Dactylopodola nadine, Todaro, M. Antonio, Perissinotto, Renzo & Bownes, Sarah J., 2015

Todaro, M. Antonio, Perissinotto, Renzo & Bownes, Sarah J., 2015, Two new marine Gastrotricha from the Indian Ocean coast of South Africa, Zootaxa 3905 (2), pp. 193-208 : 196-199

Dactylopodola nadine n. sp.

Figs. 1–5

ZooBank lsid:zoobank.org:act:64E36F93-DFF3-44A4-A0C5-4257310AB6BE

Type locality. South Africa, KwaZulu-Natal, Cape Vidal, iSimangaliso Wetland Park (Latitude 28°07’18” S; Longitude 32°33’43” W); about 2.5 m water depth in fine to very fine well sorted sand (mean grain size, 0.225 mm, sorting, 0.43). Values of salinity and pH of coastal waters around the time of sampling were 36.8 and 8.4, respectively, with temperatures ranging from 27 to 28° C.

Type specimens. Holotype: the 227 Μm long adult specimen shown in Figure 2 , no longer extant (International Code of Zoological Nomenclature, Articles 73.1.1 and 73.1.4), collected on 12 February 2013 (MAT legit).

Additional material examined. Four adults and one subadult specimen, all collected by the first author from the type locality, all were observed alive and are no longer extant. Four additional identified specimens were fixed in alcohol and are kept in the collection of the first author.

Ecology. Frequency of occurrence: common in sediment outside the wave-breakers along the ocean shore of the iSimangaliso Wetland Park. Abundance: numerous in sub-littoral sediment at 2.5 m where found.

Diagnosis. A Dactylopodola , up to 230 Μm in length; PhIJ at U24; head rounded, with medial bulge slightly forward, body well partitioned into head/neck/trunk/caudum regions. Sensory hairs: sparse, but more numerous on head especially its lateral surfaces, occurring in dorsolateral columns down the body length. Epidermal glands absent. Adhesive tubes: TbA, 3 per side, of different length; TbL arranged as 1+1+2; TbP, 4 per side, 2 arising distally from caudal lobes and 2 arising laterally on each side in front of these. Ventral locomotory ciliation: longitudinal field running nearly the whole length of the body, split throughout the intestinal region. Reproductive system: protandrous, simultaneous or alternating hermaphrodites; testes paired in mid-intestinal region; ovaries paired in posterior intestinal region, eggs developing toward the anterior in a more medial position. glandular caudal organ embracing the terminal portion of the intestine; frontal organ or allosperm not visible.

Etymology. The species is dedicated to the late Nadine Gordimer, South African writer, civil right activist and recipient of the 1991 Nobel Prize in Literature.

Description. The description is based mostly on the adult holotype specimen of 227 Μm in total length. Head rounded anteriorly, with a slight medial bulge forward in conjunction with the mouth; body well-delineated into head/neck/trunk/caudum regions; widths of head\neck\trunk\caudal base 30\19\28\14 µm at U10\U22\U57\U87, respectively. The Caudum consists of a relatively short, broad peduncle that ends in paired lobes that indent medially to U92. Head bears numerous sensory hairs of mixed length (6–15 µm), most occurring laterally; other sensory hairs occur in dorso-lateral columns from U14 to U86, 8–10 evenly-spaced hairs per side (8–13 µm in length). Epidermal glands not noted. Longitudinal muscles are visibly striated, which is characteristic of members of this family.

Adhesive tubes. TbA, 3 per side, inserting directly on the body surface and radiating from a more-or-less common base at U11; one shorter (8 Μm in length) inserted more medially and two longer (11–12 µm in length) projecting laterally. TbL, 5 per side, arranged as 1+1+2 at U35, U46, U61 and U66 respectively; the lengths of the first two tubes are 13–15 Μm, while the lengths of the final two tubes are progressively shorter (11–9 Μm). TbP, 4 per side, two arising distally from the caudal lobes (10–12 µm in length) and two arising laterally on each side in front of these (8–9 Μm in length).

Ventral ciliation. A longitudinal field of sparse cilia extends from U05 to U92, splitting into two bands throughout the intestinal region, U22-U80, and eventually forming separated tufts posterior to the anus; individual cilia of the bands are 10–20 µm in length.

Digestive tract. Mouth of medium size (ca. 5.5 Μm in diameter), projecting very slightly ventrally and leading progressively into a 53 Μm long pharynx measured from the anterior margin of the mouth to the pharyngeointestinal junction; pharynx muscular, roughly cylindrical (12 Μm in diameter), showing pharyngeal pores near the base, at U22; pharynx connected to sac-like intestine at pharyngeo-intestinal junction at U25; intestine straight, narrowing posteriorly, anus ventral at U80.

Reproductive tract. Protandrous, simultaneous or alternating hermaphrodites; testes occur as irregular, paired clusters of spindle-like spermatocytes in the midintestinal region, measuring 55–62 µm in length by 6–14 µm in width, with individual cells approximately 1 µm in length yielding several tens per side; ovaries are paired in the posterior intestinal region, with one or two maturing eggs attaining their development by shifting anteriorly and dorsally in a more medial position; Glandular caudal organ (about 17 Μm in length) embracing the terminal portion of the intestine; frontal organ or allosperm not seen (absent).

Variability and remarks. The body length of the other four adult specimens was very similar: mean = 476.6 µm, SD = 5.3 µm. Two specimens exhibited both testes filled with sperm and a fairly large caudal organ but with immature eggs inside; the other two specimens had no sperm in the testes and a smaller caudal organ and a large, mature egg dorsal to the posterior intestine ( Figure 4 ). Other characteristics matched those reported for the holotype. The studied subadult ( Figure 5 ) was 186 µm in TL and possessed a full set of adhesive tubes i.e., 3 TbA, 1+1+2 TbL and 4 TbP.

Taxonomic affinities. According to the recently updated key to the genus Dactylopodola , there are currently nine formally recognized (described) species worldwide ( Gilsa et al. 2014). Among these, D. nadine n. sp. is most similar to D. baltica and D. roscovita in that it also bears eye-spots. However, the new species can easily be distinguished from the latter two species by its smaller size (LT = 230 Μm vs 275 Μm and 450 Μm, respectively) and by the lower number of adhesive tubes of the anterior, lateral and posterior series (on each side: 3, 4 and 4 vs 5, 6 and 8 and 2, 9 and 12–15, respectively). In terms of body size, presence of eye spots, and number and distribution of adhesive tubes, D. nadine n. sp. is extremely similar to D. cf baltica , which was found by the first author in the Arabian Gulf ( Kuwait). The 18 rRNA gene sequence of D. cf baltica (GenBank accession code JF357650 ) has been included in several phylogenetic studies of Gastrotricha (e.g., Todaro et al. 2011a, 2012a, 2014), thus future comparisons based on molecular markers may reveal the relationships between these two taxa.

Figures

FIGURE 1. Dactylopodola nadine n. sp.. Schematic drawing. Habitus as seen from the ventral side. CO, caudal organ; ES, eye spots; Ph, pharynx; PhIJ, pharyngeo-intestinal junction; Php, pharyngeal pores; TbA, anterior adhesive tubes; TbL, lateral adhesive tubes, TbP posterior adhesive tubes; Te testes, Ov, ovaries.

FIGURE 2. Dactylopodola nadine n. sp.. Habitus of the holotype. A) Ventral side. B) Different focal plane showing the red eye spots and the ripe testes.

FIGURE 3. Dactylopodola nadine n. sp.. Holotype. A) Close-up of the ventral side of the anterior end showing the insertion of the anterior adhesive tubes and the locomotory ciliation. B) Internal anatomy of the trunk region showing the ripe testes (arrowheads), the ovaries (arrows) and the caudal organ (asterisks).

FIGURE 4. Dactylopodola nadine n. sp.. Adult specimen in a female phase. A) Habitus. B) Internal anatomy of the trunk region showing the anterior end of the intestine filled with diatom frustules and a fully developed egg (see text for additional details).

FIGURE 5. Dactylopodola nadine n. sp.. Subadult specimen. A) Habitus, ventral side. B) Different focal plane showing the red eye spots and the intestine filled with diatoms.