Identification of Y-Nauplii (Facetotecta) in Andaman Sea, India

Abstract

The Facetotecta is among the lesser known groups in the world ocean. The present study recorded two types of Facetotecta in the Andaman Sea, off Andaman Islands. These two types of Facetotecta were observed during the period of August 2015, July 2016 and October 2017 and identified as Type I Hansenocaris corvinae and Type IX Hansenocaris leucadea. However, the cursory analysis suggested that the Type IX is a new type of Facetotecta and named it as Type XII Hansenocaris portblairenae sp. (nov). This finding suggests that this Facetotecta observation is the first report in the Andaman Sea, as well as in the Indian Ocean Region.

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

“…In the Pacific Y-larvae were also found in equatorial [Kolbasov et al, 2007], tropical including Hawaii [Grygier, 1996, own data], subtropical and boreal regions [Mileikovsky, 1970;Itô, 1984Itô, , 1985Itô, , 1989Grygier, 1996, Ponomarenko, Korn, 2006own data]. In the Indian Ocean facetotectans were described from equatorial and tropical waters including the Red Sea, the Gulf of Aden and the Rodrigues, Seychelles and Andaman Islands [Almeida Prado-Por, Por, 1988;Böttger-Schnack, 1995;Conway et al, 2003;Swathi, Mohan, 2019]. In the Arctic Ocean Y-larvae were found in the Barents, White and Kara seas [Mileikovsky, 1968;Kolbasov, Høeg, 2003;own data].…”

“…COMPARISON. Seven described valid facetotectan species were established on the basis of Y-cypris characters, while the other six on the nauplius y phase [Steuer, 1905;Itô, 1985;Belmonte, 2005;Kolbasov et al, 2007;Swathi, Mohan, 2019]. Although the species established on the basis of the naupliar instars are distinguishable from one another, none are linked to any form of cypris y and none can be compared directly to previously described nominal species of Hansenocaris that are based on the cypris stage.…”

“…Currently, Facetotecta encompass seven species, established on the basis of Y-cyprid morphology and assigned to a single genus, Hansenocaris [Itô, 1990;Kolbasov et al, 2007]. Additional six species of Hansenocaris were described on the basis of naupliar stages [Steuer, 1905;Itô, 1985;Belmonte, 2005;Swathi, Mohan, 2019], but they remain dubious, because they were not established on the basis of Y-cyprid morphology.…”

“…Different facetotectan nauplii from West Indian, equatorial Atlantic waters and from the Bay of Kiel in the Baltic were first described in detail more than 100 years ago by Hansen [1899]. Subsequently Y-larvae were reported from almost all oceans in the world [Kolbasov, Høeg, 2003;Belmonte, 2005;Ponomarenko, Korn, 2006;Swathi, Mohan, 2019]. A post-naupliar instar or 'Y-cyprid' resembling other thecostracan cypridiform larvae was first described by Bresciani [1965].…”

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.)

“…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.…”