Mazocraeoides rotundus, Sailaja & Shameem & Madhavi, 2019

Sailaja, Bade, Shameem, Ummey & Madhavi, Rokkam, 2019, Four species of Mazocraeoides Price, 1936 (Monogenea: Mazocraeidae), including two new species from clupeiform fishes off Visakhapatnam coast, Bay of Bengal, Zootaxa 4608 (2), pp. 233-246 : 234-236

Mazocraeoides rotundus n. sp.

( Figs.1–4 )

Type -host: Ilisha filigera (Valenciennes) (Pristigasteridae) .

Type -locality: Visakhapatnam coast, Bay of Bengal .

Site in host: Gills.

Material deposited: Zoological Survey of India, Kolkata, India. Holotype W10437/1, paratype W10438/ 1. Natural History Museum, London. Paratype NHMUK 2019.3 .15.1.

Prevalence and mean intensity: 17.85% and 11.6 worms per infected fish.

ZooBank registration: The Life Science Identifier (LSID) for Mazocraeoides rotundus n. sp. is urn:lsid:zoobank.org:act:0CE24CAF-B1F2-4845-95F9-28553EC20A3C

Etymology: The specific name indicates the round shape of the body.

Description: (Measurements based on 4 specimens) Body typically pot-like with broad rounded posterior region and narrow neck-like extensile anterior region. Some specimens appeared oval and plump probably due to contraction of anterior region. Body size small, 900 (832–976) long, 372 (336–432) wide. Clamps four pairs, of equal size, 23 (20–29) in diameter, sessile, closed type, embedded in body margins in posterior half of body, arranged equidistantly with first pair at distance of 520 (448–608) from anterior extremity, last pair close to posterior extremity. Clamp skeleton typical of Mazocraeoides comprises five sclerites: scleritum arcuatum-anterius (SAA), scleritum antero- supplementarium (SAS), scleritum medio-basale (SMB), scleritum medio-supplementarium (SMS) and scleritum labiatum (SL). Oral sucker oval, 26 (24–28) x 20 in size. Pharynx rounded, esophagus long, ceca broad, terminate at posterior region of body. Lappet not differentiated. Instead posterior region of body bears two pairs of anchors and one pair of hooks. Outer pair of anchors 43 (36–48) long, with broad shaft and prominent spur, curved tip. Inner pair of anchors smaller, 11 (8–12) long, hooks very small, visible only in some forms.

Genital pore near intestinal bifurcation at distance of 143 (116–164) from anterior end. Testis single, oval, 150 (140–160) long, situated in intercecal field of posterior third of body. Seminal vesicle elliptical lies in front of testis. Genital complex prominent, situated near bifurcation point, muscular, 21 (20–24) long, 30 (28–32) wide. Genital armature consists of five pairs of small pointed hooks arranged in two vertical rows and a pair of fairly large lateral hooks with broad plate-like base and forked tip.

Ovary oval, anterodextral to testis. Mehlis’s gland preovarian. Eggs fairly large. Only four individuals contained eggs each with single egg occupying major part of uterus. In two individuals eggs contained long filaments, while in others eggs appeared perfectly oval without filaments; probably these represent newly formed eggs and the filaments are yet to develop. Genito-intestinal canal and vagina not visible. Vitelline follicles numerous, extend from intestinal bifurcation level to almost posterior end of body. Vitelline reservoir Y-shaped immediately preovarian, prominent.

Remarks: As indicated in the introduction, out of 25 species reported in Mazocraeoides , only 13 spp. are retained as valid. The 25 species and the two new species are listed in Table 1 , together with their hosts, localities and authors. Mazocraeoides rotundus n. sp. differs from all the other species in the genus, in the peculiar pot-like shape of the body, alignment of clamps in the body proper, the clamp organization and the number and arrangement of genital hooks. In many respects, especially in the small body size and alignment of gonads, M. rotundus n. sp. resembles M. prashadi , but differs from it apart from the body shape, in the structure of the clamp, in the smaller genital complex and in the number and arrangement of hooks of genital complex. In M. prashadi the genital complex is large and prominent, sucker-like armed with five pairs of median hooks arranged in two vertical rows and a pair of long, sickle-shaped lateral hooks whereas in the present form genital complex is small and the armature consists of five pairs of small, pointed and inwardly directed hooks arranged in two vertical rows and a pair of lateral hooks with a broad plate-like base and forked tip. Another species that shows some resemblance to the new species is Mazocraeoides jimeiensis Zhang, Yang & Liu, 2001 reported from Sardinella perforata and Sardinella clupeoides from South China Sea but in this species the body is elliptical in shape, much larger, genital hooks are larger in size and the clamp skeleton has a different organization. In M. jimeiensis the ovary is present in the middle of the body anterior to the testis whereas in the new species the ovary is situated in the posterior third of the body antero-lateral to the testis.

Figures

FIGURES 1–4. Mazocraeoides rotundus n. sp. 1. Entire worm, ventral view; 2. Genital atrium; 3. clamp; 4. Anchors and hooks. Scale bars: Fig. 1, 200µm; Figs. 2–4, 10µm. Abbreviations: SAA, Scleritum arcuatum-anterius; SAS, Scleritum antero-supplementarium; SL, Scleritum labiatum; SMB, Scleritum medio-basale; SMS, Scleritum medio-supplementarium