Limits...
Convergent Reduction of Ovariole Number Associated with Subterranean Life in Beetles.

Faille A, Pluot-Sigwalt D - PLoS ONE (2015)

Bottom Line: We discuss the multiple convergent evolutions in ovariole number and the potential link between a reduction of ovariole number and troglobiomorphism in a phylogenetic context.A reduction to one ovariole has occurred independently at least twice in this subterranean group.A reduction in the number of ovarioles in ground beetles is one of the striking consequences of subterranean specialization and it is correlated with another remarkable adaptation of subterranean beetles, a reduction in the number of larval instars.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, Zoologische Staatssammlung, Munich, Germany.

ABSTRACT

Background: Some species of obligate cavernicolous beetles are known to possess a unique feature-a contraction of the larval cycle. In contrast to many other subterranean beetles, life-cycle contraction in Trechini ground beetles (Carabidae) is correlated with a reduction in the number of eggs and a drastic reduction in the number of ovarioles. This remarkable peculiarity has only been reported for a small number of closely related species.

Results: We give a description of the female internal reproductive system for six species of Trechini, including five subterranean species, with a particular focus on the western Pyrenean radiation of Aphaenops, a group for which nothing is known regarding the early life stages. We redescribe the internal female genitalia of A. crypticola Linder. Study of the ovarioles allowed us to infer the postembryonic development of the larvae for each species examined. We then used a phylogenetic framework to recognize two independent reductions in the number of ovarioles in the Pyrenean lineage. We discuss the multiple convergent evolutions in ovariole number and the potential link between a reduction of ovariole number and troglobiomorphism in a phylogenetic context.

Conclusions: There is an extreme reduction in ovariole number and size within the species studied; the eggs produced by small ovarioles have a remarkably large size. A reduction to one ovariole has occurred independently at least twice in this subterranean group. A reduction in the number of ovarioles in ground beetles is one of the striking consequences of subterranean specialization and it is correlated with another remarkable adaptation of subterranean beetles, a reduction in the number of larval instars.

No MeSH data available.


Related in: MedlinePlus

Female ectodermal genital ducts restricted to their cuticular intima lining by KOH treatment.Dorsal and more or less lateral views in order to show the different elements. (A) Trechus bordei. (B) Aphaenops loubensi. (C) Aphaenops ochsi ssp. cabidochei. (D) Aphaenops leschenaulti. (E) Aphaenops crypticola; the vaginal secretory units are indicated by asterisks. Scale bars: A = 5 mm; B = 1 mm; C-E = 0.5 mm. Abbreviations: ap = apodeme-like structure, bc = bursa copulatrix, co = common oviduct, gl = defense gland, mt VIII = mediotergite VIII, pp = protruding part of genital duct, s = spermatheca, su = secretory unit, v = vagina, vd = vaginal diverticulum, vp = vaginal pouch.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4494710&req=5

pone.0131986.g003: Female ectodermal genital ducts restricted to their cuticular intima lining by KOH treatment.Dorsal and more or less lateral views in order to show the different elements. (A) Trechus bordei. (B) Aphaenops loubensi. (C) Aphaenops ochsi ssp. cabidochei. (D) Aphaenops leschenaulti. (E) Aphaenops crypticola; the vaginal secretory units are indicated by asterisks. Scale bars: A = 5 mm; B = 1 mm; C-E = 0.5 mm. Abbreviations: ap = apodeme-like structure, bc = bursa copulatrix, co = common oviduct, gl = defense gland, mt VIII = mediotergite VIII, pp = protruding part of genital duct, s = spermatheca, su = secretory unit, v = vagina, vd = vaginal diverticulum, vp = vaginal pouch.

Mentions: Examination of the female ectodermal genital tract after KOH treatment revealed several details through the cuticular intima lining. The female genital ducts of the five species examined are illustrated in Fig 3. A full description falls out of the scope of this paper and we only treat their general characteristics here, which have already been observed by Deuve [29] in other Trechini. There is a great diversity in the architecture of the genital ducts, even within the same genus (Fig 3B–3E). The following features are noticeable: i) the common oviduct, located ventrally as in other Adephaga, which is either long and straight or curiously collapsed upon itself (Fig 3B), as it is the rule in many insects, its intima bears internal minute spines; ii) the bursa copulatrix is present (Fig 3A, 3C and 3D) or absent (Fig 3B and 3E); iii), the spermatheca is lost, except in A. crypticola (Fig 3E); iv), the vagina is wide, being either simple (Fig 3A, 3D and 3E) or equipped with a posteriorly rounded diverticulum (Fig 3B) or with a large dorsal pouch (Fig 3C). Furthermore, in A. crypticola alone, we have observed numerous cuticular ductules scattered on the vaginal intima close to the opening of the spermatheca (Fig 3E), these being the efferent ductules of the secretory units of class III according to the classification of Noirot and Quennedey [39]. Except for these scattered secretory units, no glands are associated with the genital ducts.


Convergent Reduction of Ovariole Number Associated with Subterranean Life in Beetles.

Faille A, Pluot-Sigwalt D - PLoS ONE (2015)

Female ectodermal genital ducts restricted to their cuticular intima lining by KOH treatment.Dorsal and more or less lateral views in order to show the different elements. (A) Trechus bordei. (B) Aphaenops loubensi. (C) Aphaenops ochsi ssp. cabidochei. (D) Aphaenops leschenaulti. (E) Aphaenops crypticola; the vaginal secretory units are indicated by asterisks. Scale bars: A = 5 mm; B = 1 mm; C-E = 0.5 mm. Abbreviations: ap = apodeme-like structure, bc = bursa copulatrix, co = common oviduct, gl = defense gland, mt VIII = mediotergite VIII, pp = protruding part of genital duct, s = spermatheca, su = secretory unit, v = vagina, vd = vaginal diverticulum, vp = vaginal pouch.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494710&req=5

pone.0131986.g003: Female ectodermal genital ducts restricted to their cuticular intima lining by KOH treatment.Dorsal and more or less lateral views in order to show the different elements. (A) Trechus bordei. (B) Aphaenops loubensi. (C) Aphaenops ochsi ssp. cabidochei. (D) Aphaenops leschenaulti. (E) Aphaenops crypticola; the vaginal secretory units are indicated by asterisks. Scale bars: A = 5 mm; B = 1 mm; C-E = 0.5 mm. Abbreviations: ap = apodeme-like structure, bc = bursa copulatrix, co = common oviduct, gl = defense gland, mt VIII = mediotergite VIII, pp = protruding part of genital duct, s = spermatheca, su = secretory unit, v = vagina, vd = vaginal diverticulum, vp = vaginal pouch.
Mentions: Examination of the female ectodermal genital tract after KOH treatment revealed several details through the cuticular intima lining. The female genital ducts of the five species examined are illustrated in Fig 3. A full description falls out of the scope of this paper and we only treat their general characteristics here, which have already been observed by Deuve [29] in other Trechini. There is a great diversity in the architecture of the genital ducts, even within the same genus (Fig 3B–3E). The following features are noticeable: i) the common oviduct, located ventrally as in other Adephaga, which is either long and straight or curiously collapsed upon itself (Fig 3B), as it is the rule in many insects, its intima bears internal minute spines; ii) the bursa copulatrix is present (Fig 3A, 3C and 3D) or absent (Fig 3B and 3E); iii), the spermatheca is lost, except in A. crypticola (Fig 3E); iv), the vagina is wide, being either simple (Fig 3A, 3D and 3E) or equipped with a posteriorly rounded diverticulum (Fig 3B) or with a large dorsal pouch (Fig 3C). Furthermore, in A. crypticola alone, we have observed numerous cuticular ductules scattered on the vaginal intima close to the opening of the spermatheca (Fig 3E), these being the efferent ductules of the secretory units of class III according to the classification of Noirot and Quennedey [39]. Except for these scattered secretory units, no glands are associated with the genital ducts.

Bottom Line: We discuss the multiple convergent evolutions in ovariole number and the potential link between a reduction of ovariole number and troglobiomorphism in a phylogenetic context.A reduction to one ovariole has occurred independently at least twice in this subterranean group.A reduction in the number of ovarioles in ground beetles is one of the striking consequences of subterranean specialization and it is correlated with another remarkable adaptation of subterranean beetles, a reduction in the number of larval instars.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, Zoologische Staatssammlung, Munich, Germany.

ABSTRACT

Background: Some species of obligate cavernicolous beetles are known to possess a unique feature-a contraction of the larval cycle. In contrast to many other subterranean beetles, life-cycle contraction in Trechini ground beetles (Carabidae) is correlated with a reduction in the number of eggs and a drastic reduction in the number of ovarioles. This remarkable peculiarity has only been reported for a small number of closely related species.

Results: We give a description of the female internal reproductive system for six species of Trechini, including five subterranean species, with a particular focus on the western Pyrenean radiation of Aphaenops, a group for which nothing is known regarding the early life stages. We redescribe the internal female genitalia of A. crypticola Linder. Study of the ovarioles allowed us to infer the postembryonic development of the larvae for each species examined. We then used a phylogenetic framework to recognize two independent reductions in the number of ovarioles in the Pyrenean lineage. We discuss the multiple convergent evolutions in ovariole number and the potential link between a reduction of ovariole number and troglobiomorphism in a phylogenetic context.

Conclusions: There is an extreme reduction in ovariole number and size within the species studied; the eggs produced by small ovarioles have a remarkably large size. A reduction to one ovariole has occurred independently at least twice in this subterranean group. A reduction in the number of ovarioles in ground beetles is one of the striking consequences of subterranean specialization and it is correlated with another remarkable adaptation of subterranean beetles, a reduction in the number of larval instars.

No MeSH data available.


Related in: MedlinePlus