Reticunassa Iredale, 1936

Galindo, Lee Ann, Kool, Hugo H. & Dekker, Henk, 2017, Review of the Nassarius pauperus (Gould, 1850) complex (Nassariidae): Part 3, reinstatement of the genus Reticunassa, with the description of six new species, European Journal of Taxonomy 275, pp. 1-43 : 9-11

Genus Reticunassa Iredale, 1936

Type species

Nassa paupera Gould, 1850 by original designation ( Iredale 1936: 322).

Diagnosis

Morphological features of the protoconch are of great importance when recognizing species of Reticunassa . Several species have a multispiral protoconch, indicating a planktotrophic/planktonic larval development, resulting in a larger range of distribution. Others have a paucispiral protoconch, indicating a short, non-planktotrophic/direct larval development. All species of Reticunassa possess an unkeeled protoconch ( Fig. 2 A–B), as do other Nassariinae genera in the Atlantic Ocean ( Galindo et al. 2016). However, Reticunassa lives in sympatry with the Indo-Pacific genus Nassarius s. str., characterized by a keeled protoconch. Protoconchs of Reticunassa can be rather broad and flattened; a few are pointed. They might possess microscopic sculpture, such as spiral ridges, axial striae and minute pustules ( Fig. 2 A–B), but frequently a much higher resolution is needed to see details of this sculpture. Due to the obvious importance of protoconch characters, the identification of specimens in this genus lacking a protoconch becomes more difficult.

Species of Reticunassa have strongly or weakly developed continuous spiral cords, from 10 to 15 on the body whorl ( Fig. 2 D–F), crossing over the axial ribs. The space between these spiral cords, the intercordal surface, can be smooth, axially striated or can display a number of (occasionally extremely) fine spiral striae ( Fig. 2F ). This makes the sculpture of the intercordal surface important for identification purposes within Reticunassa . Fig. 1 A–B shows that differences on these intercordal surfaces are useful synapomorphies to separate SC1 from SC2.

Species within Reticunassa have an axially-ribbed teleoconch ( Fig. 2C ). These axial ribs may become weaker or absent on the body whorl towards the base and/or the outer lip. Ribs can be round or flat. The number of ribs differs among species. Most species develop a strong varix near the outer lip. The suture is usually deeply impressed.

The aperture is oval to sub-circular, the inside of the outer lip with a number of denticles or lirae ( Fig. 2 G–H). A columellar callus is present and varies in shape and sculpture. It can be limited to the columella or partly extend over the body whorl.

In some species, the color is variable; generally, it is cream-yellowish to orange, or white to dark brown. Banding with darker colors may also be present. Sometimes only some of the spiral cords are darker than the remaining part of the shell.

Reticunassa species are small, usually varying between 5 and 12 mm, but one is up to 16.5 mm ( R. goliath sp. nov.). Most species live in littoral to sublittoral ecosystems, only empty shells having been found in waters deeper than 260 m. Their occurrence is in the Indo-Pacific Ocean, from the Miocene to the present.

Remarks

The genus name Reticunassa was introduced to group together “species around pauperus Gould ” by Iredale (1936: 322). Cernohorsky (1984: 175) regarded Reticunassa as a synonym of the subgenus “ Hima Leach in Gray, 1852 ”, within the genus Nassarius Duméril, 1805 . However, Hima is not an available name, but an incorrect subsequent spelling of Hinia Leach in Gray, 1847 ( Gray 1847a: 269), since “ Hima ” included the same three species as in the original description of Hinia (during a period in which original descriptions only consisted of introducing new names). Nonetheless, “ Hima ” and not Hinia was listed by Adams & Adams (1853). Cossmann (1901) considered both Hinia and “ Hima ” as valid names, with “ Hima ” treated sensu Adams & Adams (1853), not Leach in Gray, 1852, and with “ type species” Nassa incrassata “Müller ”. Woodring (1928) noted the misspelling and this was reiterated by Lee (2013). Despite this, the error in the use of “ Hima ” has persisted. On the other hand, Hinia Leach in Gray, 1847 is a junior objective synonym of Tritia Risso, 1826 as they have the same type species, Buccinum reticulatum Linnaeus, 1758 , designated for both genera by Gray (1847b: 139). Molecular results of Galindo et al. (2016) indicated that species considered part of the Nassarius pauperus complex, including “ Nassarius pauper ”, form a clade distant from Buccinum reticulatum (accepted as Tritia reticulata ), the type species of Tritia (= Hinia), also shown in Fig. 1A . The only available genus group name for this pauperus clade is Reticunassa Iredale, 1936 , which is herein reinstated with full generic status.

Other species might be confused as members of the genus Reticunassa because of their morphological similarities. As it is impossible to treat all the small and ridged species, we focus on the following characters: (1) Reticunassa is an Indo-Pacific group of molluscs, not occurring in Atlantic waters ( Galindo et al. 2016); (2) species of Reticunassa lack keeled protoconchs (all species with this keel belong to the genus Nassarius ); (3) fine spiral striae or axial striae on the intercordal surface ( Fig. 2 D–F) may be an indication of at least kinship with Reticunassa ; (4) all species of Reticunassa have a distinct, elongate and slender shape ( Figs 3 , 8 ). These criteria exclude from Reticunassa any Mediterranean species, such as Tritia incrassata ( Strøm, 1768) (previously Nassarius incrassatus ), West African species, such as Tritia senegalensis ( Von Maltzan, 1884) (previously Nassarius senegalensis ) and Caribbean species, such as Phrontis candidissima (C.B. Adams, 1845) (previously Nassarius candidissimus ) ( Galindo et al. 2016). Most Indo-Pacific species, such as Nassarius vanuatuensis Kool & Galindo, 2014 , can be distinguished from Reticunassa by the protoconch features. Additionally, Kool & Galindo (2014) demonstrated a 19% genetic distance between Nassarius vanuatuensis and Reticunassa paupera . Naytia priscardi ( Bozzetti, 2006) from Madagascar is a member of the sister group of Reticunassa and exhibits great morphological similarity to some species of this genus. Molecular synapomorphies indicate that N. priscardi belongs to Naytia .

Figures

Fig. 2. Characters of Reticunassa Iredale, 1936. A–B. Protoconchs. A. R. paupera (Gould, 1850), MNHN IM-2007-31782. B. R. silvardi (Kool & Dekker, 2006). C. Suture detail of R. paupera. D. Axial striae in R. silvardi. E–F. Intercordal spirals. E. R. tringa (Souverbie, 1864). F. R. paupera. G–H. Columellar details of R. paupera. I–L. Type series of R. paupera. I–J. Lectotype, USNM 5726, length 9.1 mm, width 4.8 mm. K–L. Paralectotype, MCZ 216602, length 7.2 mm, width 3.5 mm. All scale bars = 200 µm.

Fig. 1. A. Bayesian tree based on COI sequences of species of Reticunassa. B. Bayesian tree based on 28S sequences of species of Reticunassa. C. Frequency of pairwise distance (K2P model) values among COI sequences. In gray, intra-specific variation. In black, inter-specific variation. PNG = Papua New Guinea.

Fig. 3. Shells of Reticunassa Iredale, 1936. – A–C. Possible neotype of R. paupera (Gould, 1850), MNHN IM-2007-31782, length 6.9 mm, width 3.6 mm, Vanuatu, Aore I., 15°36.6′ S, 167°10.1′ E, 10–18 m. – D–I. R. tringa (Souverbie, 1864). D–E. Hologenophore, MNHN IM-2007-31753, length 9.5 mm, width 4.6 mm. F–H. Lectotype, MHNBx 2004.TY.89.1, length 9.0 mm, width 5.0 mm. I. Protoconch of the hologenophore. – J–M. R. visayaensis sp. nov. J–L. Holotype, MNHN IM- 2007-31912, length 9.5 mm, width 4.6 mm, Philippines, Panglao I., 9°35.7′ N, 123°44.7′ E, 0–3 m. M. Protoconch. – N–Q. R. poppeorum sp. nov. N–P. Holotype, MNHN IM-2007-31779, length 9.0 mm, width 4.5 mm, Vanuatu, Aore I., 15°34.4′ S, 167°12.6′ E, 2–3 m. Q. Protoconch. Scale bars: I, M, Q = 200 µm.

Fig. 8. Shells of Reticunassa Iredale, 1936. – A–D. Reticunassa annabolteae sp. nov. A–C. Holotype, MNHN IM-2009-12843, length 11.5 mm, width5.3 mm, S Madagascar,Ambatobe, Bavarama,25°27.9′ S, 44°57.6′ E, 0–1 m. D. Protoconch. – E–H. R. goliath sp. nov. E–G. Holotype, MNHN IM-2000- 22724, length 15.5 mm, width 7.9 mm, New Caledonia, Nouméa, leg. D. Massemin, ex coll. H. Kool. H. Protoconch of paratype, MNHN IM-2000-28394. – I–L. R. intrudens sp. nov. Holotype, MNHN IM-2000-22726, length 7.9 mm, width 4.3 mm, New Caledonia, Touho, 20°44′ S, 165°14′ E, 49–59 m. L. Protoconch. – M–P. R. thailandensis sp. nov. M–O. Holotype, ZMA Moll.4.09.047, length 7.35 mm, width 3.8 mm, Thailand, Gulf of Thailand, 6°40.313′ N, 101°43.852′ E, 3–15 m. P. Protoconch. Scale bars: D, H, L, P = 200 µm.