Biology, distribution and geographic variation of loliginid squids (Mollusca: Cephalopoda) off southwestern Atlantic

Abstract

The biology and ecology of southwestern Atlantic loliginid squids have been intensively researched in the last few decades, mostly off the Brazilian southern coast. However, information gathered by scientific research cruisers, either past or recent, is limited. Three species of loliginid squids – the warm-tempered Doryteuthissanpaulensis (Brakoniecki, 1984), plus the tropical D.pleii (Blainville, 1823) and Lolligunculabrevis (Blainville, 1823) – were sampled along 16 degrees of latitude on the southwestern Atlantic (22–38°S). The samples were obtained mostly from oceanographic surveys, but also included squids caught by commercial fisheries, and a few specimens from museum collections. Squid response to abiotic variables, morphological variation and circadian behaviour were surveyed in detail. Doryteuthissanpaulensis can be divided into at least six distinguishable geographical groups, which do not form a cline. In contrast, D.pleii can be divided into only two morphological groups that are very similar. Doryteuthis spp. were heterogeneously distributed on the shelf, whereas L.brevis was confined nearshore. Our data extended the southernmost distribution range of D.pleii by at least nine degrees of latitude, owing to specimens obtained at ~38°S (Mar del Plata, Argentina). Small, immature D.sanpaulensis were sampled inside the Patos Lagoon estuary (~32°S). The morphologically similar Doryteuthis spp. apparently avoid direct competition by concentrating at different depths, displaying different thermal preferences, and inverse circadian levels of activity. The information reported herein may be regarded as a “snapshot” of the ecology of sympatric squids in a marine environment that has not been deeply affected by climate change.

Squids caught by shrimp trawlers off the coast of Sergipe, northeastern Brazil

“…Only one specimen of D. pleii was captured: a male with 23.3 cm ML (137.7 g WW), caught in November 2015. Its size corresponded to 67% of the maximum size registered for this species (Vaske Júnior and Costa, 2011) and was larger than the size at first maturity (L m ) for males, which corresponds to 8.7 cm ML in southeastern-southern Brazil (Martins and Juanicó, 2018) and to 14.7 cm ML in southern Brazil (Martins and Perez, 2007).…”

Ficha de Lolliguncula brevis

“…Essas pequenas capturas revelam que L. brevis eventualmente formam concentrações abundantes o suficiente para sustentar pequenas e esporádicas capturas comerciais, fato não conhecido a partir de cruzeiros de pesquisa realizados na região (e.g. Martins & Juanicó, 2018).…”

Ficha de Doryteuthis pleii

“…Endêmica do Brasil: Não Doryteuthis pleii é uma espécie nerítica que se distribui no Atlântico Ocidental e possui registros da Nova Jersey (EUA) ao Rio Grande do Sul (Brasil), com ocorrência rara em Península Valdez, na Argentina (Haimovici et al, 2009, Martins & Juanicó, 2018. É comumente encontrada no mar do Caribe e Golfo do México, Bermudas e Bahamas.…”

“…Espécie migratória? Não O padrão migratório é incerto, porém, o grande tamanho dos machos e a quase uniformidade morfológica sugerem um elevado grau de deslocamentos latitudinais em animais adultos (Martins & Juanicó, 2018 Comprimento máximo do macho 380 mm comprimento de manto (ML) (Martins & Perez, 2007). A maturidade ocorre em diferentes tamanhos variando com a estação do ano e local.…”

“…Demersal-pelágico, adultos e juvenis normalmente ocorrem sobre fundos moles, desde a região costeira até a quebra da plataforma (~ 200 m)(Rodrigues & Gasalla, 2008).É uma espécie principalmente nerítica, sendo que suas ocorrências são em geral em profundidades inferiores a 200 m(Martins & Juanicó, 2018) …”