Primno, Guerin-Meneville, 1836

Genus Primno View in CoL

Juvenile specimens of the genus Primno are difficult to identify due to the highly variable claw-like structure and denticle patterns on the carpus of pereopod #5 (P5). We identified two specimens as Primno brevidens , which had 11.4% sequence divergence between them, but also grouped with a Genbank sequence of the same nominal species from the Pacific. We further recovered three additional distinct clades in phylogenetic analyses of CO1 sequences from 91 Primno specimens

A * Primno latreillei B

evansi FL _ US

CONTRIBUTIONS TO ZOOLOGY 94 (2025) 261–291

( fig. 8 View FIGURE 8 ). Average genetic distance between these clades was 16.9% (range 9.1–20.9%), with limited variation observed within the clades (0.4%, range 0.2–0.9%). Re-examining the morphology of adult specimens of each clade resulted in identifying the three clades as Primno johnsoni , Primno latreillei and Primno abyssalis , each with distinct denticle patterns on the carpus of pereopod #5 corresponding to the original descriptions. Specimens of P. johnsoni were found across subtropical and tropical Atlantic waters (NATR, WTRA, SATL). Primno latreillei was abundant in the southern convergence waters (SATL, SSTC) and Primno abyssalis was found in the colder and eutrophic waters of the subantarctic province (SANT-KFLD, fig. 8 View FIGURE 8 ). According to Bowman (1985), P. abyssalis is restricted to the subarctic province of the North Pacific and is closely related to Primno macropa Guérin-Méneville, 1836 . However, the denticle pattern on the carpus of P5 observed in adult specimens in our material corresponded with the original description.