Relocation of Dodecaseta McCammon & Stull, 1978 (Annelida, Capitellidae) in Notodasus Fauchald, 1972

Abstract The capitellid polychaete genus Dodecaseta McCammon & Stull, 1978 is relocated in Notodasus Fauchald, 1972. Two species are redescribed based on examination of type material and three new combinations are proposed: Notodasus oraria (McCammon & Stull, 1978), N. eibyejacobseni (Green, 2002). N. fauchaldi (Green, 2002). N. kristiani (García-Garza et al., 2009), is synonymized under N. oraria. Some comments on Dasybranchus lumbricoides Grube, 1878 are included.


Introduction
The study of capitellid polychaetes has been complex. Determination at the generic level is based mainly on the number of thoracic segments, the number of chaetigers with capillary chaetae, a mixture of capillaries and hooded hooks, complete (with notopodium and neuropodium), or incomplete (with notopodium only) first chaetiger, as well as the position of the transition between thorax and abdomen (Fauchald 1977). However, these characters have caused erroneous determinations when the organisms are in initial stages of growth since the capitellids display great morphological variability in these characters at different stages of development (Blake 2000).
Capitellids in early developmental stages have the first three segments with capillary chaetae while the following segments bear hooded hooks which will later be replaced by capillary chaetae in subsequent stages (Ewing 1984, George 1984. In addition to its simple morphological structure, and sometimes due to improper relaxation, fixation and preservation of specimens, confusion can occur in the establishment of new genera or species and misidentifying species by identifying immature stages. With this variability in the chaetal formula we may infer that some monotypic genera could be described from juvenile organism however this needs an in depth study of each case. In this work a review of a species belonging to Dodecaseta McCammon and Stull, 1978, confirmed that these species have morphological characters placing them in Notodasus Fauchald, 1972.

Material and methods
Material from the Natural History Museum of Los Angeles County, Allan Hancock Foundation Polychaete Collection (LACM-AHF) and the Colección Poliquetológica de la Universidad Autónoma de Nuevo León (UANL). Methyl green staining was used to determine specific patterns of glandular areas. Specimens were submerged for a maximum of two minutes in a solution of methyl green in 70% ethanol and washed in several alcohol changes (Warren et al. 1994). Photographs were taken with a stereomicroscope Olympus SZ61 equipped with a digital camera Olympus C-7070. Editing of photos was performed using Adobe Photoshop CS6.
Remarks. The genus Dodecaseta was established by Mc Cammon and Stull (1978) to include Dodecaseta oraria, a species from Southern California. These authors considered that D. oraria differed from the genus Notodasus by presenting the first thoracic chaetiger biramous and capillary chaetae in the first abdominal segments. In the original description of Notodasus, Fauchald (1972) described the genus with the first chaetiger being uniramous.  reviewed the Notodasus genus based on the examination of type material, and they observed that the holotype N. magnus (type species of the genus) has the first chaetiger biramous, not uniramous as originally described.
The holotype of D. oraria is a small specimen of 12 mm long and 0.8 mm wide (LACM-AHF POLY 1248). McCammon and Stull (1978) included 12 specimens in the original description, but they did not include variation in body size of these specimens. Based on this discrepancy in the description (and other factors) we believe that the genus Dodecaseta should be synonymized with the genus Notodasus. Blake (2000) had previously felt that Dodecaseta should be synonymized with Notomastus since the only known species form the Southern California Bight varied from Notomastus only in that it has notochaetae in the first abdominal chaetiger, and the presence of abdominal capillaries is not a considered generic character of capitellids. Green (2002) expands the genus Dodecaseta, in order to describe two new species from the Andaman Sea (D. fauchaldi and D. eibyejacobseni) including the following characters, 12 and 13 chaetigers with capillary chaetae, with the last one or two transitional in appearance with expanded neuropodial lobes, and protruded lateral organs. However, the ammended diagnosis proposed by Green for Dodecaseta agrees with the diagnosis of the genus Notodasus Fauchald, 1972. Consequently, we believe that D. fauchaldi and D. eibyejacobseni should also be reassigned to the genus Notodasus.   Redescription. Holotype of D. oraria incomplete with 89 segments, 12 mm long, 0.8 mm wide in abdomen. Color in alcohol white-translucent. Prostomium conical with palpode. Eyespots not seen. Peristomium to the eighth thoracic chaetiger tessellated, remaining segments smooth. Thorax with 11 chaetigers, with bilimbate capillaries in both rami, first chaetiger biramous, transition between thorax and abdominal segments marked by abrupt shorting of abdominal segments. (Fig. 1A). Thoracic and abdominal segments biannulate. Notopodia lateral in first thoracic segments, in subsequent segments located dorsally. Lateral organs, between notopodia and neuropodia throughout body, those of thoracic region closer to notopodium; thoracic lateral organs larger than abdominals. Genital pores not seen. Notopodial lobes of abdominal chaetigers 3-7 fused dorsally (Fig. 1B, F), each line of hooded hooks completely separated, with around 18-20 hooks per fascicle. Neuropodial lobes project to dorsal region and separate ventrally, with chaetal fascicles with about 77-80 hooded hooks (Fig. 1A, C). Notopodial and neuropodial abdominal hooded hooks similar along body, with long anterior shaft, bulbous node, indistinct constriction, developed shoulder, short hood, posterior shaft longer than anterior one. Four rows of teeth above triangular main fang, basal row with five teeth, middle basal row with seven, middle apical row with nine and distal row with two teeth (Fig. 1D). Branchiae emerge from a ventral pore. Pygidium not seen.
Habitat. Mud with high content of organic matter (Varadero beach), in soft sediments retained into Nastier boxes (Santa Marina bay), and mud pockets between Mytilus edulis beds (Los Angeles Bay, Municipal beach).
Distribution. USA: Southern California Bight, Waianae outfall and Mamala Bay, Sand Island outfall, Hawaii; Mexico: Gulf of California and western coast of Baja California.
Remarks. Type material of Dodecaseta oraria was examined and compared with type material of Notodasus kristiani, and we found similar morphological characters in both species: lateral notopodia in the first thoracic segments, in subsequent segments located dorsally; abdominal notopodial lobes fused dorsally (Fig. 1B, F); neuropodial lobes expanded to the dorsal side ( Fig. 1A-B, E-F) and separated ventrally (Fig. 1C, G).
Based on examining type material of both species, we conclude that the specimens identified as D. oraria were juveniles exhibiting variation in chaetal counts, leading to a mis-identification. We conclude therefore, that Dodecaseta oraria is a junior synonym of Notodasus kristiani. (Green, 2002), comb. n. Figure 2 Dodecaseta fauchaldi Green, 2002: 312-313, fig. 23A Redescription. Paratype incomplete (lacking posterior end) with 44 segments, 19 mm long, 0.71 mm wide in abdomen. Color in alcohol light brown. Prostomium conical with palpode, eyespots present. Peristomium to seventh thoracic chaetiger with epithelium longitudinally striated, remaining segments smooth. Thorax with 11 chaetigers, with bilimbate capillaries in both rami first chaetiger biramous. Transition between thorax and abdomen marked by a slight reduction in the size of the first two abdominal segments (Fig 2B). Thoracic and abdominal segments biannulated, notopodia lateral in first thoracic segments, in subsequent segments located dorsally ( Fig. 2A). Lateral organs between notopodia and neuropodia throughout body, those of thoracic region closer to notopodium. In segments 12 and 13 the lateral organs protrude, just as abdominal ones. Genital pores not seen. Abdominal chaetigers 1-9 with notopodial lobes fused dorsally (Fig. 2B), each line of hooded hooks completely separated, with around 13 hooks per fascicle. Neuropodial lobes projected to dorsal region and separate ventrally (Fig. 2C), chaetal fascicles with 81 hooded hooks. Notopodial and neuropodial abdominal hooded hooks similar throughout, with long anterior shaft, bulbous node, indistinct constriction, developed shoulder, short hood, posterior shaft longer than anterior one, four rows of teeth above triangular main fang (Fig. 2D). Pygidium not examined.

Notodasus fauchaldi
Methyl green staining pattern. Peristomium and first seven chaetigers with light green, chaetiger 9-11 with moderate green, chaetiger 12th and pre-chaetal part of the 13th dark green ( Fig. 2A). Abdominal chaetiger with two longitudinal bands stained with an intense green, disrupted by neuropodial lobes and lateral organs (Fig. 2B); with a longitudinal ventral line stained with a moderate green along the body (Fig. 2C).
Habitat. Sediment characterized as sandy mud, muddy sand and sand with shell fragments, 21 to 55 m.
Distribution. Only known for the type locality, Andaman Sea, Thailand. Remarks. In the description of D. fauchaldi, Green (2002) mentioned that the species had a tessellated epithelium up to chaetiger 4 or 5, hooded hooks with three lines of small teeth over the principal fang, and the ventral abdominal segments did not stain with methyl green. However the paratype reviewed has tessellated epithelium from the peristomium to segment 7, hooded hooks with four lines of small teeth over the principal fang, and methyl green staining revealed a longitudinal abdominal line with moderate green along ventral body. It is worth mention that in Green´s description, the legend of figure 23 B, F and G has a mistake, in figure B chaetiger 9-14, must actually be 11-16: in figure F chaetiger 10-15, must actually be 12-17, and in figure G chaetiger 10-14, must be 12-16.  (Green, 2002), comb. n. Green, 2002: 249-343, fig. 24A-G Remarks. The type material of Dodecaseta eibyejacobseni could not be review because it could not be located in the Phuket Marine Biological Center (Aungtonya, per. comm.). However, the original description of Green (2002) and the figure 24 A-G, provides evidence of morphological characters that are present in the genus Notodasus. Thus, we considered that this species needs be reassigned to the genus Notodasus. Green (2002) states that she compared specimens of N. eibyejacobseni with specimens identified by Hartman (1947) as Dasybranchus lumbricoides Grube, 1878 (LACM-AHF n 2222,1451-42, n2170, 14913-F2676), from intertidal areas of southern California, lower California and other parts of western Mexico. Green found similarities between Hartman´s specimens and her own specimens from the BIOSHELF material. However, as D. lumbricoides was originally described from Pandanon Island (Philippines) there is a possibility that specimens from Thailand by Green and those from California and Mexico by Hartman do not belong to the same species as demonstrated below.

Dodecaseta eibyejacobseni
We  Hartman, 1947. Ewing (1984 reported D. lumbricoides from the northern Gulf of Mexico, Florida however, based on his description, these specimens belong in the genus Notodasus but we do not have access to specimens in order to corroborate our observations.