Spinanycta Espinasa, Gutierrez & Niemiller, 2024

Espinasa, Luis, Gutierrez, Abrianna, Hinkle, Amata & Niemiller, Matthew L., 2024, A new genus and species of nicoletiid silverfish (Insecta, Zygentoma, Nicoletiidae) from caves of northern Alabama, USA, Subterranean Biology 49, pp. 1-17 : 1-17

Spinanycta Espinasa, Gutierrez & Niemiller gen. nov.

Diagnosis.

An American nicoletiid with Urosterna II – VII subdivided into two coxites and one sternite. Urosterna I, VIII and IX of male entire. Coxites on segments II – IX with styli. Urosternum I of males modified with a central pointy extension. Urosternum VIII of male flat posteriorly, without emarginations or projections in between the styli of this segment. Paramera with a distal semi-eversible vesicle and short chaetae, their length being about 1 / 4 the width of the paramera. Subgenital plate of females subtriangular. Tergum X with one distinct macrochaetae on posterior angles. Cercus of male with sensory pegs (spines) and appendix dorsalis without sensory pegs.

Description.

Pedicellus of adult male with unicellular glands. Mouthparts not specialized. Mandible strongly sclerotized apically with usual teeth. Apex of galea with two conules; one longer than wide and the other wider than long. Lacinia heavily sclerotized distally. First process of lacinia pectinate. Labium without prominent lateral lobes.

Tarsi with four articles. Praetarsi with three simple claws. Median claw glabrous, slender and smaller than lateral claws. Urosterna II – VII subdivided into two coxites and one sternite. Urosterna VIII and IX of male entire. Median portion of sternites with 1 + 1 sublateral macrochaetae at hind borders, as well as 1 + 1 macrochoetae near suture at about middle of segment. Coxites on segments II – IX with styli. Eversible vesicles on segments II – VI, pseudovesicles on VII. Urosterna I of males modified with a central pointy extension. Urosterna III and IV of adult males apparently without modifications. Urosternum VIII of male straight posteriorly, without emarginations or projections in between the styli of this segment. Tergum X with 1 + 1 distinct macrochaetae on posterior angles.

Point of insertion of paramera apparently slightly deep. Paramera with a distal semi-eversible vesicle, but less prominent than in Texoreddellia ( Wygodzinsky 1973) or Speleonycta ( Espinasa et al. 2010) and with distal chaetae short, their length being about 1 / 4 the width of the paramera. Stylus IX apparently without sensory pegs in males as seen in some species Prosthecina Silvestri, 1933 or Anelpistina Silvestri, 1905 (= Cubacubana Wygodzinsky & Hollinger, 1977 ; syn. = Neonicoletia Paclt, 1979 ) ( Espinasa et al. 2007). Opening of penis longitudinal. Cercus of male with sensory pegs. Appendix dorsalis without sensory pegs. Female with a subtriangular subgenital plate.

Molecular diagnosis.

Sequences generated for the mitochondrial 16 S rRNA locus for all ten specimens from the three different caves were 529 bp long and identical. BLAST analysis showed this 16 S haplotype to be quite different from any sequence available in GenBank (maximum of 77.26 Per. ident.). Within the American Nicoletiidae , Spinanycta differs from the genus Allonicoletia Mendes, 1992 by 130 bp (24.5 %), from Speleonycta by 132 bp (24.9 %), from Texoreddellia by 134 bp (25.3 %), from Squamigera Espinasa, 1999 by 138 (26.0 %), from Gibboletia Espinasa & Smith, 2023 by 145 bp (27.4 %), from Prosthecina by 148 bp (27.9 %), from Anelpistina by 155 (29.3 %), and from Nicoletia Gervais, 1843 by 153 bp (28.9 %). Using the 16 S rRNA fragment sequences of nicoletiid species across the subfamily Cubacubaninae ( Espinasa et al. 2007) , it can be observed that pairs of specimens from different populations of the same species differ by an average of 3.4 nucleotides (range 0 to 13; n = 22) and by 31.2 nucleotides (range 10 to 64; n = 14) among sister species. The 130 + bp between the Alabama specimens and any previously described species of American nicoletiid suggests these populations represent a new species and genus.

Maximum-likelihood phylogenetic analysis showed that members of genera Speleonycta , Allonicoletia , Texoreddellia and Nicoletia form a well-supported clade, with the Alabama specimens as sister to this group, and also in a clade distinct from other nicoletiid genera including Anelpistina . These results indicate that the Alabama nicoletiids belong to a group independent from any previously described genera for which 16 S rRNA sequences are available. Acanthonima Espinasa, 2005 has yet to have its DNA sequenced, but morphologically it is very different from the Alabama specimens (See below). Resolving the placement of all aforementioned genera within subfamilies was beyond the goals of the current study.

Type species.

Spinanycta alabamensis sp. nov.

Etymology.

Spinanycta . From spina = Greek for spine. It references the diagnostic spine in urosterum I, and nycta = Greek for night. It references in Greek mythology the occupation of caves by Nyx, the primordial goddess of night.

Remarks.

Spinanycta alabamensis belongs to the American Nicoletiidae characterized by subdivided abdominal sterna II – VII and fused coxites of abdominal segments VIII and IX ( Cubacubaninae + Nicoletiinae; Mendes 1988), or to a still undescribed subfamily that shares these characteristics. Spinanycta alabamensis is distinguished from all genera of these subfamilies by the urosterna I of males modified with a central pointy extension, although male sexual secondary characters in urosterna I – IV are highly variable among species.

The type species of the new genus shares some characteristics with Speleonycta , Allonicoletia , Texoreddellia , and Nicoletia , such as the paramera with semi-eversible vesicles, urosternum VIII of male straight posteriorly without emarginations or projections in between the styli of this segment. None of these characteristics are present in any of the other genera of Cubacubaninae . The new genus can easily be distinguished from Speleonycta because it lacks the very long and specialized chaetae in the distal semi-eversible vesicle of the paramera. From Allonicoletia they can further be differentiated by the presence of styli on urosternite II. From Texoreddellia and Squamigera by the absence of scales. From Prosthecina by the absence of conspicuous lateral lobes bearing numerous glandular pores in the submentum. From Anelpistina as defined by Espinasa et al. (2007), by its urostenum VIII without emarginations or projections in between the styli of this segment and its distinctive paramera. From Acanthonima by the absence of sensory pegs in the appendix dorsalis. From Nicoletia by its gonapophysis with more than 12 annuli.

Distribution.

This genus is known from just three cave systems on the north side of the Tennessee River Valley in southern Madison and southeastern Limestone counties, Alabama, within the Highland Rim section of the Interior Low Plateau physiographic province (Fig. 1 ).

Figures

Figure 1. Distribution of cave-dwelling nicoletiid genera in northern Mexico and the southern United States. Shaded areas are municipalities and counties in Mexico and the United States, respectively, with documented occurrences for each genus. Dark gray shaded areas are karst exposures in the United States. Inset is the distribution of Spinanycta alabamensis sp. nov. in northern Alabama with Alabama Cave Survey cave codes labeled. Bobcat Cave (AMD 1283) is the type locality.