Ventromma halecioides (Alder, 1859)

Humara-Gil, Karla J. & Cruz-Gómez, Christopher, 2018, New records of benthic hydroids (Cnidaria: Hydrozoa) from the coast of Oaxaca, Mexico, Zootaxa 4455 (3), pp. 454-470 : 462-464

Ventromma halecioides (Alder, 1859)

FIg. 6

Plumularia halecioides ALdER, 1859: 353, pL. 12, fIGS. 1‒5.

Plumularia inermis .—FRASER, 1948: 278.

Ventromma halecioides .—MEdEL & VERVOORt, 1995: 45, fIG. 19. (SyN.)—CALdER, 1997: 4, fIG. 1 (SyN.).—CALdER, 2013: 45, fIG. 13f. —MARONNA et al., 2016: 16.

Type locality. CULLERcOATS ANd ROKER, ENgLANd (ALdER 1859).

Material examined. FIVE cOLONIES: UMAR-HYDR-009, fIVE cOLONIES ON SUbmERgEd ROPE ( SANTA CRUZ BAY, OAXAcA, 15°45’07’’N 96°07’52’’W, 0.2 m, 28 NOVEmbER 2015, cOLL. C. CRUZ-GómEZ).

Description. COLONIES PINNATE, 0.7–1.3 µm hIgh, ARISINg fROm A cREEPINg hYdRORhIZA. HYdROcAULUS

mONOSIPhONIc OR POLYSIPhONIc; mOSTLY STRAIghT, bUT SOmEWhAT cURVEd AT dISTAL ENd. STEm dIVIdEd INTO INTERNOdES bY dISTINcT NOdES; EAch INTERNOdE WITh A hYdROcLAdIAL APOPhYSIS ANd A dISTAL, AXILLIARY NEmAThOThEcA. PERISARc ThIcK ON hYdROcAULUS, gETTINg ThINNER ON hYdROcLAdIA. APOPhYSES ALTERNATE, bEARINg hYdROcLAdIA WITh UP TO fOUR hYdROThEcAE. HYdROcLAdIA OccASIONALLY bRANchEd, WITh A VARIAbLE NUmbER Of ThEcATE ANd AThEcATE INTERNOdES; ThE LATTER USUALLY OccURRINg bETWEEN TWO ThEcATE INTERNOdES. ThEcATE INTERNOdES WITh A dISTAL hYdROThEcA ANd TWO NEmATOThEcAE, ONE PLAcEd bELOW EAch hYdROThEcA ANd OThER ON ITS UPPER SIdE. NEmATOThEcAE SmALL, LESS ThAN 20 µm LONg ANd 10 µm WIdE. HYdROThEcAE cUP-ShAPEd WITh SmOOTh mARgIN, AdNATE; OccURRINg ONLY ON hYdROcLAdIA. AbcAULINE WALL 37 µm LONg; AdcAULINE WALL AdNATE TO hYdROcAULUS 15 µm LONg, 18 µm fREE. HYdRANThS LARgER ThAN hYdROThEcAE, WITh dOmE- ShAPEd hYPOSTOmE ANd AbOUT 17 fILIfORm TENTAcLES. GONOThEcAE bARREL-ShAPEd, ANNULATEd, AbOUT 800 µm LONg, 340 µm WIdE AT mIddLE; ARISINg bY A ShORT PEdIcEL fROm hYdROcAULUS.

Remarks. ThIS SPEcIES IS SOmETImES ASSIgNEd TO ThE gENUS Kirchenpaueria JIcKELI, 1883. ThERE ARE fEW SIgNIfIcANT mORPhOLOgIcAL dIffERENcES bETWEEN Kirchenpaueria ANd Ventromma STEchOW, 1923, WITh ThE TWO gENERA SOmETImES bEINg REgARdEd AS SYNONYmS. Ventromma dIffERS fROm Kirchenpaueria IN hAVINg NEmATOPhORES ThAT ARE PROTEcTEd bY NEmATOThEcAE (CALdER 1997, 2013). REcENT mOLEcULAR STUdIES SUch AS ThOSE Of MARONNA et al. (2016) PROVIdE EVIdENcE Of gENETIc dISTANcE bETWEEN bOTh gENERA.

Distribution. Ventromma halecioides WAS REcORdEd bY FRASER (1948, AS Plumularia inermis ) fROm BAjA CALIfORNIA. IT IS cONSIdEREd A cOSmOPOLITAN SPEcIES IN ShALLOW TROPIcAL ANd WARm-TEmPERATE WATERS (MEdEL & VERVOORT 1995; CALdER 1997, 2013). ThIS IS ThE fIRST REcORd Of ThE SPEcIES IN OAXAcA.

Figures

FIGURE 6. Ventromma halecioides (ALdER, 1859). A, cOLONy; B, GONOthEcA; C, ALtERNAtE hydROcLAdIA; D, hydROthEcA; E, hydROcLAdIum wIth tERmINAL hydRANth. ScALE bARS: 50 µm (D, E), 200 µm (C, B), 5 mm (A).