Bougainvillia leizhouensis Xu, Guo & Wang, 2021

Wang, Xuefeng, Lu, Liyi, Zhang, Shenzeng, Lin, Linkun, Xu, Zhenzu, Guo, Donghui & Huang, Jiaqi, 2021, Two new species of hydromedusa (Cnidaria) from the Leizhou Bay, the northern South China Sea, Zoological Systematics 46 (3), pp. 193-199 : 194-196

Bougainvillia leizhouensis Xu, Guo & Wang , sp. nov. ( Figs 1–4 )

Material examined. Holotype (AOB-HL 332), a specimen collected from the Leizhou Bay of the northern South China Sea, S 8 station (20°40'N, 110°35'E), depth 9.5 m, November 2018, coll. Xuefeng Wang and Liyi Lu.

Diagnosis. Umbrella near bell-shaped, with round dome top, jelly thick, but thinner toward the bell margin; manubrium cylindrical, no gastric peduncle and perradial lobes, about 1/4 height of subumbrella cavity; mouth with 4 proximal simple lips; with 4 perradial oral tentacles, inserted above mouth rim, oral tentacles basal trunk short, divided 3–4 times; eight gonads in adradial pairs on the upper part of the manubrium; bell margin with 4 perradial furrows, 4 perradial tentacular bulbs sunk into a narrow furrow between two marginal lobes, tentacular bulbs broad U-shaped, each with 9–11 tentacles; ocelli adaxial on the tentacular bulbs.

Description. Umbrella 5 mm in height, 4 mm in width; bell-shaped, with round dome top; jelly thick, one-third, or more of bell height at apex, but thinner toward the bell margin; manubrium cylindrical, no gastric peduncle, with a broad base, no perradial lobes, about 1/4 height of subumbrella cavity; mouth with 4 prominent simple lips; 4 perradial oral tentacles arising above the mouth opening, basal trunk of oral tentacles short, oral tentacles divided 3–4 times, ending with nematocyst knobs; eight gonads in adradial pairs on the upper part of the manubrium, not contacting each other perradially, gonads ellipse-like, with smooth surface; 4 radial canals and a circular canal; in preserved specimen the extension of epaulette-shaped covered the interradial part of bell margin, forming a narrow, perradial notch between two extension of epaulette-shaped, tentacular bulbs located on the notch of bell margin; tentacular bulbs facing downward, broadly U-shaped, each with 9–11 solid long tentacles and corresponding number of ocelli; ocelli adaxial, black, round, on tentacular bulb near base of tentacles; velum moderately broad.

Distribution. The northern South China Sea (Leizhou Bay).

Etymology. The species name is from the Latin leizhouensis , meaning Leizhou, refers to the type locality of the new species.

Remarks. This new species has four perradial clusters of identical marginal tentacles, born on four tentacular bulbs; four perradial oral tentacles dichotomously branch, inserted above mouth rim; gonads located on manubrium. These are consistent with the general characters of the genus Bougainvillia Lessen, 1830 .

At present time, 29 valid species are known in Bougainvillia (Vannucci & Rees, 1961; Xu & Huang, 2004a, 2006; Bouillon et al., 2006; Xu et al., 2006, 2007, 2014; Nogueira et al., 2013; Batistić & Garić, 2016). Among them, B. crassa Fraser, 1938 and B. meinertiae Jäderholm, 1923 are only reported with the hydroid forms, while B. aberrans Calder, 1993 and B. rugosa Clarke, 1882 are only reported with the newly released medusae.

This new species is similar to B. vervoorti Bouillon, 1995 , but can be separated by: 1) the new species has the manubrium short cylindrical, without perradial lobes, while B. vervoorti has a cruciform manubrium with four large basal perradial lobes; 2) the new species has eight gonads in adradial pairs on the upper part of manubrium, while B. vervoorti has four pairs of gonads along the adradial sides of manubrium and extending on the perradial lobes; 3) the new species has four tentacular bulbs sinking into furrows of the bell margin, while B. vervoorti has four perradial tentacular bulbs situating on four exumbrellar lobes.

Key to all known species of genus Bougainvillia excluding hydroids and newly liberated medusa.

1. Gastric peduncle present, distinct.........................................................................................................................................................2

Gastric peduncle ambiguous or absent .................................................................................................................................................6 2. Without ocelli; gonads perradial present on manubrium, lamella-shaped; oral tentacles divided twice.................................................

................................................................................................................................................ B. lamellata Xu, Huang & Liu, 2006 *

With ocelli............................................................................................................................................................................................3 3. Ocelli crescent-shaped on tentacles; gonads present on interradial of manubrium wall................ B. superciliaris (L. Agassiz, 1849) *

Ocelli present on marginal bulbs; gonads present on perradial outgrowth of manubrium....................................................................4 4. Each marginal bulb with two tentacles; oral tentacles divided twice ................................................... B. bitentaculata Uchida, 1925 *

Each marginal bulb with more than two tentacles................................................................................................................................5

5. Each bulb with 4–9 tentacles; oral tentacles with moderately long basal trunk .................. B. pyramidata (Forbes & Goodsir, 1851) Each bulb with 30–65 tentacles; oral tentacles with short basal trunk .................................................. B. macloviana ( Lesson, 1830)

6. With medusae budding from manubrium.............................................................................................................................................7 Without medusae budding from manubrium...................................................................................................................................... 10

7. Manubrium flat; basal trunk of oral tentacles absent or short ..............................................................................................................8 Manubrium flask-shaped or cylindrical-shaped; basal trunk of oral tentacle long ...............................................................................9

8. Oral tentacles with basal trunk absent ................................................................................................. B. platygaster (Haeckel, 1879) * Oral tentacles with basal trunk short and thick, first branches about 1/2 length of oral tentacles .......................................................... ........................................................................................................................................ B. chenyapingae Xu, Huang & Guo, 2007 *

9. Manubrium flask-shaped; 8 tentacles present in each marginal bulb; ocelli present on marginal bulbs............ B. niobe Mayer, 1894 * Manubrium cylindrical-shaped; 3 tentacles present in each marginal bulb; without ocelli .......................... B. frondosa Mayer, 1900 *

10. Gonads separated from manubrium (adult males); peduncle shallow; top of subumbrella flat, bell base quadrangular; each bulb with 7–10 tentacles; sexually dimorphic male with gonads ........................................................................... B. dimorpha Schuchert, 1996 Gonads present on manubrium........................................................................................................................................................... 11

11. Gonads perradial present on manubrium............................................................................................................................................ 12 Gonads interradial or adradial present on manubrium .......................................................................................................................15

12. Oral tentacles with four clusters, each consist of four main oral tentacles; oral tentacle with basal trunk short, divided 6–7 times ...... ................................................................................................................................... B. paraplatygaster Xu, Huang & Chen, 1991 * Oral tentacles without cluster............................................................................................................................................................. 13

13. Oral tentacles with basal trunk long, about 5/6 length of oral tentacles; 4–6 tentacles present in per bulb............................................ ........................................................................................................................................................ B. longistyla Xu & Huang, 2004 * Oral tentacles with basal trunk short, up to half of the length of oral tentacle; more than 6 tentacles present in per bulb ................. 14

14. Each bulb with 50–60 tentacles...................................................................................................... B. multitentaculata Foerster, 1923 Each bulb with 7–16 tentacles.............................................. B. pagesi Nogueira, Rodriguez, Mianzan, Haddad & Genzano, 2013

15. Gonads adradial .................................................................................................................................................................................16 Gonads interradial..............................................................................................................................................................................21

16. Ocelli present on tentacles ................................................................................................................................................................. 17 Ocelli present on bulbs.......................................................................................................................................................................18

17. Oral tentacles with long trunk, divided 4–6 times; each bulb with 12–17 tentacles............................... B. britannica (Forbes, 1841) * Oral tentacles with short trunk, divided 6–8 times; each bulb with 15–20 tentacles ........................ B. fulva Agassiz & Mayer, 1899 *

18. Exumbrella with reticular papillae; oral tentacles with long and thick trunk, divided twice; each bulb with 8–9 tentacles................... ........................................................................................................................................................ B. reticulata Xu & Huang, 2006 * Exumbrella smooth, without reticular papillae................................................................................................................................... 19

19. Tentacular bulbs long, epaulette-shaped, not shorter than intervals; each bulb with 20–40 tentacles .................................................... .......................................................................................................................................................... B. principis (Steenstrup, 1850) * Tentacular bulbs U-shaped ................................................................................................................................................................. 20

20. Manubrium cruciform, with 4 large basal perradial lobes; 4 pairs of gonads along the adradial side of manubrium, extending on the perradial lobes.......................................................................................................................................... B. vervoorti Bouillon, 1995 * Manubrium short cylindrical, lacking perradial lobes; 8 gonads present in adradial pairs on upper part of manubrium ....................... ....................................................................................................................................... B. leizhouensis Xu, Guo & Wang , sp. nov. *

21. Without ocelli..................................................................................................................................................................................... 22 With ocelli.......................................................................................................................................................................................... 24

22. Tentacular bulbs near crescent-shaped, with a short, papillar-shaped endodermal process extending to radial canals; manubrium quadrangular very flat adnate to subumbrella ......................................................................... B. papillaris Xu, Huang & Guo, 2014 * Tentacular bulbs triangular-shaped or hemispherical-shaped............................................................................................................. 23

23. Basal trunk of oral tentacles long, up to half length of oral tentacle; <2 mm in height; each bulb with 2–3 tentacles .......................... ............................................................................................................................................................. B. aurantiaca Bouillon, 1980 * Basal trunk of oral tentacles short, about 1/5 length of oral tentacle; 3–5 mm in height; each bulb with 3–7 tentacles ......................... ................................................................................................................................................................... B. muscoides (Sars, 1846)

24. Ocelli present on tentacles; manubrium long and narrow, about 1/2 height of umbrella cavity; oral tentacle with basal trunk long, divided twice................................................................................................................................... B. carolinensis (McCrady, 1859) * Ocelli present on bulbs.......................................................................................................................................................................25

25. Each bulb with up to 60 tentacles; each oral tentacle divided 7 times........................................................... B. involuta Uchida, 1947 Each bulb with less than 60 tentacles .................................................................................................................................................26

26. Each oral tentacle divided twice; without apical canal............................................................................... B. muscus (Allman, 1863) * Each oral tentacle divided up to 3 times; adult medusa with an apical canal ............................................. B. triestina Hartlaub, 1911

Figures

Figures 1–4. Bougainvillia leizhouensis Xu, Guo & Wang, sp. nov. 1–2. Lateral views. 3. Dorsal view of gonads. 4. Part enlargement of the tentacular bulb. Scale bars=0.5 mm.