Cossura yacy, Sousa & Nogueira Júnior & Cutrim & Oliveira, 2019

Sousa, Lorena K. S., Nogueira Júnior, Miodeli, Cutrim, Marco V. J. & Oliveira, Verônica M. de, 2019, Cossura yacy sp. nov. (Cossuridae, Annelida) from a tropical Brazilian estuary, Iheringia, Série Zoologia (e 2019021) 109, pp. 1-9 : 2-4

Cossura yacy sp. nov.

urn:lsid:zoobank.org:pub:023027E2-D1CC-4C4A-8C1A-B22910702C75

( Figs 2 – 15 )

Type material. The holotype is a complete specimen with 79 segments, 10 mm length and 0.5 mm width, São Marcos Bay , São Luís do Maranhão, Brazil, 2°30.0’S, 44°27.0’W, 20 m, 28 October 2014 ( CIPY –1736). Paratypes: 59 paratypes complete and incomplete, length ranging from 2.0 to 10.0 mm and chaetiger numbers from 23 to 80. All sampled at São Marcos Bay, São Luís do Maranhão port complex, Brazil, 2°30.0’S, 44°27.0’W, 20 m, 28 October 2014 ( CIPY –1735) .

Diagnosis. Two pairs of nuchal organs at lateral margins of the peristomium. Branchial filament arising from median region of the 3 rd chaetiger. Bundles of short and long capillaries chaetae in both parapodial rami. Both chaetal types are smooth with spinulosa on distal half.

Description. The holotype has body elongated and cylindrical, with tapered posterior end ( Fig. 2 ). Conical prostomium, longer than wide and slightly flattened dorsoventrally, without eyes and usually with a pronounced dorsal fold ( Figs 3 , 5-8 ). Division between the prostomium and peristomium not well defined ( Figs 3, 4 ). Two pairs of nuchal organs at the lateral margins of peristomium ( Fig. 7 ). Inverted proboscis with tentacles observed through dissection in one paratype. Body divided in thorax and abdomen evidenced by a body narrowing ( Fig. 4 ). The thoracic region reaches the 28 th segment and has glandular inflations divided by a dorsal groove perpendicular to the body axis. Thorax dorsoventrallY flattened and more rigid than the abdomen. Branchial filament dorsal, annulate, arising from median region of the 3 rd chaetiger, and exceeding the body length ( Figs 2, 3 ). Parapodia rudimentary and without great variation, with acicula absent throughout the bodY ( Figs 9-11 ). First chaetiger with uniramous parapodia, and all others with biramous parapodia; all biramous parapodia alike and laterally positioned on each segment. Parapodial lobes are absent and thus chaetae emerge directlY from the bodYwall. Two types of capillary chaetae short and long with end curved; short chaetae exceed half the length of the long chaetae and are thinner ( Figs 12-14 ). Both chaetal tYpes are smooth with spinulosa (fine hairs) on the distal half. The same two chaetal types occur in the thorax and abdomen and in the neuropodia and notopodia, with predominance of long chaetae in the notopodia. The number of chaetae varies among the different regions of the bodY in all studied specimens: the 5 th parapodium bears seven notopodial and five neuropodial chaetae; the 20 th parapodium bears nine notopodial and seven neuropodial chaetae; the 43 th parapodium bears five notopodial and six neuropodial chaetae ( Figs 9-11 ). Pigidium with three long anal cirri without intercirral processes, one median dorsal and two in the lateral margins of the anal opening, reaching the last four chaetigers ( Fig. 15 ).

Colour. Preserved specimens without pigmentation.

Habitat. Substrate with dominance of silt, clay and fine sand.

Geographical distribution. Atlantic Ocean, São Marcos Bay, Maranhão, Brazil.

Etymology. The species name is derived from the Tupi word yacy (moon).

Figures

Figs 2-4. Cossura yacy sp. nov., paratype: 2, dorsal overview; 3, dorsal view of anterior region; 4, Narrowing dividing the thoracic and abdominal regions (arrow). Scales: Fig. 2, 0.5 mm; Fig. 3, 0.2 mm; Fig. 4, 0.5 mm.

Figs 5-8. Cossura yacy sp. nov., paratype: 5, anterior view; 6, two lateral nuchal organs (arrows); 7-8, Dorsal view of the division between the prostomium and peristomium (arrows). Scales: Fig. 5, 0.2 mm; Fig. 6, 0.4 mm; Figs 7, 8, 0.3 mm

Figs 9-11. Cossura yacy sp. nov., parapodia from a paratype, in anterior view: 9, parapodium 5; 10, parapodium 20; 11, parapodium 43. Scales: Fig. 9, 0.1 mm; Figs 10, 11, 0.05 mm.

Figs 12-15. Cossura yacy sp. nov. Scanning electron microscopy of the chaetae: 12, parapodium 4 and 5; 13, parapodium 5; 14, parapodium 43. Fig. 15, Detail of the pygidium region with anal cirri, in dorsal view. Scales: Figs 12, 0.05 mm 13, 0.0 mm; Fig. 14, 0.1 mm; Fig. 15, 0.04 mm.