Doriopsilla aroni, Maniei & Wägele, 2024

Maniei, Fatemeh & Wägele, Heike, 2024, Dendrodorididae (Heterobranchia, Nudibranchia) from Persian Gulf with a description of a new species of Doriopsilla and remarks on the family, European Journal of Taxonomy 943 (1), pp. 179-217 : 194-198

Doriopsilla aroni sp. nov.

urn:lsid:zoobank.org:act:9EE37DDA-5EBD-4D95-A124-44495753DB69

Figs 2F , 7–9

Diagnosis

Size up to 40 mm or slightly longer. Coloration cream yellow to deep orange or vermilion; a tiny white line along the rim of the gill pocket present. Dorsal notum covered by tubercles, in which many spicules intrude. Spicules also forming a thick layer around visceral cavity. Oral tentacles fused. Five gill plumes present; small gill glands present at their base. Anus eccentric. Pyloric gland present. Prostate gland forming a large mass. Penial hooks arranged in longitudinal lines in the proximal part of eversible penis.

Etymology

Doriopsilla aroni sp. nov. is named after the first author’s young son, Aron.

Material examined

Holotype

IRAN • 38 mm; Bandar Lengeh ; 26°33′29″ N, 54°52′50″ E; intertidal; 14 Feb. 2015; Fatemeh Maniei leg.; ZMH 141485 .

Paratypes

IRAN • 3 specs; same data as for holotype; ZMH 141486 • 1 spec.; same data as for holotype; ZMH 141487 histological slide series .

Description

GENERAL APPEARANCE. Body length of preserved animals: holotype 38 mm, paratypes 20–40 mm. Colour of living animals varying from cream yellow to deep orange or vermilion. White pigmentation in the form of dots or lines on notum or rhinophores absent ( Fig. 2F ), except for a thin white line around the rim of the gill pocket. Body oval. Notum covered with rounded spiculate tubercles of approximately the same size, becoming smaller only along mantle margin; their colour sometimes a little paler than the notum. Hyponotum nearly translucent or cream in colour, stiffened by a network of spicules ( Fig. 2F ). Cylindrical rhinophores with 11–13 lamellae, same colour as tubercles but with a brighter apex. Five gill plumes (two pointing forward and three backward) located in a gill pocket. Anus eccentric to the left of the gill. Oral tentacles small and fused. Fleshy muscular foot rounded anteriorly and more acute posteriorly.

HISTOLOGY. The preserved specimen ZMH 141487 used for histological examination had a length of 40 mm. The slide series is deposited in the collection of the LIB, Zoological Museum Hamburg.

INTEGUMENT. Dorsal notum epithelium with many single subepithelial glandular cells staining red to violet and glandular follicles composed of several large bluish gland cells. These glandular follicles surrounded by muscle layers ( Fig. 7A ). Spicules mainly present in the tubercles, around the visceral cavity ( Fig. 7A–B ), and in the foot.

DIGESTIVE SYSTEM. A schematic outline of the digestive tract is given in Fig. 8A . Mouth opening non glandular. Proximal oral tube highly folded with few epithelial mucus glands staining reddish. Subsequent part widening, with increasing number of epithelial acid mucus cells. Distal part of oral tube widening considerably, surrounded by muscle fibres and dorsally with subepithelial glands staining violet. Gradual transition into pharynx. Pharynx oval, surrounded by muscle fibres and with a slightly folded, glandular epithelium. Subepithelial glands reaching into muscle layer. No cuticle observed. Transition of pharynx into oesophagus marked by the location of the ganglionic nervous system ( Fig. 7C ). At this transition, two lateral retractor muscles attached. Salivary glands absent. Tubular oesophagus with Y-shaped interior lumen and no glandular epithelium ( Fig. 7D ), subsequently entering a highly muscular portion without Y-shaped lumen ( Fig. 7E ) and with few subepithelial glands, staining pale blue. Two small retractor muscles arising from this muscular part. After the muscular part oesophagus transiting into a small tube before entering the stomach. Stomach completely embedded in digestive gland; characterised by folded and ciliated epithelium. Transition into intestine with folds, but without a distinct typhlosole ( Fig. 7D– E ). Pyloric gland opening immediately after transition of stomach into intestine; internally folded but without glandular cells and filled with stomach contents ( Fig. 7D ). Interior lining of the intestine highly folded and ciliated, especially in the anal papilla. Intestine surrounded by a muscular layer throughout its course ( Fig. 7F ). Besides the oral gland layer, no ptyaline or salivary glands present. No caecum found.

REPRODUCTIVE SYSTEM. A schematic outline of the genital system is provided in Fig. 8B . Gonad in mature phase with sperm and eggs formed in the same follicles. A distinct ampulla not found. Vas deferens leading into strongly lobulated, bulky prostate gland ( Fig. 9A ), showing pristine glandular areas, with small cells and large nuclei, other areas with elongate cells and vesicles with blue stained droplets, as well as some areas where the prostatic material was already exuded. Distal vas deferens (ejaculatory duct) coiled, lying in muscular sheath ( Fig. 9B ); penis long, inverted, with hooked spines only in the proximal part, which lies in the wider part of the penial sheath. Spines arranged in longitudinal lines along the proximal penis. Size of spines ca 200 µm, some of them smaller and thinner in the region where spines start. Distal part without spines ( Figs 8B–C , 9C ). Bursa copulatrix stalked and filled with decaying sperm and prostatic material; epithelium thin and characterised by apocrine secreting cells ( Fig. 9E ). Muscular receptaculum seminis empty, indicating a recent fertilisation process ( Fig. 9F ). Fertilisation chamber with a few eggs ( Fig. 9D ). Female glands well developed with typical three glandular parts staining violet or reddish; opening into a joint non glandular vestibulum with vas deferens and the vaginal duct.

NERVOUS SYSTEM. Statocyst between cerebropleural and pedal ganglia, with many otoconia ( Fig. 7C ).

CIRCULATORY AND EXCRETORY SYSTEM. Blood gland large, surrounding the central nervous system and also the anterior part of the oesophagus. Syrinx highly folded and rather small (compared to species of Dendrodoris ). Kidney thin, covering gonad and digestive gland.

Additional features

Body cavity surrounded by a thick muscle layer, especially in the hind part of the body. One thick gill retractor starting close to gills and running ventrally towards anterior part of body. Small gill glands with pale bluish cells present at the base of gills, opening into gill pocket. A few unidentified parasites lying in the notal tissue, as well as close to the oral tube ( Fig. 7B ).

Figures

Fig. 2. External appearance of live animals. A. Dorsal view of Dendrodoris nigra (W. Stimpson, 1855) with black mantle and yellow spots. B. Dendrodoris nigra with black mantle, white spots, and a thick distinct red submarginal band; inset shows ventral view. C. Dendrodoris fumata (Rüppell & Leuckart, 1830) black form. D. Dendrodoris fumata red form. E. Dendrodoris fumata pale brown form. F. Dorsal view of Doriopsilla aroni sp. nov.; inset shows ventral view.

Fig. 7. Histological sections of Doriopsilla aroni sp. nov. A. Cross section of tubercles containing spicules. B. Cross section of the mantle with spicules; two parasites can be seen in the notum tissue. C. Cross section of oesophagus and part of cerebropleural/pedal ganglia with statocyst. D. Cross section of oesophagus and opening of intestine into stomach with pyloric gland. E. Cross section of muscular oesophagus. F. Cross section of highly ciliated and muscular intestine. Abbreviations: Cplg = Cerebropleural ganglion; G = Glandular vesicle containing mucopolysaccharides (stained in violet); GF = Glandular follicles surrounded by muscle layers; In = Intestine; Oe = Oesophagus; P = Parasite; Peg = Pedal ganglion; Pgl = Pyloric gland; Sp = Spicules; St = Statocyst with otoconia.

Fig. 8. Schematic outline of digestive and genital system of Doriopsilla aroni sp. nov. A. Digestive system. B. Genital system and separate schematic outline of inverted penis. C. Penial spines of different shapes. Abbreviations: Bc = Bursa copulatrix; Cplg = Cerebropleural ganglion; In = Intestine; MO = Mouth opening; MP = Muscular portion of oesophagus; Ngl = Nidamental gland; Oe = Oesophagus; Ov = Oviduct; P = Penis; Peg = Pedal ganglion; Ph = Pharynx; Pgl = Pyloric gland; Pr = Prostate gland; PS = Penial sheath; Rem = Retractor muscle; Rs = Receptaculum seminis; Sp = Spine; Va = Vagina; Vd = Vas deferens; Ves = Vestibulum.

Fig. 9. Genital system of Doriopsilla aroni sp. nov. A. Highly lobulated prostate gland. B. Transition of penis into penial sheath. C. Detail of penis showing the area, where spines start; note the various shapes. D. Fertilisation chamber containing a few eggs. E. Bursa copulatrix. F. Empty receptaculum seminis in vicinity of bursa copulatrix. Abbreviations: Bc = Bursa copulatrix; Pr = Prostate gland; Rs = Receptaculum seminis; Va = Vaginal duct; Vd = Vas deferens.