The spermatozoon structure of Coptothyris adamsi (Davidson, 1871) (brachiopoda, Rhynchonelliformea) and analysis of the 18S and 28S rRNA sequences

Abstract

The position of brachiopods in the animal system remains controversial, with morphological data often being inconsistent with the results of molecular phylogenetic analysis. In this study, we investigated the structure of the spermatozoa and determined the combined sequences of the 18S and 28S rRNA genes of the articulate brachiopod Coptothyris adamsi (Davidson, 1871). The spermatozoa of C. adamsi are similar to those of other articulate brachiopods. Two types of sperm structure can be distinguished within Brachiopoda: the first type is characteristic of the articulate brachiopods (Rhynchonelliformea), the second type, the inar ticulate brachiopods (Linguliformea and Craniiformea). Rhynchonelliformea spermatozoa are similar to those of the deuterostome animals, in particular to the sperm of the Echinodermata, whereas Linguliformea and Craniiformea spermatozoa are similar to the typical sperm of the Trochozoa, such as annelids and mol lusks. Molecular phylogenetic analysis has shown that the brachiopods and phoronids form two monophyl etic groups within the group Brachiozoa, where phoronids are united in a separate basal clade, while brachi opods are divided into two clades.

Spermatogenesis in the deep‐sea brachiopod Pelagodiscus atlanticus and the phylogenetic significance of spermatozoon structure

“…Rhynchonelliformea is the most advanced and diverse group of brachiopods. Data on spermatozoon structure of several rhynchonelliform species have been published (Drozdov et al, ; Hodgson & Reunov, ; Reunov, ; Williams, James, Emig, Mackay, & Rhodes, ). The rhynchonelliform spermatozoon has advanced features, such as a single ring‐shaped mitochondrion that surrounds two centrioles, which are almost in line with each other (Figure ).…”

“…Data on the ultrastructure of brachiopod spermatozoa are fragmentary and limited to only a few shallow-water species (Afzelius & Ferraguti, 1978;Chuang, 1983;Drozdov, Vladychenskay, Lomov, Tyurina, & Petrov, 2015;Hodgson & Reunov, 1994;James et al, 1992;Sawada, 1973). The brachiopod spermatozoon can be classified as an ancestral-classical in some cases or as an ancestral type with modified elements in other cases.…”

Complete mitochondrial genome ofLaqueus Japonicus(Brachiopoda, Terebratulida, Laqueidae)

“…The phylum Brachiopoda are relict marine invertebrates with approximately 4500 named genera grouped into 109 superfamilies, 26 orders, eight classes, and three subphyla (Carlson 2001 ; Drozdov et al. 2015 ). Among these three, the Rhynchonelliformea is the most diverse subphylum (WoRMS Editorial Board 2017 ).…”