Small pholcids (Araneae: Synspermiata) with big surprises: the lowest diploid number in spiders with monocentric chromosomes

Author(s)

Lomazi, Rafael Lucena ^[1] ; Araujo, Douglas ^[2] ; Carvalho, Leonardo Sousa ^{[3, 4]} ; Schneider, Marielle Cristina ^[1]

Affiliation

^[1] Univ Fed Sao Paulo, UNIFESP, Dept Ciencias Biol, Av Prof Artur Riedel 275, BR-09972270 Diadema, SP - Brazil

^[2] Univ Fed Mato Grosso do Sul, UFMS, Inst Biociencias, Setor Biol Geral, BR-79070900 Campo Grande, MS - Brazil

^[3] Univ Fed Piaui, UFPI, Dept Ciencias Biol, Campus Amilcar Ferreira Sobral, BR 343, Km 3-5, BR-64800000 Floriano, Piaui - Brazil

^[4] Univ Fed Minas Gerais, Posgrad Zool, Belo Horizonte, MG - Brazil

• Document type: Journal article
• Source: JOURNAL OF ARACHNOLOGY; v. 46, n. 1, p. 45-49, APR 2018.
• Web of Science Citations: 1

Abstract

Even though less than 2% of pholcid species have been karyotyped, previous studies documented a wide diversity of diploid numbers and sex chromosome systems. Here, we increase the number of native Brazilian cytogenetically investigated pholcid species from three to eight and discuss implications of chromosome evolution in this group. The species analyzed here share a X0/XX sex chromosome system and biarmed chromosomes, but vary in diploid numbers, i.e., 2n male - 17 in Mesabolivar spinulosus (Mello-Leitao, 1939) and Mesabolivar togatus (Keyserling, 1891), 2n male - 15 in Carapoia sp., and 2n male - 9 in Micropholcus piaui Huber, Carvalho \& Benjamin, 2014 and Micropholcus ubajara Huber, Carvalho \& Benjamin, 2014. Chromosomal data indicate that most Mesabolivar species share a 2n male - 17, X0, while Mesabolivar luteus shares with Carapoia sp. a 2n male - 15, X0. This lends further support to the idea that M. luteus is in fact misplaced and more closely related to Carapoia Gonzalez-Sponga, 1998. The diploid number of the two Micropholcus species is the lowest reported so far for spiders with monocentric chromosomes. The 2n male - 9, differs strongly from the 2n male - 17 previously reported for Micropholcus fauroti (Simon, 1887). As the number of autosomes of M. piaui and M. ubajara is exactly half of that found in M. fauroti, we hypothesize that the reduction occurred by an ``all or nothing'' fusion event. The low diploid number observed in M. piaui and M. ubajara is the first morphological synapomorphy that would support the establishment of a new genus to allocate the New World Micropholcus species. (AU)

• FAPESP's process: 11/21643-1 - Meiosis in scorpions (Arachnida): model to understand the evolution in species with achiasmate chromosomes
• Grantee: Marielle Cristina Schneider
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 12/10679-8 - Comparative cytogenetic analysis in Pholcidae spiders (Araneomorphae, Haplogynae)
• Grantee: Rafael Lucena Lomazi
• Support Opportunities: Scholarships in Brazil - Scientific Initiation