Prosadenoporus olympiae, Kajihara, 2020

Kajihara, Hiroshi, 2020, Three Species of Ribbon Worms (Nemertea) from Cebu, the Philippines, Species Diversity 25, pp. 251-273 : 258-265

publication ID	https://doi.org/ 10.12782/specdiv.25.251
publication LSID	lsid:zoobank.org:pub:718AB490-40FA-4C06-B862-FA64D4804FDE
persistent identifier	https://treatment.plazi.org/id/577E87FA-6337-FFE9-FC40-5BFAFE8CFD90
treatment provided by	Felipe
scientific name	Prosadenoporus olympiae
status	sp. nov.

Treatment

Order MONOSTILIFERA View in CoL Suborder EUMONOSTILIFERA Family Prosorhochmidae Bürger, 1895 Genus Prosadenoporus Bürger, 1890 Prosadenoporus olympiae sp. nov. ( Figs 7–10 View Fig View Fig View Fig View Fig ; Tables 2, 3)

Prosorhochmidae View in CoL sp.: Kajihara et al. 2007: 126; Sundberg et al. 2016: NemBar0832, 0833.

Etymology. The specific name is dedicated to Dr Minerva Olympia (University of the Philippines), a Filipino food scientist who supported my collecting trip in Cebu.

COI barcodes. KU 840159 View Materials (513 bp) from the holotype; KU 840160 View Materials (513 bp) from one of the paratypes ( PNM 4646 View Materials ) ( Sundberg et al. 2016) .

Material examined. Holotype, PNM 4645 View Materials , female, serial transverse sections of anterior end of body (24 slides), intestinal region (28 slides), posterior end of body (21 slides), and proboscis (16 slides), total 89 slides . Paratypes: PNM 4646, female, serial longitudinal section of anterior end of body (14 slides) and transverse sections of intestinal region and proboscis (28 slides), total 42 slides; PNM 4647, male, serial transverse sections, total 50 slides.

External features. Body pale brown dorsally ( Fig. 7A View Fig ), cream-white ventrally, without obvious marking; transition of dorso-ventral coloration indistinct; about 6–9 cm long in fully stretched state, 1 mm wide. Head spatula-shaped ( Fig. 7B View Fig ), wider than succeeding body region, with median depression on anterior margin from above ( Fig. 7B, C View Fig ); anterior horizontal cephalic furrow [“prosorhochmid smile” of Maslakova et al. (2005) and Maslakova and Norenburg (2008)] present ( Fig. 7D View Fig ); posterior cephalic furrow completely encircling head, mid-dorsally forming V-shape pointing backward; two pairs of eyes anterior to posterior cephalic furrow, anterior pairs are larger than the posterior pairs. Brown cephalic patch on dorsal surface of head, posteriorly continuous with dorsal body coloration, middorsally paler ( Fig. 7A View Fig ), lateral edges distinct ( Fig. 7D View Fig ), giving an impression that there is a pair of longitudinal dorsal stripes on head, depending on direction of view. Tail slightly pointed.

Body wall and musculature. Composed of ciliated epidermis, connective tissue basement membrane, outer circular muscle layer, diagonal muscle layer, and inner longitudinal muscle layer ( Fig. 8A, B View Fig ). From anterior foregut region forward, body-wall longitudinal muscle layer internally sending fibres; these separated from main longitudinal layer by thin connective tissue membrane, as well as by posterior extension of cephalic glands where they present (mainly in dorsal and dorso-lateral portions); most of these fibres contributing to proboscis insertion ( Fig. 8C View Fig ); circular muscles developed around oesophagus–foregut junction ( Fig. 8C View Fig ); precerebrally, rhynchodaeum and oesophagus surrounded by longitudinal fibres ( Fig. 8E View Fig ). Dorsoventral muscles present in posterior foregut and intestinal regions. Extracellular matrix not well developed, found around brain and in intestinal region below rhynchocoel.

Proboscis apparatus. Proboscis pore subterminal. Rhynchodaeal wall unciliated, composed of cells with acidophilic cytoplasm ( Fig. 8E View Fig ). Rhynchodaeal sphincter present just in front of proboscis insertion. Rhynchocoel extending almost to hind end of body, its wall consisting of inner longitudinal and outer circular muscle layers. Anterior proboscis composed of inner glandular epithelium, inner circular, middle longitudinal, and outer circular muscle layers; proboscis nerves 18 in holotype (15 and 19 in paratypes). Central stylet length (S) 170 µm in holotype (150 µm and 140 µm in paratypes), basis length (B) 220 µm in holotype (210 µm and 220 µm in paratypes), S/B ratio 0.78 in holotype (0.66 and 0.67 in paratypes); three accessory stylet pouches, each containing two to three accessary stylets ( Fig. 9A View Fig ).

Alimentary system. Oesophagus opening to ventral wall of rhynchodaeum, its wall composed of ciliated cells containing acidophilic cytoplasm, basally associated with longitudinal muscle fibres ( Fig. 8E View Fig ). Stomach with folded epithelium containing both acidophilic and basophilic glandular cells ( Fig. 8C, I View Fig ); pylorus less glandular, but containing both acidophilic and basophilic glandular cells, opening to dorsal wall of intestine; intestinal caecum anteriorly forked under pylorus, each branch possessing antero-lateral diverticula ( Fig. 8I View Fig ), reaching almost to brain; intestine with well developed lateral diverticula ( Fig. 9B, C View Fig ).

Blood system. Pair of cephalic vessels mid-dorsally meeting in front of brain at level of posterior ocelli, running forward latero-distally among cephalic glands, then curving posteriad at level of anterior ocelli, running beside rhynchodaeum; after passing through cerebral ring, left lateral vessel giving off single mid-dorsal vessel, that penetrates into rhynchocoel to form single vascular plug ( Fig. 9D View Fig ); no pseudometameric transverse connectives between mid-dorsal and lateral vessels.

Nervous system. Brain with outer neurilemma ( Fig. 8C View Fig ), but without inner neurilemma; neurochord cell abutting on medial side of fibrous core of ventral ganglion on each side ( Fig. 8D View Fig ). Lateral nerve cord without accessory lateral nerve; containing muscle bundle on medio-dorsal side within fibrous core ( Fig. 8B, C View Fig ).

Glandular system. Frontal organ about 200 µm long, its wall anteriorly composed of cells with acidophilic cytoplasm, laterally differentiated into strongly acidophilic epithelium ( Fig. 8G, H View Fig ); posterior wall composed of cells with neutrophilic cytoplasm, from where basophilic cephalic glands discharge ( Fig. 8F View Fig ). Cephalic glands voluminous, containing both acidophilic glandular mass and basophilic lobes ( Fig. 8E View Fig ); orange-G staining acidophilic glandular mass located dorsally and dorso-laterally, extending posteriorly to pyloric region ( Fig. 8I View Fig ); basophilic glandular lobes extending posteriorly to foregut region.

Sensory system. Anterior and posterior eyes about 100 µm and 90 µm in diameter, respectively ( Fig. 8E View Fig ). Cerebral sensory organ, about 100 µm in diameter, situated in front of brain ( Fig. 8E View Fig ); cerebral organ canal opening ventro-laterally shortly behind anterior eyes.

Excretory system. Thin-walled collecting tubules, about 6 µm in diameter, only confirmed in precerebral region, embedded in extracellular matrix around cephalic vessels ( Fig. 10A, D View Fig ), opening into frontal organ from each side ( Fig. 10A–C View Fig ). Flame cells binucleate, 14 µm long and 4–5 µm wide, with 7–8 transverse support bars ( Fig. 9E, F View Fig ).

Reproductive system. Sexes separate. Gonads arranged in single row on each side, alternating with intestinal lateral diverticula ( Fig. 9B, C View Fig ). Each ovary containing up to 10 oocytes. Of the three specimens examined, only one of the paratypes was male, which did not contain fully developed spermatozoa ( Fig. 9C View Fig ).

Remarks. Among the characters observed in the present Cebu specimens, the following features are characteristic for Prosadenoporus : i) the ‘prosorhochmid smile,’ ii) the welldeveloped, long frontal organ with laterally differentiated epithelium, iii) well-developed cephalic glands including orange-G staining acidophilic glands, iv) recurved cephalic vascular loop, and v) excretory system with binucleate terminal flame cells reinforced by transverse support bars ( Moore and Gibson 1988; Maslakova and Norenburg 2008).

In addition to nine species considered as valid in Maslakova and Norenburg’s (2008) taxonomic revision of Prosadenoporus , there are four nominal species that were earlier deemed to be invalid by Moore and Gibson (1988) ( Table 2). Prosadenoporus olympiae can be differentiated from all the 13 congeners by the characters listed in Table 2 except P. buergeri Punnett, 1903 from Laccadive, for which some diagnostic morphological characters—such as the presence or absence of the neurochord cell and the number of accessory-stylet pouches—are unknown. Furthermore, the number of the proboscis nerves reported for P. buergeri , being 19 ( Punnett 1903), is the same as that observed in one of the paratypes (PNM 4646) of P. olympiae . However, these two are different in the body colour in life, which is pinkish white in P. buergeri but dorsally pale brown and ventrally cream white in P. olympiae .

Prosadenoporus olympiae showed 0.012 intraspecific variation between two specimens sequenced (holotype and one diagonal) based on 513 bp partial sequences of the mitochondrial COI gene along with their locality and accession number.

of the paratypes) in terms of both uncorrected p -distance and K2P based on 513-bp COI sequences. Among the five species for which COI barcodes are available in public databases, P. olympiae is most closely related to P. floridensis Maslakova and Norenburg, 2008 , differing by 0.097 –0.105 in p- distance and 0.122 –0.134 in K2P distance ( Table 3).

In the field, the specimens were found between crevices of exposed rocks during ebb tide. When placed in a plastic case half filled with seawater, they crawled upward escaping from the seawater. These observations suggest P. olympiae prefers upper intertidal zone, if not semi-terrestrial as in some congeners.