Tetraneuronemertes lovgreni, Sundberg & Gibson & Strand, 2007

Sundberg, Per, Gibson, Ray & Strand, Malin, 2007, Swedish nemerteans (phylum Nemertea), with description of a new hoplonemertean genus and species, Journal of Natural History 41 (37 - 40), pp. 2287-2299 : 2293-2298

publication ID	https://doi.org/ 10.1080/00222930701589939
persistent identifier	https://treatment.plazi.org/id/D57187C9-FF9C-FFBC-70C0-B1ADFE88B9A9
treatment provided by	Felipe
scientific name	Tetraneuronemertes lovgreni
status	sp. nov.

Treatment

Tetraneuronemertes lovgreni View in CoL sp. n.

( Figures 3–5 View Figure 3 View Figure 4 View Figure 5 )

Hoplonemertean sp. 2 Strand and Sundberg 2005b, Table 1, Figures 1 View Figure 1 , 2 View Figure 2 .

Type locality

Dredged from 33 m depth from a bottom consisting mainly of mixed coal slag and clinker, Humlesäcken (58 ° 169050N, 11 ° 249520E), 13 November 2002, two specimens.

Holotype

Female, series of transverse sections, deposited at the Göteborg Natural History Museum ( GNM Nemertea 82), 18S rRNA sequences of the holotype are deposited with GenBank (accession number AY928350 View Materials ).

Etymology

The species is named after Olof Lövgren who found the specimens on which the description is based.

External features ( Figure 3 View Figure 3 )

Small, slender, body more or less uniform width throughout, ending in a bluntly rounded tail. When moving, head was slightly wider than remainder of body, tapering anteriorly to end in a shallow anterior notch. Body translucent white, intestine appearing grey with obvious lateral diverticula alternating with the gonads. Rhynchocoel, visible in life, extends for about 50% of body length. Four small eyes arranged to form the corners of a trapezoid shape; anterior eyes larger and more closely set together than the posterior.

Internal features ( Figures 4 View Figure 4 , 5 View Figure 5 )

Body wall, musculature and parenchyma. Tall epidermis a more or less uniform appearance throughout body and presents no unusual features. Body-wall musculature moderately strongly developed consisting of outer circular and inner longitudinal layers; no diagonal layer. At the rear of the brain dorsal cephalic gland lobes separate longitudinal layer into inner and outer zones. Inner fibres running close around brain lobes and then interiorly contribute to pre-cerebral septum, other fibres radiating inwards from the undivided ventral and lateral longitudinal musculature forming remainder of septum; this is thus a mixed-type septum. No evidence of dorsoventral muscle bundles could be found in the intestinal region. Connective tissues moderately developed throughout body.

Proboscis apparatus. Rhynchodaeum mostly thin-walled but becomes thicker after oesophagus emerging from its ventral wall, close in front of the brain. Rhynchocoel extends for about 50% of body length. Thin wall with separate outer circular and inner longitudinal muscle layers. Proboscis comparatively slender and divided into the typical three regions. Measured central stylet 50 Mm long, basis 47 Mm long and 23 Mm in maximum diameter. Basis with shallow but obvious ‘‘waist’’ about half way along its length and posteriorly rounded. Two accessory stylet pouches, each containing three or four accessory stylets. So far as could be determined, eight small proboscis nerves.

Alimentary system. Oesophagus opens from ventral wall of rhynchodaeum close in front of brain. Moderately thick-walled and ciliated, but lacking gland cells. As it passes below the brain it begins to expand and, close behind ventral cerebral commissure, merges into anterior portion of stomach; this short region is characterized by possessing only acidophilic gland cells, whereas main stomach wall, which is deeply folded, also possesses basophilic glands. Main stomach about half body width in diameter. Posteriorly, stomach gradually becomes reduced in size as it merges into pyloric region of foregut. Long intestinal caecum projects interiorly below the pylorus as far forward as stomach. Caecum with neither anterior pouches nor lateral diverticula. Intestine itself bears fairly deep lateral diverticula alternating with the gonads.

Nervous system. Dorsal and ventral brain lobes of similar size, with dorsal and ventral cerebral commissures located in the same plane. Longitudinal nerve cords with single fibrous core; no evidence of either accessory lateral nerves or neurochords. An unusual feature of the nervous system is a pair of large dorsolateral nerves in the foregut region, similar in cross-sectional size to the main ventrolateral nerve cords. These additional nerves branch off from the ventrolateral nerve cords close behind the brain, pass back alongside the rhynchocoel, and then rejoin the main nerve cords in the pyloric region of the foregut.

Blood vascular system. Blood system difficult to distinguish, but for most of body length appears to consist of the typical hoplonemertean arrangement of three longitudinal vessels, with no evidence of pseudometameric transverse connectives. In head a pair of cephalic vessels continues through cerebral ring, each forming a small ventrolateral vascular plug close behind ventral cerebral commissure. Posterior to these two plugs the pair of vessels appears to join to give rise to the single mid-dorsal blood vessel, continuing for remaining body length.

Excretory system. No certain evidence of excretory tubules, although small, dark-staining structures located dorsoventrally in foregut region of body may represent slender collecting tubules. Neither efferent ducts nor nephridiopores could be traced.

Sense organs. Well-developed frontal organ consisting of a ciliated pit opening into cephalic notch at tip of head, just above proboscis pore. Cephalic glands well developed and exhibit a typical vacuolate appearance. In anterior half of head, glands are dispersed, with longitudinal muscle fibres running between them, but as the brain is approached they become concentrated into two glandular lobules, one dorsal and one ventral. Ventral lobe terminates just in front of where oesophagus emerges from ventral wall of rhynchodaeum, a short distance in front of ventral cerebral commissure, but dorsal lobe passing back over the brain, where it divides body--wall longitudinal muscle layer into inner and outer layers before ending close behind brain; glands appear to discharge via frontal organ, and no evidence of improvised ducts could be distinguished. Ciliated cerebral canals open from extremely short and shallow cephalic furrows situated about 70 Mm behind tip of head. Cerebral sensory organs are small and simple and do not reach brain.

Reproductive system. The specimen examined histologically is a female with ovaries between and alternating with the intestinal diverticula along the sides of the body. Each ovary contains one to a few large eggs possessing distinct nuclei.

Systematic discussion. The presence of four longitudinal nerve cords in the foregut region of the body ( Figure 5 View Figure 5 ) is considered a species unique character. See also systematic discussion for the genus.