Open-access Cossura yacy sp. nov. (Cossuridae, Annelida) from a tropical Brazilian estuary

ABSTRACT

The family Cossuridae is monogeneric for Cossura Webster & Benedict, 1887 which currently has 28 known species, three of which already recorded for Brazilian coast. In the present study we describe Cossura yacy sp. nov. increasing to 29 the number of known Cossuridae species. We have found and analyzed 60 individuals of C. yacy sp. nov. from São Marcos estuarine complex (ca. 02°S; 44°W) around São Luís Harbor (Maranhão, Brazil). It differs from other species of genus also by the presence of the two pairs of nuchal organs at lateral margins of the peristomium, branchial filament in the median region of the third chaetiger and by short and long capillary smooth chaetae with spinulosa on the distal half. These two chaetal types are present through the body both in the neuropodia and in the notopodia. Adults specimens of the Cossura yacy sp. nov. have seven notopodial and five neuropodial chaetae in the 5th parapodium; nine notopodial and seven neuropodial chaetae in the 20th parapodium; five notopodial and six neuropodial chaetae in the 43th parapodium. Pygidium has three long anal cirri, reaching the fourth posterior segment.

KEYWORDS Taxonomy; Morphology; Polychaeta; Brazil; Tropical

Cossuridae is a small polychaete family with 28 known species all placed in the genus CossuraWebster & Benedict, 1887 (Read & Fauchald, 2018). The genus was monotypic for Cossura longocirrata Webster & Benedict, 1887 until 1955 when Cossura candida was described by Hartman (1955). This genus was formerly assigned to Cirratulidae until the establishment of the family Cossuridae in 1963 (Day, 1963; Read, 2000). Two other genera were erected within Cossuridae to embrace those species with spines in the abdominal chaetigers instead of capillaries (Ewing, 1987): Cossurella Hartman, 1976 and Heterocossura Wu & Chen, 1977, both currently considered junior synonyms of Cossura (Read & Fauchald, 2018).

Species of Cossura are characterized by the body regionalized in thorax and abdomen, a conical prostomium tapering to a sharp or rounded tip or extended laterally as horns (Liñero-Arana & Díaz-Díaz, 2010; Jumars et al., 2015) and usually without eyes. First chaetiger uniramous and the others along the body biramous (Hilbig, 1996). A long branchial filament is present in the dorsal region. Simple chaetae, which may be smooth or have the exterior margin with small spines (spinulosa). Pygidium with anal cirri of variable shape and length (Ewing, 1984). The most used characters to distinguish the different species of the genus are the shape of the prostomium, the chaetiger which the branchiae first appear, chaetal type and anal cirri with or without intercirral processes in the pigidium (Egremy-Valdez, 2009; Fournier & Petersen, 1991). These polychaetes typically inhabit sandy or muddy marine sediments, in shallow or deep waters (Zhadan, 2015). They are non-selective surface deposit-feeders, using their oral tentacles to accomplish so (Jumars et al., 2015).

Among the 28 species currently known in the genus (Read & Fauchald, 2018; Tab. I), nine have been recorded from South America, three of them on Brazil (Amaral et al., 2013). However, most of the studies are from south and southeast Brazilian coast, close to the historically consolidated research groups (e.g. Lana et al., 2017). The North and Northeastern Brazilian tropical estuaries potentially have a very high diversity, but are largely unexplored, as exemplified here with the description of a new coastal species.

MATERIAL AND METHODS

Sampling of biological material. Benthic samples were collected in the canal of the São Marcos Bay, Maranhão, Brazil, in areas under influence of dredging activities (Fig. 1). All stations had unconsolidated muddy sediment and ca. 20 m depth. On each station benthic material was sampled with a 20-L van Veen trap and the material sampled was fixed in 4% formalin. In the laboratory the material was sieved (0.5 mm) and analyzed under stereomicroscope.

Fig. 1.
Collection sites in the São Luís do Maranhão port complex, Northeastern Brazil.

Preparation and identification of material. Slides were mounted for detailed observations of the morphology of parapodia and chaetae. The specimens were identified using stereoscopic and optical microscopes. Descriptions were prepared following external body-morphology such as prostomium, branchiae position, parapodia, chaetae and anal cirri. Measures of width included only parapodia, without considering the chaetae. For improved contrast while checking for papillae, Shirlastain dye have been used.

Photographs were taken using a Zen AxioCam ICc5 of Zeiss attached to the stereoscopic and optical microscopes and the software Axion vision 4.8. The parapodia were dried and coated on a double carbon tape and examined in a scanning electron microscope (Hithachi TM-3030 from Universidade Federal do Maranhão). The type material was deposited at “Coleção de Invertebrados Paulo Young” (CIPY) from Universidade Federal da Paraíba, João Pessoa, PB.

RESULTS

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 3rd 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 28th 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 3rd 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 body-wall. 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 5th parapodium bears seven notopodial and five neuropodial chaetae; the 20th parapodium bears nine notopodial and seven neuropodial chaetae; the 43th 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).

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.

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).

DISCUSSION

Most Cossuridae species have conical prostomium, likewise C. yacy sp. nov., although in some the prostomium may be more rounded (e.g. Zhadan, 2015; see Table I and references therein). The exceptions are Cossura ginesiLiñero-Arana & Díaz-Díaz, 2010, with well-developed lateral horns in the prostomium (Liñero-Arana & Díaz-Díaz, 2010), and Cossura rostrataFauchald, 1972, with prostomium wider than larger in adult specimens (Fauchald, 1972; Hilbig, 1996). In C. yacy sp. nov. the first parapodium is uniramous while all others are birami, similar to other cossurid species. Cossura yacy sp. nov. has the branchial filament in the median region of the third chaetiger, differing from Cossura laeviseta Hartmann-Schröder, 1962, Cossura chilensis Hartmann-Schröder, 1965, Cossura abyssalis Hartman, 1967, Cossura simaFauchald, 1972, Cossura dayi Hartman, 1976, Cossura duplexTamai, 1986, and Cossura consimilisRead, 2000 from Atlantic and Pacific oceans, with branchial filament in the anterior region of the third chaetiger (Reish, 1958; Read, 2000; Soto & Lemus, 2016; see Table I); differs also from Cossura soyeri Laubier, 1964, Cossura heterochaetaOrensanz, 1976, Cossura longocirrata, Cossura ginesi, Cossura pygodactylata Jones, 1956 and Cossura flabelligera Zhadan, 2017 all with branchia in the second chaetiger (Bachelet & Laubier, 1994; Zhadan, 2015; Tab. I) and from Cossura alba Hartman, 1967, Cossura dimorpha (Hartman, 1976), Cossura modicaFauchald & Hancock, 1981 and Cossura pettiboneae (Ewing, 1987) with branchia in the fourth chaetiger (see Table 1 and references therein). Cossura yacy sp. nov. differs from other species of the genus mainly by the presence of the two pairs of nuchal organs at lateral margins of the peristomium. Since the only species of Sewing that have nuchal organs are C. ginesi nuchal organs located on lateral side of the prostomium, C. keablei lateral organs localized behind chaetae bundle beneath notopodia and C. consimilis with low transverse ridges of dorsal nuchal organs visible at posterior lateral margin the prostomium. Cossura yacy sp. nov. has two types of smooth capillary chaetae with spinulosa on distal half, differing from Cossura delta Reish, 1958 which also have two chaetal types with spinulosa in the external edge, but has limbated chaeta restricted to the anterior neuropodial segments (Reish, 1958). Cossura heterochaeta has curved acicular chaetae with abrupt tips only in the anterior neuropodia (Orensanz, 1976). Similar to most other species of the family (Tab. I), C. yacy sp. nov. has three long anal cirri, one ventral and two dorsal reaching the fourth posterior segment. This is different from C. brunnea with anal cirri surpassing the fourth posterior segment (Egremy-Valdez, 2009), from C. pygodactylata with anal cirri with digitated lobes in both sides of the pygidium (Bachelet & Laubier, 1994; Zhadan et al., 2012), from Cossura coasta with branched anal cirri, from C. laeviseta, C. modica and C. duplex with three short anal cirri and from Cossura pseudakaina Ewing, 1987 with pygidial papillae and a single short anal cirrus (Read, 2000), (Tab. I and references therein).

Tab. I.
Comparison of main characteristics of Cossura species known worldwide.

Acknowledgements

We thank support from the Universidade Federal do Maranhão (UFMA) and to the Oceanography Graduate Program from UFMA. The Phycology Laboratory (UFMA) helped with laboratory facilities. Mr. Edilausson Moreno Carvalho and Dr. José Bauer for helping in the photographs with the electron microscope from UFMA. Dr. Hilton Tulio Costi, Coordinator of the Institutional Laboratory of Electronic Microscopy of the Museu Paraense Emílio Goeldi. Dr. Wagner Magalhães helped to improve the text. LKSS received scholarship support from “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior” (CAPES).

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Publication Dates

  • Publication in this collection
    30 May 2019
  • Date of issue
    2019

History

  • Received
    04 July 2018
  • Accepted
    07 May 2019
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