Gnathostomula cf. salotae Sterrer, 1991

Sterrer, Wolfgang, 2006, Gnathostomulida from the Otago Peninsula, southern New Zealand, Zootaxa 1172, pp. 1-19 : 13-18

Gnathostomula cf. salotae Sterrer, 1991

(Fig. 7.1–7.8)

Material Six adults, one juvenile from samples SI 10 and SI 16.

Distribution Tonga ( Sterrer 1991a). Description

Organization and behavior. Adults are small and plump, ranging from 300 to 400 µm (mean 352.50 µm) in length, and 55 to 70 µm in width (66.25 µm) at U 53.08 (body index 5.43). There is a short tail region. Rostrum 50.75 µm long and 52.50 µm wide at U 11.46 (index 0.99). Of the sensorium, apicalia were to 15 µm long, frontalia to 35 µm, and lateralia to 40 µm.

Digestive tract. The basal plate is 7.33 µm long and 20.00 µm wide (index 0.37). Its medio­rostral margin is finely dentate, with a stronger, medially pointing tooth at the anterior tip. The lateral wings may be curved rostrally. Jaws are 15.60 µm long, with 6 teeth in the dorsal, 8 in the median, and 11 teeth in the ventral row. The crescent­shaped jugum is 7.33 µm long and 16.00 µm wide.

Male system. The paired, follicular testes extend from U 56.67 to U 80.42. The penis extends from U 66.46 to U 82.53. It is 39–60 µm (50.60 µm) long but only 2.8 µm wide. Sperm is tiny, 2 µm in diameter, with a round to bean­shaped dense core that is often surrounded by a lucid coating.

Female system. The largest egg, about 50 µm in diameter, extends from U 41.7 to U 56.7. The bursa copulatrix is immediately behind it, measuring 35 µm in length and 15 µm in width.

Discussion

Gnathostomula is the most widespread and eurytopic of all genera, occurring from arctic to tropical waters, and from the intertidal to 400 meters depth. It is also taxonomically the most elusive genus, combining a paucity of species­specific characters (of which most ­ such as jaw teeth — are at the lower limit of light microscopy) with high intra­specific variability ( Sterrer 2001) — each specimen looks just a little different. Of 20 currently valid species (plus several unidentified spp., Sterrer 2001), one ( G. maorica Sterrer, 1991 ) was described from New Zealand, but differs from Portobello specimens by its much greater body length (450–730 µm) and much shorter penis stylet (26–33 µm). Penis stylet length also rules out G. armata Riedl, 1971 (65 µm), G. axi Kirsteuer, 1964 (65 µm), G. brunidens Riedl, 1971 (61–68 µm), G. costata Ehlers & Ehlers, 1973 (17 µm), G. jenneri Riedl, 1971 (( 61–68 µm), G. karlingi Riedl, 1971 (32 µm), G. maldivarum Gerlach, 1958 (18 µm), G. mediocristata Riedl, 1971 (80µm), G. microstyla Riedl, 1971 (18–35 µm), G. murmanica Mamkaev, 1961 (92–96 µm), G. nigrostoma Riedl, 1971 (37 µm) and G. uncinata Sterrer, 1998 (35 µm). Of the remaining species, G. salotae (described by Sterrer 1991 from Tonga) is in best agreement with most features of the Portobello specimens, with one exception: the round sperm, which are otherwise only reliably reported from G. jenneri Riedl, 1991 .

Suborder Conophoralia Sterrer, 1972

Family Austrognathiidae Sterrer, 1971

Austrognatharia australis n. sp.

(Fig.8.1–8.7, 9.1–9.4)

Type material Holotype one adult from sample SI 16, in squeeze preparation, NZNM W.1536. Further material: One juvenile from the same sample.

Etymology This is the southernmost species of the genus.

Diagnosis

Slender Austrognatharia (body index 13.63) with slender rostrum (index 1.15) and abundant adhesive papillae in the tail region. Basal plate 7.00 µm long, 26.00 µm wide (index 0.27). Jaws 26.50 µm long, with one tooth in dorsal and 3.00 teeth in ventral row. Conuli to 23 µm long and 7 µm wide (index 3.54), with inconspicuous cingulum; hat flat, taking up less than 20% of total conulus length.

Description:

Organization and behavior. The single adult had a slender body (length 1090 µm, width 80 µm at U 32.1; body index 13.63). The rostrum is slender (78 µm long, 68 µm wide at U 4.3; rostrum index 1.15). The tail region ends in a blunt cone which contains many adhesive papillae composed of bundles of rhabdoids. Of the sensorium, apicalia 1 were 20 µm long, frontalia 51 µm, and ventralia 45 µm. Animals glide slowly, and occasionally perform peristaltic contractions.

Digestive tract. The elongated mouth opening is surrounded by prepharyngeal glands. The somewhat goggle­shaped basal plate is 7.00 µm long and 26.00 µm wide (index 0.27). Its rostral edge lacks a median lobe whereas the lateral lobes are comparatively prominent. There are 11 caudo­dorsally pointing teeth of which the median tooth and the lateral­most pair are much larger than the rest. Jaws are 26.50 µm long, with a strong terminal tooth, a single, thin but broadly based dorsal tooth, and 3 delicate, equal teeth in the ventral row. The cauda is 7 µm long.

Male system. The unpaired, dorsal testis extends from U 80.7 to U 87.2 where it empties into a glandular penis. The male pore is located ventrally at U 95. The testis contained 17 conuli of which two had twin cones. The largest conuli 23 µm long and 7 µm wide (conulus index 3.54). Conuli are slender, with a flat hat that takes up no more than 20% of total conulus length, and is no wider than the cone. The cingulum beneath the hat is inconspicuous, and sometimes curved upwards.

Female system. The single specimen did not have a mature egg. Located between U 75.2 and U 80.7, the soft, globular bursa contained three fused conuli, with their cones in a grainy condition.

Discussion

Jaws with only 1–2 teeth in the dorsal row, and a basal plate with flat to non­existing rostral lobes characterize the genus Austrognatharia Sterrer, 1970 (emend. Sterrer, 1991). Of 10 species known in this genus, the following can be excluded from further comparison because of their greatly differing conuli dimensions and proportions: A. sterreri (Kirsteuer, 1969) , A. strunki Farris, 1973 ; A. atraclava Ehlers & Ehlers, 1973 ; A. homunculus Sterrer, 1991 ; A. pecten Sterrer, 1991 ; A. mooreensis Sterrer, 1991 ; A. stirialis Sterrer, 1998 ; and A. medusifera Sterrer, 1998 . Of the remaining two species, A. kirsteueri Sterrer, 1970 has considerably shorter jaws (21.7 µm) and a smaller basal plate (6.4 µm by 20.1 µm) as well as shorter (18.25 µm) and plumper conuli (index 2.36) than A. australis n. sp. Conversely, these dimensions are much greater in A. boadeni Sterrer, 1971 (jaw length 30–31 µm; basal plate 8–9 µm long by 28–30 µm wide), which has also longer (to 38 µm) and more slender conuli (index 4.5) than A. australis n. sp.

Acknowledgments

I am grateful to my friends John and Marge Wells for their hospitality in Wellington, to Bev Dickson for making our stay at the Portobello Marine Laboratory so pleasant and productive, and to Susan K. Young for help with sample collecting. This paper has been prepared with support from NSF Grant No. DEB­0118804.