Labrorostratus Saint Joseph, 1888

Hernández-Alcántara, Pablo, Cruz-Pérez, Ismael Narciso & Solís-Weiss, Vivianne, 2015, Labrorostratus caribensis, a new oenonid polychaete from the Grand Caribbean living in the body cavity of a nereidid, with emendation of the genus, Zootaxa 4048 (1), pp. 127-139 : 128-132

Genus Labrorostratus Saint Joseph, 1888

Type species Labrorostratus parasiticus Saint Joseph, 1888

Diagnosis (emended). Prostomium without antennae, with four eyes along posterior margin. Peristomium with two apodous rings. One or two pairs of small maxillary plates, sometimes reduced to one pair of broad plates without teeth, or absent. One pair of long maxillary carriers, partially or completely fused, sometimes with an additional unpaired one. Mandibles well developed, wing-shaped, narrowly joined along median line. Parapodia uni- or sub-biramous. Chaetae simple, geniculate with smooth margin; simple modified ventral chaetae present or absent. Acicular spines absent. Pygidium rounded, with up to four small anal cirri.

Remarks. Taxonomic difficulties for the identification of oenonids are usually attributed to the scarcity of external characters, so that the maxillary apparatus is essential to differentiate taxa ( Steiner & Amaral 2009). The maxillae show different degrees of reduction in seven parasitic oenonid genera, but all previously known parasitic species have maxillary plates ( Table 1).

Up to now, only Biborin , a free-living taxon from California, was known to lack a maxillary apparatus ( Chamberlin 1919). However, the reduction of maxillae is not rare among parasitic oenonids. Oligognathus benelliae and Pholadiphila turnerae , parasites found in echiurids and mollusks respectively, and the only oenonids found inside non-polychaete hosts, have three pairs of maxillae, which also occur in Oligognathus parasiticus Cerruti, 1909 , a spionid parasite. In other taxa, such as Haematocleptes and Drilognathus , the maxillary apparatus is even more reduced ( Table 1). In Haematocleptes , the maxillary carriers are often fused as one solid rod, but bearing a pair of small pieces free from the carriers ( Hartman & Fauchald 1971), while in Drilognathus , a monospecific genus recorded from South Africa, the maxillary plates are absent and maxillary supports are reduced to a black cuticular ridge ( Table 1).

In Labrorostratus , the seven species described, including the species from the Caribbean, are mostly endoparasites of other polychaetes (syllids, nereidids and trichobranchids) ( Table 2 ). Labrorostratus jonicus has been collected as free-living among algae, but it may have come out from a syllid after sampling or further handling ( Tenerelli 1961). These endoparasitic relationships are associated with an evident reduction of the maxillary apparatus, but the main characteristic of Labrorostratus’ species are the wide variability in their jaw shapes: L. jonicus , L. luteus , L. parasiticus and Labrorostratus sp. San Martín & Sardá, 1986, have two pairs of maxillary pieces, while L. prolificus Amaral, 1977 has only one pair of maxillae with no teeth. That is why the presence of a jaw apparatus represented only by an elongate rod-like maxillary carrier as found in the Caribbean’s species is not surprising. This, together with the fact that Labrorostratus is the only genus of a parasitic Oenonidae bearing simple modified ventral chaetae, made it possible to assign the new species to this genus. However, it was also necessary to emend the diagnosis of the genus, to include species without maxillary plates; this emendation is based on a previous ones by Steiner & Amaral (2009) adding our own observations.

Species Maxillae Mandibles Eyes Simplemodified Shape of chaetae Acicular spines Acicula Number of

ventral chaetae projecting neuroacicula

from lobe Drilognathus capensis Day, Black cuticular ridge, Wing shaped Two Absent Chaetae absent Absent Occasionally 1 1960 reminiscent of the long maxillary

supports; no distinct maxillary

plates

Labrorostratus jonicus Two pairs of very small pieces. I: Two subtriangular Four Present Limbate Absent Absent 1 Tenerelli, 1961 small with 3 teeth; II: same plates with 2

rounded teeth along

inner margins

Labrorostratus luteus Two pairs of long, slender. I: Two subtriangular Four Present Limbate Absent Absent 1 Uebelacker, 1978 large, anvil-shaped; II: minute plates with outer

with 4 teeth edges smooth

……continued on the next page Species Maxillae Mandibles Eyes Simplemodified Shape of chaetae Acicular spines Acicula Number of ventral chaetae projecting neuroacicula from lobe

Labrorostratus parasiticus Two pairs of very small pieces. I: Two small curved Four Absent Limbate smooth Absent Absent 3 Saint Joseph, 1888 small with 4 teeth; II: same plates with outer

edges smooth

Labrorostratus prolificus A pair without teeth or spines, Two subtriangular Four Absent Limbate Absent Absent 2 Amaral, 1977 with very long stems attached all plates

the way

Labrorostratus sp. San Martín Two pairs of very small denticled Two subtriangular Four Absent Limbate Absent Absent 2 Sardá, 1986 (maybe L. pieces. I: 2 teeth; II: same plates parasiticus fide Martin &

Britayev, 1998)

Labrorostratus zaragozensis Two pairs of very small denticled Two subtriangular Absent Absent Limbate Absent Absent 2 Hernández-Alcántara & Solís- pieces. I: a distal tooth and 5 plates

Weiss, 1998 small teeth; II: a large tooth, 2

distal teeth, 4 middle denticles

Notocirrus ? spinifera (Moore, Incompletely developed, with Wing shaped Four Absent Limbate serrated Absent Present 1 1906) (young) elongated rod-like maxillary

carriers and developing denticled

maxillae

Oligognathus bonelliae Three pairs, each recurved and U-shaped, with two Four Absent Limbate serrated Absent Absent 1-2 Spengel, 1882 unidentate wing-like pieces of

rods united by

transverse band

Oligognathus parasiticus Three pairs, each recurved and U-shaped, with two Absent Absent Limbate smooth Absent Absent 1 Cerruti, 1909 unidentate wing-like pieces of

rods united by

transverse band

Pholadiphila turnerae Dean, Three pairs of equal maxillae Two large plates, Absent Absent Capillary hirsute Present Absent 1 1992 smooth, shield-like, spinosus united medially

......continued on the next page Species Host Number of parasites by Locality/depth Citations

host

Tables

TABLE 2. Host, number of parasites by host, and distribution of parasitic Oenonidae with reduced maxillary apparatus.

Species 1) Drilognathus capensis Day, 1960	Host Onuphis holobranchiata Marenzeller, 1879 (Onuphidae)	Number of parasites by host 5	Locality/depth Lamberts Bay. South Africa; 29 m	Citations Day, 1960
2) Drilonereis benedicti Pettibone, 1957	Americonuphis magna (Andrews, 1891) (Onuphidae)	1	Tampa Bay, Florida; 22 m	Pettibone,1957
3) Drilonereis caulllery Pettibone, 1957	Nothria conchilega (Sars, 1835) (Onuphidae)	1	Off Massachusetts to off Virginia, USA; 182-571 m	Pettibone,1957
4) Drilonereis forcipes (Hartman, 1944) 5) Drilonereis parasiticus (Caullery, 1914)	Eunice sp. (possibly Leodice antennata Savigny, 1818 fide Hartman, 1944 ) Terebellidae (unidentified)	1 1	San Benito Island, Baja California; 119-146 m Near Timor, Dutch East Indies; 73 m	Hartman, 1944; Pettibone,1957 Caullery, 1914 ; Caullery & Mesnil, 1916; Pettibone, 1957
6) Haematocleptes leaenae Hartman & Fauchald, 1971	Leaena minima Hartman, 1965 (Terebellidae)	1	Northwestern Atlantic Ocean; 1,102 m	Hartman & Fauchald, 1971
7) Haematocleptes terebellidis Wirén, 1886	Terebellides stroemi Sars, 1835 (Trichobranchidae)	1	Off Sweden; 130 m	Wirén, 1886
8) Labrorostratus caribensis n. sp.	Nereis sp. ( Nereididae )	1	Chinchorro Bank, Mexican Caribbean; 4.5 m	This study
9) Labrorostratus jonicus Uebelacker, 1978	Free-living among algae; fide Tenerelli (1961) it may have emerged from syllids	-----	Lachea Island, Mediterranean; infralittoral	Tenerelli, 1961
10) Labrorostratus luteus Uebelacker, 1978	Haplosyllis spongicola (Grube, 1855) (Syllidae) , and free-living	1	Grand Bahama Island; 15-17 m; Western Florida and Alabama; 37- 69 m	Uebelacker, 1978, 1984