Species of Lensia ( Cnidaria : Hydrozoa : Siphonophorae ) from southeastern Brazilian waters

The siphonophores of the Brazilian coast are poorly studied, despite their abundance and ecological importance. Lensia is the most diverse genus within Siphonophora, with twenty-six valid species. A total of twenty species of Lensia are recorded for South American marine waters. This study presents morphological descriptions and an identification key to the species of Lensia that were collected in two oceanographic campaigns throughout the southeastern Brazilian coast. A total of sixty-one specimens were photographed, described, schematized and measured, and fifteen species of Lensia were identified.

Siphonophores are a group of cnidarians belonging to the class Hydrozoa (subphylum Medusozoa).They are exclusively marine and mostly holoplanktonic organisms (ToTTon 1965).Their body structure, consisting of polypoid and medusoid zooids with varied functions, is interpreted by many authors as a sophisticated version of a colonial life style (Haeckel 1869, Mackie 1963).
Although often overlooked or underestimated in macroplankton samplings, siphonophores are amongst the most abundant and efficient carnivorous animals in the oceans (Haddock & dunn 2005).In view of their abundance, these organisms have great ecological importance (PugH 1999), and may affect, by predation, the supply of copepods, which also feeds economically important fish species (Pagès et al. 2001).
Siphonophores have been traditionally divided into three groups: Cystonectae, characterized by the presence of a pneumatophore and absence of nectophores; Physonectae, characterized by the presence of both a pneumatophore and nectophores; and Calycophorae, characterized by the presence of nectophores and absence of a pneumatophore (ToTTon 1965, PugH 1999, MaPsTone 2014).
The majority of known siphonophore species form small rocket-shaped colonies, rarely exceeding 20 cm in total length (grossMann et al. 2014).Most of these species belong to the calycophoran family Diphyidae Quoy & Gaimard, 1827 (MaPsTone & scHucHerT 2015).Lensia Totton, 1932, composed of small diphyid calycophoran siphonophores, is one of the most species-rich genera within the Siphonophora.These diphyid siphonophores have a complex life cycle, composed of multiple different life stages that share few morphological similarities (grossMann et al. 2014).
The largest life stage, which may also be the most durable, is the polygastric stage, usually composed of two large zooids, the anterior and the posterior nectophores, and a siphosomal stem containing many cormidia.The cormidia, composed of gonads, a stomach (gastrozooid) and tentacle, and a protective shield (bract), are released from the posterior end of the polygastric stage in several diphyid species, to form free-living sexual units, called "eudoxids".In calycophoran siphonophores, identification is commonly, and sometimes exclusively, associated with the morphology of the anterior nectophore of the polygastric stage (grossMann et al. 2014).
The species of the genus Lensia belong to the suborder Calycophorae and the family Diphyidae, which contains the greatest number of siphonophore species.This family presents a polygastric stage usually including two serially arranged nectophores (kirkPaTrick & PugH 1984).The nectophores are asexual medusoid structures, which contain a muscular structure known as the nectosac, and an opening known as the ostium.Strong contractions of the nectosac force water out of the nectophore, through the ostium, and propels the colony forwards, or in some cases the ostium is directed forwards to allow backward swimming (Mackie 1964).
The anterior nectophore presents a somatocyst, while the posterior nectophore lacks this structure.The somatocyst usually contains oil droplets that may help controlling the flotation of the colony, and also act as a food store.The nectosac occupies most of the nectophore's length, allowing for fast and active swimming (kirkPaTrick & PugH 1984).Additionally, the siphosomal stem can be totally withdrawn into an external hollowed-out chamber known as hydroecium (MaPsTone 2009(MaPsTone , 2014)), which is usually reduced in the anterior nectophore (PugH 1999) (Fig. 1).
Lensia includes the Calycophorae, whose anterior nectophores of the polygastric stage are pentagonal, and may contain up to 15 or more longitudinal ridges.The somatocyst is usually small.The hydroecium is shallow and bordered by a short and divided mouth plate.The radial canals do not possess commissures.The nectosac almost reaches the top of the nectophore (alvariño & WojTan 1984).
Siphonophores are poorly studied due to the extreme difficulty in collecting and preserving specimens, as most of them are found only in deep waters and are very fragile (dunn et al. 2005).According to oliveira et al. ( 2016), twenty species of Lensia are found along the South American coast, fifteen of them occurring in Southeastern and Southern Brazilian waters (nisHiyaMa et al. 2016).In this study, we discuss these species of Lensia obtained from two oceanographic campaigns made throughout the southwestern Atlantic Ocean.

MATERIAL AND METHODS
The studied specimens were obtained from two oceanographic campaigns made along the southeastern Brazilian coast (FINEP III and Habitats Project).The FINEP III campaign was conducted between Cabo Frio, Rio de Janeiro (23°S) and the south region of Santa Marta Grande Cape, Santa Catarina (29°S), in May 1976.The Habitats Project campaign was conducted in the Campos Basin, Rio de Janeiro (located between 24°S and 20.5°S), from February 2009 to February 2010 (Bonecker et al. 2014).Specimens were conserved in 4% formaldehyde solution and dyed with fuchsine.The anterior nectophores of the analyzed specimens were placed on a hollowed-out microscope slide, and were photographed using a stereomicroscope with digital camera attached (Figs.[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].After photographs were taken, the specimens were identified using identification keys and descriptions available (e.g., ToTTon 1965, kirkPaTrick & PugH 1984, Pagès & gili 1992, PugH 1999).Morphological descriptions of the anterior nectophores of the identified species were made, as well as drawings of the best-preserved specimens using the Adobe Illustrator software .Additionally, all examined specimens were measured using the AxioVision software (Table 1).
Table 1.Measure intervals (mm) of the fifteen species of Lensia examined (numbers in parenthesis refer to the quantity of specimens measured).(ANH) Anterior nectophore height, (ANW) anterior nectophore width, (NH) nectosac height, (OW) ostium width, (SL) somatocyst length.The posterior nectophores, when present, are fragile and,are smaller than the anterior nectophores, being truncated proximally, with a rounded and undivided mouth plate, and no ostial teeth (Bouillon et al. 2006).The bracts, present in the eudoxids, are structurally simple and helmet-shaped.A special nectophore is absent and the gonophores are truncated at the anterior region, with a small and rounded mouth plate (ToTTon 1965).

Glossary of terminology
Anterior nectophore: Upper nectophore in diphyid calycophorans with two serially arranged nectophores.
Bract: Asexual zooid present in most calycophorans, which functions as a shield for the other zooids.
Cormidium: Group of serially repeated zooids on the siphosomal stem.It is usually composed of gonads, gastrozooids, tentacles and bracts.
Distal lamella: Slim extension from the ostial region of the anterior and posterior nectophores in several diphyid calycophorans.It is usually divided into two lappets in the anterior nectophore.Also designated as "mouth plate" in diphyid calycophorans.
Eudoxid: Free-living sexual stage in the life cycle of most calycophorans.It originates as a cormidium detached from the posterior end of the siphosomal stem.It is composed of bract, gastrozooid, and gonophore.
Gastrozooid: Asexual zooid responsible for feeding, present in the cormidia and the eudoxids.
Hydroecium: Hollowed out external cavity on the proximal or lower surface of a calycophoran nectophore.It houses the siphosomal stem.
Longitudinal ridge: Line that runs along the nectophore, usually from its apex to its base.
Lower-basal facet: Lower surface of the anterior nectophore.
Nectophore: Asexual medusoid structure responsible for swimming, containing the muscular nectosac for propulsion.
Nectosac: Internal cavity of the nectophore with an opening (ostium) and muscular walls.It contracts rhythmically to pump out water for colony propulsion.
Ostium: Distal opening of the nectosac.
Pneumatophore: Anterior gas-filled structure in physonect and cystonect siphonophores, responsible for the flotation of the colony.
Polygastric stage: Dominant asexual stage in the life cycle of a siphonophore.Also known as the colony.
Radial canal: Gastrovascular canal present in the nectosac.
Siphosomal stem: Region of the colony bearing the cormidia.
Somatocyst: Structure associated with the gastrovascular system, which may aid in flotation and nutrient storage.
Special nectophore: Asexual nectophore present in eudoxids of some calycophorans, with propulsive function.
Tentacle: Structure arising from the gastrozooid, responsible for prey capture.
Zooid: Unit homologous to a solitary, free-living animal, which forms the siphonophore colony.It may be of polypoid or medusoid origin.

TAXONOMY
A total of sixty one specimens were analyzed, and fifteen species of Lensia from Brazilian waters were identified.All identified species had been previously recorded for the southwestern Atlantic Ocean (nisHiyaMa et al. 2016).The morphological descriptions were consistent with the literature, with the exception of some specimens that were damaged or poorly preserved.In those cases, some structures could not be easily distinguished and were not described or measured.For some species, there was only one specimen available, which was damaged, making the observation of some structures difficult.Most species were easily identified by the presence of remarkable structures, such as the varied shape of the somatocyst, the number of longitudinal ridges and the position of the hydroecium and the somatocyst in relation to the ostium.Species descriptions follow the terminology used by Haddock et al. (2005) and MaPsTone (2009  Description.Anterior nectophore: Laterally compressed and measures 2.38 mm in height and 1.33 mm in width.The apex is slightly twisted and obtuse.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 1/2 the width of the nectophore.The mouth plates are small, divided and rounded.The longitudinal ridges are barely visible.The lower-basal facet is bent towards the lower facet of the nectophore at an angle of approximately 45°.The hydroecium is very shallow.The somatocyst is short, ovate, bent slightly toward the lower nectophore surface and measures approximately 1/4 the height of the nectophore. Examined material.Brazil, Rio de Janeiro: Cabo Frio (collected at 5:45 a.m., 2721 m depth, 24°24.8'S-41°07.5'W),one specimen preserved in 4% formaldehyde, 05/09/76, collected by FINEP III campaign, station 1701 leg., LabGel (UFABC); Cabo Frio (collected at 1:00 a.m., 1120 m depth, 23°55.5'S-41°43.0'W),three specimens preserved in 4% formaldehyde, 05/10/76, collected by FINEP III campaign, station 1708 leg., ZUEC CNI 46, Museu de Zoologia "Prof.Dr. Adão José Cardoso" (UNICAMP).Santa Catarina: Cabo de Santa Marta Grande (collected at 5:00 a.m., 64 m depth, 25°13.6'S-46°42.2'W),two specimens preserved in 4% formaldehyde, 05/19/76, collected by FINEP III campaign, station 1770 leg., LabGel (UFABC).
Remarks.This species is recognized by its small size, and by the apical end, which is twisted in preserved specimens (ToTTon 1965).
Lensia conoidea (Keferstein & Ehlers, 1860)  Description.Anterior Nectophore: Large, with five complete longitudinal ridges converging at the apex.It measures 6.81 mm in height and 3.52 mm in width.The basal end of the upper ridge forms a tooth extending below the level of the ostium.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 3/5 the width of the nectophore.The somatocyst is spindle-shaped, measuring approximately 1/2 the height of the nectophore, reaching the midpoint of the same.The mouth plate is shallow but broad.The hydroecium is basal and very shallow.
Remarks.This species is distinguished by its large somatocyst, measuring half the height of the nectophore, and its anterior nectophore containing five longitudinal ridges (ToTTon 1965).Totton, 1941 Figs. 4, 19 Eudoxia macra Totton, 1954:   Lensia grimaldii Leloup, 1933 Figs. 6, 21 Lensia multicristata forme grimaldii Leloup, 1933: 37. Description.Anterior Nectophore: With a variable number of longitudinal ridges.Only the two lower ridges are complete, and only five ridges reach the apex.The upper-lateral ridges bend towards the upper surface at their basal ends and bifurcate, forming the velar ridge.It measures 7.43 mm in height and 3.71 mm in width.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 7/10 the width of the nectophore.The hydroecium is deep, opens as a deep cleft in the narrow lower facet, and this opening extends above the level of the ostium.The somatocyst is club-shaped, has a small stalk, and measures approximately 1/10 the height of the nectophore.
Remarks.This species can be recognized by the dorsal bending of the dorso-lateral ridges.
Lensia hardy Totton, 1941 Figs. 7, 22 Anterior Nectophore: With five complete longitudinal ridges.It measures 4.73 mm in height and 2.06 mm in width.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 1/2 the width of the nectophore.The hydroecium is located below the level of the ostium.The somatocyst is spherical, with a short stalk.It measures approximately 1/14 the height of the nectophore.
Remarks.This species is very similar to L. fowleri (ToTTon 1965), but its somatocyst is located above the level of the ostium.Totton, 1941 Figs. 8, 23 Description.Anterior Nectophore: With seven complete longitudinal ridges, the lower-lateral ridges bending towards the lower surface and passing down onto the mouth plate.It measures 5.8 mm in height and 3.29 mm in width.The nectosac measures approximately 9/10 the height of the nectophore.The  Geographic distribution.In South America, it occurs in the Atlantic Ocean: Brazil to Argentina, from 0° to 67°S (alvariño 1981, PugH 1999, MigoTTo et al. 2002, silveira & Morandini 2011).

Lensia havock
Remarks.The main characteristics of this species are the hydroecium located above the level of the ostium, and the ventro-lateral ridges bending basally towards the mouth plate.
Lensia hotspur Totton, 1941Figs. 9, 24 Lensia canopusi Stepanjants, 1977: 72. Lensia peresi Patriti, 1970: 103.Description.Anterior Nectophore: With five complete longitudinal ridges.It measures 5.32 mm in height and 3 mm in width.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 3/5 the width of the nectophore.The hydroecium is reduced and located below the level of the ostium, with the hydroecial roof obliquely inclined.The mouth plate is divided into two rounded and slanting lappets.The somatocyst is short, obliquely inclined, ovate, and has a short peduncle.It measures approximately 1/10 the height of the nectophore.
Examined material.
Remarks.This species is distinguished by the oblique inclination of its somatocyst.Totton, 1941 Figs. 10, 25 Description.Anterior Nectophore: With seven straight longitudinal ridges.The upper-lateral ridges do not meet the ostial margin.The lower-laterals do not meet the apex, but curve down and around to meet the lateral edges of the oblique mouth plate.It measures 12.43 mm in height and 5.11 mm in width.The nectosac mesures approximately 9/10 the height of the nectophore.The ostium measures approximately 4/5 the width of the nectophore.The hydroecium is located below the level of the ostium with the roof curving around gradually to merge with the lower facet; the lower-lateral ridges both curve around proximally on each side of the hydroecium to meet the lateral edges of the mouth plate.The somatocyst is short, bilobed, and measures approximately 1/7 the height of the nectophore.
Lensia leloupi Totton, 1954 Figs. 11, 26 Lensia nagabhushanami Daniel, 1971: 150.Description.Anterior Nectophore: With five straight longitudinal ridges, the laterals not reaching the ostium.It measures 4.26 mm in height and 2.05 mm in width.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 3/5 the width of the nectophore.The mouth plate is oblique.The hydroecium is bell-shaped, extending above the level of the ostium.The somatocyst is filiform and measures approximately 1/3 the height of the nectophore.
Remarks.This species resembles Lensia subtiloides, but is larger and has a deeper hydroecium (ToTTon 1965).
Lensia lelouveteau Totton, 1941 Figs. 12, 27 Lensia multicristata forme grimaldii Leloup, 1934: 36.Description.Anterior Nectophore: With groups of longitudinal ridges, most of them complete.It measures 6.72 mm in height and 3.96 mm in width.It has a velar ridge, crossing the longitudinal ridges, and located above the ostium.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 4/5 the width of the nectophore.The lower ridges curve towards the mouth plate at their ostial ends.The hydroecium is deep and open on the lower surface as a long slit in the lower facet; it also extends above the level of the ostium.The somatocyst is squat and kidney-shaped, measures approximately 1/20 the height of the nectophore, and is very difficult to distinguish.
Remarks.The presence of a velar ridge and the shape of its somatocyst distinguish this species.
Lensia meteori (Leloup, 1934) Figs. 13, 28 Galetta meteori Leloup, 1934: 15.Description.Anterior Nectophore: Delicate, with rounded apex, apparently without longitudinal ridges.It measures 2.61 mm in height and 1.75 mm in width.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 4/5 the width of the nectophore.The hydroecium is narrow, high, and slants upwards towards the lower surface.The roof of the hydroecium is located above the level of the ostium.The mouth plate is divided into two lappets.The somatocyst is spherical, expanding laterally, with a short stalk, and measures approximately 1/10 the height of the nectophore.
Remarks.The anterior nectophore of this species is very similar to that of Lensia subtilis, except for the almost vertical basal facet, the larger mouth plates, and the short peduncle and laterally expanded shape of the somatocyst (ToTTon 1965).
Remarks.This species can be recognized by its long, filiform somatocyst, reaching almost half the height of the anterior nectophore in most specimens, and its anterior nectophore, which has seven longitudinal ridges.

Figures 17 -
Figures 17-31.Comparison of the anterior nectophore morphology of Lensia from southeastern Brazilian coast, shown from the same aspects as in Figs.1-16.Scale bars: 0.5 mm.

Figs
Figs. 15, 30Diphyes subtilis Chun, 1886: 681.Description.Anterior Nectophore: Conical, laterally compressed, with rounded apex, and apparently without longitudinal ridges.It contains four longitudinal folds and measures 2.56 mm in height and 1.32 mm in width.The nectosac measures approximately 9/10 the height of the nectophore.The ostium measures approximately 3/5 the width of the nectophore.The lower ridges bordering the lower facet are rounded at their proximal ends, and the mouth plate is small and divided, each distal lamella being rounded distally.The roof of the hydroecium