Naupliar development of Facetotecta (Crustacea: Thecostraca) and the nature of the first nauplius instar in the Crustacea - pro et contra the Hexanauplia concept

Two New Species of Lecithotrophic Nauplius y with Remarkable Labra from Okinawa, Japan, and a Family-Group Name for y-Larvae (Crustacea: Thecostraca: Facetotecta: Hansenocarididae fam. nov.)

“…Nomenclature of body parts. The morphological terms used herein usually follow Olesen et al (2022), but also Kolbasov et al (2021a) when necessary. There is no existing terminology for the few setae and many pores on the body surface of nauplius y.…”

“…The only described genus, Hansenocaris Itô, 1985 (q.v. ), was established with four nominal species, and more have been gradually added since (Itô 1986b(Itô , 1989Belmonte 2005;Kolbasov and Høeg 2003;Kolbasov et al 2007Kolbasov et al , 2021aSwathi and Mohan 2019;Olesen et al 2022). A para-taxonomy exists alongside the formal taxonomy, started already by Hansen (1899) as noted above, and continued by Schram (1970Schram ( , 1972, Itô (1986aItô ( , 1987a, Grygier (1987), and Watanabe et al (2000), whereby distinct "types" of naupliar larvae have been assigned Roman-numeral designations.…”

A new species of the Y-larva genus Hansenocaris Itô, 1985 (Crustacea: Thecostraca: Facetotecta) from the Azores, with notes on its morphology and biogeography

“…P.341-350. doi: 10.15298 A recent study revealed seven naupliar instars in Hansenocaris itoi Kolbasov et Høeg, 2003, instead of the five that were previously supposed for the Facetotecta [Kolbasov et al, 2021]. This number of naupliar instars is unique not only for Facetotecta, but also for Thecostraca and Hexanauplia as well.…”

“…The enigmatic Y-larvae represent the last significant group of Crustacea for which the adult forms are still unknown [Grygier, 1996;Kolbasov, Høeg, 2003;Glenner et al, 2008;Høeg et al, 2014;Kolbasov et al, 2021]. Their naupliar and cypridiform larvae have been found in the marine plankton worldwide.…”

Larvae of Rhizocephalans with a Kentrogonid Type of Development and their Significance in the Taxonomy and Phylogeny of Parasitic Crustaceans

“…As an example, the first stage of B. tenellus [66] morphologically corresponds to the second stage, so there are probably six naupliar stages in this species [57]. Recently, it was found that the cold-water facetotectan Hansenocaris itoi in the White Sea has seven naupliar stages [45], while only five naupliar stages were described for the warm-water H. furcifera [40]. It is possible that the number of naupliar stages in Rhizocephala varies from four to six, with a basic value of five [26].…”