Research Article: Description of a new species of Surazomus (Arachnida: Schizomida), with comments on homology of male flagellum and mating march anchorage in the genus

Date Published: March 20, 2019

Publisher: Public Library of Science

Author(s): Gustavo R. S. Ruiz, Roberta M. Valente, Patrick R Stephens.

http://doi.org/10.1371/journal.pone.0213268

Abstract

Surazomus saturninoae sp. nov. is described from eastern Amazon. The male has a pentagonal flagellum, similar to those of three other species in the genus. These four species are herein gathered as the arboreus-group of Surazomus. We present a brief synopsis of chaetotaxy description in hubbardiines and several homology proposals for the flagellum of the species in the arboreus-group: the posterior lobes may be homologous to the lateral lobes of hubbardiine species with trilobed flagella; the setal brush with 4–5 setae on the posterior lobe may be composed of one Dl2 seta and enlarged lobular microsetae; the single, median posterior coupling pocket may be homologous to the pair of posterior pockets seen in other hubbardiines; the single, median anterior coupling pocket may be homologous to the pair of pockets on the anterior border of the flagellum seen in other hubbardiines. Based on the morphology of these pockets and the chelicerae within Surazomus, we discuss the anchoring mechanism during the mating march.

Partial Text

Schizomids are small arachnids that display short-range endemism [1,2,3] and generally occur in humid tropical and sub-tropical forests, mainly in leaf litter, caves, tree bark or under stones [4]. The extant diversity of about 300 species of Schizomida is divided into the families Protoschizomidae and Hubbardiidae, the last with two subfamilies: Hubbardiinae and Megaschizominae [5]. They are all known as short-tailed whip scorpions, due to the presence of a short flagellum in males and females. The flagellum of the male is highly modified and held by the chelicerae of the female during copulation [6,7], in a phase called as Paarungsmarsch (= mating march) [7], when she is dragged forward onto the spermatophore. The anchoring mechanism is still poorly understood, but the male flagellum is certainly sexually selected, as it has diverse forms throughout the order, rendering them useful in systematics [8,9,10]. Albeit diverse, the flagellum of schizomids bears multiple setae that are mostly constant within species and are present across the major taxonomic groups, being largely used in species descriptions and hypotheses of setal homology since the 1990s [11,9,12,13,14]. Recently, Monjaraz-Ruedas et al. [15] compared the setae of Protoschizomidae, Hubbardiinae and Megaschizominae to reevaluate homologies and reconstruct the phylogeny of the order. Even with the achievements of that study, the homology of some setae is still debatable, such as the lateral pair over the flagellar stalk of some male hubbardiines [16].

The type specimen is deposited in the Museu Paraense Emílio Goeldi, Belém, Brazil (MPEG, A.B. Bonaldo). Multifocus colour photographs were taken with a Leica DFC420 digital camera attached to a Leica M205A microscope, and stacked with Leica application suite version 3.4.1, which was also used to take the measurements, expressed in millimeters. Drawings were prepared with a Leica DM 1000 microscope and a drawing tube. For illustration of chelicera setation and pedipalp setation, the whole structures were dissected and immersed in clove oil.

 

Source:

http://doi.org/10.1371/journal.pone.0213268

 

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