Disentangling cryptic species in Parastenocarididae (Copepoda: Harpacticoida) with an integrative approach: the case of Stammericaris similior sp. nov. and Stammericaris destillans Bruno & Cottarelli 2017

Stammericaris similior sp. nov. is described combining light microscopy, scanning electron microscopy, and genetic barcoding. The new species was collected from rimstone pools in Scrivilleri Cave, a cave in Sicily with so far unexplored microcrustacean fauna. The new species is particularly interesting because it is morphologically very similar to Stammericaris destillans, an epikarstic parastenocaridid endemic to a different Sicilian cave; however, the phylogenetic analysis based on the mitochondrial COI gene of sixteen parastenocaridids shows that these two Stammericaris are two distinct species, with an uncorrected p-distance of 22.9, and the sequences of Stammericaris similior sp. nov. cluster together in a well-supported monophyletic clade, with two different haplotypes. To our knowledge, the presence of different species of almost identical morphology had not been recorded before for the genus Stammericaris. The integrated molecular and morphological analysis, the latter conducted with the support of SEM, allows disentangling the affinities of the new species and identifying a few distinctive characters: the males of the new species are characterized by the caudal rami shorter than the anal somite; the morphology of the P3, which is thin and slightly arched, with three proximal spinules on exp-1; the peculiar structure of the P4 enp; the P4 basis ornamented with two spinules of different length, the one closest to the endopod being the shortest one, and a half-moon shaped lamella. The new species differs from S. destillans for its larger size, the presence of: three spinules, instead of two, on the P3 exp-1; the half-moon shaped lamella on the P4 basis; a row of spinules along the inner margin of P4 exp-1. We also provide data on the ecology and distribution of the new species, a list of the other copepod species collected, and a dichotomic key for the males of all species presently assigned to the genus.  

[1]  D. Blair,et al.  Ceriodaphnia (Cladocera: Daphniidae) in China: lineage diversity, phylogeography and possible interspecific hybridization. , 2022, Molecular phylogenetics and evolution.

[2]  M. Bruno,et al.  The genus Stammericaris Jakobi (Copepoda: Harpacticoida: Parastenocarididae) in the Nearctic subregion: description of Stammericaris remotaepatriae sp. nov., proposal of Stammericaris palmerae (Reid 1992) comb. nov., and remarks on other North American Parastenocarididae. , 2021, Zootaxa.

[3]  F. Marrone,et al.  Morphological and molecular characterization of three new Parastenocarididae (Copepoda: Harpacticoida) from caves in Southern Italy , 2020 .

[4]  F. Marrone,et al.  An account on the taxonomy and molecular diversity of a marine rock-pool dweller, Tigriopus fulvus (Copepoda, Harpacticoida) , 2019, Ciencias Marinas.

[5]  F. Marrone,et al.  An exhaustive phylogeny of the combtooth blenny genus Salaria (Pisces, Blenniidae) shows introgressive hybridization and lack of reciprocal mtDNA monophyly between the marine species Salaria basilisca and Salaria pavo. , 2019, Molecular phylogenetics and evolution.

[6]  G. Ficetola,et al.  The Racovitzan impediment and the hidden biodiversity of unexplored environments , 2018, Conservation biology : the journal of the Society for Conservation Biology.

[7]  Sudhir Kumar,et al.  MEGA X: Molecular Evolutionary Genetics Analysis across Computing Platforms. , 2018, Molecular biology and evolution.

[8]  A. Petrusek,et al.  Divergent clades or cryptic species? Mito-nuclear discordance in a Daphnia species complex , 2017, BMC Evolutionary Biology.

[9]  H. Hauffe,et al.  Morphological and molecular analyses of epikarstic Parastenocarididae (Copepoda: Harpacticoida) from two Sicilian caves, with description of a new Stammericaris. , 2017, Zootaxa.

[10]  F. Sene,et al.  Mito‐nuclear discordance with evidence of shared ancestral polymorphism and selection in cactophilic species of Drosophila , 2015 .

[11]  S. Prosser,et al.  A new set of primers for COI amplification from freshwater microcrustaceans , 2013, Molecular ecology resources.

[12]  Cuong Q. Tang,et al.  The widely used small subunit 18S rDNA molecule greatly underestimates true diversity in biodiversity surveys of the meiofauna , 2012, Proceedings of the National Academy of Sciences.

[13]  V. Ivanenko,et al.  Remarks on the “Subcoxa” hypothesis from Bäcker et al. (2008) , 2009 .

[14]  P. Corgosinho,et al.  Three new species of Remaneicaris Jakobi, 1972 (Copepoda, Harpacticoida, Parastenocarididae) from the Ribeirão do Ouro River, Minas Gerais, Brazil, with some remarks on the groundpattern of the Parastenocarididae , 2007 .

[15]  D. Galassi,et al.  Towards a revision of the genus Parastenocaris Kessler, 1913: establishment of Simplicaris gen. nov. from groundwaters in central Italy and review of the P. brevipes‐group (Copepoda, Harpacticoida, Parastenocarididae) , 2004 .

[16]  P. Richterich,et al.  Estimation of errors in "raw" DNA sequences: a validation study. , 1998, Genome research.

[17]  J. Thompson,et al.  CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. , 1994, Nucleic acids research.

[18]  J. Reid.  Diacyclops albus n.sp. and Parastenocaris palmerae n.sp. (Crustacea: Copepoda) from the meiofauna of a stream bed in Virginia, U.S.A. , 1991 .

[19]  H. M. Pedley.  Sedimentology and palaeoenvironment of the southeast Sicilian Tertiary platform carbonates , 1981 .

[20]  H. K. Schminke.  Stammericaris Jakobi, 1972 redefined and a new genus of Parastenocarididae (Copepoda, Harpacticoida) , 2013 .

[21]  G. Pesce.  A new Harpacticoid from phreatic waters of Lesbos, Greece, and notes on the "Rassenkreise" of Elaphoidella elaphoides (Chappuis) (Copepoda: Ameiridae) , 1985 .