Loimia minuta Treadwell, 1929

Londoño-Mesa, Mario H., 2009, Terebellidae (Polychaeta: Terebellida) from the Grand Caribbean region 2320, Zootaxa 2320 (1), pp. 1-93 : 39

Loimia minuta Treadwell, 1929

Figures 10 A-J

Loimia minuta, Treadwell, 1929:10–11 , Figs 28–30.— Londoño-Mesa & Carrera-Parra, 2005:21–22 , Figs 5 H-N, reinstated.

Type material: Holotype AMNH 1992 (1) Dry Tortugas, Florida, 1910.

Additional material: Mexican Caribbean : Quintana Roo State: ECOSUR TERE-11 E2 (1) Leeward of Contoy Island (21°30'8.4"N 86°47'45.3"W), X.1983 , by trawling. TERE-11 (1) Majahual (18°40'9.6"N 87°43'1.4"W), 22.III.2000 . TERE-11 (1) Paraiso Beach, Cozumel Island , 5.VI.1995 . TERE-11 (1) Leeward of Contoy Island (21°30'8.4"N 86°47'45.3"W), 3.III.2001; 2m.

Diagnosis: Holotype incomplete, with 43 segments, 11mm long, thorax 7mm long, 2.5mm wide ( Figs 10 A-C). Body brown. Abdomen thinner than thorax, with visible segmentation. Tentacular membrane short, narrow, rounded edge visible on ventral side; eyespots absent; tentacles missing. Upper lip short, narrow, semi-circular, projecting forwards ( Fig. 10D ). Lower lip short, swollen and somewhat hidden by segment 1 ( Fig. 10E ). First pair of lateral lappets projecting forwards, laterally surrounding tentacular membrane, and lower lip ventrally; second pair with short base, not connected to ventral shield, and with dorsal edge slightly developed, not covering base of branchiae. Sixteen ventral shields from segment 2; first three shields shorter and wider; next 9 shields swollen but decreasing in size posteriorly; last 4 shields divided transversally in two parts; abdomen with mid-ventral longitudinal groove. Nephridial papillae not seen. Notopodial glandular tissue absent. Branchiae branched, spiralled, slightly decreasing in length posteriorly; branchiae on dorsal left side and second right one absent. Notochaetae of two lengths, asymmetrically bilimbate, pointed; chaetae with some longitudinal striations ( Fig. 10G ). Neuropodia with uncini avicular, with five aligned teeth; uncini from segment 5–10 ( Fig. 10H ) PP developed, angular; PF absent; Oc long, concave; Cp with 1 vertical row of five teeth, decreasing in size in proportions of 3/4 the above; USr concave; SrP well-developed, rounded and directed anteriorly; LSr concave; AP with AF thin, projected downward; Bs slightly concave. Uncini from segments 11–20 ( Fig. 10I ) with four aligned teeth; abdominal uncini smaller, with five aligned teeth, distal tooth small ( Fig. 10J ). Abdominal neuropodia well developed, as swollen lappets with short rows of uncini, straight or semi-curved. Pygidium missing.

Staining pattern: Lateral lappets, first four segments, dorsally, and notopodia, also dorsally, stain deeply. Small longitudinal lateral bands to last two ventral shields and ventral gap between thoracic neuropodia stain lightly. Ventral shields and rest of structures remain pale.

Variation: Complete specimens from the Mexican Caribbean have 102–105 segments, 62mm long, thorax 13mm long and 3mm wide, tentacles small, smooth, posterior ventral shields trisected, and pygidium with 6 long digitate papillae.

Discussion: This species was synonymized with Loimia medusa (Savigny in Lamarck, 1822) by Fauvel (1914) because of the then current belief in wide (cosmopolitan) distribution of L. medusa in warm seas. Hartman (1956) followed this concept since the species apparently matched with Savigny’s description. Nevertheless, some important differences were also found in the uncini of the present material, additional to those presented by Hutchings & Glasby (1995); L. minuta has anterior thoracic uncini with 5 teeth, posterior thoracic uncini with 4 teeth and abdominal uncini with 5 teeth, all uncini with thin AF in this species, while L. medusa has posterior thoracic uncini and abdominal ones with 4 teeth. On the other hand, L. bermudensis is a similar species too, but it differs from L. minuta in having all uncini with 5 teeth. Thus, according to this character, it is a distinct species and should be regarded as valid.

Type locality: Dry Tortugas, Florida. Intertidal .

Distribution: Florida to the Mexican Caribbean coast.

Figures

FIGURE 5. Lysilla caribe sp. nov., (UMML 22.1000 2Cc): A. Ventral view. B. Fascicle of notochaetae from segment 4. C. Parapodia from segment 8. Polycirrus angeli sp. nov., (Holotype UANL 6490): D. Thoracic region in dorsal view. E. Thoracic region in ventral view. F. Fascicle of notochaetae from segment 8. G. Uncini from segment 8. Scale bars: A,D,E: 1mm; B,C,F: 0.5mm; G: 0.02mm.

FIGURE 10. Loimia minuta (Holotype AMNH 1992): A. Thorax in lateral view. B. Thorax in ventral view. C. Thorax in dorsal view. D,F. Anterior end in lateral view. E. Anterior end in ventral view. G. Bilimbate notochaetae from segments 18. H. Uncinus from segment 5. I. Uncinus from segment 11. J. Uncinus from segment 25. Scale bars: A,B,C,E,F: 1.3mm; D: 1.1mm; G: 0.05mm; H,I,J: 0.02mm.