based on type material.
Detailed redescriptions of Microcyclops finitimus and M. minor were based on the morphological and morphometric analyses of adult females recorded as the original material from the type localities. The evaluation included analyses of holotypes deposited in the Copepoda collection of the Muséum national d`Histoire naturelle, Paris (
To normalize the data, meristic magnitudes were square-root transformed and examined to perform two multivariate analyses with the software Multi Variate Statistical Package MVSP 3.1 (Anglesey, UK). A cluster analysis (with UPGMA as a clustering method and Euclidean distance measurement) that grouped specimens with similar morphology and one principal component analysis (PCA) was performed to identify traits that produced the most distinct groups between species (
The terminology for each appendage follows
A1 antennule;
A2 antenna;
Md mandible;
Mxl maxillule;
Mx maxillae;
Mxp maxilliped;
Bsp basipodite of swimming legs;
Enp endopodal segment;
Exp exopodal segment;
P1–P5 first to fifth swimming legs;
II lateral;
III outermost;
IV outer median;
V inner median;
VI innermost terminal; and
VII dorsal caudal setae.
Biological material deposited in Smithsonian Institution (
The sources for the morphological data considered in the multivariate analyses were the type, paratype(s), and other museum specimens (Suppl. material
In lack of material, the character states were verified in the original description of the next species: Microcyclops varicans (G.O. Sars, 1863); M. anceps pauxensis (Herbst, 1962); M. mediasetosus (Dussart & Frutos, 1985); M. pumilis (Pennak & Ward, 1985); and M. medius (Dussart & Frutos, 1986).
The matrix showing the distribution of the 28 characters for each species is shown in Table
Averages (Av), maximums (Max), and minimums (Min) of the characters analyzed. The abbreviation and state of each character, as noted in Methods.
M. pumilis | M. anceps pauxensis | M. minor | M. mediasetosus | M. medius | M. ceibaensis | M. dubitabilis | M. inarmatus | M. echinatus | M. finitimus | M. anceps anceps | M. varicans | M. elongatus | M. furcatus | ||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A2_DistalCaudal | Av | 1 | 1 | 1 | 2 | 1 | 1 | 2 | |||||||
Max | 1 | 1 | 1 | 2 | 1 | 1 | 2 | ||||||||
Min | 1 | 1 | 1 | 2 | 1 | 1 | 2 | ||||||||
A2_DistalFrontal | Av | 1 | 1 | 1 | 1 | 2 | 2 | 1 | |||||||
Max | 1 | 1 | 1 | 1 | 2 | 2 | 1 | ||||||||
Min | 1 | 1 | 1 | 1 | 2 | 2 | 1 | ||||||||
MxBsp_BasalSeta | Av | 3 | 1 | 1 | 2 | 3 | 3 | 2 | |||||||
Max | 3 | 1 | 1 | 2 | 3 | 3 | 2 | ||||||||
Min | 3 | 1 | 1 | 2 | 3 | 3 | 2 | ||||||||
MxBsp_Claw | Av | 2 | 2 |
2 | 2 | 1 | 1 | 2 | |||||||
Max | 2 | 2 | 2 | 2 | 1 | 1 | 2 | ||||||||
Min | 2 | 2 | 2 | 2 | 1 | 1 | 2 | ||||||||
MxEnd_ProxSeta | Av | 2 | 2 | 1 | 1 | 2 | 2 | 2 | |||||||
Max | 2 | 2 | 1 | 1 | 2 | 2 | 2 | ||||||||
Min | 2 | 2 | 1 | 1 | 2 | 2 | 2 | ||||||||
MxEnd_DistSeta | Av | 2 | 1 | 1 | 2 | 1 | 1 | 2 | |||||||
Max | 2 | 1 | 1 | 2 | 1 | 1 | 2 | ||||||||
Min | 2 | 1 | 1 | 2 | 1 | 1 | 2 | ||||||||
BspP1_Medial | Av | 2 | 1 | 2 | 1 | 1 | 2 | 1 | 1 | 1 | 2 | ||||
Max | 2 | 1 | 1 | 2 | 1 | 1 | 1 | ||||||||
Min | 2 | 1 | 1 | 2 | 1 | 1 | 1 | ||||||||
BspP1_Spine Ornament | Av | 3 | 3 | 3 | 3 | 1 | 2 | 1 | 2 | 2 | 3 | 3 | 1 | 1 | 1 |
Max | 2 | 1 | 2 | 2 | 3 | 3 | 1 | ||||||||
Min | 2 | 1 | 2 | 2 | 3 | 3 | 1 | ||||||||
Enp2P1_pores | Av | 3 | 3 | 1 | 2 | 3 | 2 | 2 | 2 | ||||||
Max | 3 | 3 | 1 | 2 | 3 | 2 | 2 | 2 | |||||||
Min | 3 | 3 | 1 | 2 | 3 | 2 | 2 | 2 | |||||||
Enp2P4_L:W | Av | 2.11 | 2.71 | 2.46 | 2.33 | 1.83 | 2.25 | 1.94 | 2.18 | 2.56 | 2.36 | 2.52 | 2.44 | 2.59 | |
Max | 2.43 | 2.18 | 2.64 | 2.75 | 2.5 | 2.75 | 2.7 | ||||||||
Min | 2.1 | 1.75 | 1.9 | 2.33 | 2.22 | 2.25 | 2.22 | ||||||||
BspP4_Medial | Av | 1 | 2 | 3 | 1 | 2 | 2 | 3 | 3.2 | 3 | 2 | 2 | |||
Max | 2 | 2 | 3 | 4 | 3 | 2 | 2 | ||||||||
Min | 2 | 2 | 3 | 2 | 3 | 2 | 2 | ||||||||
P4_LMedSpn: LLatSpn | Av | 1.37 | 1.52 | 1.95 | 1.22 | 1.55 | 1.45 | 1.90 | 1.98 | 2.07 | 1.39 | 1.33 | 1.40 | 1.75 | |
Max | 1.7 | 2.5 | 2.19 | 2.26 | 1.39 | 1.5 | 1.50 | ||||||||
Min | 1.45 | 1.1 | 1.58 | 1.9 | 1.38 | 1.16 | 1.25 | ||||||||
P4_LMedSpn: LEnp2 | Av | 0.57 | 0.76 | 0.73 | 0.76 | 0.7 | 0.64 | 0.85 | 0.91 | 0.81 | 0.78 | 0.76 | 0.88 | 0.49 | |
Max | 0.74 | 1.02 | 0.97 | 1.02 | 0.8 | 0.82 | 1 | ||||||||
Min | 0.6 | 0.71 | 0.86 | 0.69 | 0.75 | 0.7 | 0.80 | ||||||||
P4_IntcxlSclrt | Av | 1 | 3 | 1 | 2 | 2 | 1 | 1 | 1 | 2 | 2 | 2 | |||
Max | 1 | 2 | 2 | 1 | 1 | 1 | 2 | ||||||||
Min | 1 | 2 | 2 | 1 | 1 | 1 | 2 | ||||||||
FSP5_L:W | Av | 2.33 | 3 | 2 | 2.66 | 2.5 | 3 | 3.51 | 3.11 | 3.77 | 2.75 | 2.58 | 3.6 | 3.5 | 2 |
Max | 3 | 4.28 | 4 | 4 | 3 | 2.85 | 4.2 | ||||||||
Min | 2.6 | 2.8 | 2.75 | 3.66 | 2.5 | 2 | 3.2 | ||||||||
FSP5_Medial | Av | 1 | 2 | 3 | 2 | 1 | 2 | 1 | 2 | 2 | 2 | 3 | 2 | 2 | 1 |
Max | 2 | 1 | 2 | 2 | 2 | 3 | 2 | ||||||||
Min | 2 | 1 | 2 | 2 | 2 | 3 | 2 | ||||||||
P5_L-FS:ApclSta | Av | 0.29 | 0.18 | 0.34 | 0.21 | 0.33 | 0.26 | 0.42 | 0.28 | 0.45 | 0.48 | 0.41 | 0.38 | 0.46 | 0.40 |
Max | 0.34 | 0.58 | 0.30 | 0.46 | 0.53 | 0.50 | |||||||||
Min | 0.23 | 0.27 | 0.26 | 0.44 | 0.44 | 0.23 | |||||||||
Genital_L:W | Av | 0.6 | 1.1 | 1.06 | 1.8 | 0.95 | 1.02 | 0.87 | 1.12 | 0.94 | 1.13 | 1.2 | 1.41 | ||
Max | 1.0 | 1.2 | 1 | 1.22 | 1.1 | 1.31 | |||||||||
Min | 0.92 | 0.9 | 0.8 | 1.04 | 0.78 | 0.96 | |||||||||
Spns_Anal | Av | 1 | 1 | 2 | 1 | 1 | 1 | 1 | 2 | 1 | 1.5 | 1 | 2 | 2 | 2 |
Max | 1 | 1 | 2 | 1 | 2 | 1 | 2 | ||||||||
Min | 1 | 1 | 2 | 1 | 1 | 1 | 2 | ||||||||
CR_L-IV:L-III | Av | 4.83 | 6.2 | 7.3 | 8.5 | 5.71 | 4.59 | 4.82 | 6.52 | 6.05 | 4.92 | 5.3 | 0.54 | 2.37 | |
Max | 6.24 | 5.5 | 5.64 | 7.26 | 6.06 | 5.67 | 5.4 | ||||||||
Min | 4.67 | 4.17 | 3.86 | 5.52 | 6.03 | 4.17 | 5.2 | ||||||||
CR_L-V:L-III | Av | 8.33 | 8.1 | 9 | 13.25 | 9.95 | 6.57 | 7.15 | 10.48 | 8.95 | 7.09 | 7.14 | 2.37 | ||
Max | 10.4 | 7.38 | 7.8 | 12.52 | 8.97 | 8.42 | 7.14 | ||||||||
Min | 9.63 | 5.58 | 6.22 | 8.54 | 8.94 | 6.11 | 7.14 | ||||||||
CR_L-VI:L-III | Av | 0.92 | 1.81 | 2.33 | 3 | 1 | 1.82 | 1.54 | 1.62 | 1.96 | 1.92 | 1.35 | 1.64 | 1 | |
Max | 2.12 | 1.72 | 1.88 | 2.31 | 2.125 | 1.74 | 1.80 | ||||||||
Min | 1.5 | 1.26 | 1.29 | 1.71 | 1.72 | 0.96 | 1.40 | ||||||||
L-VI:L-CR | Av | 0.44 | 1.44 | 1.16 | 2.7 | 0.28 | 0.81 | 1.35 | 1.46 | 0.56 | 1.05 | 0.80 | 0.93 | 0.25 | 0.4 |
Max | 0.9 | 1.68 | 1.51 | 0.65 | 1.26 | 1.08 | 1 | ||||||||
Min | 0.85 | 1.1 | 1.4 | 0.51 | 0.85 | 0.58 | 0.85 | ||||||||
L-VII:L-CR | Av | 0.48 | 1.55 | 0.6 | 0.95 | 0.58 | 0.75 | 1.02 | 0.89 | 0.50 | 0.65 | 0.55 | 0.53 | 0.37 | 0.2 |
Max | 1.0 | 1.22 | 1.17 | 0.71 | 0.78 | 0.9 | |||||||||
Min | 0.56 | 0.7 | 0.71 | 0.36 | 0.53 | 0.4 | |||||||||
CR_L:W | Av | 2.9 | 2.4 | 3.15 | 2.29 | 4.35 | 3.37 | 2.51 | 2.51 | 5.97 | 3.40 | 3.78 | 3.39 | 5 | 6.66 |
Max | 3.8 | 3 | 2.93 | 6.3 | 4.1 | 4.25 | 3.68 | ||||||||
Min | 3.1 | 1.88 | 1.78 | 5.3 | 2.7 | 3 | 3 | ||||||||
CR_Base-II | Av | 1 | 1 | 1 | 2 | 2 | 2 | 1.08 | 1 | 2 | 1 | 1.08 | 1 | 2 | 1 |
Max | 2 | 2 | 1 | 2 | 1 | 2 | 1 | ||||||||
Min | 2 | 1 | 1 | 2 | 1 | 1 | 1 | ||||||||
CR_Base-III | Av | 1 | 2 | 2 | 2 | 2 | 2 | 2 | 1 | 2 | 2 | 2 | 1 | 1 | 1 |
Max | 2 | 2 | 1 | 2 | 2 | 2 | 1 | ||||||||
Min | 2 | 2 | 1 | 2 | 2 | 2 | 1 | ||||||||
Position-II:CR | Av | 65.5 | 68 | 78 | 56.25 | 68.96 | 69.55 | 70.12 | 58.92 | 73.26 | 74.70 | 71.12 | 68.11 | 62.5 | 80 |
Max | 72.5 | 76.2 | 63.15 | 76.54 | 75.56 | 73.33 | |||||||||
Min | 65 | 61.54 | 54.00 | 70.13 | 73.85 | 69.12 |
Principal components analysis, variable loadings in bold (analyzing 28 variables for 54 specimens). Data square-root transformed.
Axis 1 | Axis 2 | Axis 3 | |
---|---|---|---|
Eigenvalues | 1.61 | 0.46 | 0.361 |
Percentage | 48.523 | 13.878 | 10.886 |
Cum. Percentage | 48.523 | 62.401 | 73.287 |
Genital_L:W | 0.078 | -0.029 | 0.011 |
Enp2P4_L:W | 0.074 | -0.024 | 0.06 |
BspP4_Medial | 0.222 | 0.005 | -0.14 |
P4_IntcxlSclrt | 0.065 | 0.271 | -0.294 |
P4_LMedSpn:LLatSpn | 0.059 | 0.033 | -0.166 |
P4_LMedSpn:LEnp2 | 0.055 | 0.012 | -0.077 |
CR_L-IV:L-III | 0.25 | -0.482 | -0.204 |
CR_L-V:L-III | 0.335 | -0.609 | -0.237 |
CR_L-VI:L-III | 0.048 | -0.116 | -0.093 |
L-VII:L-CR | 0.008 | 0.01 | -0.184 |
L-VI:L-CR | 0.022 | -0.002 | -0.231 |
CR_L:W | 0.007 | -0.089 | 0.275 |
CR_Base-II | 0.006 | -0.1 | 0.038 |
CR_Base-III | 0.042 | -0.104 | 0.054 |
Position-II:CR | 0.036 | -0.071 | 0.197 |
Spns_Anal | -0.028 | 0.054 | -0.078 |
FSP5_L:W | 0.038 | 0.075 | -0.138 |
FSP5_Medial | 0.064 | -0.097 | 0.303 |
P5_L-FS:ApclSta | 0.012 | 0.02 | 0.042 |
BspP1_SpineOrnament | 0.024 | -0.174 | 0.35 |
BspP1_Medial | 0.16 | 0.09 | -0.015 |
MxBsp_BasalSeta | 0.385 | 0.097 | 0.405 |
MxBsp_Claw | 0.311 | 0.261 | -0.278 |
MxEnd_ProxSeta | 0.318 | 0.26 | 0.027 |
MxEnd_DistSeta | 0.304 | 0.142 | -0.019 |
A2_DistalCaudal | 0.285 | 0.159 | -0.035 |
A2_DistalFrontal | 0.284 | 0.153 | 0.202 |
Enp2P1-Pores | 0.339 | -0.05 | 0.137 |
According to
Order Cyclopoida Burmeister, 1835
Family Cyclopidae Rafinesque, 1815
Subfamily Cyclopinae Rafinesque, 1815
Microcyclops finitimus
Dussart, 1984: 57, 58, fig. 19A;
Holotype. One dissected adult female on a slide labelled as Microcyclops finitimus female nov. sp. ‘Lagoon’ with Trapa between Coporito and Barrancas, Venezuela 24.X.1981, 8h40. Collector Bernard Dussart, and det. B. Dussart (
One dissected, adult female on a slide labelled as Microcyclops finitimus female. Rorota, prés Guyane 21.X.1985. GUYANE. Collector Bernard Dussart, and det. B. Dussart (
Female: body length excluding furcal setae = 0.89 mm (as described by
Microcyclops finitimus. Adult female (
Antennule 12-segmented: each segment was armed with setae (s), spines (sp) or aesthetascs (ae) in the following order: (1) 8 s; (2) 4 s; (3) 2 s; (4) 6 s; (5) 3 s; (6) 1 s + 1 sp; (7) 2 s; (8) 3 s; (9) 2 s + 1ae; (10) 2 s; (11) 2 s + 1 ae; (12) 7 s + 1 ae.
Antenna with two groups of spinules on the basal margin of the basis in caudal view. In the frontal view antennal basis with two groups of spinules: one next to the exopodal seta, on the distal region (arrowed in Fig.
Maxillule (Fig.
Maxillary syncoxal surface smooth (Fig.
Maxilliped with syncoxa (3 setae, one broken off), basis (2 setae), and two-segmented Enp bearing one and three setae, respectively. Syncoxa, basis, and Enp1 with rows of spinae: basis on frontal and caudal surfaces; syncoxa and Enp1 only on the frontal surface (Fig.
Medial margin of basipodites of P1–P4 with long hair-like setae. There is no medial spine on the margin of BspP1 (Fig.
Microcyclops finitimus. Adult female (
P4 as illustrated and described by
Fifth pediger bare, with dorsal hyaline membrane serrated posteriorly (Fig.
Dorsal caudal seta (VII) 0.5–0.7× as long as caudal ramus, innermost terminal caudal seta (VI) 1.05× as long as caudal ramus. Length ratio between outer median (IV) and outermost terminal seta (III) is 6.0; and between medial median (V) and outermost terminal seta (III) is 8.9 (Fig.
Microcyclops anceps var. minor Dussart, 1984: 57, fig. 17.
Holotype. Dissected, adult female on slide labelled as: Microcyclops anceps var. minor [nov. var.]. Charca I, near Unaré river at Clarines (Venezuela), 13.4.1981, Collector Bernard Dussart, and det. B. Dussart (
Dorsal margin of prosomal somites smooth (unfigured). Because of the position of the specimen, it was not possible to observe the buccal appendages.
As per the illustration by
Fifth pediger bare, with dorsal hyaline membrane smooth posteriorly; P5 is a cylindrical free segment that bears one apical seta and one projected medial spinule (Fig.
Relative lengths of terminal caudal setae from outermost to innermost caudal seta are 1: 6.2: 8.1: 2.33 (Fig.
In Fig.
In all species from various geographical regions (Suppl. material
The three groups with the least distance between specimens (the more compact groups in Fig.
According to the PCA, all features related to maxilla ornamentation are important characters that explain the model variability in the first axis (Table
In addition to the characters mentioned before, in Axis 2, the model points that are important characters the ornamentation of the spine on the inner basis of BspP1 (when it is present) and the ornamentation of the intercoxal sclerite of P4 (Table
Axes 1 and 2 together explain 62.4% of the variability, and Axis 3 adds 10% more. In this third axis with values of importance lower than 0.41 (Table
With the analyses performed here, it was clear that the American species M. inarmatus and M. dubitabilis are not morphologically similar to M. varicans (recently redescribed by
Some differential morphological characteristics between M. anceps pauxensis and M. minor had already been previously described in
The majority of Microcyclops species occur in the Neotropical region (
Microcyclops anceps anceps appears to be a Neotropical species with a large geographic range including southeastern Mexico, Guatemala, Venezuela, Guyana, Uruguay, Brazil, and Chile. Microcyclops dubitabilis is also widely distributed in the Neotropics (southeastern Mexico, Florida, Haiti, Guadeloupe, Uruguay, Brazil, and Venezuela).
Microcyclps ceibaensis occurs in southeastern Mexico, Central America, and Brazil. Microcyclops elongatus was recorded in Brazil and Paraguay, and M. inarmatus appears to be distributed in Florida, Haiti, and southeastern Mexico (
Microcyclops inarmatus, M. varicans, and M. dubitabilis share the character of an armed seta on the maxillary basipodite. In contrast, in M. anceps anceps, M. finitimus, M. echinatus, and M. ceibaensis, the ornamentation of this seta is absent or reduced (in M. echinatus). The maxilla has some special features in these four species, such as the row of strong spines on a bump on the concave side of the claw-like seta (in M. finitimus or M. anceps anceps); the proximal seta of the maxillary distal coxal endite only ornamented on one side (in M. ceibaensis, M. finitimus, and M. anceps anceps); the smooth distal seta of the maxillary distal coxal endite (in M. ceibaensis and M. echinatus). The distribution of these features explains the arrangements in the cluster analysis.
Microcyclops finitimus, M. minor, M. anceps pauxensis, M. pumilis, M. mediasetosus, and M. anceps anceps are the American species that share the absence of spine on the medial margin of the basipodite of first leg. Except for M. finitimus, we were not able to observe the buccal structures of most of these species. However, they appear as independent entities (see Fig.
Recently, the maxillary and antennal basis microstructure, as well as the structure of swimming legs, especially the ornamentation of intercoxal sclerites and medial margin of basipodite, have been suggested by
With this work, it was determined that, indeed, the length ratios (ranges and average) between terminal caudal setae IV:III and V:III are very informative for distinguishing species. These characters are also relatively easy to distinguish using light microscopy; fortunately, they have been illustrated/described in most original descriptions (see
For the American Microcyclops species the statistical analysis also improves the definition that can be achieved in combination with morphological analysis for species resolution, as has been tested with other aquatic species (
Other characteristics that have traditionally been used to differentiate some cyclopoid species are the length ratio of caudal rami, the length ratios in structures on distal endopod of the fourth leg, or the length ratio between dorsal caudal seta and caudal ramus. However, similar to other genera such as Mesocyclops or Eucyclops, after the analysis surveyed here, these characters can be considered as not informative for differentiating the American Microcyclops species because they are shared or have overlapping features (see Table
Additionally, the species M. echinatus (in caudal view), M. finitimus, M. anceps anceps, and M. varicans (in frontal view) share the presence of a group of spines on the distal region of the antennal basis, whereas in M. inarmatus, M. dubitabilis, and M. ceibaensis, this region is bare. The importance of species-specific patterns of teeth and spines on BspA2 has been widely reported in the genera Macrocyclops, Eucyclops, and Ectocyclops in Eucyclopinae (
Two insufficiently known South American species, M. finitimus and M. minor were redescribed based on type material. According to the classification and ordination models, the microstructure of cephalic appendages, the medial area of thoracic appendages, and the caudal setae of caudal rami (identifiable with light microscopy) were strongly supported as morphological characters that improves resolution between the American Microcyclops as well as in species with wide geographic distribution.
We are grateful to Danielle Defaye, Paula Rodríguez Moreno-Martin Lefèvre, Hubert Höfer, Hans Walter Mittmann, and Chad Walter who allowed us to review material deposited in biological collections. We are grateful for the academic editing of two native English-speaking reviewers, with M Hołyńska, KH George, and an anonymous reviewer, who substantially improved the manuscript with their comments.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This work was supported by the Universidad Autónoma del Estado de Quintana Roo.
Conceptualization: MAGA. Data curation: MAGA, ACM. Formal analysis: ACM. Funding acquisition: MAGA, ACM.
Martha Angélica Gutiérrez-Aguirre https://orcid.org/0000-0002-9329-820X
Adrián Cervantes-Martínez https://orcid.org/0000-0002-8947-8558
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Biological material examined
Data type: Morphological
Distribution of characters by specimen; abbreviation is explained in data analysis
Data type: Morphological