Phrosina semilunata, Risso, 1822

Phrosina semilunata View in CoL

We observed morphological variation among specimens of Phrosina semilunata , mainly in denticle formation on the carpus of pereopods #4 and #5 and the shape of the head. This species was sampled from 39 °N to 35 °S across subtropical and tropical waters in the Atlantic Ocean ( table 1; fig. 5 View FIGURE 5 ). ABGD and phylogenetic analyses placed the 13 P. semilunata CO1 sequences into four OTUs or clades ( fig. 5 View FIGURE 5 ). Pairwise genetic distances between these clades ranged from 3–10% and within clades from 0 to 1% (table S4). Clades A (N = 5) and C (N = 2) were restricted to subtropical and tropical regions in the Atlantic Ocean. Clade B (N = 3) was only found in the North Atlantic Ocean and grouped with a sequence of P. semilunata from Florida. Clade D (N = 3) was only found in

CONTRIBUTIONS TO ZOOLOGY 94 (2025) 261–291

A B

Phronimopsis spinifera B

Phronimopsis spinifera A

0.06

A B Phrosina semilunata A

A D C B

Phrosinasemilunata HI_ US

Phrosina semilunata D

Phrosina semilunata C

Phrosinasemilunata FL_ US

Phrosina semilunata B

0.01

C

the convergence region (SATL-SSTC) and interestingly, grouped with a sequence of the same species from Hawaii ( fig. 5 View FIGURE 5 , table S2).