Leodamas maciolekae Blake, 2017, new species

Leodamas maciolekae new species

Figure 27

Material examined. Argentina, IBM Sta. Comp IV-62, 21 Mar 1964, 37°50′S, 57°21′W, 14 m, holotype (USNM 1013916).

Description. A single nearly complete specimen measures 3 mm wide and 50 mm long for 167 setigers. Body anteriorly flattened, with first five segments somewhat inflated dorsally due to contained proboscis. Thorax 40 setigers long, with last two segments somewhat transitional; branchiae long, narrow, from setiger 29; first neuropodial postsetal lamellae from setiger 34. Color in alcohol: brown.

Prostomium sharply pointed (Fig. 27 A), with distinct anterolateral nuchal slits at junction with peristomial segment. Anterior thoracic parapodia simple rings; with short notopodial postsetal lamella (Fig. 27 A–B); abdominal notopodia elongate, narrow. Neuropodial postsetal lamellae first present from setiger 34, grading into abdominal neuropodial morphology on transitional setigers 39–40; abdominal neuropodia elongate, with a single laterally directed ventral cirrus (Fig. 27 C); interramal cirri lacking.

Thoracic notosetae all thin, crenulated capillaries; anterior abdominal notosetae including a single emergent spine, 6–8 long capillaries, and 1–4 furcate setae bearing unequal tynes connected by row of delicate needles on inner edges (Fig. 27 D). Thoracic neuropodial uncini maximally numbering about 40, arranged in two rows, with anterior row curving ventrally under second row and continuing dorsally to enclose second row as a short third row or extension (Fig. 27 B, inset); uncini simple, most worn, slightly curved, lacking distinct ribs (Fig. 27 E–F); capillaries entirely absent in thoracic neuropodia. Abdominal neurosetae including a single thin acicula, a single, very thin capillary (Fig. 27 H), and a single flail seta; flail setae with abruptly tapering mucron-like tips (Fig. 27 G).

Etymology. This species is named for Dr. Nancy J. Maciolek, polychaete systematist, in recognition of her prior work on similar species of Orbiniidae.

Remarks. Leodamas maciolekae n. sp. is referred to Leodamas because the thoracic neuropodial setae are dominated by large, conspicuous uncini and capillaries are absent. Leodamas maciolekae n. sp. belongs to the group of species having branchiae from posterior thoracic or anterior abdominal setigers (Table 1). There are four species that are closely related to L. maciolekae n. sp.: L. minutus, L. platythoracicus, L. texana, and L. treadwelli.. The main characters differentiating these five species are listed in Table 1. L. maciolekae n. sp. differs from the other four species in having many more thoracic setigers (40 instead to 11–22), complete absence of accompanying capillaries in the thoracic neuropodia, in having abdominal neuropodial flail setae instead of lacking them, by having the branchiae from a late thoracic setiger instead of transitional or abdominal segments. In the latter character, the species is closest to L. treadwelli. Further, the arrangement of thoracic neuropodial uncini into two rows, branchiae first present from posterior thoracic setigers and a distinctly dorsoventrally flattened thorax is also similar to that of L. treadwelli. However, the greater number of thoracic setigers (40 vs. 14–22) and the presence of very delicate flail setae in the abdominal neuropodia of some setigers in L. maciolekae n. sp. have not been reported for L. treadwelli and its relatives.

Distribution. Argentina, shallow subtidal.